Currently 78 L48 with failing Q Jet, Eldebrock 2101 Performer intake and Headman Shorty Headers ( OBX Headers and Side Pipes will be installed).
Done alot of reading on carbs and need some advise as I am used to juel injection.
I want to replace the Q Jet with a Holley for ease of tuning. Can someone who has already made this swap help me with the parts list required so I have everything needed. I will need electric choke.
Which Holley (650cfm)? Any vaccum fittings, throttle linkage brackets, kick down cable bracket and A/C Idle Solenoid bracket needed? Fuel line modifications and is a fuel pressure gauge necessary? Pics to show off your work would be appreciated.

 

Partial answer/opinion. I rebuilt my '74 stock 350 with a 285 hydraulic roller cam/lifter setup and Dart aluminum heads. Replaced an old Edelbrock 750 cfm Q jet with a Holley 670 Street Avenger with electric choke on a 2101 manifold. It dyno'd 3 hP less than the 750,but is plenty for what I do The Street Avenger has a vacuum advance for smoother power application. The carb came with the necessary dual feed fuel lines.

The throttle linkage still needs a bracket to fix it to the block or manifold so it will operate properly. Mine is temporarily held with Mechanics wire. I will keep an eye on this thread to see if anyone has a good suggestion. I have seen several at Summit.

Hope it helps,

Ray

Ray

 

Thanks Ray do you have AC?

 

Factory AC.

 

Did you have issues with the AC ldle solenoid mounting to the carb or is it necessary to replace with one made for a that carb?

 

OK I found out , looking online they are available for that carb

 

Hi Nivensid, i'm just now setting up a new carb on a new engine I had built. The Carb I'm installing is a Quickfuel 650cfm. It is just about a clone to a Holley 4150 or 4160 double pumper. I've had a few issues to solve along the way. My new intake is an Edelbrock Performer. Oh yeh, my previous carb was a Q-Jet.
-The rear bowl of the new carb covers the vacuum boss on the Edelbrock intake. The Carb literature says to take the accessory vacuum off the small front port of the carb. If the manufacturer says it will work, I guess it might, but I'm **** about some things and I wanted to use the larger vacuum port on the manifold not the base of the carb. I have to run the Transmission Vacuum Modulator as well as the Accessory Vac so I wanted the larger port. My TorboHydramatic 400 trans does not use a kick-down cable. So I eventually found a very shallow brass plug to thread into the manifold boss, it gives me just enough room under the rear carb bowl to put a 1/4 nipple into it for a 1/4" vacuum hose. I Tee off of that for accessories and Transmission.
The carb came with a hard dual fuel line that comes out to the front of the block to connect with the fuel line coming up from the fuel pump.
But the union where the two hard lines come together sits directly over top of the boss for the heater hose to connect to the intake manifold.
So again after some searching, I found a brass hose pipe fitting that is a 90 degree bend so that the heater hose now comes to it by a gentle sweep around the front of the engine instead of over the valve cover.
The new carb has the PCV port at the back of the carb, and the Q-Jet was at the front. I didn't want to run a black hose over the valve cover and to the back of the engine, so I fabricated a 3/8" copper tube
that is formed to lay very close and low to the inside of the valve cover to run to the back of the engine then a bit of hose to connect it to the carb. But i had to change my PCV valve because the original one was straight up, and to make my new copper pipe lay down low a had to get a 90* PCV valve.
My Q-Jet throttle cable bracket doesn't fit with the new carb. It took 2 tries with Summit before I had one that looks like it is going to work. But I also had to Modify it alittle to make it work. the 1st one (I don't have the number) was very large and bolted to the studs on the left side of the carb and stuck out in the front and the back. It interfered with the PCV line. The second one i got was part number CSI-610c at Summit. This is the one I am going to use, But I had to modify it. It was designed to have the throttle return spring attach at the rear of the bracket. I bought a kit of assorted springs and none of them would fit because the stretch needed was just too far. So I filed a notch in the bracket at the front and attached a shorter spring to the top of the linkage arm instead of the bottom of the linkage arm. It seems to work pretty good.
Another flaw in the design of this bracket is the way the throttle cable attached to it. My throttle cable is the original one to the car I'm pretty sure because I have owned and driven this car for over 30 years.
So my cable is just a round smooth ended cable about 1/4" round. It has no threaded end and it does not snap into a plastic fitting like some GM cables do. This CSR bracket that I'm using does have a hole and set screw for such a cable, but I am told that if you tighten the set screw to much you could bind your cable. And if you don't tighten it enough, the cable will come loose. So I made a clasp that fits around the end of the cable and is held in place by cap bolt in place of the set screw. This is holding the cable very well.
There is another bracket made by Lokar that appears to work very well but you have to change the throttle cable too. I didn't want to do that because if I ever want to go back to a Q-Jet I don't want to have to get under the dash to change the cable. the numbers are: SRK-4000 & TC-1000u.
I think the only pic I have of the whole deal is one of the vacuum fitting under the rear carb bowl. I will try to dig it up. You would think that since Holley and Edelbrock have been around forever that they would have solved these issues for GM Q-Jet/Holley conversions.

 

nivensid,

To do this conversion will cost you hundreds of dollars and a lot of fabricating and fiddling, all very well if you MUST have a Holley carb. However, I suggest that you at least send an email to Lars Grimsrud in Denver CO and seek his help. Unless your Qjet is irrepairably damaged, Lars can rebuild it to better than new and every connection will bolt right up.

Do a search if you must, but give Lars a call. I think his address is V8fastcars.com, but I stand to be corrected. I believe that he has even built carbs for some of us antipodeans, so good is his well earned reputation.

Regards from Down Under.

aussiejohn

 

Another note: The reason I went to a Holley was the Dart SHP heads didn't have the proper openings to support the old choke. I couldn't run the engine without babying it in place for 15 minutes to get the temperature up. I couldn't find an electric choke conversion for a Q Jet. Thus the change to a Holley.

Ray

 

For Corvettes, 75 is the first year with an integral choke - and these can be swapped for electric.

I've *heard of* electric chokes for divorced choke carburetors, but have never seen one...

 

I rebuilt my matching numbers 350, 1971. used WEIAND street warrior and Edelbrock thunder 750. 380 hp and 400# tq. on the dyno nice.

 

hello niven

Just went through this myself.
Replaced intake with a performer eps and a holley ultra street avenger.

Bought a lot of random parts (fuel lines an fittings, linkage adapters, etc...)

My thread is on the bottom of the first page here if youd like to see my work. Called it chrome is bad round 1.....

Be happy to round up all the part numbers I put in it if youd like if of course you like what I did!

Good luck either way

 

PM sent....

 

Thanks oldchev.... looks like you have it figured out after a lot of work. Good job and now its my turn.

 

PM recieved. Ill get that together shortly



Just sent. Need anything else, let me know--