|04-09-2012 12:27 PM|
|lmsport||Must have dome pistons. All passenger car HP engines had domes. A 20cc dome in a big block is only about .100" tall.|
|04-09-2012 10:01 AM|
the heads are completely stock they were in a completely stock 454 that i bought for 250 the block casting numbers say its from a 85-89 truck 4 bolt main
can flat top pistons get me there or i would need dome pistons to get to the 9 cr
|04-08-2012 12:15 PM|
That said, say the heads are 118 cc like they're supposed to be. To get the CR to 9.4:1 with an unmilled block and a HG thickness of 0.040", you'll need a dome volume of 23-24 cc. If you can get the quench down to ~0.040", the dome would then need to be about 18 cc. Changes to the CR from different volumes or CR targets can be easily made using a CR calculator.
I had a set of PP heads on a 454, ran fine w/3.31 rear gears in a '81 Camaro.
|04-07-2012 11:33 PM|
The heads you have are called peanut port heads. The are good up to about 4000 rpm. Plus they would have to ported and the intake port matched. They are not any good for performance. You would be better off finding a pair of 781s or 049s. They are the best oval port heads for performance. You would like to have 110cc chambers, with KB203 .133 dome would give you 9.781 compression.By the way with the 268H you will need K11-242-3 which is the kit. you can not use the stock springs with that cam.
|04-06-2012 01:25 PM|
There isn't any info on what size chambers the 360 castings have. As they all just say "Open" which leaves a large margin.
If the chambers are around 116cc's you'll need a piston with a dome on it around 16cc's to get the compression ratio to the 9:1 spec as recommended for your cam. Since chevy used various chamber sizes on open chamber big block heads unless you measure it or someone else already has it's really a shot in the dark, as they could have 122cc chambers. If they do then you would need a piston with around a 22cc dome.
|04-06-2012 08:12 AM|
am currently building a 454 bbc standard bore out of my 1990 454ss truck, and i would like to add a comp cams 268h cam i would like to know what pistons can i use to get the recommended compression ratio for the cam thanks in advance...
Mods: 454 bbc standard bore
stock cylinder heads casting numbers 14092360 2.06 intake and 1.77 exhaust open chamber oval port with 3 angle valve job
long tube headers
750 cfm carb
performer rpm intake