has anyone had any problems with a holley marine carb.any thoughts on quadrajet compared to holley.i have a 502 mag.
thanks for your input

From what I have been told the Q-Jets give you a more efficient cruise then the Holly. The Q-jets are great carbs but are very tweeky when it comes to what motor they go on.

Jon

No problems at all with Holleys. Very easy to make adjustments and a lot of books out there to help you fine tune them.

I did a lot of work on my 330's and got the q-jets to perform great with just a little tweaking. If your not going over 500 hp or 5500 rpm's I would stick with the q-jet. It flows 750 cfm which is plenty unless you go above the 500 hp or 5500 rpm mark.

Bo

I vote the holleys. I have spent a lot of money and time on Quads on both autos and boats and never got them to develop the top end the Holleys would. I do believe there are good ones and bad ones of both.

There are many things about the q-jets that I like. However, I have been messing around with one for two years, and I still don't think I'm getting the top end out of this engine that I should. I would like someone to tell me how they are "tweaking" these q-jets. I've just about given up and ready to try something else. Maybe go to a single plane manifold also.

Whiteknuckle,

What have you done to the carbs so far ?

Bo

Bo,
I have mostly played around with the secondary metering rods. We also have a different accelerator pump in for a larger squirt. As a matter of fact, my carb guy, "Q-Jet Specialist" is going to fatten up the primarys some. Also, just had a problem with the fuel leaking out of the bowl when the boat sits overnight.

This engine started out as a Mark IV, 330 HP. After some changes, (version #1) we put in on a dyno and it pulled 386 HP. That was with the stock Q-Jet. We then took a tricked out 830CFM Holley set up for a Busch Grand National Engine and put it on the engine. HP went to 422. Now if you do the math the 750 CFM Q-jet should be enough carb, but in reality there is more HP to be had. Would that Holley work on the boat in the real world? Most likely not, it was made for straight up racing and not for a boat that needs to idle for long periods and get up on plane. But I'm sure you see my point.

Whiteknuckle,

Pretty interesting results with the Holley. I am running a Q-jet on mine as well. Right now I have it set up with the 502 primary & secondary jets and metering rods. It runs a little rich for this engine. I have been considering switching back to the 330 primary jets and rods. I don't think my engine is making the kind of power it is capable of either. I might try out a friend's 800 CFM Holley that he runs on his 502, but once again I am afraid that it might be a little rich for this application. Let us know what you end up with if you switch over.