Jared, you may consider stock LT1 (f-body) gaskets to *try*. The only reason I say that is because there have been a handful of fast guys that have ran them in the past with no problems. I think they are a good gasket...just thick for most people .049" and I believe the bore is slightly smaller than 4.125" but I may be wrong.

It may be worth a try....stock gaskets and ARP studs.
Jason

 

Yeah I was thinking that too Jay.... why go thru the BS when GM has one for ya.

Bret

 

Have run a measured .030 on the street with a tight fitting piston..0035-.0040
I was told some 30 year ago by a well respected engine builder that "they run their best when the piston just kisses the head" and I have run a few engines like that to see and he is right. The amount of clearance is determined by how brave ya are or how much experience ya have with such things.RPM's plays a big part too as well as piston fit. Your measuring tools had better be calibrated RIGHT too.

 

I don't see where the gains in power are going to come from .005" tighter quench... You want it tight but too tight is REALLY bad. Personally "kissing the head with the piston" is a sure fire way to lead parts to a early failure... I'd hate to see what the pins look like when it's all said and done.

Bret

 

That depends on how ya kiss.
It' a bitch when the car comes in after qualifying and it sounds like ya got an exhaust leak,but you know it's not a leak. Time to break out the wrenches and go a tad thicker.
Ya don't touch the head ya just come very very close like blowing a kiss at it.

 

lol thanks again guys. I think I am going to keep the chastity belt on my pistons. They are too young to be going out and experiementing with those "heads".

Ive decided to tear apart the motor first and then do my parts ordering after carefully getting some good measurements. Ill post back up after all is said and done.

 

Just keep um in the hole and you'll be allright.

 

Pins, sure..... main and con-rod bearings too..... can you imagine what the shocking does to those babies? None of it is good.

I've seen back to back dyno tests with tighter and tighter quench (Circle Track years ago) and there comes a point of diminishing returns. Too many variables for an accurate approximation. Street car... "NO".... race car.... "NO" is good there too.

-Mindgame

 

My take here as it applies to the word kiss. My interpretation of kiss is consistant to that of Larry's. Technically, that being ZERO clearance. Is it practical? Regardless, striving for any given figure, first you need an accurate method of checking. Do not even consider clay when it comes to determining clearance. Get comfortable using a good depth mike... accurately. Block MUST be 'square'. Assure yourself pistons are (and remain) square in hole before bothering to measure. Time is money, and I'm not talking taking a couple of minutes to check/measure quench. If the checking/measuring is not accurate, it's value will be questioned..

 

Measuring "accurately" is not even half the battle. We're not just talking about build up clearance here... we're talking about "running clearances". If you want to take that a step further you would need to account for thermal expansion and any con-rod stretching that goes on at high rpm... off-throttle especially. Everything is a spring... some stiffer than others.

And again, what is the gain? As I recall, "near zero" vs " ~.020 was worth something on the order of .005% for a 700hp race engine.

-Mindgame

 

Yeah if you want to replace piston pins, go for it. 4340 ones are cheap, Honda sized DLC coated ones are not. Hell Tool Steel or 9310 pins aren't cheap in my book!

Bret

 

I didn't say to HIT anything. As long as ya don't touch what's the dif.
Like I said,with the a forged bottom end @7000 there is no need to be afraid of .030 and that includes all the "stack" clearances ya can add. Like I also said ya better be able to measure correctly. Been there done that.
Already have a couple running with .030 in them.Would they have run as good with .035,maybe,but not with .045-.060.
Ya don't win races following somebody.
Am I saying .030 is for the masses-- NO. I am saying it can be done with experience in doing it. If ya don't want to do it, then don't.But if ya come out with .035,then there is no sense in spending heavy bucks for a gasket to go to .040 or more.

What do ya think the intentions of someone is that profiles a set of dome piston's. This makes the whole top of the piston quench and ya better have a tight piston fit and more than.030 in them

Try to find a rod manufacturer to tell ya how much rod stretch their rod has at any given RPM
and temp. Try to get crank flex and block wiggle spec's.Good luck..


Edit: Don't try this with a stock bottom end-- It won't work. I use a particular set up that I know works.

 

No I gotta Larry..... IMHO I don't care if WJ told me that the piston should kiss the head, I'm not going to do it.

Bret