sharkthehunter77

I can only go with flat top pistons because i gotta keep my cylinder heads( dont have another grand to spend). but, this could be a blessing in disguise becuase i may still get the compression that i want to complement the performer manifold/camshaft without having to spring for new cylinder heads. Now, i do believe i read that the performer package did require a compression bump, but i feel domed pistons are just out of the question as i fear detonation/ pump gas issues!!! The engine builder i am buying my new bottom end from has speedpro, JE and other "name brands". The performer package offers a "sweet" spot of up to 5500 rpm.

VegasJen

TRW, speedpro or keith black hypereutectic. ask your engine builder what the cc of your current heads are (probably 76cc) and then you can just find the appropriate pistons in a summit or jegs catalog. i'm thinking you would be safe but get best power with a total static compression of about 9.2:1. this is definately the time to get really friendly with the engine guy, you might want to start being a real frequent beer buying buddy.

sharkthehunter77

Thanks for the reply. We did discuss compression on the phone about an hour ago and we like flat tops. One website says speed pro domed tops will raise the compression to 9.34:1 with 76cc heads, so hopefully flat tops will bring me in just underneath that at the 9.2:1 compression you mentioned. My biggest concern is using the original "smog" heads, but money is a factor and cleaning up the heads while off the block will have to do.

VegasJen

you'd be surprised at the amount of 'clean up' work you can do with just a dremel. i don't know if you have one or not, and it takes considerably longer than a die grinder would take but it works. i've done two sets with one. just to port match them to the intake and knock off alot of the rough casting edges. port matching the intake and blending the bowls will wake up a street engine more than you might think. if you have your heads off and disassebled, you can get an idea of what i'm talking about. put your finger in the bowl area by the valve guide and feel the way the bowl is shaped from there up to the valve seat. there is a ring where the two halves are cast that is just bad, it's not even parallel to the seat. if you can, especially around the short side,the side where the 'floor' of the port dumps into the bowl, knock off as much of the casting flash and make it as smooth as possible.
ironically, for a street engine, you don't want a full port and polish type head job anyway. the rough casting helps keep the fuel in suspension at the lower RPMs street engines normally operate in.
the biggest problem is that it takes alot of time. figure spending every night for a week just to get a good job on just the bowls and ports.

hudman

I just went with the Speed Pro's, which I believe are TRW's aren't they? At least they have a TRW in the product # from Summit.

My engine builder pretty strongly suggested the forged pistons over the Keith Blacks, and they were not that much more money (@$100 more).

Good luck

Matt Gruber

it will take a .125 pop-up piston to get 9.2 with 76cc heads.
i have the OEM TRW 11:1 forged replacement pistons in my 61 with 73 cc heads it is 9.65.
would be 9.2 with 76cc.
well worth the extra $100; i did the same thing.
.
i know where you can get a set of new cast for $90. e-mail me if you want them.


[Modified by Matt Gruber, 2:06 PM 3/18/2003]

sharkthehunter77

Great info, thanks. Domed pistons are a great solution for increased compression. However, if i go with domed .125, then what size tyhickness head gasket is best, if for some reason i stick with the flat tops ( still likely) thewn i obviously need thicker gaskets, to achieve that same compression, right???

Matt Gruber

with pop ups i assume a composite gasket .038-.040

can't get to 9.2 with flat tops. maybe 8.8 with a .015" shim,
maybe not