formula31

I have 2 stock 330 quadrajets that I would like to set up for my 454's on steroids so I can run them against my Holleys for power and fuel comparions. I know next to nothing about quadrajets. I do have manuals. Can someone give me some ideas on what to change and good starting points? Engines are M4 454's .030 over, 8.8-1 compression. flat tappet cam-224, 232, .527, .553 at 114 lobe sep, intake timed at 106, mildly ported large oval port heads with 2.19, 1.88 valves, single plane Torker 2 manifold, gil exhaust. Should make 425+ hp. Plugs are very difficult to get at. What do I need to buy and change? Thanks.

Scott

"What do I need to buy and change?"

Oh man did you set yourself up with that question

Dennis Moore

Just install it with an adapter, squarebore to spreadbore. Wire open the choke and make sure the fuel pressure is 7 1/2 to 8 psi (no more). I wouldn't change a thing as far as jetting goes.

The Quadrajets horsepower limitation comes at about 500 horsepower (with a limited amount of fuel flow) through the single needle and seat and single float bowl.

Should be interesting, I have done this before and haven't seen any improvement with the Holleys.

Sincerely
Dennis Moore

formula31

Oh, I have done this with an engine identical to these and there was a 400 rpm wot difference betwen the quad and the holley. Thats why I ended up going to the holleys years ago. My manifolds will handle either carb design. Wierd, the quad pooped out at 4600 and the holley would run to 5000 and more, no other changes. However the fuel mileage suffered considerably, obviously.

H2Xmark

what holley an 850? i think Dennis is on the money unless you are using a bigger Holley carb [650 are bigger] and you can make the power upstairs in the RPM band pushing more than 500 HP
Mark

formula31

I use 780 cfm 3310's heavily modified. Never had any luck with 850's on this size engine, hard to start and sucked a ton of gas and didnt go any faster and accellerated like crap. Took a few years to get the vacuum secondary and all the ports right but I like these now for WOT.

goob

I built the basically the motors you are talking about. I used the 850's and never had a problem. 3000to about 3300 still in primary and never saw a lean condition. Just have to take your time dialing them in. Never really liked a vac secondary on the boat.
Mike

goob

I also built a motor for a guy the same way and he used a Quadrajet because he didn't want to spend money for holley. It seemed to flatten out about 4500 or so. Ran great but could use a little more carb I thought. His is hooked to an alpha. I told him to take it easy on the drive and he does now after exploding four of them. LOL
Mike

jafo

Tom-
I went through the Q-Jet tuning process on my engines in the Formula. If your'e short 400 rpm at WOT compared to your Holleys, you can make this up easily with a secondary metering rod change. These are readily available from Edelbrock and can be purchased from P.A.W., Summit, or any other speed shop.
The secondary metering orifices are of a fixed diameter and can't be changed on the Q-Jet, so you simply decrease the size of the metering rod itself.
There are identifying letters stamped on the rods, and once you get into the catalog (or one of Dennis' books) you can figure out which ones you should have in your 'kit' for your sea-trial. The rods are cheap, and can actually be changed with the engine running (I didn't though- I could just see that little hanger screw going down into the carb....). The process takes only minutes for both engines, and you will be pleasantly surprised at the results.
Primary jetting and metering should need nothing.
I gained over 450 RPM by upping the sec. rod size, one size at a time until I saw no more gain, then I went back one size.
Jim

HOTROD2

If your looking for Holley carb anserws go to Prosystems.cc and look at his marine carbs. we have used them and dyno'd with them. the idle and mid range is really good, and see tourque and hp on every one we have tried. (15 to 48 hp over holley hp) I like the idle return while docking, the engines don't stall while shifting from rev. to forward like they use to.. If you call Patrick and ask what he does he can explain but he talks over my head...