Guys, I'm building a 383 LT1 for my daily driver 1995 Caprice Wagon. I'm using some slightly domed Speed Pro hypereutectic pistons (the teflon coated ones) and Sealed Power moly rings.
My machinist recommended a .026" top ring end gap :eek:
That seems like a helluva big gap to me. His reasoning was, with the stroker pistons (for 5.7 rod, not 6") the ring lands are so close to the top of the piston that the top ring runs hotter and requires a larger end gap.
I know somewhere in the .018 range is recommended for a stock N/A motor, and I asked a friend of mine who's been at it for a LONG time. He suggested about .020 on the top ring.
What do you guys think?

383 late model LT1
Comp 290HR cam
12:1 static comp. 9.000 dynamic
Speed Pro .100 dome, coated, hyper. pistons
Sealed Power moly rings

Thanks!

What does the manufacturer recomend. I know the KB pistions need a wide gap, but not sure about the speed pro`s.

I don't know.... Federal Mogul is oh-so-helpful. I have not been able to find a way to pry technical help out of them. :rolleyes:

Dave,
Those pistons do not need any extra gap.
.018 is fine & .020 won't hurt a thing if you are nervous about it.
We have ran 10.0 engines with that style piston at .016.
The KB's are the only hyper I know of that needs the extra end gap & trust me, they do need it :eek:

Thanks Mike!

Dave,
.020" to .022" is good gap for the F-M hypers. If you are using Speed Pro rings (ductile top ring), you could go to .018" but there is really no benefit in trying to get it that close on a street engine.

I am curious on how you are going to manage a 12:1 motor as a daily driver?? It's not like a 95 Caprice wagon is a light car either.

Thanks Bill, I think I'm going to shoot for about .020 now that I have several people saying the same thing.

Jim, I'm not sure how I'm going to manage it either....I should have thought the motor out a bit better before I went and bought parts. My reasoning is this. Unfortunately, my quench is going to be abysmal at around .075 if I use the thick F-Body head gaskets and iron heads. In reality, the static compression is closer to 11.5 and I'm running a rumpity rump cam with an intake closing at 73* ABDC which puts my DCR at ~8.6:1. From everything I've read, 9:1 is right on the envelope for a pump gas street motor. I'm gambling on the benefits of the reverse-cooling of the LT1. The stock Caprice/Impala motors are running 10:1 on 87 octane with a much smaller cam. I'm going to have to be careful with the spark tables and do LOTS of data logging. Should be fun! :D

95 Caprice Wagon: 4750lbs of GM goodness smile.gif

Thanks for the help guys!
-Dave

Originally posted by Daves70:

95 Caprice Wagon: 4750lbs of GM goodness smile.gif

4750... :eek:
I am at 11.2:1 with a horrible .100+ quench, (don't ask). I run pump gas no problem, but I have 4.10's and a stick and don't weigh in at 4750#.
Best of luck to you!