Changing to Holley
 

I'm switching out an old Quadrajet carb for a new Holley. I have a question about the throttle linkage. How do you link up the new throttle linkage to the Holley. It doesn't look like the old bracket that was used to hold the Mercathode and the throttle linkage will work. Is there a kit you can get to make the conversion?
The motor is a 502 and the carb was from a 454.
Thx,
Eric

Re: Changing to Holley
 

Marine aftermarket suppliers offer brackets that will adapt the merc linkage to a Holley carb. One style bolts between the carb and manifold and another bolts onto the top of the base plate. Give Fred a call at Trick Marine.

Re: Changing to Holley
 

Why? You could rebuild the Q jet. The Holley wont make any difference in performance.
Also The Q jet is a spreadbore, the Holley is a probably squarebore, are you planning on changing intake manifolds or using an adapter plate?
Gary

Re: Changing to Holley
 

I agree, if you have a spread bore manifold, have the Q-jet rebuillt, and get it set up correctly for your engine. The q-jet will idle well and milage is great. Just to change to a Holley for the sake of changing will get you nothing. You can purchase the bracket for your throttle through Summitt or Jegs or any race shop.

Re: Changing to Holley
 

Thanks for the responses. The reason I'm changing is the carb I had on there was too small (came off a 454). I think it's a 600cfm AFB built by Weber. It was running my motor lean. I was looking at changing it out for a 750 qjet, but figured I'd give Holley a try. I'm putting on an 850 holley worked over by Nickerson.
I do have a spreadbore manifold, with a one inch squarebore spacer. All cylinders seem to get equal mixtures with that setup.

Re: Changing to Holley
 

Cast iron intake ? With squarebore adapter ?
http://www.cfm-tech.com/images/marin...ladapter-s.jpg

Get rid of it.

Re: Changing to Holley
 

That was going to be my next upgrade, along with removing the Mercathode unit. What's a good replacement for the manifold and the Mercathode?

Re: Changing to Holley
 

You will need both the Merc/Holley Linkage Adapter 710-717-7 and a Holley 4150 Throttle Bracket

Re: Changing to Holley
 

I don't want to keep sounding negative, but an 850 CFM is a little large for your engine. You may not like throttle response. A 750 or 800 at the largest would work a lot better.

Re: Changing to Holley
 

I'm pretty sure all the Q jets were 750's. Just different metering rods.

Re: Changing to Holley
 

I agree :D

Re: Changing to Holley
 

Yep...that is the only difference if i remember correctly

Re: Changing to Holley
 

Like 40 bucks for a edelbrock tuning kit for that weber will help you fatten it up and get those plugs a nice shade of brown again. Edelbrock are the same as the weber. Went through this in the summer with mine. Lots of info on them on the site. Why spend all that money on new carbs and have to tune them too cause they probably won't be dead on out of the box. The webers are much easier to tune , change of the metering rods takes like 5 mins and no removal of the carbs.

Re: Changing to Holley
 

Yep...that is the only difference if i remember correctly

Re: Changing to Holley
 

Before you make the guy not use this Holley, there are some unknowns here:

1) He stated this 850 was done by Nickersons for, and installed on, a 454. Whaqt kind of mods and what build up for this 454 ?

2) He stated he has a 502 but not which HP one, nor if any mods have been done to it.

1st Baja - give us more info and we can help, or better yet, get all info on the 454 (incl owners name so Nickerson can look it up) and all info on your 502 and call Nickersons to see what changes may need to be done.

2nd guys - a high performance dual plane intake can use a bigger cfm carb than a single plane. Reason - more signal. Just like why many mild (350-400hp) SBC's with dual plane's prefer 750's.

Re: Changing to Holley
 

Originally the boat came with a 454. The guy swapped out the 454 with a 502 crate motor. I don't know if it's a Mercruiser 502 or a GM crate motor (not sure how to tell). I was told its a Gen VI motor.

When the guy swapped motors, he ended up using the original carb. I sent that out to the carb shop to see if they could do anything with it. They said it was an AFB carb built by weber (625cfm). Nothing they could do with it to increase cfm.

So I gave Nickerson a call about it and they set me up with this Holley 850. Looks like a nice unit. They said I can bolt it right up to the mercruiser manifold and I won't have any problems.

So I'm going to install it this weekend and see what happens.

Re: Changing to Holley
 

The intake manifold opening (where the carb mounts to) is similar to the Edelbrock performer opening.

Re: Changing to Holley
 

I have a 750 cfm Qjet carb off a 454 Mag. Worked great. I would rebuild it before install. $100
PM me

Re: Changing to Holley
 

So I got the Nickerson Holley 850 bolted up to the 502 over the weekend and tested it out. What a difference. Great midrange power over what I had plus I got the boat up to 61 mph GPS with 1,000 lbs of people and tools along with 90 gallons of fuel. Beat my last best of 59 mph GPS. Now I need to work on the prop a little bit. I have an old Mirage that is pretty beat up.

Re: Changing to Holley
 

Good move going to Nickerson I did the same thing and got GREAT results. Forget the Quadro-junks and AFB's Nickerson makes POWER.