What carburetor jetting as a starting point?

Posted By: mshred

What carburetor jetting as a starting point? - 05/24/12 04:15 AM

Hey guys, looking for a jetting recommendation as a starting point for the following combo (sorry if its a little long, copied it from another post)

360 LA roller block bored .030" over
3.58 stock stroke, Scat I beams, SRP flatops
10.25:1 compression
RHS heads ported by Brian at IMM (291 cfm at .600 lift on the intake, 212cfm at .600 lift on the exhaust)
Custom Comp Hydraulic roller cam spec'd by Brian at IMM- 108 lsa installed straight up, 240/248 duration at .050", 630/580 lift split
Eddy RPM air gap intake, 750HP holley
1-5/8 headers, 3" exhaust dumped
4.10 gear dana 60, 28"x 12.5 ET streets, 4 speed

I'll probably be shifted between 6600-6800rpms, not sure on leave rpm yet (two step)

Carb is currently 74 primary jet, 80 secondary jet, with 35 squirters front and back- I think the car wanted more jet last year with the old combo, but I never got around to it....so what would you guys recommend as a starting point?

Thanks!

Posted By: Cab_Burge

Re: What carburetor jetting as a starting point? - 05/24/12 05:01 AM

Start with what you got, drive it at part throttle and check the plugs, adjust accordling

Once you got it like you want that part then try WOT, look at the plugs and go from there

BTW, is the Holley stock with all parts or modified some? If stock what list number including the dash # is it? I can look it up and post the stock jetting for you

If stock I like to start with the stock jetting, put the power valve in it that it needs to idle in gear and go from there, adjust as needed

Posted By: 383man

Re: What carburetor jetting as a starting point? - 05/24/12 06:17 AM

I agree that I would start at what you have in it now as that may not be to far off for your combo. Then as Cab stated you can work from there if needed. I take it this is in that very fine super clean Scamp you have ? I really like your Scamp as it is one fine looking car. Good luck and keep us posted on the progress.

Ron

Posted By: MR_P_BODY

Re: What carburetor jetting as a starting point? - 05/24/12 12:18 PM

Go to the Holley web site and see what the stock settings
are and start there or 2 jet sizes up on all 4

Posted By: radar

Re: What carburetor jetting as a starting point? - 05/24/12 12:22 PM

I think stock on a 750dp is 72/80 6.5pv

Posted By: MR_P_BODY

Re: What carburetor jetting as a starting point? - 05/24/12 01:18 PM

Quote:

I think stock on a 750dp is 72/80 6.5pv

He needs to look up his carb number... they did vary

Posted By: Cab_Burge

Re: What carburetor jetting as a starting point? - 05/24/12 08:07 PM

Quote:

Quote:

I think stock on a 750dp is 72/80 6.5pv

He needs to look up his carb number... they did vary

The dash number makes a difference on the jetting

Posted By: mshred

Re: What carburetor jetting as a starting point? - 05/25/12 04:26 AM

Hey all, thanks for the responses!

First off, I will have to look up the number on the carb...If I remember correctly stock jetting was either 72/80 as mentioned, or 75/80, with a 6.5 pv and I think 28 squirters. Either way I will look it up tomorrow.

I could definitely start where I am and jet up from there once I get to the track, but I figured if I could get a little closer before firing it up I would. The carb is absolutely stock, other than changing from pink pump cams to a blue one

And yes, this is the new 365" that is going in the scamp....Fire up is only a few days away now, not much left to do to finish it up.

Thanks for the help so far guys

Posted By: mshred

Re: What carburetor jetting as a starting point? - 06/01/12 04:17 AM

Hey guys,

so it has been a while since I last posted in this thread as I was so busy with other stuff on the car that I kept forgetting about this...I finally got around to it today though, and im ready to fire the car up.

The list # is 82751 and then underneath that there was another number 0840

Not sure where I can look these up??? Hopefully this will help with the starting point suggestions for jetting

Posted By: RobX4406

Re: What carburetor jetting as a starting point? - 06/01/12 07:44 AM

75 p
80 s

http://static.summitracing.com/global/images/instructions/hly-199r10319-1.pdf

Posted By: Cab_Burge

Re: What carburetor jetting as a starting point? - 06/01/12 07:45 AM

I looked at Holley tech archives and couldn't find that carb. # there

Sorry

Posted By: Mr.Yuck

Re: What carburetor jetting as a starting point? - 06/01/12 12:46 PM

might like a little more jet but that's a good starting point. One easy way to find out...

Posted By: Triple Threat

Re: What carburetor jetting as a starting point? - 06/01/12 05:51 PM

I'd go up a couple just to be safe, but you probably aren't that far off.

Posted By: Paul_Fancsali

Re: What carburetor jetting as a starting point? - 06/01/12 06:27 PM

Small block Mopars don't need exceptional jet changes with a Holley esp DBL pumper . Keep in mind that carb is rich already. Stay with what you have and jet at the track after plug pull etc I would start with 70-71 frt and 76-77 rears and make sure your powwer valve is correct that makes a big difference. The squiters are little big in my estimation I would try 31-32s. Again use what the engine /carb want.

Posted By: mshred

Re: What carburetor jetting as a starting point? - 06/01/12 09:17 PM

Quote:

75 p
80 s

http://static.summitracing.com/global/images/instructions/hly-199r10319-1.pdf

LOL thanks Rob, your the man!

I thought that was the stock jetting, turns out I was right...Now, that being said, what does everyone think? Just start there, or jet up from now? Like I said before, im pretty sure last years combo wanted more jet, but I never got around to actually trying it with a busted dual feed line at the track.

As for squirters, 35's were the only size that killed the huge hesitation I had before with the stock squirters on tip in throttle

Posted By: Brian Hafliger

Re: What carburetor jetting as a starting point? - 06/01/12 09:40 PM

Are you running a 1" open spacer under the carb?

Posted By: mshred

Re: What carburetor jetting as a starting point? - 06/01/12 09:46 PM

well I bought 1" that I bolted on yesterday, but the throttle cable angle is way off with it, so im ordering a new throttle cable bracket...For this week it won't have it, but once I get the new bracket im putting the 1" back in plus the cheater plate, so i'd like to jet it now for what it should be if I can avoid having to drain the fuel in a week just to jet up

Posted By: RobX4406

Re: What carburetor jetting as a starting point? - 06/01/12 09:52 PM

Open spacer and a juice plate. Step up the jetting 2 on both sides to start, 77/82

I'd put the juice plate on first then your spacer.