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decent power on low octane?

994 Views 8 Replies 4 Participants Last post by  firestone
is there a way i can build a sbc 350 to make decent power on regular 87 octane pump gas?

i figure i need to keep compression down, but what about the heads and cam? i would like to make 300-350, is this posssible? it is just a thought. the engine does need to make decent torque down low as it is going in a '59 chevy truck.
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thanks! i wasn't sure how feasable of an idea it was, but it looks like it will work.

ok this is what i have planned out so far:

-trick flow twisted wedge alumium heads 64cc combustion chambers, 195cc intake runners.

-trick flow hydraulic camshaft with a 210°/216° duration at .050, .440/.454 in. lift, with 1.5 ratio rockers and a 110° lobe separation.

-performer rpm intake manifold
-holley 600 cfm carb

i am trying to figure out my compression ratios. i was playing with the numbers, using 12cc dish pistons

with a head gasket of .039x4.125, and a deck heigth of .010 would put me at a static CR of 9.41
any clue on the DCR? i don't know the intake valve closing point.

does this setup sound like it will make good power on 87 octane?

the top end kit is marketed by trick flow to make 350 HP at 5,500 rpm's, 400 ft-lbs. at 3,500 rpm's and holds
400lbs through 4,100 rpm's....
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compression ratio

There are several things you need to have to figure your static compression ratio.

CC of the heads
CC of the hole in the head gasket. Use the formula V=pi x r squared X H, then convert to CC's.
CC of the unswept area in your cylinder. The area not filled by the piston when it is at top dead center.
CC of the dish in your pistons, if you are running dished pistons.
Add 4 CC's to your total for the flycuts in your pistons if you are running flat tops.
If you plan to run domed pistons, you will need to know what the CC is of the dome, and subrtact that from all the rest of your CC calculations.
Figure out the CC's of one cylinder of your engine, add them all together then divide by the previous computations.
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thank you for your input, but i know what my SCR will be, i am trying to figure out my dynamic compression ratio
compression ratio


Head gasket= 4.125 bore and .039. = 2.72 CC.
Unswept cylinder volumn is 2.06 CC
Combustion chamger is 64 CC
Piston dish is 12 CC.
Total combustion area displacement is 80.78 CC
Cylinder displacement is 716.54 CC

I am coming up with 9.87:1 compression ratio
You should be able to run your engine safely on 91 or 93 octane gas.

Check this web site, it will give you the way to figure your Dynamic Compression Ratio, hopefully.
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i am getting 9.41:1 for my static CR using both of these calculators:

thanks for the link. i emailed trick flow about the timing specs of their cam and haven't heard back yet.

and i was planning on running 87 octane. is 9.4:1 to high to run 87 octane with aluminum heads with no detonation?
I am pretty sure that 87 would be ok with aluminum heads as long as you get down to around 9:1-9.5:1. Have you looked into AFR heads? I would highly recommend the AFR 180 cc heads for your application. You would make more hp and torque than the unported trick flows, and the AFR's are only $275 more, that is as cheap a port job as you will find.

The trick flows are $1025 unported out of summit

AFR 180s are $1300 from AFR with CNC ported intake runners, exhaust runners and combustion chambers.

This is a combonation on the AFR website, it made 420 hp @ 5500 RPM and 435 ft lbs @ 4200 RPM.

350 cid Small Block Chevy Package
AFR 180cc Street Heads
9 to 1 Compression
1 5/8” Headers
AFR FloPower RPM #5029 and 600 cfm Holley Carb
110E Hydraulic Cam
Intake: .460 lift/218º @ .050, Exhaust: .470 lift/223º @ .050
110 lobe center, 800 RPM idle, 16 lbs. of vacuum

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