I have my engine at a very reputable builder here in San Diego, and he has yet to be able to find pistons that will work. I'm getting worried because of all the work that has already been done to everything by him. My heads are closed chamber 101cc oval ports. The block is .040 over. Does anyone know of any pistons for a 427 that will keep compression under 10:1 with my setup? I hope to not need custom pistons which will cost a fortune. Any help from anyone at this point will be much appreciated.

Thanks,

Rick

Rick,
I think the biggest problem is the .040" bore. The TRW L2300F's are right at 10 to 1 but only available in 30 & 60. Hate to say it but if you want to stick with .040 you are probably looking at custom.

I don't think the machinist wants to overbore to .060 since there is one sleeve installed in the block. Do other manufacturers have anything that would put compression down around 9.5:1? I just hope he can come up with something. I cannot find anything. How about dished pistons?

maybe stupid but how about a set of open chamber heads.maybe a thought.i know some one with a set if you need them.custom pistons alot of money. throw it buy your rebuilder.

Does anyone know roughly how much custom forged pistons run? I would get open chamber heads, but I already have these and they are in awesome shape. I guess if I'm forced to I will, but there has to be a piston out there that fits my needs.

like i said open heads are cheaper than closed heads.but pistons and got to be casted may be alot of money but not sure. my friend had a big block with 1200 hp with nitrous cost him 4000 bux a piston.and he pulled a 7.70. i see you dont want to go that fast.so talk to engine rebuilder as i said.

$4,000/piston??? I'm hoping that was a typo.

Has anyone here used Closed Chambers with a 427 without getting too high a compression?

if the pistons are dome top,what about milling some of the dome off to lower compression.just a thought.

http://rosspistons.com/
iF ANYBODY HAS THEM IT'LL BE rOSS. dAMCAPS:mad: Lock was on. Sorry

If anybody can make them it'll be Ross. Bendover though. It hurts.

Boring to 60 would be cheaper, and more cubes too. That's just 10 more off the wall of your sleeve. What's wall on a 4.25 sleeve Bill? 80? 100?


edit:looks like 800bux. Not that painful
http://rosspistons.com/uploads/8_cylinder_custom_a_chev.pdf

Well, the machinist called me today, and he found pistons. One type would allow me to keep it .040 over but it would take 6-8 weeks. The other set, are Keith Black Forged, and he'll have them this week. He will be going .060 over. He told me today that he never said it was a bad idea boring over the sleeve, but I know he did. Then he reminds me that he had told me how he doesn;t like KB Pistons, but it's the Hypers he doesn't like. Does anyone have any experience with KB Forged Pistons here? What's wrong with Hypers?

My wife just made me sit through a really dark movie. This thread is reminding me of the same thoughts! What are you worried about? My 427 has been 12.5 CR since 1968. I bought it the year before the car. It works great. Still the same .060 over-bore. Like I said, works great. Think 'open-chamber'. Good stuff. And those Hyper-pistons,,,well, I haven't read anything good about them. Except maybe they're cheap. Sounds like your machinist is on to something.

12:1 works great? what gas are you using? I was about to build up my BBC with the old ZL-1 12:1 pistons and iron hipo heads and everyone is telling me it wont run on pump gas. I cant afford $6.50/gal when I get about 6 miles/gal.

I'm curious about that too. I've been researching this for sometime, and all I read is that 10:1 is about max for high test pump gas. My builder tells me I'll still need 91 octane or better with 9.5:1. Maybe your timing is set to handle the compression? I'm no expert, so if there's something you know that I don't, I'm always willing to learn. Thanks for all the great responses so far.

I think Fred is trying to tell you he is running high CC heads with 12:1 pistons, his real CR is probly NOT 12:1 for pump gas. Don't want to put words in Fred's mouth though, did I understand you correct Fred?


Ain't nuthin wrong with KB or hypers. :)
What happens is folks don't read the damn instructions and set the ring butt-gap wrong. Or they put a 200 shot of juice on a hyper piston, and blame the destruction on a piston that was designed to have tighter cylinder to bore clearances in order to cut down on cold oil consumption ... the design was originated to meet emissions.

I've run more than 1 set of KB hypers. They are definitely a step up from cast, and nobody claims they are forged.

Hopefully everything turns out ok with my build.I'm not looking for really high HP, but rather just a fun car to drive. Reliability will hopefully be good too!