11 to 1 on pump gas

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My 360 has 10.6:1 static compression and cranks 195-205 psi and runs fine on 89 octane. I have tried 87 but I need to be careful. even on 100+ degree days it runs fine on 89.

The key to this high compression on iron heads is a tight quench. The magnum heads I am using ate closed chamber and the pistons are at zero deck, with the .039 thick head gasket I have an
Ideal quench that makes the engine very detonation resistant.

Note: good cylinder turbulence requires less timing. I run 33 with it all in at 2500 rpm. Initial timing is 17.
 
You know, just cause you might not hear the motor knocking, doesn't mean it isn't

Forged pistons can withstand some abuse

I got a feeling those with high compression and 91 octane gas also have a very loud exhaust. Muffler it down so you can lightly speak and be heard and then see if you can't hear the motor rattling at times
 
10.5.1 is about pushing it with iron heads & pump gas, that extra .5 point won't yield you any more power, but the chances of detination are going to be there, i'd shoot for 10.3-10.4 with good quench & call it good, it'll work on pump premium & you'll be able to put alittle timing to it, if you have to pull timing for .5 point your defeating the purpose & you won't be happy, my machinest stronger recammended i stay just below 10.5 on my 406 sbc or it WILL detinate, i trusted his word & i'm very happy, it runs on 91 with 36* timing, it also has a smaller cam, Dynamic #s are around 8.1, Static is 10.4x.
 
My static on new engine is 10.18 but dynamic will be 8.8-8.9, BUT I have magnum heads and a cam at 251-260 @50
 
Ok, so what's different about Magnum heads? Are they more efficient as far as detonation somehow?
 
I am running 11.8:1 and I run on pump gas most of the time. I dial it down to around 24 degrees and give up the horsepower. Every so often I dial the timing back up to 36 degrees and run race gas. The power is incredible, and the smell ........ damn that stuff smells so good.
 
StrokerScamp said:
Ok, so what's different about Magnum heads? Are they more efficient as far as detonation somehow?
Click to expand...

You still up, man i'm ready for bed...lol
Guess it's just the quench deal, i really don't like pushing comp. ratio to far. Carb. tuning and timing can make up for most of the difference imo.
Good night SS.
 
StrokerScamp said:
Ok, so what's different about Magnum heads? Are they more efficient as far as detonation somehow?
Click to expand...

They are a closed chamber design, that is, the chamber in the head is not as big as the cylinder bore so a portion of the deck surface of the head protrudes over the bore. When combined with a flat top piston that comes up flush to the deck surface of the block it is the thickness of the head gasket that keeps the piston from contacting the cylinder head. If this gap is maintained in the .035-.045" range the mixture in the cylinder will be very violently squeezed over to the other side of the cylinder creating a very uniform mix of fuel and air. The uniform mixture eliminates hot spots that cause detonation. Virtually every current engine design uses this principle and it allows for higher compression without detonation.
 
dodge freak said:
You know, just cause you might not hear the motor knocking, doesn't mean it isn't

Forged pistons can withstand some abuse

I got a feeling those with high compression and 91 octane gas also have a very loud exhaust. Muffler it down so you can lightly speak and be heard and then see if you can't hear the motor rattling at times
Click to expand...

Well my exhaust is relatively quite; X pipe and Super Turbos. When I have tried 87 it is quite easy to hear it rattling when i load it. In any case I am fast approaching 50k miles on my build and after the first few K miles of getting the engine dialed in with 93 the rest has been on 89
 
Had a friend and neighbor that had an original 11:1 DZ 302 Camaro (Iron Head).Used to run 93 octane and add 1 gal of race gas and didn't have any problems !! That's what I'll try first seeing as I'm expecting compression ratio to be between 11-12:1 !! Just bought 5gals of 100 octane race gas,$45 !!Let's see,16 gal tank @ 9.00 /gallon = $ 144 !!Guess I won't be doing too many road trips with Dart !!!
 
The people claiming higher compression useage near the ocean do not have Houston heat or constant humidity. California, Oregon, and Maine do not have Houston humidity. (Even the Oregon rains are not the same...the heat in Houston slaps you in the face immediately after sunrise with instant sauna in June, July, August, and September.

turbodart68 said:
Yes, if it has a loose converter and 3.91 or better gear. All day long.
Click to expand...
- Location: St. Helens Oregon





65Vsignet said:
I run over 11.1 on pump gas! iron headed 360, at sea level in the heat no problem and i only get 91 octane california crap fuel.
Click to expand...
- Location: Fair Oaks Ca,



Fst73_360 said:
I am just going by what others are telling me and what engine builders like MRL and IMM have told me. You do not need to listen to me, my car is also in Ca at Sea Level. I had Kb107 at 0 deck which was actually 10.9 with 62-63cc magnum heads and a xe274.[/QUOTE



dgc333 said:
My 360 has 10.6:1 static compression and cranks 195-205 psi and runs fine on 89 octane. I have tried 87 but I need to be careful. even on 100+ degree days it runs fine on 89.

The key to this high compression on iron heads is a tight quench. The magnum heads I am using ate closed chamber and the pistons are at zero deck, with the .039 thick head gasket I have an
Ideal quench that makes the engine very detonation resistant.

Note: good cylinder turbulence requires less timing. I run 33 with it all in at 2500 rpm. Initial timing is 17.
Click to expand...

My 360 has 10.6:1 static compression and cranks 195-205 psi and runs fine on 89 octane. I have tried 87 but I need to be careful. even on 100+ degree days it runs fine on 89. - Location: Pembroke, MA
Click to expand...
 
Well I was aware they were closed chamber, but I was hopin there were some other qualities that made them better at keeping detonation down. I'm running the stock four eyebrow flat tops that sit in the hole a bit. That's why I'm only going as far as about 9.2 with my 318.

dgc333 said:
They are a closed chamber design, that is, the chamber in the head is not as big as the cylinder bore so a portion of the deck surface of the head protrudes over the bore. When combined with a flat top piston that comes up flush to the deck surface of the block it is the thickness of the head gasket that keeps the piston from contacting the cylinder head. If this gap is maintained in the .035-.045" range the mixture in the cylinder will be very violently squeezed over to the other side of the cylinder creating a very uniform mix of fuel and air. The uniform mixture eliminates hot spots that cause detonation. Virtually every current engine design uses this principle and it allows for higher compression without detonation.
Click to expand...
 
I'm running 11.0-1 on my 360' j heads,,full port, big solid comp cam, single plane Holley strip dominatrix intake, Holley 870 street avenger carb.
Run 93 pump gas and a bottle of octane boost on fill up.
34 deg total timing....idles around 1-k. Runs cool but hot summer days it may climb a bit.

No problems for the past four years.
 
I have stock 340 compression, around 10.5 with stock J heads, it likes a splash of racing gas to make it happy even with the timing retarded.

Go aluminum heads and you would be OK from what I have been told, and at the cost of aluminum heads why wouldn't you?

I had mine done years before SBM aluminum heads were as available as they are today, should have bought a set the last time it was apart.
 
1968FormulaS340 said:
Sure it will run. I am at 11+ with iron heads. I can rumble through town if I keep the load off.

But it's really kind of pointless. You will have all this power that you can't use. Hell, a Geo Metro would probably beat you in a drag race, at least it won't be in chronic detonation when hammering on it, like you would be.
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I ran 11:1 on pump gas and iron heads, with 4.10s, and, yeah, I had to back off the timing (a lot) to keep the detonation at a point where I didn't cringe (too much) when I hit it.

But the only drag race I ever lost was a half-length to a built 350 with a 150 shot of nitrous (and, in his words, "I was on the button hard"):D
 
Well I will be installing the motor in the next week or so. I had a operation on my ankle and I'm off my feet right now. I was thinking about going with a thicker head gasket but the guy I bought the motor from said I would lose the quench. I don't mind blending a little. I talked to a engine builder here in Houston and he says if the motor has really good quench that would be at the limit with 93 octane. I'm not stuck with these heads I thought it would be cool to expirment for 3 or 4 months and see what they can do. I am worried about he summer though 100* with 85% humidity might be stetching it. There seems to be some pretty sharp guys on here so keep your eyes open I'm going to need help
 
greymouser7 said:
The people claiming higher compression useage near the ocean do not have Houston heat or constant humidity. California, Oregon, and Maine do not have Houston humidity. (Even the Oregon rains are not the same...the heat in Houston slaps you in the face immediately after sunrise with instant sauna in June, July, August, and September.

- Location: St. Helens Oregon





- Location: Fair Oaks Ca,



Fst73_360 said:
I am just going by what others are telling me and what engine builders like MRL and IMM have told me. You do not need to listen to me, my car is also in Ca at Sea Level. I had Kb107 at 0 deck which was actually 10.9 with 62-63cc magnum heads and a xe274.[/QUOTE





My 360 has 10.6:1 static compression and cranks 195-205 psi and runs fine on 89 octane. I have tried 87 but I need to be careful. even on 100+ degree days it runs fine on 89. - Location: Pembroke, MA
Click to expand...

Im in san jose and no we do not havw 100% humidity, but we have close to it with 65-75% not like So Cal.
Click to expand...
 
Even though your at sea level in Cal., the air is dryer, less chance for detination, but whatever the OP decides, its his engine, i personally would'nt be wanting 11.1 over 10.5 just for bragging rights & chance detination with diminishing returns do to lack of timing.
 
95teetee said:
But the only drag race I ever lost was a half-length to a built 350 with a 150 shot of nitrous (and, in his words, "I was on the button hard"):D
Click to expand...

You got beat by a chevy, shame on you, tell you what, i'll run you with my 78 cutty, its a 406 sbc & doesn't have nitrous :D
 
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