Jan 7th, 00, 05:57 PM
I am building a 396 bored .030 and wanting
to run 9.5 to 10.5 CR with 110 cc semi-open
chamber heads (GM signature oval ports). I
am looking for some pistons either forged or
hyperutectic. Does anyone know a good manufacturer or had good experiences with
big block pistons. I was looking at KB but
there is no selection for a 396/402....thanks
Jan 7th, 00, 08:09 PM
Check out a Summit Racing catalog, or www.summitracing.com (http://www.summitracing.com) . Silv-O-Lite KB hypereutectic would be a good street piston, so long as you don't put the Nitrous or a blower to it. Summit # UEM-KB160-8 is 4.125 bore (396+.030) .180 dome and 8.5-11.2 C.R. depending on CC's of heads,gskt.etc.$245.39.
TRW-L2328F 4.125 bore dia. std.,.030,.060. 10.82:1 comp. w/106.9 cc chamber. stock type race piston w/.319 dome. $375.60.
TRW-L2240NF (closed chamber) 396 std.,.030,.040,.060. 8:1-9.7:1 .$228.00.
TRW-L2242F 396 std.,.030,.060. 10.59:1 comp. w/109.4 cc's. stock type race piston.$335.60.
'68 Camaro SS 427
'66 Yenko Stinger #YS-100
Jan 8th, 00, 03:30 AM
I'm using SRP(By JE) pistons, they were a little more expensive than TRW but of higher quality. When the engine was being assembled, we compared the weight of the SRP to TRW and the SRP was noticable lighter and went into the cylinder easier with tighter clearences.
68 468 700R4
[This message has been edited by MarkM (edited 01-08-2000).]
Jan 8th, 00, 01:28 PM
Street/strip or racing only?
In the first scenario iŽd go with a set of JE/SRP too.
For pure racing iŽd use a "softer" one.
Ross and Venolia comes to mind.
482 cubes of fogger injected thunder in a 71 z.
Jan 8th, 00, 02:18 PM
OK this is the deal. I just installed a set of TRW 2240 Forged Pistons (.030 over) in my 396 motor (yes I will run nitrous). I started with Edelbrock "advertised" 110 cc aluminum oval port heads and milled them a total of .035. This yields using the NASCAR compression formula a 9.6 to 1 compression ratio (By the way, GM claims 9.6 to one on their 502/502 crate motor but the actual figure is closer to 9.2 to 1 using the heads you mentioned).
You lose a total of 1 cc in chamger size for every .007 you cut from the edelbrock heads although edelbrock claims 1 cc per .005 cut. Therefore the .035 cut yields a decrease of just over 5 cc's. I cc'ed the heads and they currently have 106.5 chambers compared to the actual measured starting point of 111.5 cc chambers. Each CC you reduce chamber size should increase your compression ration by .1 of a point.
Austin, it doesn't matter what the specs say. I deal in reality, would you feel more comfortable buying a motor from a person that says his motor specs out at 400HP or would you feel better if you will able to see that same motor on a dyno actually producing 400 HP??? I along with everyone else have spent literally thousands of dollars on parts on the basis of what the specs are and I am sick of it. The purpose of these forums is to deal in reality. Specs can be a starting point but that is all. The 502/502 was actually MEASURED at 9.2 to 1 compression and that is a fact.
As you noticed in my earlier comments, if a tech support person from a company such as Edelbrock doesn't even have the specs right concerning his own product (incorrect mill specs on chamber size reduction), how in the H--L would I or anyone else have the right information to proceed with??? The answer is that we wouldn't UNLESS we could learn from someone else that had the same experience with the parts that we are working with and that also is a fact.
END OF SERMON
[This message has been edited by sr71bb (edited 01-09-2000).]
Jan 8th, 00, 07:16 PM
All the specs on the 502 I've seen say 8.7 to 1. With exeption of the $6000. modified ones.