|With the head, flywheel, sheetmetal, and any other external bolt-on parts removed (basically down to the short block) the first thing I do is measure piston pop-up or the amount the piston is in the hole and the stroke and write it down for later use.
From there I remove the side cover, pull the cam and lifters. Next is to remove the rod bolts. If they are still the factory T-27 rod bolts I do the following. Make sure you have a GOOD T-27 bit. I use a T-27 bit that fits a 1/4" drive ratchet. With the piston a TDC start rolling the crank in the counter-clockwise rotation until you can get the bit into the top bolt. Continue rolling it counter-clockwise until the head of the ratchet rest against the front of the block. Put a little pressure on the crank which holds the bit firm in the bolt head and loosen the bolt. Once it is broken loose you can roll it to whever it makes it easy for you to remove the bolt. Do the same for the bottom bolt. Take the two T27 bits and throw them in the nearest trash can and replace them with the hex head bolts Briggs# 555654. If you are putting an new rod in the motor, clamp the rod upside down gently in your vise (lined with aluminum jaws) and remove the T27 bolts.
With the rod bolts out, remove the rod cap and push the rod & piston out through the top of the bore. With the rod & piston out, remove the crankshaft.
If your piston is an older style piston it will have only one clip in it, if it is a new piston it will have a clip on both sides. Take a pair of needle nose pliars and remove this (or these) clips. Use a 5/16" nut driver (or 5/16", 1/4" drive socket on an extension) and push the piston pin out.
Carefully remove the rings from the piston. Make note as you take them off that the top ring has an "o" on it facing up with the chamfer on the inside of the ring facing up. On the middle ring it has an "o" on it facing up with the inside chamfer facing down. The bottom ring has no particular orientation but does have a ring expander behind it, remove both.
Now you have the short block completely disassembled and laid out in front of you.
|Inspection of Parts:
First thing I do if it's a new or used block is deburr and clean it. I use a bearing scraper and run around all the sharp edges of the sidecover, head, and top of block area. The edges Briggs leaves on these blocks will cut you like a razor.
If the block is a Gen 1, 2, or 3 I inspect the bearing pocket area for cracks. Look closely in the bottom groove in the corners of the groove is typically where I have seen the cracks start. You will have to look close and make sure you have good lighting. I have even went as far as using Dye Penetrant to check for cracks if I was unsure. If there is a crack, the dye will definately find it.
If you find a crack, no matter how small, the block is junk. I have used all types of external bracing and welding on the inside, bottom line is, if it's cracked, you can not repair it and last for long.
Good news is, Briggs fixed the problem with the Gen 4 and 5 blocks. To this date, if there has been a problem in the bearing pocket area of the new blocks, I am unaware of it. The Gen 4 and 5 blocks also fixed a few other problems, but I'll get into that later.
Me personally, I will not use anything but a Gen 4 or 5 block in a sprint, enduro, or modified motor. Stock and restricted engines on the oval tracks seem to be fine and don't experience near the bearing pocket failures that the sprint, enduro, and modified engines do.
Once the bearing pocket area is verified to be good, do a quick look over the rest of the block. Pay close attention to the bottom of the bore on the inside of the block. I have seen a few blocks where the aluminum casting hangs out right near the inside of the bore. It may not be close enough to affect anything, but I don't like it. I take a sharp chisel and knock the flashing off away from the base of the bore.
While you are at the base of the bore, take a close look and see if there is a sharp edge on the base of the bore. I take 1000 grit wet sand paper and polish the edge at the base of the bore. If you noticed the piston when you pulled the sidecover off the engine, you know the piston comes a good way out of the bottom of the bore. Polishing this edge at the base of the bore solved a lot of piston skirt scuffing for me. If you bore or hone the block this will need to be done or re-done after boring or honing.
|Rod: Not much to inspect here. First off, there have been two Animal rods. The first Animal rod had a long dipper with a big ball out near the end. If you have this rod, throw it in the nearest trash can. I believe at one time around 80-85% of ours had the dipper breaking off, I suspect due to vibrations and the big ball out so close to the end of the dipper. The newer rods have a much shorter dipper (around 1" long) and is much beefier than the first generation rods. The new rod is the one you want to use.
A good dial bore gauge and micrometer are required to make sure you have the proper rod to crank clearance. A dial caliper will work, but I have seen some cheaper dial calipers read .002" difference between the inside and outside jaws. That is a HUGE difference when measuring a critical measurement like rod to crank clearance. The good news is, so far I have not seen an Animal rod with less than .0025" clearance from the factory and that is enough to run fine. Where you will get into trouble is on a used engine. Personally I like .0025"-.003" clearance on the rod. NO MORE than .003". I know guys using as much as .005" and they are also breaking rods on a consistant basis. Whatever works for you, but that is my preference.
Check the length of the rod with the thin portion of the blades of a dial caliper. The WKA spec minimum is 2.419" and 2.429" maximum.
If the rod looks fine (no visual flaws) and measures fine, set it to the side.
|Piston: Again, not much to inspect dimensionally here. Look around the bottom of the piston skirt for burrs and get rid of them. Something I have noticed lately is a burr on the piston pin clip notch in the piston. It keeps the pin from sliding in and out freely but does not affect normal operation. The bearing scraper again does a good job knocking this burr or lip down. It doesn't take but just a swipe to remove it.
Rings: Again, not much to inspect dimensionally. You can check the height and thickness and compare to the ring land width, but there is not much you can do about what you have unless you just get one that looks way out in left field to swap for new part. So far, I have not come across any problems in the rings and or ring lands.
Lifters: Check the head diameter and overall length on your lifters. Depending on the cam you are running, I have different things I look for. I always look for the longest lifter overall length I can find. On the head diameter, if I'm running a Dyno AN001 or a cam like it that is conservitive on the profile, I try to find the biggest head lifters I can get. If you are running other cams that are pushing the limits of the profile checks, a smaller head could help out. Have to get more into that in the camshaft section.
Crankshaft: Hopefully before you tore into the short block you measured the stroke. Maximum stroke is 2.204". Most I have seen are pretty close to that or at least close enough I don't think anyone will be marketing "max stroke" Animal cranks. Check the main crank pin. New it should measure 1.098" plus or minus .0005" and should be round. The Animal cranks are cheap (comparitively) so if they go more than .0005" out of round (that is HALF THOUSANDTH) I throw them out and put a new one in. Again, I'm having MUCH better luck with rods than other guys, I do believe it has to do with the oil I run and recommend AND how picky I am on crank/rod clearance. Other thing to look close at is the ground edge left around the crank pin. Again Briggs has left us a razor sharp edge here. I take a dremel tool with a 1/8" stone and debur this edge. Notice I said debur and not "round off". Excessive grinding will surely get you a DQ. Just take enough to remove the razor edge. Do the same for the flywheel key slot and clutch key slot.
That pretty much ends the inspection process I do for the short block.
|Prior to assembly let’s look at a few things and make sure what you have is going to work. This article is geared more toward taking what you have and building it so I will be passing over a few things like alternative rings and checking bore alignment to crank.
First off, your motor can not be clean enough. I stress again, it can NOT be clean enough. Any residue left over from honing, dirty oil, or even dust is enough to promote scuffing of the piston skirt and bore and other “rubbing” surfaces. Anything you can do to reduce friction in these motors leads to HP so don’t give it away or prematurely wear out your parts due to poor cleaning. Different builders have different processes for cleaning, and I’m not going to go into all the different ways, other than to just say, make sure it’s clean and if you wipe it with a white cloth or paper towel and you get any discoloration on the cloth, it’s not clean enough.
In front of you for the short block you should have the following: Block, Sidecover with bearing, Crankshaft with flywheel bearing, Rod, Piston Pin, Piston, Ring Set, Camshaft, Lifters, PVL Coil/Ignition, PVL Flywheel & Fan, Sidecover Gasket, and Crankshaft Shims.
Block: Briggs does a good job honing the block. The most I have seen one out of round or tapered from the factory so far is .0005” and puts a good cross hatch in it. Some argue it’s too rough of a finish, but for this article and general purposes, it works just fine. I have seen the deck height (piston popup or amount in the hole) as much as .020” in the hole and .004” piston popup from the factory. I recommend getting the block decked by a kart shop or machine shop with a milling machine. A flat deck surface is a must to ensure proper head gasket seal. Most shops charge between $15-$25 and it’s worth it to ensure its right. If you do get the block decked, go back and debur the opening around the lifter galley.
Sidecover: Not much to pick from here as long as you have an Animal Sidecover. Pay close attention to the PTO oil seal as it has a small spring behind the lip that slips over the crank to ensure proper seal. Watch this spring close as you assemble the motor or move the Sidecover around. This spring likes to jump out of place VERY easy.
Crankshaft: If you are using a stock connecting rod, not much to do here. If you are running a billet rod with insert, you might consider polishing or getting the main journal polished for you to a mirror finish. Some cranks have a rough bearing surface and will literally chew away at the Babbitt bearing surface until the clearance opens up and hammers the rod into submission (and a bad day at the track). I have not seen where this is a problem with the stock rod for whatever reason.
Rod: I use a 320 grit flex hone on both ends. Just a few quick passes with honing oil to put a cross hatch in, not for material removal.
Piston: Use the 320 grit hone again on the piston pin bores. Again, not for material removal, just to put a cross hatch in. Look at the bottom of the piston skirt. Right in the center of the piston the skirt should roll off right at the bottom. Just to the sides of that, you will see where the machined marks blend into the cast piston. Take a very close look here. Sometimes there are burrs or rough spots here. I use a “lapping stick” from Mondello Racing (which is a smooth ½ round stone for deburring edges in motors) and LIGHTLY debur these edges followed up by 1000 grit WET sandpaper. I stress LIGHTLY and WET on the sand paper because I don’t want you to think I mean to roll these edges off. Rolling the edges will definitely draw you some criticism in the tech room. You just want to make sure the sharp edge is gone, that’s it.
Ring Set: The rings definitely need to be lapped on the top & bottom surfaces. And if you have to cut the ring gaps, make sure you debur the edges after grinding or filing. I lap my rings with a ring holding fixture using honing oil on 500 grit sand paper on top of my surface plate. If you don’t have a surface plate, a piece of glass works well. A good place to get a piece of glass is a copier repair company. They will change out the glass on a copier from time to time when it gets scratched up, and it typically a thick piece of glass and works well for what we are doing. The stock rings are a source for a LOT of drag in the rotating assembly. A look into ways to reduce this friction is good. And that friction has little if anything to do with ring gaps. For ring gaps, I have not seen any adverse reason in using fairly large ring gaps as compared to what we typically used in the flathead motors. I have found it is much more important to get a good ring seal than a tight ring gap. Top ring, I have used .002” up to .018” and not seen a noticible difference on the dyno or track. By that I mean, there are more things that will affect overall HP of the engine more than the ring gap, like ring seal or poor valve seal. Do your own testing to convince yourself. And if you find concrete evidence otherwise, let me know. Middle ring, .004”-.018”. Bottom ring .006”-.018”. On your bottom/oil ring there is a ring expander behind it. In stock form it creates WAY more drag than is needed for proper oil control. Who you talk to depends on what answer you get, but you want as low of drag as you can get and still retain oil control. With the expander installed in the ring, squeeze the ring end gaps together with your hand and see how much resistance there is before the gaps touch. When you cut the expander, you don’t want the ring ends to touch or the motor will smoke like a freight train. But you do want it cut some. A whole chapter could be written on ring drag, ring seal, ring and bore prep alone. It is a source for lost and gained HP in the Animal engine.
Camshaft: In short, drop in a Dyno Cams AN001 or Comp Cams OHV1 (your choice) if you are oval racing and go. Both cams profile fine, both cams will perform similar on the track. Both are huge supporters of the sport and do a ton of R&D in this area. There are other cams out there; some push the legal profile limits a little closer than others. And it appears the cams that approach the profile legal limits on duration tend to have a little more top end. But for the most part, the AN001 and the OHV1 has won a LOT of races and will get the job done and keep you out of trouble in the tech barn.
Lifters: Not much prep to do here. If you have a double handful to pick from, sort them and put the lifters in with the biggest head diameters. Mark your intake or exhaust when you put it in the block so if they fall out later on teardown you will know which lifter is which.
Discussion: Jimmy Glenn---
I like some of the aftermarket chrome rings. Specifically the ones from PPS. They tend to be a bit softer and break in easier. Break in is a bit of an issue with this motor due to the chrome rings. 320 Final bore finish for most rings sets. break in with diesel oil(lots' of Zddp) and gas for temp.)
Second ring.... take a look at what we used to do to the old original Raptor oil ring. Nuff said
oil ring........... the expander spring on a STd piston can be cut down a bit to reduce pressure. Anything around 8" and you're on your own so go slow
Summerlin---......and I usually end up cutting about 3/8" off the length of the oil ring expander. For a quick check, put the expander inside the oil ring and put both in the cylinder bore (and compare that to the feel of just the oil ring) there should be NO additional tension felt from the expander but I want it just long enough for the two ends to bottom out against themselves so that I ain't flopping arround in there anymore than usual.
Above I went through everything to "look for" during tear down or parts selection. Now we can put it all together.
Again, I can not stress how important it is for ALL the parts to be spotless and clean. Not only clean to your sight, but clean enough when you wipe them with a cleaner on a white rag, the rag stays clean. If you are not sure, clean it again!!
First off, I'll tell you what I use for assembly oil. And nearly every builder has their own mix they use or off the shelf brand they prefer. It's really hard to say anyone does it wrong if it works for them and I'm not here to tell you the way I do it is the ONLY way, just what works for me. I use 16 ounce squeeze bottles (like a restaurant squeeze ketchup or sauce bottle). I get the bottles from my local restaurant supply house, they are cheap. I put 2 ounces of STP Oil Additive in the bottle then fill the rest with Wal-Mart Supertech 5w-30 cheap petroleum oil and shake vigorously for several seconds to make sure it is all shaken up. The reason I use this mix is, the STP additive is loaded with zinc (zddp) which prevents scuffing of the piston, rings, and bore which the Animal is prone to during assembly. My theory on assembly lube is you can NOT use enough. I typically use 4 to 8 ounces of assembly lube putting the motor together. Sure, you have to drain a little out when you are done, but I know it’s in there and I know it’s got it where it needs it.
If it is not already in the block, first install the flywheel side oil seal. Take care and pay close attention to not hit the seal surface (rubber part) during installation. Install the seal just past flush with the outside of the block. In the block you will see a small chamfer; just past this chamfer is what you are looking for. If you don't have a seal driver of the right size, a large socket will work. Just make sure it's driven in straight.
Next the crankshaft goes in. Unless you have removed the flywheel side bearing it is pressed on the crankshaft. If you did remove it, the bearing must be installed before putting the crankshaft into the block (unless you "slip-fit" the crank & bearing). For whatever reason, the bearing to block fit on the flywheel side is terrible from Briggs. I believe this helped start a lot of the block cracking problems in the early Animal blocks. To try and reduce some of the slop in the fit and I’m sure induced harmonics and vibration from this fit, I put a thin coat of Loctite 620 bearing “retaining and gap filling compound” on the outside of the bearing surface where it mates with the block. Just be sure to not use too much so that you get some dripping into the bearing, you don’t want that. On the crankshaft end that slips through the seal, put a good coat of oil on it and put a good coat of oil into the bearing. The oil on the crank will ensure as you slip the crank into the seal it does not damage it and there is no “dry start” on the seal when you fire the motor up.
Now you have the block sitting there with the crankshaft installed.
Next we assemble the rod, piston pin, and rings. The easiest way to make sure you get it together right is to lay the piston on it’s side so that you are looking at the bottom of the piston and the arrow on the piston is pointing to your right side. Next put the piston pin lying right behind it (it can go in either direction, it is not directional sensitive). Next lay the rod below the piston pin so that the “Mag Side” is to your right. If the rod cap is on, take it off. Use your assembly lube and coat the piston pin bores, the piston pin, and the piston pin bore in the rod. Take the piston pin and slide it into one side of the piston, push the rod up into the piston to where it lines up with the piston pin, and slip the pin through the rod into the other side of the piston. Install your piston pin(s). A set of needle nose pliers works great for installing the clip(s). Grab the clip by the straight portion of the clip, put the end of the rounded section into the clip bore and “roll” the clip into the hole. Just personal preference, but I like to install the clip where the straight portion is in the vertical position when done.
The rings go on next. I install all the rings and expander over the top of the piston down into the grooves. I also use just my hands to install the rings, but I have also been doing this a long time and have a knack for it. If you have not installed rings before, a ring expander might make the job a little easier, but you must also pay close attention to not OVER stretch the rings as you can add additional drag into the ring or worse yet, break the rings as they are very brittle. I slip the expander over first and put the gap in the expander to the PTO side of the engine (away from the arrow). Next I slide the oil ring over. The second ring gets installed so the “o” dot on the ring is up and the inside chamfer is DOWN. The top ring gets installed so the “o” dot on the ring is up and the inside chamfer is UP. Make sure you get these installed correctly. As for ring gap placement, I put the ring expander to the PTO side, the oil ring to the flywheel side more toward the pushrod side of the bore, the middle ring pointed directly to the clutch/PTO side of the engine, and the top ring pointing toward the flywheel favoring the top of the bore (just make sure the top and bottom ring do not overlap and have approximately ¼” between the gap ends. Roughly each gap will be on opposite sides of the piston pin bore.
To install the rod & piston into the bore you will need some type of ring compressor. I have seen everything used from fingers, to hose clamps, to professional compressors. Again, I’m not here to tell you there is a wrong way to do it, but you want to ensure however you get the piston in the bore that you do NOT scuff or scratch the piston, rings, or the bore. I like the stainless steel tapered compressor from Goodson. Make sure the crankshaft is turned DOWN before installing the piston so you don’t gouge the crankshaft main journal when pushing the piston in the hole. Prior to pushing the piston in the hole, give the cylinder bore, the piston skirt, and rod and crankshaft main journals a good heavy coat of oil. Make sure you do NOT get oil into the rod bolt holes.
You now have the rod installed into the bore and should be right at the top of the bore. Take the crankshaft and rotate it around slowly counter-clockwise until the crankshaft main journal comes up to the rod bore. Make sure the rod is turned right so that the crankshaft slips right into the rod bore. You can now push the piston down into the bore about ½ ways down the bore. This will bring the crank and rod into position so you can install the rod cap. First, put a good dose of oil on the rod cap making sure to keep oil out of the rod bolt holes. The rod cap will “snap” into place and should hold it’s self. The rod cap dipper should be pointed toward the cam/lifter portion of the block. Grab the rod bolts and put 3-4 drops of BLUE Loctite on the end of the threads (some people use Red, but I have not seen the need). Install the rod bolts to 115inch/lbs of torque with your torque wrench. I torque my bolts at 55, 85, and 115in/lbs.
Take your lifters and coat them good on the stems and face and place them in the lifter bores. I always engrave an “X” on the top of my exhaust lifter so if they fall out when tearing the engine down, I know which the exhaust is and which the intake is. Put a good dose of oil in the blocks camshaft bore, coat the camshaft lobes down with oil good and install the camshaft into the block. When you install the camshaft, make sure the “o” dot on the camshaft and crankshaft gears mate/line up. Being even 1 tooth off can throw the cam profile well out of alignment.
You are now ready to put the side cover gasket on the block, slip it over the dowels to hold it. The crankshaft shims go between the crankshaft gear and the bearing in the side cover. I like about .010”-015” crankshaft endplay. Some guys like more, some less, but that is what works for me. You will have to slip the Sidecover on with the gasket and tighten down a few bolts to check your end play. Most of the time, you will end up with the one thick spacer and possibly a single thin spacer. Just have to check it to make sure.
Then a good coat of oil on the end of the camshaft and a good dose in the Sidecover camshaft bore. Put some oil in the Sidecover bearing and make sure the spring is still in the PTO oil seal in the Sidecover. Put a little bit of oil on the crankshaft end where the bearing slips over and slide the Sidecover onto the crankshaft and down over the dowels in the block to line it all up.
With the side cover slid into place, you are ready to tighten the Sidecover bolts. Again, I use the blue Loctite here and tighten them also to 115in/lbs just like the rod bolts.
Flip the block around to the flywheel side and you are ready to install the ignition. If you do not have a degree wheel or dial indicator, use the following recommendations. For the new PVL ignition a stock key works just fine. Some will argue that higher ignition timing works better, and it may in certain situations, but if you don’t have a way to measure what you have, the stock key will work just fine. For the older billet flywheel and standard Briggs ignition coil, a #8 key works well. The above recommendations are for unrestricted Animal engines. Restricted engines will work with these setting but will most likely need fine tuning to get the most HP. We will discuss this later on.
If you have not already lapped your flywheel to the crankshaft, this is your last chance to do it before you put the flywheel on it. And YES, it needs it. I like to use 400 grit lapping compound. Put a couple dabs on the crankshaft taper and push the flywheel onto the crankshaft. Twist it back and forth several times to ensure you get it lapped well. Take the flywheel off and clean the taper on the crank and the taper inside the flywheel VERY well with brake cleaner and a paper towel. Make sure you get it all out of the slots also.
Now you are ready to install the flywheel. Again, if you don’t have a dial indicator with the right bracket or a degree wheel, put in the proper key and you are ready to torque it down. Briggs makes a strap wrench to hold the flywheel. It is the proper tool for the job. I use a ½” drive torque wrench set at 95foot/lbs to torque the flywheel nut with. Notice I said FOOT/LBS for the flywheel and INCH/LBS for the side cover and rod. They are two different torque wrenches. Unlike the rod bolts, I go straight to the 95ft/lbs in one shot on the flywheel.
Next, the coil air gap. That is the gap between the outside edge of the flywheel and the ignition coil legs. I use .035” for the old style and new style ignition coils for the air gap. You now have your flywheel and ignition coil installed.
Your short block assembly is complete, you can now push it to the side and let’s work on the head.
|Cylinder Head Pt.1
First off, if you have a head with the casting number "54" you better check it or have someone check it with the no-go that is supposed to stop before it hits the valve guide. So far, every #54 head I've seen this no-go will drop ALL THE WAY through the port and hit the guide, they are not even close. The #54 head is the ony head I have seen that has this problem.
-Next problem. If you have been running the Fire Ring head gasket from Briggs in your Animal and have been running the head for a while, you better check the exhaust with the proper no-go gauge. There is a WKA update coming that from what I hear will change the width of the no-go that will help resolve the tech issue, but not the root cause of the problem. Problem is, with the fire ring head gasket, the metal ring portion of the gasket does not compress but the rest of the gasket does. What happens is, the head then "warps" around the metal ring since the head bolts are located toward the outer portion of the head. If warping of the head is not bad enough, what this also does is warp the exhaust port and the no-go will drop right in the port in one certain spot.
Once the head is off the engine, remove the carburetor and intake from the engine and set to the side. Remove the rocker balls and rocker arms. The rocker balls can be removed with a 5/8" ratchet or socket. Once you have the rockers off, we need to remove the valve springs, keepers, and locks. The quick and easy way to remove the keepers/locks is to take a 5/8" socket and lay it on the table with the 5/8" side of the socket facing up. Turn the head over and set the retainer right down onto the top of the socket. Now put your thumb on the top of the valve and push the whole head down onto the socket. It should drop the locks right out of the keepers and INTO the socket so they don't hit the floor and bounce who knows where. Do the same for both valves. If the locks are stubborn or stuck, take a small hammer and LIGHTLY tap around the edge of the keeper and then turn it over and try it again. If you have the stock Briggs valve springs in the engine, toss them in the trash and set the valves, keepers, and locks to the side. Next remove the keeper plate and gasket. You now have the bare head ready for inspection and machine work.
|Cylinder Head Pt.2
|If you do not have the WKA no-go gauges, I would recommend at least taking the head to someone and get it checked. Better safe then sorry.
There are some of the early heads you also have to pay close attention to. Some were illegal and not able to be fixed right from the factory on the depth checks.
Other than the no-go checks and depth checks on the head, there's really not much to inspect.
Do your inspections and right your depth checks down so you know how much to take off. Now, here is the important part you have to pay CLOSE attention to. There are several WKA depth and thickness heads on the head. And once you start machining one surface on the head, you better be checking ALL your depth AND head thickness measurements. It is VERY possible to not even be close on the head shallow portion depth check but get very close or go below the mininum head thickness check. It is VERY important you measure these depths and thicknesses properly.... measure twice, cut once to ensure you stay legal when doing machine work. Your best bet is to let an experienced machine shop familiar with the rules do this work for you if you are not familiar with it yourself. Most shops will deck a head pretty cheap (a lot less than buying a new head).
If you have it or access to it, I hone the valve guides with a 1/4" 320 grit Flex-Hone. You don't need to take out any material, just put a cross hatch in for oil retention.
Once your head is decked it's time to look at the valve seats. I cut the valve seats with Sioux valve seat grinding stones. Some do it with Neway cutters and when the Animal first came out, I tried it that way also. Quite honestly, you just can't get a good cut on the Animal valve seats with the Neway cutters (as compared to the Sioux stones). And valve seal plays a MAJOR part in how the Animal makes HP and KEEPS making HP for a long time. I like a VERY wide valve seat for two reasons. Reason #1 is my flowbench says I can pick up 1.0 to 1.5cfm with a WIDE intake valve seat. Reason #2 is my personal belief is we need wide valve seats in the Animal to help dissapate heat from the valves to the head to keep the valves cool and also prevent the valves from beating "rings" into the valve faces (have seen it done). BUT, if you do not have access to or the ability to cut the seats, Briggs does a pretty good job with the valve job from the factory. You can simply lap the valves to the factory seats and go racing. I would recommend pulling the head every 3 races and relapping the valves if you do use the factory grind though.
That brings us to lapping the valves. I like to use a 600 grit lapping compound and hand lapping stick. If the seats were cut good it shouldn't take but just a short time to lap the valves in. If you are using the factory seats and valves without grinding, 400 grit works good. If you have to use anything courser than 400 grit (like 220 or 150) you have a MAJOR valve seal problem and you should get your valves and seats ground by a shop with the proper tools. Leaking valves is a MAJOR source of lost HP in the Animal.
Valve length, read the rules you are running under. WKA allows the valve to be cut to 3.250" total length. You want to check your valve length close. WKA is changing this rule for 2009 so starting Janurary, 2009 your valves will have to be stock length (+/- .010"). Cutting the valve to the minimum length helps get your running lift right to the maximum so you have to keep an eye on that so you don't get tossed in tech. I recommend cutting the intake and exhaust to 3.260" and then checking everything from there. That should keep you from going over the maximum running lift and it also leaves a few thousandths in case your valves wear between rebuilds (typically .002"-.003" will wear from them, especially the exhaust valve).
Before we go any further, tap the two bosses on the back of the head with a 1/4"-20 tap. We will use these later for header bracing.
Once your head is decked, valves are lapped, and valves cut to length we are ready for assembly.
Prior to assembly, again, just like the block, make sure EVERYTHING is spotless and clean. Make sure ALL the valve lapping compound is removed from the head and the valves.
Put the valve plate gasket on and the valve spring plate. Bolt the top plate bolts to 115in/lbs. You are now ready to put the valves in.
Coat the valve stem with a coat of oil. Slip the intake valve into the hole. I like the Comp Cams springs for Gold Plate and Unrestricted racing. Put the spring over the valve and slide the keeper onto the top of the spring. If you have decent hand strength you can push the keeper down enough to slide the locks in. But it's probably a better idea to use a valve spring compressor for the job. Just faster for me to do it that way, but I have done a ton of them that way. Next put the exhaust in the same way.
You now have a complete head sitting there ready to go.
|For the "average" racer that wants to build his own carb for the stock unrestricted class but doesn't have a clue about it. Buy the alky jet kit from Briggs. Put the .40mm pilot jet in and the 1.35mm main jet it. Install the alky fuel nozzle that is in the kit. Set the float height at .860". Use the ORIGINAL gas needle (BGB needle) and set the clip in the #5 (bottom slot closest to tapered end) position. Set your idle mixture screw (small screw closest to air filter) at 3/4 turns out.
That setup works without any other drilling or any other modifications to the carb and is a darn good setup that has won a lot of races for a lot of racers and shops.
Things to watch on the PZ carb is the floats and the inlet needle. If you race the Animal a lot, go ahead and buy a few extra inlet needles, they are cheap. Go ahead and keep an extra float kit also.
The inlet needle is important. All the fuel that gets to the engine must pass through here. If the carb/needle does not get flushed properly it can swell up and restrict fuel flow. The spring in the needle also gets week. I replace them at every rebuild whether they need it or not. It's a cheap part that can ruin your day so it's better to just change them.
After watching the floats for a while in several motors and comparing notes with other builders, I can not figure out why, but the floats actually gain weight over time. Don't believe me, get a gram scale and weigh your float. Go run it for a month or so and then pull it back out and weigh it again. I can't explain it, but I have to assume it affects the tuning of the carburetor so they also get changed at every rebuild.
There is a lot of debate about what is best to "flush" your carburetor with after the race day is done. Gasoline, Gasoline with a 2cycle oil mix, Gasoline with Marvel Mystery Oil mix, and WD-40 are probably the most I hear about. I have used them all with good success. The only problem I have seen is if you fill the carb with Gasoline or any of the Gasoline mixes make sure you leave the carb bowl FULL of fuel until the next race. If you drain the carb bowl and let it sit around for a few weeks the left over fuel droplets evaporate and leave a varnish looking coating on the carb bowl and carb parts.
If you plan on storing the engine for over a month I recommend pulling the bowl off the carb and spraying WD-40 through ALL the holes in the carb to completely flush out any methanol or gasoline or any other liquid you have in your carb. Make sure ALL the gasoline and methanol is gone. Clean out your fuel lines and fuel pump also. Anywhere gasoline or methanol can accumulate during engine storage is a BAD thing. Make sure they are clean.
Now, I have been told by a few people they are using Gasoline with Stabil additive and that keeps the gasoline from going stale and leaving the varnish finish. I have not personally tried it for myself so I don't really know but sounds like a good idea.
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