Bracket Talk
Gas vs Alky Jets

This topic can be found at:
https://drr.infopop.cc/eve/forums/a/tpc/f/80760912/m/9207040296

November 22, 2019, 08:22 PM
Wallace Cleaver
Gas vs Alky Jets
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?


Multi-time First round runner up extraordinaire
November 23, 2019, 06:16 AM
chasracer
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.
November 24, 2019, 10:04 AM
jmarkaudio
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.




Mark Whitener
RFD Heads
FTI Converter
Fab Shop Headers
Home built 2 circuit Dominator :-)
www.racingfuelsystems.com
____________

Good work isn't cheap and cheap work can't be good.
November 24, 2019, 10:56 AM
Cashflow
Wallace,

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


Clowns to the left of me, Jokers to the right. Here I am.......
November 24, 2019, 07:10 PM
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


Multi-time First round runner up extraordinaire
November 25, 2019, 07:29 AM
Alaskaracer
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...


Mark Goulette
Owner/Driver of the Livin' The Dream Racing dragster
www.livinthedreamracing.com
"Speed kills but it's better than going slow!"
Authorized Amsoil Retailer
January 23, 2020, 03:29 PM
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.


Dan "Jim" Moore
Much too young to feel this damn old!!
January 23, 2020, 06:56 PM
3677
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
January 23, 2020, 07:57 PM
Alaskaracer
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.


Mark Goulette
Owner/Driver of the Livin' The Dream Racing dragster
www.livinthedreamracing.com
"Speed kills but it's better than going slow!"
Authorized Amsoil Retailer
January 24, 2020, 11:48 AM
511camaro
it would be safe to double the jet then start leaning it out for best performance, I believe its 1.88pct of gas
January 24, 2020, 05:36 PM
sr4440
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


Without data, you’re just another guy with an opinion.