mcrsr

i am surprised that i had no gain in power switching from qjets to holley 750 vac secondary carbs-what is up w/ this???? engines started life as 330's, now they have 049 heads(large oval port), performer intakes, comp cams xm 262's, harland sharp roller rockers,stainless marine exhaust-any suggestions????

1BIGJIM

iTrader: (1)

I did the exact same with little results. Is that a Pachanga?
Did you remove the mufflers?
When I switched to the large oval heads I did not install larger valves. Saw little if any gain. So bumped it up with 110cc Edelbrocks with the large valves and gained about 200 RPM.

Whiteknuckle

mcrsr,
Why would you see a difference? You most likely changed from one 750 CFM carb to another! The Q-jet is a great carb if set up correctly. I don't think you will see a change unless you increase your engine displacement. In fact, I bet the q-jet has better idleing and low end response. Just because it is a Holley does not make in automatically better. Just my $.02

Liberator21

I have to agree.

SB

iTrader: (1)

What they said is true. However, was the quadrajet tune 100% for this motor ? Is the Holley tune correct for this motor?

The performer is low rpm stuff and sized for peanut port heads. You may want to consider an RPM that is properly sized for large oval and designed for more grunt upstairs.

The cam used probably won't want to make any power past high 4's or 5k, largely dependant on what cyl head work was done / not done.

Lastly, do you have a flame arrestor that's properly sized ? Is your prop letting you run at max hp rpm ?

MOP

Qjets are a damn fine carb in a boat, I will be ripping a 750 Holley off my stroker and replacing it with a Qjet.

Phil

cuda

Damn, I was about to make this exact same swap. I'm also swapping the pancake intake with a Performer. Is that what you used?

Whiteknuckle

Cuda,
I used the exact combo, a 750 Q-jet on a Edelbrock Performer for the small ovals a few years ago. It worked great. Then I move the carb onto an Weiand accelerator to go on a set of reworked 049 heads. I have again stepped the engine up another notch and had to go to a larger carb, an 800 Holley, but there is absolutly nothing wrong with the Q-jets.

mcrsr

it is on a 32 pachanga w/ 2 454's, i rebuilt the engines using speed pro pistons and moly rings, bored .030, anyway, cam is rated to 5000, i spin them at 4850, i am using the regular performer intake that i port matched to the heads, so i figured this would be a good intake for this application, the qjet was a stock 330 hp piece, i never rejetted it so i was concerned that it would be too lean, but apparently not- it is way more difficult to get tuning parts for the qjet then the holley-i am just surprised-also the boat has no mufflers-it still exits in the stock spot and i use the forward facing collector still

1BIGJIM

iTrader: (1)

I thought the Performer has large oval ports. I went with a B.G. Sea Demon and love it. Noticed maybe 50 rpm change.