[Paul E]

Working on a 468 stroked Pontiac 400 block
72 CC Edelbrock heads CNC chambers (round exhaust)
Icon IC938 pistons +030
10.6 cc dish
11.4 Static Compression !
3.08 rear gear in a 70 lemans Convertible
TH-400 trans
Performer RPM intake
Holley 850 Vac secondary
Nice Street car
Looking to use a hydraulic roller cam and get some of the Dynamic compression down and use 1.65 rockers
Pump gas is a must.

Can this be done reasonably? The block has not been zero decked yet. Have the heads and pistons purchased machine shop said no problem just need the correct cam. Kind of worried

Thanks,
Paul

[PAUL K]

Unfortunately no, not with 11.4 actual compression, 3.08 gears and a major mismatch.
However are you sure your 11.4 with a 10.6 cc dish....
Nevermind I came up with 11.4 also.

Have you CC'd the heads? It shouldn't be hard to get the to 75 and that'd give you 11.1. But I still don't think you would get that to work properly with a cam that'll function with your 3.08's.

[AG]

I run 93 octane in my 11.2 CR race motor no problem with eddy heads, but my cam is probably bigger than yours.

[max 93]

If the shop said it’s no problem, ask them for a cam recommendation

[steve25]

I get a compression ratio of 11.2 .
This is with zero deck clearance.
Fel Pro 1016 gasket.
72CC heads of which there are likley closer to 74!
10.6 dish.
4.180 Bore.
4.250" stroke.
1.5 CCs for ring land back clearance.

If you want to throw in even just .020" of deck clearance into the mix then your at 11 to 1, but either way you should be fine with 93 rated fuel with normal engine temps!

[Cliff R]

I have a similar engine set-up in my car. It's a 428 four bolt main block with a 455 crankshaft, forged "I" beam rods, flat top JE pistons with 2 valve reliefs, 76cc aluminum heads from Dave at SD. Pistons are right at the top of the block at TDC and just bump a straight end laid over the pistons. .039" Felpro head gasket, compression ratio is 11 to 1 if not a tad higher.

Been running it on pump gas with zero issues since 2009. I've even ran it on a steady diet of 87 octane at times, but on race days will add at least half a tank of 92-93 octane to it.

The camshaft is the Old Faithful from Dave at SD, he also supplied the heads CNC ported. The cam was installed at 109.5 ICL, specs at 289/308, 236/245 on a 112LSA. Makes 13.5" vacuum at 750rpms with only 10 degrees timing. Total timing is at 30 degrees, another 15 from the vacuum advance via ported vacuum. Runs flawlessly and I've never once heard or had any evidence of detonation.

The only negative symptom in all these years is that on the very hottest summer days when the engine is well heat soaked I've had it "run-on" a few times when shut down, but only on 87 octane. Doesn't happen on 89 or higher so I try to keep better fuel in it in the hottest summer months......Cliff

[Gary H]

Also, keep in mind that the Butler head gaskets are closer to .043 crushed thickness versus the .039 Fel Pro's. If you wanted a little more cushion you could use them.

[Skip Fix]

I'd cc the heads also . I think most of mine are about 75cc.

["QUICK-SILVER"]

Originally Posted by Paul E

Nice Street car

Need your definition of "nice street car".

While back I saw or read where Butler had a 90 something cc CNC program for the E-heads. Could use a lot more street friendly cam and not need a big stall converter if you went that route.

Clay

[Paul E]

Thanks that does make me feel better about the situation.

Sounds like Cliff really likes the stump puller is that with 1.5 or 1.65 rockers was looking at Harland Sharps.

Looking at trading the heads out / selling and buying 87 CC and having 9.5 compression and not being concerned.
Appreciate the input a lot.

Paul

[Steve C.]

Cliff's cam is the Old Faithful with 236 degrees intake duration.


.

[ponjohn]

Originally Posted by AG

I run 93 octane in my 11.2 CR race motor no problem with eddy heads, but my cam is probably bigger than yours.

But you're not lugging 3.08 gears.

[ponjohn]

Originally Posted by Paul E

Thanks that does make me feel better about the situation.

Sounds like Cliff really likes the stump puller is that with 1.5 or 1.65 rockers was looking at Harland Sharps.

Looking at trading the heads out / selling and buying 87 CC and having 9.5 compression and not being concerned.
Appreciate the input a lot.

Paul

That's too low unless you gonna boost it.



You need to be around 10.5 - 1.

[hurryinhoosier62]

Originally Posted by ponjohn

That's too low unless you gonna boost it.



You need to be around 10.5 - 1.

X 2. I think it was Ken Crocie who said 10.5:1 was the max static compression ratio he would use with pump gas. David at SD says 1-1.5 points higher that what you would run with iron heads. Once again, cam timing, cooling system efficiency and carb tuning are variables that would affect the octane requirements .

[steve25]

I would stick with the heads you have now and run 93 which you will likely find you can cut with some 87 once the motors tune is dead on even in hot weather!

[AG]

Originally Posted by ponjohn

But you're not lugging 3.08 gears.

3.90 gears with a 29" tire.

[tpssonic]

Plus, Cliff is running Kaufmann heads with the "fast burn" chambers, which usually require less timing/octane. You did not specify if you were using "upgraded" E-head chambers.

That being said, I think you could run that combo with 93 octane all day long- even with a splash or two 87 octane, as steve25 suggested. I run 10.33:1 with "Old style" E-heads and lug the engine at 1800-2500 rpm for hours on end on back road or highway speeds (200R4 with 3:42 gears. OF cam on a 114 LSA). I have yet to hear a ping. I have yet to run 87 octane, however. I am in a lot of parades in very hot weather and my car temp has reached 200 degrees during a couple very long events- still no ping. Ensure your tune is on.

[Paul E]

The heads are the new CNC chamber

[ta man]

Originally Posted by ponjohn

But you're not lugging 3.08 gears.

FWIW My engine is 10.8 to 1 can run on 87 octane..lugging a 3.08 gear..seems to work ok.

[PunchT37]

Originally Posted by hurryinhoosier62

X 2. I think it was Ken Crocie who said 10.5:1 was the max static compression ratio he would use with pump gas. David at SD says 1-1.5 points higher that what you would run with iron heads. Once again, cam timing, cooling system efficiency and carb tuning are variables that would affect the octane requirements .

And DA along with temps, humidity, etc. That`s why one needs to be careful when listening to a person saying he can run this and that fuel with this compression. He may be correct but, he`s not running his engine where you are.

Here in south Louisiana, one better be conservative on compression and/or have to run better fuel than most locations.