Guru_4_hire

OK so I have this here camshaft with 288/300 at 112 LSA with 4 degrees of advance ground in, with a 236/249 duration at .050.

I calculate my IVC to be 72 degrees

I calculate my static compression ratio to be about 11.1

When I enter my IVC into the KB dynamic compression ratio calculator I get

8.341 less depending on gasket bore, I assume a 4.1" gasket bore.

I was wondering is this gonna work with 93 octane?

holley505

I had something pretty close in my camaro.
solid roller cam
245/256 duration .610/.617 lift

I ran the small dome TRW forged piston, dart II heads 64cc, block was cut .060 over. I ran MSD-6AL about 34 degrees. I could run pump gas without problem (93 only) car loved the race gas...

the trick is, the overlapp on the cam will lower the compression ratio because the values stay open longer..... I BELIEVE (TECHIES?)... my car was just under 11to1

It could run 13.1 to 12.8 on muscle and 11.7 on the gas.


SO I WOULD GUESS YES WITH A GOOD MSD SYSTEM....

MotorHead

YOu should be OK, I am 11:1CR and run a 242/248 deg cam. Where you might run into problems IMHO is the added advance from a vacuum can

Guru_4_hire

Vacuum can?

zwede

You're on the edge w/ aluminum heads. Over the edge if they're iron. Make sure you have a good cooling system. Cold air induction is a plus. You will problably have to retard timing in the summer.

MotorHead

Vacuum advance, little can on the distributor

I was assuming aluminum heads ?

I just used the calculator and came in a ~8.4 DCR I run 92 octane and have never had a detonation problem

Guru_4_hire

Ahhhh OK.

gkull

Who makes that cam?

Most 4 inch bore gaskets are 4.060

Guru_4_hire

Cammotion

Would you like the lobe numbers?

That might be a problem, the gasket bore thing. 8.379 DCR

Guru_4_hire

The Keith Black Piston
Summit number #
UEM-KB122030-8

Takes me a little further from the edge with its -7cc reliefs

This gives me a known pump gas friendly 8.171:1 and a static compression of 10.9:1

I still intend to ceramic coat the pistons, chambers, exhaust ports.

I am also plumbing in water to under the siamesed exhaust ports.

So will these KB pistons mess with my world?

mandm1200

Your engine is quite a bit different than mine. I'm running (trying to run) a 388ci on 94.5 octane and can't. Currently running a 280* duration hydraulic flat tappet cam with iron Vortec heads with 11.3 compression. With the alum heads and slightly bigger cam you may get away with it. You may not know until it's running. I'm definetly going to a bigger cam and a possible head gasket change (.038" to either a .051" or .062").
Using their calculatot my dynamic compression ratio comes out to 9.97. That quite a big difference than 8.3.

nastee383

I have an 11:1 383, 242/248 hyd roller, 8.2 DCR, alum heads, vacuum advance. I've run it with as much as 38 degrees plus the vac adv (12) with no detonation on 93. I was getting a "lean miss" during cruise at 38 so I backed it off to 36 and it went away.

Little Mouse

SCE-011069, .093 compressed, 19.729 compressed volume,
4.060 bore.

Guru_4_hire

You guys are running about 6 degrees more duration than I am. Those KB-pistons are more and more inviting.

63mako

I wouldn't run KB Hyper's in my lawnmower. Especially since you know you will be on the verge of detonation. Ask Msvetteman. Do a search on these on the forum and other HP Chevy sites. My machine shop won't even build an engine for you if you want to use them. Go forged if you are that close to 8.5 DCR.

big_G

I would go with SRP's (forged) if the budget allows. I wouldn't use KB's in 63mako's lawnmower either!

442olds

In my BB I'm running 11.75:1(dynamic 9.121) with iron heads. I run 195 on a hot day 170 on cooler days. 92 Octane without any problems, at the track I have to run a little higher octane, but other than that I have no problems on the street. One other thing that is helping me out is .4" longer connecting rods.

I've run a 383 with 10.265(8.039) on pump gas without any problems either.

Be sure to setup the quench height properly and if you really worried about it have the piston tops coated and the combustion chambers coated. Make sure you debur the piston tops and chambers to make sure you don't have any sharp points that would create any hot spots.

holley505

Alum heads will help with pump Gas.

bigger cam with more Duration will help with compression and Pump GAS... of course a GOOD MSD system will help for sure.

63mako

Guru_4_hire

I am looking at the KBs because they back me off the point of detonation.(8.171)

Its not a budget constraint that I am looking at a hyper piston.