Is there a formula or something that can tell you what jets will be in the ballpark if you switch from a gas carb to an alcohol carb of the same design and cfm? Say I ran 85 square, what would a starting point be for alcohol?

I remember reading some early conversion work on Holleys where the general practice was to drill a hole just above the jet in the regular gas metering block to .100-.125, then use gas jets to tune it in.

That would indicate that a starting point could be .185 for your application and of course it's going to be dependent on the size of the engine, compression, cam, etc, etc. On our small blocks (421-434s) we are in the area of 174-176, a BBC (555) is running 184-188s. All of them are in the range of 14:1 or higher.

85 square might be like a 950 Holley, 1.375 venturi and 1.75 throttle blade. 85 Holley jet has about a .095" hole. For methanol you may be in the .150 range with that carb. However there is more to it. All passages past the jet have to be sized larger as well. Mainwell, angle channel, and booster leg all add to the jets restriction until they are at least double the diameter.

Wallace,

If you want to save yourself some headaches just box the carburetor up and send it to Mark. Problem solved.

I should have been more specific.

The car I just bought has a 377" with a 250 blower making 12 lbs. It has a carb shop 1050 dominator on gas.

I have purchased a Quick Fuel 1050 alcohol dominator.

I was just curious where to start jet wise on the alky one vs the gas one so I don't hurt the motor being lean. Boost + Lean = my retirement from racing

quote:

Originally posted by Wallace Cleaver:
I should have been more specific.

The car I just bought has a 377" with a 250 blower making 12 lbs. It has a carb shop 1050 dominator on gas.

I have purchased a Quick Fuel 1050 alcohol dominator.

I was just curious where to start jet wise on the alky one vs the gas one so I don't hurt the motor being lean. Boost + Lean = my retirement from racing

Vern said it best, send it to Mark and let him set it up for you....You'll be either dead on or very close and will save a bunch of headaches tuning it...

Speaking of Mark Whitener, (Jmarkaudio on here), anybody got a phone # or email address for him?
I have tried sending him a PM a few days ago, but I know that isn't always the most effective way to reach somebody...
Mark (or anyone who can provide me with contact info for him), a PM will be appreciated, or please email me at danm400@gmail.com

Thanks.

I HAVE RAN A METH 1050 ON TOP OF 250 BLOWER 461BBC IT LIKED 190 JETS ID SAY START AT 180 GO FROM THERE ,YOU BETTER HAVE A GOOD PUMP I WENT WITH A BELT DRIVE BLP PUMP

quote:

Originally posted by FootbrakeJim:
Speaking of Mark Whitener, (Jmarkaudio on here), anybody got a phone # or email address for him?
I have tried sending him a PM a few days ago, but I know that isn't always the most effective way to reach somebody...
Mark (or anyone who can provide me with contact info for him), a PM will be appreciated, or please email me at danm400@gmail.com

Thanks.

Shoot me a pm. I'll give you his phone number. Just have to make sure he says it's ok. I know he's been busy lately.

it would be safe to double the jet then start leaning it out for best performance, I believe its 1.88pct of gas

you could always do the math to figure it out.

1st find the area of the jet. https://www.wikihow.com/Calcul...the-Area-of-a-Circle

then muliply that number by 2.2.

now you know the area for your methanol jet, all you need is the diameter.
https://www.wikihow.com/Find-t...ircle-Using-Its-Area

now you have your answer.

Joe