Theres alot of material to cover here but iam going to try and past around what ive Learned over the years to help people build there own motors. This sport has gotton $$$$$ enough just to get there now is an arm and leg to most working people that have a love for this sport,so if anyone whats to join in and offer there Knowledge please offer up. I have the school of hard knocks to back me up and lots of time and plenty of 11,500 rpm motors to prove it and i spin bbc to 10,500 at times. OK iam crazy i know but thats me.

So heres goes nothing. The valve train in my mind is the most important part of the motor,it allows the pistons or the bottom end to get the job done,when valve train is not working motor as a whole doesnt go anywere. The most important aspect is keeping the valves from getting bent by the pistons as each cycle takes place within each combustion chamber.
There are basicly two ways to check for clearances most of you know this A= the clay method and B= light spring method, oh i forgot C= it should be ok opps bent valves Hard Knocks.
Both mothods are very important and should be used together as they both give you information the other cant provide.
With both methods valve lash should be at running clearances,or Hyd. lifters at proper turns also. Remember when you were a kid and you finally got the idea on how to tie your shoes and knot you first tie you were feeling with your fingers and learning your senses, well some of that comes into play here and you have to get that feeling back again or maybe you havent lost it, a very important aspect for building motors not a job for all thumbs so pratice makes perfect just like your shoe laces.
Everyone has a basic though on how much valve to piston clearance you need to safley run your motor but that question all hinges on what you are doing with your motor and what kind of valve spring pressures your using with your camshaft. Iam not getting into camshafts here but cams do determin what kind of spring pressures you need to run to keep lifters tracking the cam lobes to a particial RPM level. AHHHH rpm level another key element here. End results spring pressure all hinges on RPM usage Valve train components weights. LIfters,valve,retainers,keepers,push rods,spring itself,and now adays boost pressure. Valve spring seat and open pressure (at lift) and camshaft lobe profile determens how well a lifter will track the lobe profile of a cam hence keeping the valve in time with the cam to a given RPM level. When you run a valve train outside these values i dont care what kind of clearances you have your going to bend valves and push rods and break lifters, or better yet punch a hole in a piston break off the valve ruin a head crack the block and your done. WOOWWW so much damage just because of a valve oh hell ya. So the real key is whats safe ansewer as much as you can get from your combiation.

So why is it, As Much As You Can Get with valve clearance? easy to protect yourself from a mishap with your valve train. A broken spring, overreving, a few CC from the combustion chamber lowering your compression abit is not worth the few extra HP lost to a blown motor. On the other hand a well preped motor looking for every ounce of HP is another story. The best tool for running valves close to smacking the piston is valve springs. Afew HP loss to rotation friction due to heavier valve springs is good insurance to keeping your motor together and not hitting pistons with a valve. Not to say that theres nice easy cams with gentle lobe profiles making it easier on spring requirments,and allowing you to pick up some rpms.
With good springs over the rpm margins of your cam type and rpm limit you can safley run valve to piston clearances as close as .010 leaving no room for mishaps. Anything beyond that is added insurance your not going to wack a valve. I am running now valve clearances of .060 exh and .070 int. just my combo i cut my pistons to get the max and that is what i came out with. The exhaust is the one to watch closley all the time as the piston is chasing the exhaust valve as its closing if anything hicupps smack, and you got it it gets within .060 of hitting it everytime. The intake valve however is chasing the piston as the piston proceeds down the bore to BDC. To keep my valve train in time with the cam i run 385# on the seat and 960# at .840 of lift. Its alittle much but at 10500 no hiccups happen. I dont always aggree with cam makers on their spring choices and dont want to line there pockets on always replacing springs either. Valve springs is another deep subject that maybe will cover another time.
The run of the mill adverage valve to piston clearance most used is Min. of .120 exh. and .090 on the intake. But that doesnt garrantee a bent valve. In most cases it will if everything stays in harmony together,and the min. spring requirment used by the cam manufacture. I say Min. because spring pressure can be bumped up from there to pick up some more rpm range and saftey insurance.

I think seat pressure is very important when talking here.

I am also a fan of using what some may call a mild cam but that cam is not as hard on the drive train and makes better power throughout the rpm range of the engine. And in many cases makes more usable power than an aggressive grind.
Clearances are vital when talking about valve to piston, if you do nothing, then as you said be ready for the headaches to follow.

I have ran racing engines solid lifter type cams 185# on the seat and 550# open at lift to 8500 plus rpms. Not a dam thing wrong with flat tappet cams with good springs. Hyd. lifters at current are alot better then i used to run so i cannot state how far you can push them with spring pressure but i would imagin anyone using a hyd. cam is not getting serious with racing,mild week end worrier hey and thats great,we need you to in this sport,no noses turned up to you guys,were all racers. You can play with spring pressure requirments by using some titanium componets to reduce seat and open pressures but loosing alot of weight in the valve train causes spring requirments to change. That can cause another problem with springs we can get into that later.

The clay method is straight forward and each and every piston should be done although people have gottan away with NOT doing all pistons when pistons and rods and crank and heads especially valve seat height in used heads are pretty equal in height and distance. Caution when your working with a used head and you just happened to choose the chamber that has the valves sunken into the seats by .040 and then the chamber thats not sunken is now .040 closer to piston, and or one head is not the same thickness then the other head because it was milled .015. So unless you really know your heads check all pistons. I cant state enough what this will mean for you but make a book of what your doing and all your measurements so the next time you change a cam or get a valve job youll know what you have.
Model clay with alittle oil on the valve side will keep the valve from picking up the clay off the piston so you get it right the first time otherwise a dry valve will pull the clay off the piston and you will have to start all over again. Clay strips should cover the entire valve pockets of the intake and exhaust of the piston, thickness of clay of about 3/16" to 1/4" thickness should be used. Motor should be assy. with headgasket your going to run or do the math and use a junk head gasket. Head should be torqued down but not nessessary if you subtract .010 or .020 thou from readings but using steel shim gaskets and then do the math in ref. to new ones compressed you can save some time and money. Valve train should be lashed at running clearances and motor hand turned over always waiting for interferance, the feel i mention earlier. You dont charge in there like a bull moose and go ape turning crank you do it easy so you can feel for any interferance of valves jamming up on piston. Now there will be a little spongee feeling as valve does get close to clay and squishes it and going thur the cycle once is enough. Iam sure there is better explainations on the internet and videos on how to do this if i miss something pass the beer then. After removing the head bring piston to top and with a oily razer blade slice the clay in half on each valve pocket, slice from exh side of head to push rod side of head remove half of the clay and you have a nice image of your clearance between valve and piston. If you didnot get a image then be very happy you have alot of clearance in your assy. But to find out youll need to double the thickness of clay and try again. Besides looking for how much valve clearance you have you also need to look at how your valve is attacking the piston face,as you know a piston changes direction with each pass thur the bore at the top and at the bottom,this causes the valve face to attack the piston on a slight angle never flat faced. The rings and piston to wall clearances will change the amount valve will attack the piston as it all wears something alot of people dont know about or think about, down the line a valve can get closer to the piston as these parts wear. Piston valve pockets dont always see the valve face flat but there close so in efforts to cut your pistons for more clearances you need to look at what part of the valve is nearer the piston as well as the oppisite end and measure this difference. While cutting piston for valve clearances you can position piston in the holder while milling pocket on a angle to pick up some more clearance without plunging to deep. IE: there can be .050 of clearence on the back side of valve while the front side is touching piston. So you can gain some compression ratio by not just plunging a cutter face first into piston and just set yourself up to angle mill the front side .050 and be flat without cutting to much piston pocket out. This is a move to pick up some compression and keep a piston stronger on the deck and and under the pocket. looking at the clap imprint you will also see were the valve gets into the eybrow as sometimes with bigger valves you will hit the radis of the eybrow before hitting the piston face of the valve pocket, meaning you now have to enlage the eyebrow to =gain clearance. I like to have atleast .025 of radial clearance between eyebrow and valve O. D. looking at the clay you can see were this interference is. Hopefully you have a dial caliper handy other wise a cheap tool to buy and nice to have if taken care of without dropping you can get within thousands of a accurate measurement, never to take the place of a micrometer,never. Using the back end of caliper you can then measure remaining clay just touching clay its feel here again dont smash the clay,easy does it. Draw a pic. of valve pocket and note your measuements on paper. And if you very careful pealing off the clay you can even measure that.
The light spring method offers more information and more accurate if done right. This method involves using a replacement spring strong enough to keep the retainer and keeper in its place and valve pulled up good and snug but weak enough to be able to push down with your fingers.I guess i could come up with a value later but the od of the spring has to fit your retainer within the steps of the retainer. Mc Master Carr sells a box of assorted compression springs that you will value the rest of your life for a small fee and do well with alot of retainer types,otherwise a good hardware store offers compression springs like Ace Hardware. Take a retainer with ya and fit the spring and cut to length with a pair of side cutters.

Good info here. Iam very familiar with this topic since we build our own motors. But I can't share everything we do on the forum. We run A/S 396/375 HP NHRA stock eliminator and we have to be competetive. But I like reading post like this.
For those that don't know stock motors are in a class of there own. Very tough to build a competetive motor and compete with the big guys.
Again great post and topic

I like the topic too, and I run big Mutha rollers mostly, BUT, I had a 83 Monte Carlo LS with a bone stock 60,000 mile Vortec , upgraded to studs/guideplates and roller rockers, and a bigger hydraulic roller. This car had full interior, AC. etc. and ran 10:88 thru the muffs on Dot tires with a 250 shot. I thought it was pretty serious at the time...

mytmouz wrote:I like the topic too, and I run big Mutha rollers mostly, BUT, I had a 83 Monte Carlo LS with a bone stock 60,000 mile Vortec , upgraded to studs/guideplates and roller rockers, and a bigger hydraulic roller. This car had full interior, AC. etc. and ran 10:88 thru the muffs on Dot tires with a 250 shot. I thought it was pretty serious at the time...

That is serious for that car.

You know how to get em down the track

Thanks Guys for your positive input, i hope i dont bore ya,s

And if you very careful pealing off the clay you can even measure that.

THE LIGHT SPRING METHOD TOOLS NEEDED One dial indicator with extra long stem with a 2" travel range assembly and magnetic stand. Cheap China one works just fine. One piece of flat steel about 1/4" thick by 3 X 4 inches or so, drill some holes along the outer edges to fit your valve cover bolt holes, you may have to use a longer piece of steel so that you can position the magnet stand close to the two valves that your working on. Some times you can use the intake manifold surface to place the magnet but indicator has to reach valve retainer. Long breaker bar to smoothly turn the engine over.
I hope your on a engine stand makes life alot easier LOL.

The light spring method offers more information and more accurate if done right. This method involves using a replacement spring strong enough to keep the retainer and keeper in its place and valve pulled up good and snug but weak enough to be able to push down with your fingers.I guess i could come up with a value later but the od of the spring has to fit your retainer within the steps of the retainer. Mc Master Carr sells a box of assorted compression springs that you will value the rest of your life for a small fee and do well with alot of retainer types,otherwise a good hardware store offers compression springs like Ace Hardware. Take a retainer with ya and fit the spring and cut to length with a pair of side cutters. You assemble the valve train and lash to proper running clearance careful heres the feel again using a flat feelers gauge lash the clearance and rocker arm without pushing down the valve stem , Its touch and go here because you dont want to slide the feelers gauge and and push the valve open also. to get real accurate here doing this use two finders and pull up on the retainer while with your other hand using the feelers gauge by pulling up on the retainer your making sure valve is into the seat better. When your done with both valves on one combustion your ready to install the dial indicator and stand. The dial indicator must be postioned so that the stem or shaft of the indicator is in near perfect alinement with angle of valve stem that your working on,the longer stem dial indicator helps keep the body of indicator away from valve retainer from interference, a 1" travel indicator may work in your application but its a pain in the ass. Set the dail indicator up with some preload on the indicator meaning you should install so that it takes up some travel of the indicator and then
placing indicator stem on outer tip of retainer useally a flat of the retainer is there,forward of the rocker tip and forward of the valve stem outer diameter of retainer. Locking down all adjustments of stand now set dial at zero by turning face of indicator. With everything ready to go turn over engine and make sure dial indicator follows the retainer movement. Make adjustments in stand and indicator as needed to get this right. The dial indicator and valve stem should be at the same angles to get a nice vertical complete stroke.

I want to back up a bit here and talk about prepping the piston before installing the heads, I like to use die makers ink and spread it around the valve pockets and up the eyebrows of the valve pockets this way you can see were the valve is making contact with the pistons pockets and become more accurate in seeing were the valve OD is really hitting either in the radius of valve pocket or flat of pistons valve pocket. With the quest for bigger valves you do run into the radius of the pocket before you really hit the piston deck surface and trimming is easier and you can gain maybe enough clearance without plunging into pocket face. So the ink die can really tell you alot on whats happening in there.

With the valve train all set up and watching thur the plug hole as to were piston is comming up the bore somewere in the last 1/2" of TDC piston travel is were it all happens as you get close to the top on the exhaust stroke and the exhaust valve is starting to close Stop and push down on the valve stem and feel whether the valve hits the piston or not if not youll be hitting retainer into valve guide seal or guide top and now you turn engine over afew degrees at a time stop push and when you start feeling valve hitting piston as your pushing down you are starting to get close so time to start watching that dial ind. readings. You will come to a point were when you turn engine (in the direction of normal Rotation) the indicator readings will start getting shorter less then .300 of travel small changes in turning the motor afew degrees and taking readings of the shortest travel readings on indicator rezeroing dial indicator on every few degrees of rotation. Keep repeating these steps untill you find the shortest stroke of the dial indicator and write that figure down and repeat these steps afew times untill you are sure that you have the shortest distance noted on D/I readings. During your ventures dont rotate the engine backwards if you happen to pass up a close reading always go around in normal running direction. If you do that what happens is piston will change thrust directions and your reading will not be correct. When you do feel satifide that you have the closest reading make a last attemp to find it and when your there stop and with two fingers under retainer pull up on retainer to make sure you have the retainer seated up into the keeper and note if reading changes on dial I/D pull squarley and even so that you dont cock the retainer. The smallest readings is your exhaust valve to piston reading. A longer bar on crankshaft always helps in doing short small smooth changes in rotation. Dont forget just a few degrees at a time will make big changes in the dial I/D reading when you are closest to the piston. Turn afew degrees stop rezero I/D push down and read. Do the same thing with the Intake valve train also and note closest readings. Doing this to all the valves on the heads will make you realize what a big effort this part of building a engine is all about,and very much nessesary.

The next biggest step not done alot by people is checking the exhaust valve and intake valve during the overlap period. I have found many engines banging valve heads together during overlap causing extreme valve guide wear and spring surge problems in the valve train. This is the period were the exhaust valve is closing and the intake is opening around tdc . Bigger valves and lots of cam duration get you into this red zone faster. Even T/F engines and Alochol motors miss this so don't fret its easy to do and see. And dont forget if valves dont hit now they may later because of some valve guide and stem wear if there isnt enough of clearance to start with. The valves will wiggle around and bang one another at the heads as valve guide wear gets worse. So when your taking your heads apart inspect the valve head circumference closley for Nicks and impact marks.
How to really check this is time comsuming but needed because you have to install heads valve train cam chain the whole deal and crank but without any pistons and rods. Lash all valves at running clearances and turn engine upside down on engine stand and now rotate cvrankshaft and watch valve operation during overlap period. So when the exh and intake are open at the same time passing each other, use a feelers gauge to get the closest readings during overlap. I like .040 the best but will take .025 as min. sometimes you can gain clearance by trimming valve od,s without getting into the valve face seat and still reduce outter diameter a bit. Different heads with diff. valve stem angles other then OEM heads get you diff. results. But left unchecked what a price to pay in the end for not. I have wrote a passed post on how much can be removed from the piston for gaining more clearence so read that here also.

So after you check all this how the hell do you get some more valve to piston clearance. Afew chocies here. Send them out to a GOOD machine shop and talk the shop talents or cut them yourself. How!!!! easy Go on E-Bay and buy afewused valve bigger then your valve OD head size and longer by inches with same stem sizes and make your own cutters right in your own garage. Youll need a bench grinder and some skills but you can get this done Any valve can be made into a cutter its all about relief in the cutting edge. You install the valve cutter you now made into your heads in place of the valve and you cut the piston for clearance right in the bore with the head bolted in place with a hand drill and some commen sence. Deburr and clean and magic. Or you can do what i did go on ebay and buy counter bore cutters used new afew dollars for several sizes, were the pilot goes in the counter bore you replace with a end mill so that your now cutting the center make a fixture to hold piston at the right angle in a BridgePort Mill and cut away first you need to get the valve stem center line marked on piston before you take them out so you know were to line up your cutter you grind a point on the end of one of them used valves you bought and stick it into the empty valve guide with piston just before the top and tap tap not bang bang, or like alot of people the easy way but costs ya alot of compression just wack off the entire valve pocket pad. I like the so called tulip cutting approach. Food for thought. I think iam done here but if i remember anything else ill post and i will post some Pixs of valves turned into cutters.

I am totally a new guy on this board and I got to say this particular post is probably the most informative and educational I have ever read on this subject Kudos to you Star393.... Dang if I could remember just what you have forgot I would be a friggin genius! Seriously Thank you for this great post

Sleeve396 wrote:I am totally a new guy on this board and I got to say this particular post is probably the most informative and educational I have ever read on this subject Kudos to you Star393.... Dang if I could remember just what you have forgot I would be a friggin genius! Seriously Thank you for this great post

Iam Happy to have helped someone YOUR WELCOME Douglas