Al2011

I've searched Summit and Jeggs and can not find a affordable flat top piston under $500 for a .030 over bore. Can someone please help. The closest I can get is the IC886-30 but they have a 14.40 dish. My machinist wants me to bring hime flat tops. I have E-brock heads and he's aiming for a compression of about 10.5. My deck is .026 but It will be a little less once he does the surface clean up. When I check the summit compression calculator the compression for flat tops is below. Sort of cofused where he gets 10.5 but he runs a race shop so i will follow his advice but need help finding the flat tops. I'm not buying parts from him just machine work so I have to do my own homework on parts. Thank all!!

Compression Ratio : 11.35 : 1Total Displacement (in.3) : 461.23Total Displacement cc's : 7561.15

cutlassefi

You'd be surprised how many machinists can't figure compression ratio, they go by whatever a book tells them. I had a cam customer building a 396 BBC for a 70 Chevelle. He took everything to a machine shop and told them he wanted 9.5:1. With the heads and pistons they ordered for him it was barely over 8.0:1.

That IC886 piston with 0 deck gives you 10.25:1+. Cut the heads a little and you're at 10.5 no problem. The SRP flat top will put you over 11.0:1 under the same conditions. You want a 0 or close deck height anyway, have him cut it to that. If he doesn't know how then have him call me, or get another machinist.

Jmo.

ah64pilot

Wallace calculator shows 10.45 compression ratio with 4.155 bore, 4.250 stroke, 14 CC valve relief, .040" gasket and 0 deck height. IMO the IC886 would be your best bet and give you close to the 10.5 ratio you're looking for.

-Steve

oldsonharmont

Venolia makes a couple pistons for the 455 (5850 or 5861), but not sure about .030 over bore. Also saw some on Mondello's site if you want to pay that kind of money, or maybe try Keith Black.

Vega

Didnt see a chamber volume for the head in there, youre assuming the 77cc for E-brocks yes? I use summit's compression calculator a lot, i like it

As far as flat tops go youre pretty much out of luck. Flat tops seem to be a Chevy thing, and since 80% of all muscle car related media/practice out there is Chevy it trickles into everything else. $500 for a set of forged Olds 455 pistons is a pretty good deal...at least for Olds. If youre on a Chevy budget sure it sounds terrible lol. This is why i plan to rebuild my motor with a set of used *gasp* high-comp 69' pistons i picked up for $50 ^_^ haha. Look into SRP, they seem to have some good options, but id say 8-14ccs is the best youre gonna get. Id suggest being patient and keeping an eye on Ebay, thatd get you the best deal eventually. Also i found a lot of good deals on misc Comp Cam stuff like cams, lifters, timing sets, etc at atlanticspeed.com and a lot of good deals on Lunati at race-mart.com. Good luck! It costs more to dare to be different but its well worth it when the 800 Chevelle guys around you cant pick apart your ride and tell you exactly what it will/can do and exactly what you did WRONG xD

cutlassefi

Yes, 77cc for the Edelbrocks, but he should check them first.

And your explanation for the reason for flat top pistons is wrong Vega.

The real reason is simple. Olds 455's had 80-82cc heads from the factory. Edlebrock heads are about 77. So you don't need a dome or even a flat top piston on an Olds in order to achieve a streetable 10.0:1, a dish will work fine, right?
Now take a 454 BBC. They originally had an average of 110cc heads. Guess what, you need a dome piston in order to get that same 10.0:1, and a flat top might get you 9.5:1. The aftermarket is typically governed by the design of the original, keep that in mind. With all due respect sometimes if you just sit and think for a second the answer may be right in front of you.

SRP and I think Probe make a -5cc piston. With 0 deck and standard Edelbrock heads they will get you about 11.4:1, that's race gas compression.

Get the KB IC886's.

Jmo.

67442HT

You can get the pistons at Egge Machine and Speed shop, www.egge.com
they make all kinds of engine rebuilding parts from about 1915 to the 1970's, great company and great products.

Vega

Thanks EFI, believe it or not i havent dealt with a big block Chevy before haha (thats not sarcasm, as unrealistic as it sounds its the honest truth lol)

507OLDS

If you go onto Summit's website,they have a lot more parts for Olds,than what is listed in the catalogs.There is a pretty good variety of flat tops made for the Olds,but probably not under $500.00 a set.The JE or SRP is probably your best bet.Not sure what the Wiseco's cost,and other ones like CP's will be even more,but very nice.

cutlassefi

True Brian, but to reach his 10.5:1 goal he doesn't need flat tops. The IC886 or similar will get him there.

Jmo

507OLDS

True also.