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Author Topic:   jets
7a
Dirt Full Roller

Total posts: 41
posted July 20, 2001 03:07 PM
think im running hot from not enough acohol
got a 750 holley old style (non pro) carb with 89 jet front 88 back elevation 5000 ft any sugjestions ??? thks

Pickel
Dirt Freak

Total posts: 239
posted July 20, 2001 09:19 PM UIN: 25419780
First of all make sure you have an alcohol carb. Second I don't believe you are high enough on jets. I know a few people who run alcohol and they run mid to high 90's on theirs.

spde
Dirt Roller

Total posts: 13
posted July 21, 2001 12:39 AM
Im running 99's all the way around. w/ a 355 mild build 500hp and a set of dart heads.
You really need to make sure it is a alki carb. We run all nite in mid mo and never get over 170 degrees. also make sure water flow is not stopped. I run just a 1/2" restricter no theromasate. good luck

Strokin3
Dirt Full Roller

Total posts: 68
posted July 21, 2001 07:46 PM
Take a real good look at your plugs with a spark plug viewer. There is a real good chance that you will begin to start melting some aluminum from the edges of the piston. I have to agree with the other post also, you
need to make sure that you have an alky carb.

------------------
Artie Perilloux

fast19
Dirt Newbie

Total posts: 3
posted August 02, 2001 08:46 AM
I run a gas carb(with Gas) and set it up on the dyno. I run 80 primaries (with a power valve) and 88 secondaries. For alky, You sure sound lean to me. Good luck

[This message has been edited by fast19 (edited August 06, 2001).]

nut3d
Dirt Roller

Total posts: 14
posted August 02, 2001 10:51 AM
You don't have the right carb. You need to get a Alkey carb and get rid of that gas carb. There is a differnce between the 2 types of carbs.

bkap
Dirt Full Roller

Total posts: 30
posted August 02, 2001 02:32 PM
I'm running a Braswell alky 750 and it seems to me it's got jets in the 140 range. Oh yeah, I'm running out in the desert at about 2000' with a pretty tame motor.

To nut3d: I think fast19 is running gas with his gas carburator. For those who haven't thought of it, if you run gas you don't need a large fuel cell to hold it. Less static weight. Then you can bolt in extra weight where you want it. Of course, you make more power with alky...

[This message has been edited by bkap (edited August 03, 2001).]

jammin
Dirt Administrator

Total posts: 3279
posted August 02, 2001 03:02 PM UIN: 16262997
Our HP is in the 140's too...

7a
Dirt Full Roller

Total posts: 41
posted August 02, 2001 03:42 PM
it's a alky holly carb set up in okla city im running norther new mexico 5000 ft elvation thks

49mtmod
Dirt Roller

Total posts: 13
posted August 02, 2001 07:19 PM
Just for reference, I am running an 800 C&S Holley carb at 4500 feet elevation and run 86 jets, primary & secondary. A lot of other factors could determine jetting, engine size, cam, etc. - and elevation is a big factor. Your jets don't sound particularly lean to me at that elevation.

I am running a 12.5:1 358 with a real mild cam - run 180 deg. all night.

[This message has been edited by 49mtmod (edited August 02, 2001).]

ZIGGY
Dirt Roller

Total posts: 6
posted August 03, 2001 08:31 AM
It is often not understood that many alky carb builders drill additional .060 or bigger holes in the metering blocks to feed the main circuit. These supply fuel additional to that coming through the jets.
Check with the carb builder or take a close look at your carb before making jet decisions.

Roadhzrd
Dirt Maniac

Total posts: 101
posted August 06, 2001 12:10 AM UIN: 28276986
Ziggy nailed it. There are so many variables from who built the carb to your engine combo and volumetric efficiency.

Iowamod20
Dirt Roller

Total posts: 20
posted August 06, 2001 03:41 PM
IF THIS IS AN ALCOHOL CARB WITH THOSE JETS, IT PROBABLY HAS SOME KIND OF BYPASS HOLE IN THE METERING BLOCKS. IF THE MOTOR HAS GOTTEN CONSISTENTLY HOT, THE RADIATOR MAY BE GOING BAD AS WELL. ALUMINUM RADIATORS GET RESTRICTED PASSAGES WHEN THE COOLANT/WATER GETS TOO HOT.

BARRY GRANT HAS GONE AWAY FROM BYPASS HOLES AND SWITCHED TO LARGE DIAMETER JETS 0.160" AND UP. THEY DID THIS BECAUSE EVERYBODY WAS RUNNING A DIFFERENT SIZE BYPASS HOLE, SO WHEN YOU TRIED TO HELP SOMEONE TUNE THEIR CARB YOU HAD TO KNOW THE SIZE. A LOT OF GUYS DIDN'T, SO THIS JUST MAKES IT SIMPLIER.

7a
Dirt Full Roller

Total posts: 41
posted August 06, 2001 04:54 PM
thanks guys the carb is drilled talking with the motor builder and the carb man every thing chks out still trying to figure the heat prob out going to post a new deal on over heating thks

rjs
Dirt Full Roller

Total posts: 38
posted August 06, 2001 09:22 PM
Here's a little trick I picked up on the Dyno, we run one size larger on the driver's side (low side in turns) and picked up 15 horses and a lot better throttle response on the track. It was noticeable. 140 range sounds about right depending on temp and humidity.

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