Is modeling clay on top the piston, then a roll thru of the crank & valve train o.k.?
And doing it on one cylinder, assuming the others will follow suit?

My set-up is a 434 SBC stroker with AFR 220 heads, Comp Cams .630 lift solid roller. The pistons are domed a bit, but the AFR heads have the huge 76cc chambers and 3/4 in. deck.

I didnt detect anything close to contact using the clay...................

 

That is how I would do it with valves lashed at zero. I would do at least four cylinders if not all of them.

Back in 1991 I made the mistake of just checking one cylinder on each side I did not realize i had only checked "Left hand" pistons. Guess what? I bent valves on 2,3,6 and 7

How about learning from my mistake

 

Left hand piston?

My pistons appeared to be symmetrical.......................

What am I missing?

 

I'll let Ellis explain that one....

I prefer to use lightweight check springs and a travel indicator. When you check with clay the get a bit of compression at the lifter (hydraulic) and that doesn't provide the most accurate reading. JMO.

-Mindgame

 

LOL I KNOW there are at least fifty people who read this who know what I am talking about

I use gutted lifters when i am doing a hydrolic

For those who do not under stand SBC engines you will notice they are not symetrical. they have four pairs of mirror image ports.

IF you look at number one you wil notice that the valves go e-i-i-e-e-i-i-e. e=exhaust i=intake.

IF you use high compresion pistons there will be four left and four right. If you hold the pistons side by side you will see that the intake notches are swapped. when held upright the pistons with the exhaust valve to the left are called "Left hand" and the ones with the Exhaust on the right are called "Right hand"

LOL IF you are building a motor you better DAMN well know where they go

Later

 

I get your point on the correct piston in the bore for valve relief alignment.

That must have been the error on the one in 91 that bent the valves? And it must have been close enuf clearance to where it cleared rolling over by hand, but then made contact when the engine was warm & revved?

 

nope had all the pistons in the right holes. We were in a hurry and just did one piston on each side. in the end it turned out that ROSS had not cut the notches as deep in four pistons as they did the others Piston to valve was perfect on four and just tapped on four.

We actually did not find it till we did leak down after four passes

 

Even if they aren't high compression pistons they are often ground with a thrust and a non thrust side, offsetting the pin slightly in the bore to cut down on some noise. Of course, if they have a dome or single valve reliefs there is not much chance of them working installed the other way.

I’m a big fan of the light spring/dial indicator setup. Clay (covered with talc so you don’t have any sticking issues) could be deceptive and sometimes what you assume is the thinnest spot is not. I’ve run into a similar problem with valve reliefs which appeared to be cut at the wrong angle. Ended up ‘flycutting’ the pistons while in the block using a dremel to get it to a race the next day. Worked fine and it’s been like that for 65K miles now with a bunch of 120mph+ passes on it (it’s a 302 ford in a big four door, so that’s more impressive then it sounds)