steveolds68

Ok felloe Olds owners. I have a 68 442 convertible. I just had a 1970 455 built. 3/4 race cam balanced blueprinted have about $5,000 into the motor. End result should be 525 horse and 600 ft lbs of tourque. There is really no race fuel options in my area other than going to local airport with 5 gallon cans to get aviation fuel. My builder who went a little crazy says i need to run a 100 ocatane fuel or better or risk detonation in the cylinders. Any body using pump gas with same motor output as myself?

Rickman48

I'd be looking for a deal on octane booster!
Did he give you a clue on compression ratio??

coltsneckbob

I would advise against using aviation fuel. My understanding is that it is highly oxygenated and has other chemicals that may harm parts of your engine.

I would use an octane booster. Also some auto parts stores (around here NAPA) can get racing fuel for you. It ain't cheap though......last summer it was $60 for 5 gallons. I buy my fuel at a nearby racetrack.....but even there I was paying $9/gallon for leaded 105 octane. Also, $13/gal for 114 octane - if you wanted/needed it. I would imagine I will be paying 50% more this summer. Of course I would mix it with pump Sunoco 93 at 50% each - which actually made the 114 octane a better deal for me.

steveolds68

11 to 1

cutlassefi

Avgas is very dry and hard on valve guides, just ask my buddy who ran it in his Vortec blown 5.0. It torched them bigtime.

Apparently your builder threw caution to the wind with the 3/4 race cam (can't believe you used that term)and too much compression. You may have gotten almost the same hp/tq with some head work, less compression and maybe only a 2/3 race cam.

Yes I'm being sarcastic but trying to make a point. Imo now it will be a bit of a chore to drive your car on the street. To me it's not worth it. You're in for running race gas or a bunch of octane booster.

Jmo.

stevengerard

I use 93 with 10.5:1 does 11:1 need that much more octane

ah64pilot

Yeah, that's why I educate myself and tell the builder what I want and not the other way around. So you're running 11:1 compression and a .750" lift cam. What else was done to the motor? What heads? What Intake? I'm just curious...

To answer your question, you need to find a place to buy 104 octane or higher. If you're running aluminum heads then you should get by with 93 and about 4 bottles of octane boost per tank. I apologize but this is just funny to me...why didn't you tame your builder?

geckonz08

[quote=steveolds68;275928] My builder who went a little crazy says i need to run a 100 ocatane fuel or better or risk detonation in the cylinders. quote]

gosh, that is an awful thing to tell you .At what point in the build were you given this delightful revelation ??? I would be pi%$ed

Help him out guys .What is the most cost effective way for him to cut his compression .???
What thickness head gaskets do you have ??
Can you carve some meat from the combustion chamber??

mike

ah64pilot

I would first be asking if the 11:1 CR is ACTUAL or ESTIMATED. I believe Dre posted this same problem thinking his SRP pistons would have 11.6:1 CR based on what SRP advertised.

Did your machinist actually calculate the CR based on piston/cylinder/gasket/head CC?

507OLDS

CutlassEFI beat me to it.3/4 race cam.Please don't use that term,as there is no such thing.What are the specs on the block,cc of the heads,gasket thickness,etc. What are the specs on the cam?

cutlassefi

It can but also has to do with the gear,vehicle and cam.

Jamesbo

FWIW stolen from hotrod.com

Yeah I know that this used to be a joke, but Cam Dynamics did make a cam they called the 3/4 race cam. They did this just because every non-knowing street person wanted a 3/4 cam.

I looked into one of my old books and here are the specs listed for the 3/4 race cam.

SBC Hyd. Rough idle, 283-400CI, good mid-range torque, OK for Auto w/street perf. conv. in 327-up CI, Power brakes req. 99590-1 Vac. res. system, aftermarket carb, int, & exh. advised.
Basic RPM 2200-5200
Cam use oval/drag Series grind # 3/4 Race 300-06 H
Dur. @ .050 218* 218*
adv. Dur 300* 300*
Lobe seperation 106*
running clearance hot .000 .000
Gross valve lift .450 .450

Thought this would make a good laugh for some people.

507OLDS

What a wonderful marketing plan.Too bad I don't have a 3/4 race car to go with it.
Like Mark said,there are a few variables that effect what type of fuel you can get away with.

steveolds68

Ok so thanks for the sarcasm about my 3/4 cam statement. my intention was to give a rough view on what was done to the motor by 3/4 i meant a very aggresive cam which i did not choose. I dont have all the specs on the cam and the motor was built while i was spending all day everyday at a good friends bed side who spent 14 days in a coma. The motor was built its done it is what it is. I was just looking for advice on pump gas,octane boosters or lead additives. Was not looking for sarcasm because of a term i used which was used when i was in my twentys. So if you have advise love to hear it if you wanna give off sarcasm save it for when we are face to face.

Thanks Steve

panos

Is there any chance at all that you could contact your builder and ask him a little more about you build and your hard earned money? Im saying this because it is only him who knows what is in this engine,everything else is just guessing!


Sorry to hear about your friend ,hope this works out for you.

507OLDS

I am curious why he picked the cam he did,and built the engine the way he did,if he knew it was for street use.

MDchanic

Steve, these guys were busting your horns because you asked a very specific question and gave them some of the most non-specific information possible to work with in giving you an answer. They can't tell you anything specific about what sort of gas will work because they don't know enough about your car and engine to do it. The "3/4 race" terminology was just the icing on the cake of a very non-specific set of information that was presented in a setting where very specific information is needed. It was sort of an "I know this guy, his name is Fred, he's six feet tall, what's his blood type?" kind of question.

If you get all of the needed "blueprint" information from you builder, I'm sure these guys can help you. If your builder can't supply it, then you've got a problem.

And I'm sorry to hear about your friend - hope he's doing better.

- Eric

cutlassefi

Well said, all of it. X2

steveolds68

I understand info was vague and in the grand skeem of things its just a car and just a motor. The stress of my friend and finding out my motor was turned into a 1/4 mile monster was too much to take. I will get more info on Monday when i go back to the builder which builds race motors for a living so i am partly to blame even though i made it clear not to go crazy on cam and compression. He was obviously the wrong guy for the job so my bad. Sorry for calling some of you out but i am the type of guy that says things to peoples faces not over a web site. Then if what i said offends someone and they wanna roll on the ground over it then im all for it. Thanks again guys my friend is out of the coma but to early to say if he will ever be himself again and that just sucks.

cutlassefi

My sympathies as well, lost a friend a some years ago at the ripe old age of 44.