I have a Holley 4160 750 single pump, dual feed, elec choke, vac sec. carb on my engine. Which is a 327, 9:1, RPM intake, Sportman II, Comp XE268H and 1 5/8" headers. The carb is dumping way to much fuel right out of the box. I was wondering if anyone could tell me the right way to jet this carb to get better performance. I am running at about 30 feet above sea level and it stays fairly warm if that helps. Any help would be great. thanks!

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Son's 67-327, Dad's twistin' wrenches again after 25 yrs.

Can you be more specific on the condition? First, I think a 750 is too big. But are you getting sooty plugs or what? Do you see gas pouring down the carb throat? They're very tunable. I like them. I have a 700 DP on my 355 that works well. Tell us more.

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Rick Dorion
69 RS Conv,355,M20,4.10's

If that's a Holley list O-3310 they come with #72 jets in the front and a metering plate in the back. Originally calibrated for the 396 big block I believe. Yes the carb is probably a little big, but with the vac secondaries, you can still make it work.

The first thing I did with my 750cfm 4160 (list O-3310) is convert it to a 4150 using a Holley kit that replaces the metering block on the secondaries with a block with jets like the primary. #76 jets in the secondary would be equivalent to the stock metering plate when you do the switch.

Then I would start reducing jet sizes 2 sizes at a time until the plugs are the right color. Alternate front to back (starting in the front) keeping the secondary side 6 - 8 sizes fatter than the front.

One thing I find helpful when trying to lean out a rich condition: buy a couple fresh plugs and install one when you switch jets. A fresh plug is easier to read than one that is already black, sooty or gummed up.

If I had to guess, I would say that if you have a fairly mild cam in your 327 you'll wind up somewhere around #68 in the front and #74 in the back.

Temperature will affect your optimum jet size as well. I think that every 20 degree increase in temp reduces optimum jet by 1 size. for example: if I find that #70 jets work best at 70 degrees and I'm racing on a day that it's 90 out, then I should switch to a #69 jet.

Hope this helps.

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68 Camaro, 383 small block with TH350 trans. 12.4's and never trailered.

The advice given just above mine is very good and knowledgeable. His jet settings should get you very close.

Also, check fuel pressure. These carbs can't handle anything above 7psi. Quadrajets can handle up to 9psi so sometimes the stock or replacement fuel pumps put out higher psi's than the holley can handle.

While your tuning the carb, double check the float level. The level is set right when you have to slightly nudge the vehicle to get some fuel drops to come out of the sight holes (brass screws on side of the bowls).

If this is your first holley I strongly recommend to buy "How to Tune A Holley..." by HP Books. They are found at large bookstores and many internet sites. Worth way more than the $20 it costs!

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8.5:1 11 second 454

Ok, I bought a Holley quick change spring kit, a set of springs, and a set of 68 jets. If I tune the springs right, can I get away with the stock size in the secondaries? It has a stock style cam driven pump, so I doubt its putting out more than a constant 6-7 psi. Thanks for the help guys, any other info would be great too.

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Son's 67-327, Dad's twistin' wrenches again after 25 yrs.

Give the 68s a try that is what most small blocks like with a 750. Which 750 do you have? I can find the jet plate sizes if I have the number. Try the sec as they are you are over carbed a bit so I wouldn't change the sec spring you really don't need to open the carb all the way.

Give 68's a try Then you may have to bore out the throat of the carb if that doesn't help..

oger - List # is 0-80508S. Any info on the plates would be great. Thanks

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67-327, 700r4 trans, 9:1 Comp XE268 Cam, Perf. RPM Intake

I tried that exact carb. on my very similar 327 and I couldn't get it to work right. I bolted on an Edelbrock 600 cfm and it works great right out of the box !

Another thing to consider is the power valve. I have a 750 holley on my 350 and I know it's a little over-carbed but my biggest problem was that I had it jetted too lean to compensate for rich running, then when the power valve openned (at higher throttle) it was too rich again. I went to a low vaccuum rated p.v.(something like a 4.5 or 3.5) and went back up on my jets a size and it runs much better now. Something to keep in mind.

I will get into the books tomorrow and see what I come up with.

I agree with Eric, get the jet conversion kit for the secondary side. Otherwise, you will not be able to tune the carb at wide open throttle (i.e., with the secondaries open).

I believe the metering plate on a list O-3310 carb is equivalent to a #76 jet. When I ordered and got my kit, the new metering block had #76's already installed in it.

IMO you might get away with leaving the secondary plate in with number 68's in front, but any smaller than a #68 and you could create a distribution problem (too rich in back cylinders and too lean in the front cylinders).

Just to test don't worry about it, but if you want to do it right then install the kit so you can change secondary jets. You'd probably get better performance with a #72 or #74 in the back if you use a #68 in the front anyway.

Don't mess with the accelerator pump cams or secondary springs until you get the main jets figured out. Then play with the cams and shooters if you need to fix an off-the-line stumble. I doubt you will ever need to mess with the secondary springs.

[This message has been edited by Eric68 (edited 08-27-2001).]

You have a 134-21 jet plate. The main jet equivalent is 75 which is close to what a SB would use without a power valve. The only problem is the idle restriction it is huge for a SB. .040. This carb is designed for a BB and it looks like most of the idle fuel is coming through the non adjustable sec side. Give it a try if the idle is not right you can change the jet plate.