Installing my heads on my 383 tonight and would like to know the procedure on doing this. I have stock L98 deck height. It wasnt 0'ed at the shop. Pistons are Speed Pro flattop with 2 reliefs. Gasket is .039 (Felpro 1010) Heads are 64cc TF's and cam is the LPE 219 219 560 560. I picked up a machinest ruler and some clay. I was told by the engine builder to have at least .100 on the intake and .125 on the exhaust. My ruler shows 16th's so that would be .1 would be 1/16 and .2 would be 1/8th? But how would one measure .125?

 

.100" is not 1/16th"
.125" is = 1/16th"
.200" = 1/5th"
.25" = 1/4"

 

Ummm.... I don't think so.

1/16" = .0625"
1/8" = .125"
1/4" = .250"

So, if your ruler shows 1/16", that's about 60 thousandths. That's about the bare minimum for a setup that's known to have perfect valve springs. Your machinist's advice is a bit conservative, but much safer, in the real world, especially where there's a chance of over-revving and valve float as a result.

Sounds to me like you have some piston machine work in your immediate future.

 

on a very related note.... how much would you consider the max to be on cutting more valve relief into a piston?

and how would you measure it?

 

nono i didnt measure it yet. I just said my ruler measures 16th's. I'm going to check tongiht. so 1/4 would be ok? should i measure also the valve to the back of the cut on the piston?

 

.125" = 1/16th"

What was I thinking???/

.125" = 1/8th" I stand corrected......

 

You must have got a brain cramp or something.

Oh well, happens to us all once in a while.

As far as how to measure it, check with the piston mfr and see what they recommend as the min thickness. You'd measure it with a mic with a large C frame and relatively sharp points, or sonically. In the real world, I doubt you'd go from safe to the danger zone on a new piston, taking off .060" or so.

 

its that thumb rule number im looking for...

if im cutting into the pistons for that, it usually means i have the shortblock together...... and really, im not taking it apart to measure it...

(i dont have a sonic checker either.... lol)

 

Well, this is one of those things where you either take it apart and fix it now, or you take it apart later and replace a whole bunch of wasted parts and fix it like you should have done in the first place after you sweep up what you can off of the track.

Hmmmm........ tough choice here.... I'm struggling with this.... let me step outside and consult my financial adviser in private on this one......

With the TF heads above all others, it makes great sense to mock a cyl up before you build it for real, just so stuff like this won't happen. They locate the valves differently from the stock position, which is part of how they get their flow.

 

i uhh... well... know thoes guys that take a POS junkyard shortblock, dont do much else besides throw a oil pump on it and then drive it till it blows and start all over?

yea... ive been doing that with me and a few friends for a lil while now... kinda embaressing cause it isnt the "right" way to do things, but its fun.

thats just toys though..


my daily driver camaro will be getting everything together right.

 

Yeah; but junkyard short blocks don't often have Trick Flow heads on them. Those are picky about that, far more so than stock heads, or most other aftermarket ones for that matter.

 

results are in. I didnt have clay so used a square of Bubble yum intake was .375 and exhaust was .187 without using the head gasket. Gasket compressed is .039 so would that be .414 and .226

 

I can hear the sigh of relief...

 

If you're checking valve to piston clearance with a hydraulic lifter you have to adjust the valvetrain differently to get accurate measurement.
because the internal plunger will "leakdown" and compress when the valve is opened as the crank is rotated by hand.

You have to adjust the valvetrain to "0 lash" with the lifter plunger fully compressed inside the lifter body.
Or use a solid lifter for checking.
The potential error in your perceived clearance is to distance the plunger body would travel when compressed.
Quite a bit.

Be sure to readjust the valvetrain back with the proper
adjustment and preload before starting the motor.