rothlane'68

I have had a holley carb and adapter plate on my 455 forever but I’d like to put a quadrajet on and wanted some input.

I know relatively little about Q-Jets so any info is good info, but a few specific questions:

Is this a bad idea (my holley works, should I just stick with it)?
If properly rebuilt and spec'd, would a q-jet from a toronado/4 door/small block work? What would need to be swapped to bring it to 442 specs?
Would I be better off opening my wallet really wide and buying one already rebuilt from someone I trust or buying a decent looking core and rebuilding?
Im pretty comfortable doing a rebuild myself, I have rebuilt holleys with great results in the past, but Ive read that Q-Jets are a bit more complicated.

This is for a 1968 442. TH-400. 71 455 with C heads and J intake. Power Steering and Brakes, AC.

Allan R

IMO, if your car is performing fine the way it is? Leave well enough alone. Q-Jets are good carbs, but you have a 71 455 in a 68 442 so it's not a numbers matching car. If you're going to buy a Q-Jet, why not a rebuilt one for a 71 455? (7041251 I believe)

tru-blue 442

Allan, good to see you back. The only thing about 7041251 is the choke won't work
with the J intake. Probably the original intake from his 68 400. They have the shallow
pocket for the divorced choke set-up.

Allan R

Ah, good point. I'm rusty, I should have read that more carefully. Maybe that's why there's a holley on it right now. Likely with an electric choke?



Divorced choke pocket obvious on the red intake.

shiftbyear

the 77-80 non computer carbs are great, good castings, adjustable part throttle and electric choke. The downside is they are very lean and require some work on a 455. Cliff Ruggles book has good tips for the do it yourselfer. Good luck.

BangScreech4-4-2

The points made by Allan and Adam are excellent. Do you have a specific reason to go back to the Q-Jet? It's a fine carburetor, but probably no better than your Holley (depending on which one you have). I doubt there will be any dramatic improvement that would make the whole enterprise worth the hassle. Unless you're really bored or something.

allyolds68

First of all, I agree with what everyone else is saying about "if it ain't broke don't fix it"

That being said, switching a carb out is about the easiest thing you can do. I have a 72 350 7042250 on my 70 455 with E heads. It took some tweaking to get it right. Secondary hanger and rods had to be changed out for thinner ones and the secondary door tension had to be increased. It still runs a little lean but I just don't beat the crap out of it. I have a 69 7029253 (69 400 4 speed carb) that I have sitting on the shelf that I need to get around to either rebuilding or having rebuilt. They are relatively simple to rebuild but if the throttle shafts are worn they need to be drilled out and bushed to get them to seal. If you have air leaks on a Q-Jet it makes them difficult to tune. There are a bunch of guys out there that are Q-jet rebuilding experts. I like Cliff Ruggles but Sparky and Dean Oliver have great reputations too.

I think there are little things that make starting with a BBO carb better than a SBO carb. As far as the choke goes, just put an electric choke on it.

RetroRanger

Agree w all if it runs good leave it.

That said I had an ebrock carb on my 455 it ran fine started ok didn't hesitate etc. I switched to a remanned Qjet from rockauto, woke the car up I added e choke to the qjet. When I got the qjet I went thru it following the CSM I think that made a big difference as there were several minor adjustments like the secondary air valve that were off.

Olds64

If your Holley runs well then don't bother, especially since you aren't concerned with keeping the car numbers matching.

The bad thing about building a Q-jet is that you can't buy a kit from Summit or Jegs with a supply of various jets, secondary hangers and metering rods. If you have these parts then go for it. If not, consider sending a Q-jet to be professionally rebuilt or leave well enough alone and stick with your Holley.

Quadrajet Power

Hard to go away from something that works, but Quadrajets are fun too. And can deliver good fuel economy and power when needed as well as any carb can.

You can find any good Olds core and set it up correctly for your engine. Like they said though, a mid to late 70's was a great design and you can convert to electric choke.

We have all the kits or parts you would need for the changes. We custom assemble for each application and have complete kits with jets, rods, idle tubes and much more.

rothlane'68

That is correct, I have an old holley 600 CFM 80457 with electric choke and vacuum secondaries.

It has worked, even worked well, but I wouldn't say its been trouble free! Used to have a bad stumble off idle and run very rich, but a rebuild and adjustment fixed these issues (so far anyway).

Several reasons for the change:
-Fuel economy, I've read the small primaries really do help
-Large secondaries: looking at the spread bore manifold I couldn't help feeling like the whole system would work better with a spread bore carb.
-originality. Again, you are all correct: The car is not numbers matching, but at least I could do away with this rubber fuel line and in line filter
-I feel like I need a bit more CFM anyway (but probably not more than 700) so if I am going to replace the carb I might as well go this route.

But this is down the list of projects a little ways either way.

So better to go for a late 70's carb for the adjustability and newer casting or should I shoot for something closer to the late 60's if I can find it?

rothlane'68

I should add that I first got the bug for this talking to Jim from Classic Olds in NC. He said he swore by Q-Jets and wouldn't run anything else, even on his race cars.
At the time he had freshly rebuilt 69 for sale for almost $600.00. That was too rich for my blood then, but as I look into the cost of a core/rebuild it seems more reasonable.

and thanks Quadrate Power, its good to know you're out there as a resource!

Quadrajet Power

For performance, I would suggest the 76-80 range as mentioned by someone above. These provide the smaller float and better float placement than the earlier Oldsmobile Quadrajets. You can also modify the air horn for access to the part throttle adjustment for fine tuning ability. Most of these are 800 cfm capable as well, so it can deliver the fuel economy and performance when you need it.