What gas needed to run 11.0 - 10.5 CR

[Canadian1968]

I am playing around with the idea of getting a set of 915 heads to swap out my current 906 set.

I am running ICON 9953 pistons my current CR is somewhere around 9.8

Switching to the 915 would up my CR over 10 . My understanding that is about the limit for your regular 91 pump gas. What type of gas would I need to run if I followed threw with bumping the compression up ? My thought is I don't drive the car really alot , maybe 2000 KM a summer? Is there a race gas that I could mix with 91 pump to get my need octane ? Or what should I be looking for. I am little clueless when i comes to different fuels. I also have the chance to get some Aviation fuel would that be help?

Please do not bombard me with comments about "why bother with iron heads.... just do aluminum" I have the chance to pick up the iron heads for very cheap and would be something I would build over time . The iron vs aluminum is not the question here.

THank you

 

[dadsbee]

 

[Jerry Hall]

I mix 90 octane non ethanol 50/50 with 100 octane LL aviation fuel. It brings the performance back to like when my cars were new. I put 4oz. of Marvel Mystery Oil in every 5 gallons of the AV gas for lubrication.

 

[440 4 speed]

I am playing around with the idea of getting a set of 915 heads to swap out my current 906 set.

I am running ICON 9953 pistons my current CR is somewhere around 9.8

Switching to the 915 would up my CR over 10 . My understanding that is about the limit for your regular 91 pump gas. What type of gas would I need to run if I followed threw with bumping the compression up ? My thought is I don't drive the car really alot , maybe 2000 KM a summer? Is there a race gas that I could mix with 91 pump to get my need octane ? Or what should I be looking for. I am little clueless when i comes to different fuels. I also have the chance to get some Aviation fuel would that be help?

Please do not bombard me with comments about "why bother with iron heads.... just do aluminum" I have the chance to pick up the iron heads for very cheap and would be something I would build over time . The iron vs aluminum is not the question here.

THank you

 

[BSB67]

I am playing around with the idea of getting a set of 915 heads to swap out my current 906 set.

I am running ICON 9953 pistons my current CR is somewhere around 9.8

Switching to the 915 would up my CR over 10 . My understanding that is about the limit for your regular 91 pump gas. What type of gas would I need to run if I followed threw with bumping the compression up ? My thought is I don't drive the car really alot , maybe 2000 KM a summer? Is there a race gas that I could mix with 91 pump to get my need octane ? Or what should I be looking for. I am little clueless when i comes to different fuels. I also have the chance to get some Aviation fuel would that be help?

Please do not bombard me with comments about "why bother with iron heads.... just do aluminum" I have the chance to pick up the iron heads for very cheap and would be something I would build over time . The iron vs aluminum is not the question here.

THank you

It won't be pump gas friendly. Kinda surprised that your can run the 9.8:1 on 91 octane. What is the cam size again, and what is your cranking cylinder pressure?

 

[440 4 speed]

It won't be pump gas friendly. Kinda surprised that your can run the 9.8:1 on 91 octane. What is the cam size again, and what is your cranking cylinder pressure?

 

[Canadian1968]

It won't be pump gas friendly. Kinda surprised that your can run the 9.8:1 on 91 octane. What is the cam size again, and what is your cranking cylinder pressure?

It's comp cams xe274.
Actually haven't done a cranking test...... should probably do that for documentation lol

 

[440 4 speed]

I have 915`s being done, but hope to be able to run pump gas. Trust our mechanic son to do it right, I ordered the cam he thought we needed from Mr sixpack. (Sp). Getting parts is slow.

 

[RJRENTON]

I mix 90 octane non ethanol 50/50 with 100 octane LL aviation fuel. It brings the performance back to like when my cars were new. I put 4oz. of Marvel Mystery Oil in every 5 gallons of the AV gas for lubrication.

Doesn't adding the Marvel Mystery Oil increase the chance of detonation due to the lower flash point of the contained oil? I realize that 4 oz. of the oil in a total of, say 20 gallons of fuel, is a very low percentage, but is it actually contributing anything? There is nothing, IMO, that needs lubrication during the combustion process, as both valves are closed, and during the intake cycle only a small percentage of the intake valve stem is exposed to the incoming fuel charge and after combustion occurs, the Marvel Mystery Oil has no lubricating value as the hydrocarbons have been consumed. I'm just asking out of curiosity.....
BOB RENTON

 

[Cranky]

Cranking pressure....cam and cam timing....and lots of other things in the combo will dictate the gas you should use....

 

[33 IMP]

Agree with that^^^^! I have run 440s with 11 1/2 and 12 1/2 pistons on pump 91. However, both those engines were really at least a compression point lower than advertised, and both had big/huge cams. The 11 1/2 engine, really 10 1/2, has a 252 at .050 cam, the 12 1/2 (really 11.25) had a 272 at .050 roller.
Now that I have access to 100LL avgas, I run at least two or three gallons avgas with five of 91. I might not need to, but it sure don't hurt.
With your cam that short, I surely wouldn't be bumping the compression up. Run a compression test on your engine. If you are at 170 lbs now, I would not swap 915s on. My opinion only. I wouldn't want to have to pay race gas prices for a street driver. (Unless like me, you can get relatively cheap avgas)

 

[Ironbuilt]

This is what I run in my car and my pickup. It's expensive, but worth it.

 

[67belvedere/225]

vp or Sunoco racing fuel, im Montreal and its easy to get , last time we bought a 205 litre barrel
was about 6-7 dollars a litre.quite pricey , smells great . love racing fuel. 112 leaded as posted above

 

[Jerry Hall]

I understand that AV fuel is a dry fuel so that air planes don't have icing at altitude in the fuel system. I add the MMO for the fuel, not necessary for the car, but feel it does help with the fact that most of my old engines don't have hardened valve seats. I also use some lead additive for this reason. I'm probably old and set in my ways and it may be totally useless, but makes me feel better and hasn't caused any problems.
I can tune my old 440's and 383's back to factory spec's and they run like they did in the day. Having to detune an engine run on 90-91 or 93 is in my opinion more detrimental than giving it what it was designed for.

 

[dadsbee]

The 100LL has more lead than you'll ever need for seat lubrication Jerry. More than premium leaded ever came with..

 

[Ironbuilt]

vp or Sunoco racing fuel, im Montreal and its easy to get , last time we bought a 205 litre barrel
was about 6-7 dollars a litre.quite pricey , smells great . love racing fuel. 112 leaded as posted above

I am able to get the 112 in at the pump, in 5 gallon cans or in 55 gallon drums from Sparks Oil Co. where I live.
A 112 5 gallon can is $69.00 and last I checked, a 55 gallon drum is $546.99.

 

[Ironbuilt]

The 100LL has more lead than you'll ever need for seat lubrication Jerry. More than premium leaded ever came with..

Please forgive my ignorance, but how does AV fuel differ from jet fuel? Jet fuel is basically kerosene, correct?

 

[dadsbee]

Please forgive my ignorance, but how does AV fuel differ from jet fuel? Jet fuel is basically kerosene, correct?

Jet fuel, diesel, kerosene all about the same. AV gas is gasoline...

 

[beanhead]

I am able to get the 112 in at the pump, in 5 gallon cans or in 55 gallon drums from Sparks Oil Co. where I live.
A 112 5 gallon can is $69.00 and last I checked, a 55 gallon drum is $546.99.

Interesting. We get 5-gallon party balls of VP110 for about $75 here, close the same neighborhood in pricing...which is surprising because I'm sure our pump gas is considerably more.

 

[Ironbuilt]

Jet fuel, diesel, kerosene all about the same. AV gas is gasoline...

So that tank feeding your Dart is 110 octane leaded gas?
How much, roughly, a gallon in American dollars?