What octane should I need?

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Valiant1

Valiant1

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I'm curious to see what other members consider the minimum octane rating needed to support my engine. It's a 340 with iron W2 heads, a mild solid cam, and 11.75:1 CR. Race gas is available in several locations near my home, but it's really expensive and it's not available everywhere. I can experiment, but I'd like to see what baseline might be acceptable. Thanks.
 
I've cured that on two fronts using av gas. It's cheaper with plenty of octane.
now coming next you'll hear everyone saying how bad it is for your car and your motor and blah blah blah blah blah. altitude additives blah blah let build up in your motor blah blah. You do plan to take off don't you? You do plan to launch don't you? Most of the blah blah from people reading too much internet. Let the people chime in who actually use the stuff. I use it and it works great but my car is 90% dragstrip also it is not in no way a daily driver at and/or I'm expecting to get 200,000 miles of service. I use it to put in my snowmobiles for the summer because it is so stable and consistent. even my lawn mower seems to like it just because I have cans of it laying around I think why not?
 
List the weight /drive train combination numbers, if available. Camshaft specs, especially....
 
j par said:
I've cured that on two fronts using av gas. It's cheaper with plenty of octane.
now coming next you'll hear everyone saying how bad it is for your car and your motor and blah blah blah blah blah. altitude additives blah blah let build up in your motor blah blah. You do plan to take off don't you? You do plan to launch don't you? Most of the blah blah from people reading too much internet. Let the people chime in who actually use the stuff. I use it and it works great but my car is 90% dragstrip also it is not in no way a daily driver at and/or I'm expecting to get 200,000 miles of service. I use it to put in my snowmobiles for the summer because it is so stable and consistent. even my lawn mower seems to like it just because I have cans of it laying around I think why not?
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Done the Av-Gas thing, it does work, in cooler temps. Seen issues with warmer weather (80+ Fahrenheit, on up). Harder starting , some idleing issues ( didn't re- adjust carb or timing base settings...)
 
The car weighs 3150# with me in it. 727 w/ 8" converter and 486:1 gears. Cam specs are:
Intake = .564" lift, 247' @ .050, and 106 CL
Exhaust = .548 lift, 256' @ .050, and 112 CL
109' LSA
 
The thing with the AV gas is that what I'd like to do is be able to go to a gas station and by gas, if I could. Can't do that with AV gas. I run race gas now and it's kind of the same problem.
 
Borderline, on that combination. I like TK-7 for octane booster/ lead substitute, it's expensive. It will be a learning curve, have you talked with your engine builder,on this?
 
My engine builder thought it was borderline, too. He suggested race gas at the track and maybe 93 with a booster and less timing on the street.
 
QUOTE=RustyRatRod;1970828488]Regarding Avgas, I have used it in the past. The only Avgas that will be of any benefit to automotive engines, which was 115/145, now is all but gone. You might want to read this.

http://www.dragracingpinoy.com/arti...-info/78-tech-tips-aviation-gas-vs-racing-gas[/QUOTE]

Nice read triple-R ! Now if I may debate (NOT argue :D ) where I live super (92) is $3.05 , av gas (100LL) is $5.20 , vp is $12. I'm sure you're well aware my theory on well written convincing Internet particles? (Bonjour I'm a supermodel!) here's something I read on the internet (my favorite kind of quote, real life experience) :

you guys can beat yourselfs to death with this debate. mike your a good guy but you sell racefuel and i wouldn't aspect you to say anything other then it's junk just like all the other racefuel sales persons. YOU DO KNOW THE BASE FOR ALL SOCALLED RACEFUEL RIGHT??? NOT ONE COMPANY WILL TELL YOU THE TRUTH BUT I HAD A VERY GOOD BUDDY THAT WORKED FOR TORCO AND YOU WOULD BE SURPRISED... av-gas has been used for 50yrs in racing and is still being used today.... i will sit back and let yeti school you youngster on gas and laugh at some of the dumbshit some of you say..... i run it in a 13 to 1 bbc and spray 200shot with the amsoil mmt octane booster.... i would say over 500 n.o.s passes and went to refreash the engine over the winter and could have used the same bearing rings where fine also....
 
I didn't debate anything. I posted a link with facts for the OP to read.
 
Valiant1 said:
The car weighs 3150# with me in it. 727 w/ 8" converter and 486:1 gears. Cam specs are:
Intake = .564" lift, 247' @ .050, and 106 CL
Exhaust = .548 lift, 256' @ .050, and 112 CL
109' LSA
Click to expand...

I run 11.2 with a slightly smaller cam 244 @.050 intake I have about 200 cranking psi with a 4,400 stall 3450lbs demon with me in it. I think you will have trouble with 93 pump. The biggest things you can do is obviously no heat crossover, fresh air intake, keep the fuel as cool as possible, and use a very cold plug I use a NGK bpr9 I think.
 
I already run the cool NGK plugs, have a fresh air intake, cool can, and no heat crossover. Any other suggestions?
 
What is your initial and total timing? When is it all in?
 
For street use;
Back off the timing and/or bring it in later. Then sneak up on the tune.
Always buy your fuel from the same pump.
If you have trouble; A) lower the Dcr with a later closing intake point,or B) Delay the secondary tip-in timing, or C) put on a smaller carb., or D) lighten the load/reduce traction, or E) consider water injection.
 
EL5DEMON340 said:
I run 11.2 with a slightly smaller cam 244 @.050 intake I have about 200 cranking psi with a 4,400 stall 3450lbs demon with me in it. I think you will have trouble with 93 pump. The biggest things you can do is obviously no heat crossover, fresh air intake, keep the fuel as cool as possible, and use a very cold plug I use a NGK bpr9 I think.
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I have a similar setup as well compression, cam, and such. I'm actually curious to see what everybody else his doing as far as timing and fuel as well. don't mind me arguing oops I mean debating with Triple R it's how we communicate O:)
 
If you scroll down the article RRR posted there's an interesting "reply" someone posted regarding Toluene. According to that you can get toluene at paint stores for pretty cheap and it's an effective octane booster (much more than the bottles of stuff at the auto parts store) which you just mix in with pump gas. Apparently it's also the main ingredient that makes race gas (unleaded) have higher octane.
 
j par said:
:banghead: debating!! LOL
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A debate involves 2 people. I am not debating or arguing. Those were not "my" facts, as you said, they are completely independent facts from a correct source. There are literally hundreds of links with similar information, so those are indeed facts. Any debate or argument is merely to get your post count up or just so you can see yourself type.
 
My timing is about 18 initial and 30 total, no vacuum advance. Keep an eye on plugs for black specs = detonation or insulator showing a yellowish color = cyl temps excessive and rising extreamly fast.
 
RustyRatRod said:
A debate involves 2 people. I am not debating or arguing. Those were not "my" facts, as you said, they are completely independent facts from a correct source. There are literally hundreds of links with similar information, so those are indeed facts. Any debate or argument is merely to get your post count up or just so you can see yourself type.
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Post count ! People care about that ? or was that a Freudian slip? see myself type? I mostly use voice command on my cell phone. I'm just not into it enough do all that typing. lol
 
EL5DEMON340 said:
My timing is about 18 initial and 30 total, no vacuum advance. Keep an eye on plugs for black specs = detonation or insulator showing a yellowish color = cyl temps excessive and rising extreamly fast.
Click to expand...
I'm at about 23/33 . For a stroker it doesn't seem to like lower rpm's. But I'm thinking that's mostly the cam talking. I've still got so much tuning left on the table .
 
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