454 build, which pistons to get to 9:1?

[txaggie]

Howdy all,

My 454 went to the machine shop today for a block dip, new bearings, and valve jobs on the heads.

I’m adding in this Howard’s hydraulic roller cam and lifters, matching springs, headers, rpm air gap intake, Holley sniper, 2.5” x pipe exhaust. My question is should I do new pistons as well? This cam is geared for 1400-4900 rpm.

Howards Camshaft Lifter Kit CL120235-12 Retro Fit Hydraulic Roller BBC Mark IV 396-502 65-96

Fits BBC Mark IV 396-502 1965-1996, Retro-Fit Hydraulic Roller, 1400 to 4600 RPM Range, .510 Int .538 Ex Lift, Includes Camshaft and Lifters (PN 91167)

cnc-motorsports.com

 

[nvrenuf]

Stock pistons typically are 7.9:1 comp, if the money is there I’d bump it up in to the 9’s.

 

[txaggie]

Stock pistons typically are 7.9:1 comp, if the money is there I’d bump it up in to the 9’s.

Wonder what pistons would do this?

 

[txaggie]

Wonder what pistons would do this?

Looking to get 8.5-9:1

Stock heads are oval port (maybe peanut)?

1978 - 87 Chevy 454 Heads Open Oval Port. Cast number 14081045 Valves & Hardware | eBay

For Sale1978 - 87 Chevy 454 Heads Open Oval Port. Cast number 14081045 W/ Valves & Hardware. Tanked, Cleaned and Magna flexed. With Valves, Springs, Studs, Hardware. Missing 3 Rockers. Ready to build.

www.ebay.com

 

[ChuckN]

Maybe the shop that helped with the block could help?

Short of that, there’s tons of compression ratio calculators online that you can use. https://butlerperformance.com/n-12872-compression-calculator.html

You could look up what chamber size you have, what head gasket and then plug it into the calculator- play with it a little and then find the piston dome/dish that fits your needs. Don’t forget to factor in the cc’s for the valve reliefs as well- piston manufacturers will list how much volume they are. Have fun!

 

[Confused]

That is a mild cam and should work even with the stock compression. That being said it wouldn't hurt to deck the block a little (if for no other reason than to make sure it is flat and square) and have them mill the heads a little as well. Thin head gasket and it all adds up.

I would have them do a hone on the cylinders and new rings as well.

 

[yevgenievich]

If trying to not mess with balance much, need to get weight of current pistons first. Then can start searching for different pistons. Is this tbi or vortec block?

 

[txaggie]

Looking to get 8.5-9:1

If trying to not mess with balance much, need to get weight of current pistons first. Then can start searching for different pistons. Is this tbi or vortec block?

Thanks guys! This is an 85 mark iv block.

 

[txaggie]

Thinking these might be the right pick:

ICON IC9920.030 ICON FHR Series Pistons | Summit Racing

Free Shipping - ICON FHR Series Pistons with qualifying orders of $109. Shop Pistons at Summit Racing.

www.summitracing.com

 

[nvrenuf]

I’m running pistons with a 230cc dome, my machine shop said I should be about 9.4 comp (781 heads).

 

[yevgenievich]

I was way off on which block. I am running flat top pistons with angle milled heads and mls gasket for 8.9:1.

 

[txaggie]

I was way off on which block. I am running flat top pistons with angle milled heads and mls gasket for 8.9:1.

What pistons are you running? Peanut port heads?

 

[txaggie]

Looking to get 8.5-9:1

That is a mild cam and should work even with the stock compression. That being said it wouldn't hurt to deck the block a little (if for no other reason than to make sure it is flat and square) and have them mill the heads a little as well. Thin head gasket and it all adds up.

I would have them do a hone on the cylinders and new rings as well.

Do you think this would be more bang for buck than just changing to a flat top overall? These are what my pistons look like now:

1985 Chevrolet K30 7.4L Engine Piston Set P5019(8).P56

1985 Chevrolet K30 7.4L Engine Piston Set P5019(8).P56

proenginerebuilders.com

 

[Confused]

If your pistons and bore are good no reason to change them IMO. If they are out of spec then a dome pistons that puts you at 9.0-9.5-1 will help power everywhere.

 

[yevgenievich]

What pistons are you running? Peanut port heads?

I had rotating assembly balanced with new flat top pistons and aftermarket heads angle milled to about 108cc.
Vortec 96-99 bbc heads have 97 to 100cc chambers and give a bump in compression. On other motor I am planning to try finding domed pistons with similar to stock weight to reduce balancing issues.