i just built a motor for a buddy of mine and to make a long story short, lets just say that some of the machone work on the bottom end failed and now we gotta do a quick R&R for a rod, rings and bearings. anyway, he's running some Silvolite pistons that i'm not sure if they will be alright with steel shim head gaskets and i was curios if anyone knew about these pistons or have done this before...(Rusty) they are a flattop with 4 valve relief's.

here's the basic specs:

390 bored .030
941 camshaft
edelbrock streetmaster intake
holley 650 double pumper carb
mallory unilite w/ 6AL ignition box
headers w/ 2 1/2" dual exhaust through dynomax's
not sure of the head #'s but they have been decked (i think the chamber is around 71-73 cc's?) and they have 1.65 exhaust valves and been slightly ported..

any help on this would be great. thanks in advance!!!

 

They'll work with the steel shim head gaskets. I'm thinking it's probably got the 1131's, no? Anyway, no incompatibilites here. You do want to make sure the block and heads are straight, as this is more critical with steel shim head gaskets than with composition head gaskets. Coat the steel shim head gaskets with a sealant, I prefer Permatex Copper Spray-a-Gasket.

Sounds like a healthy motor.

The only incompatibility would be if the pistons aren't below deck by at least .010" at TDC. In other words, the deck clearance needs to be at least .010". This is necessary to make sure the pistons wont hit the heads at high rpm. You shouldn't need to worry about this with Silvolite pistons, or most others for that matter. But it would be a good idea to take a quick measurement anyway. It would help figuring up the compression ratio.

 

when i put it all together we were at .015" deck clearance so it looks like i got my evening planned.. LOL thanks a bunch!!! i was guessing to be about 10:1 or so with the steel shim....

yeah, the ole girl ran pretty hard even with the rod problem.... i drove it a while back after he got it broke in to help him get it tuned in a bit better, and he's got 35x12.50's on it with 4.10 gears but it got a bit hairy when i stabbed 3rd gear at 40 mph and broke the back end loose... LMAO
That's what I'm talking about!!!!!

 

.015"? Was the block decked at all? Usually those Silvolite pistons run around .030". They must have some quality control issues or something. Anyway, it's your gain, as it means .035" quench distance, which is the absolutely perfect number!

What rod problem was it? Spun bearing?

 

could they possibly be TRW-L2291 pistons? those have a deck clearance of 0.015 and are flat top with 4valve reliefs. if that is the case then it is going to be running about 8.7 dynamic cr with the 941 and the steel shim gasket.

 

the blocked was decked to true the surface... weeeeelllllllll..... had a funny knock that wasn't deep enough for a rod-or so i thought- and so i thought he was tapping a valve or something with the piston. pulled it apart and didn't see any problems so we pulled the pan and found a spun bearing. no big deal right? pulled all the rods and had the crank repolished and when we were getting ready to slide the pistons back in i felt something funny when i was hammering it into the hole... i pulled it back out and looked it over and didn't see nothing wrong so tried again and just had an uneasy feeling so i pulled back out again and eyeballed it over hard!! he had the rods resized and they rebushed the wrist pin ends and the bronze bushing was beat to pi$$!!! i pushed on it with my finger and it fell right out.. doubled checked the others and found they were a bit loose also... whoever bushed the rods must have put in the wrong size bushin cause the wrist pins all mic'ed out fine and consistent... called the machine shop and he redid it himself that night and threw in new gaskets and bearings to boot!!!! i have never thought to check those bushings but i will from now on... live and learn, live and learn...