I've read opinions on who makes a good carb for a mild engine many times, but I'd like to get some feedback from the Olds crowd. I'm referring to my Olds 350, which will get mostly bolt ons - aluminum intake, roller tip rockers, headers, things like that. MAYBE a mild hyd. roller cam. Should I consider a rebuilt Q-jet (some love 'em, some hate 'em)? Edelbrock? Holley 670 Street Avenger? I'm not exactly what you'd call a carb expert. Right now, it's got what appears to be the original Q-jet - 7029250 is the number on it.
Thanks in advance!

- GoldOlds

 

I think you would do better to keep you Q-jet. If it is working fine now, no need to do anything to it, if not, you are still better off having it re-built. Why roller tipped rockers? I don't see where you would need them.

 

I was always under the impression roller tip rockers are a good way to "free up" a few hp. As for the carb; I'm not against hanging on to the Q-jet that's on there now, although all the carbs I've ever used had electric chokes. This one seems to be vaccum operated (like I said before, I don't know carbs very well) with a little lever that goes down into the intake manifold. Exactly what it does down there is beyond me. Do Edelbrock intakes make provisions for this? Anyway, the only problem my Q-jet has now is that it bogs to the point where the engine almost stalls when I apply more than about quarter throttle from a stop. The engine idles a bit high too, but even a carb dummy like me can fiddle with that.

- GoldOlds

 

If you want to part with the Q-jet, let me know, I am looking for one. Also looking for the answer to your original question, as my motor has no carb on it, so I need one no matter what. I am not having any luck finding them on ebay (had a couple that I lost in the last few seconds), and I am no where near a good auto-wrecker. I need a carb and a rad so I can see if this thing will fire for me.

 

Hi
Dont mean to hijack thread, but this is for Skinny. I have a remanufactured carb 4bbl off of my 350 , 71 cutlass that I can part with. I took it off and put my original back on. I tend to keep everything for a long time, but if you want it let me know. It might work fine as is but you may want to rebuild it. It has been sitting in a box for a while so I dont know how good it is. I will sell it to you cheap, but I dont know how much shipping to Canada would be.
Mike

 

Personally I like Edelbrock. I like the company and the history of the company. I've heard many good things about Edelbrock carbs. I heard that the Holley double pumper is a pain to get running right, but once it does, it's good too.

I had a Q-Jet on the 307, but I'm dumping it for the Edelbrock because the Q-Jet is CPU controled and the '68 motor isn't CPU controled.

Q-jet is a great carb, but a royal pain in the butt to get running right. And it's very touchy and not too easy to rebulid

If you go aftermarket, go electric choke

 

Another thought is a Holly, their good, cheap, and universal, just as Edelbrock.

Electric choke is a good idea.

 

Well, I suppose you would experience less friction with roller tip rockers compared to stockers and if you want to use them it's your choice.

The choke you described has a connecting rod that is attached to a bi-metal spring housed in that little box on the manifold. The spring activates the choke plate when cold and as the engine heats up the spring uncoils some causing the choke to back of slowly. With electric chokes a small electric current does the same thing and you don't have to have that rod and the external linkage associated with it.

Your Q-jet is probably bogging because it isn't adjusted correctly or could be it isn't the correct carb for your engine. A previous owner may have put it on and it might not have the correct needles and jets for your engine. Lots of variables there that remain un-answered. My immidiate response to your description is that the accelerator pump may be too large or mis-adjusted. I don't have a lot of experience with Q-jets either but it might be a great carb for you engine and just be needing a good tune-up. Post the numbers off the side, there are some guys here that have references and they could tell you if it is the correct carb for you car. That might be a first step.

 

Thanks, everyone, your input is much appreciated! I'd definitely like to find a "no fuss, no muss" carb, which is why I'm considering a Holley Street Avenger (670 cfm, electric choke). The # on the side of my Q-jet is 7029250, which makes me think it MIGHT be the orginal carb. If I put an aftermarket carb on it, I'll probably hold onto the Rochester.

- GoldOlds

 

Late jump in here, but the roller-tip rockers give you an adjustable valve train. Check the pushrod length, too. I've not known many in the kits to be the "right" ones and pop the extra $ for KoolNuts. Those crimp-style ones in the kits are cr@p.

JMHO

C.J.

 

Roller tips will not show enough power gain to measure on a dyno, or a timeslip. The actual ratios on those rockers are said to be more accurate than OEM. If true, it is still not enough to make a difference in anything but a full on racing engine.

Subject engine was described as "mild" so, unless it uses a solid cam, adjustability is not needed. An exception might be a smaller base circle, on an aftermarket cam, that could cause geometry issues. They would be addressed on a case by case basis.

Norm

 

Thanks for the tip on the rockers (no pun intended)! It looks like you've just saved me some money. Is the "base circle" of a cam the diameter of a lobe minus the section that causes lift? If a specific cam requires an adustable valvetrain (certain Comp cams, even a few hyd. flat tappet ones, have footnotes that say an adjustable valvetrain is needed) is roller tip rockers all I would need to make my valvetrain "adjustable," or would it need roller lifters too? Is it even possible to use roller lifters with a hyd. flat tappet cam?
Thanks again!

- GoldOlds

 

Lots of people are spending money they don't need to.

Except for the terminology, you have it right. The cam lobe is added to the base circle (heel) and it's the part that raises the lifter.

Solid lifters (flat tappet or roller) must have some method of adjustment. The method of choice, for these engines, is adjustable rockers.

Hydraulics (flat and roller) were designed for use in non adjustable applications. If there are any dimension changes that fall outside the design specs of the engine, they must be compensated for. For instance, if the heel diameter of an aftermarket cam is ¼” less, the pushrod would need to be ⅛” longer. In this case, one cold address two "problems" by using restricted pushrods.

Or one could choose to use adjustable rockers, but the valvetrain geometry might be upset, and longer pushrods would have to be used anyway.

Yes and no. Roller tips have nothing to do with adjustment, but since they are part of the adjustable rockers, it doesn't matter much.

In all cases, the cam is ground to use a specific lifter. They cannot be mixed.

Norm

 

I'd definitely consider rebuilding the qjet once you determine that it is the correct one. There is a polish guy in my neighborhood that used to rebuild carbs for fun a few years back. I wonder if he is still doing the hobby. I haven't talked to him in about 4-5 years because last time I saw him was when he rebuilt it haha. I remember him mentioning my edelbrock intake and putting in some needles from an 87 montecarlo ss. Perhaps I can talk him into opening up a pop shop for our forum.

 

I'm definitely considering keeping my Q-jet, since the performance upgrade choice that I make (which ever that will be) will be a mild street-strip application that I believe most Q-jets could handle. My Q-jet's ID numbers indicate that it is the original 1969 carb. The only problem might be the choke; I'll probably opt for the Performer or Performer RPM intake and my Q-jet has the choke inside the intake (is that what's called a "Divorced" choke?). I'm not sure any aluminum intakes can accomodate such a choke. Would it be possible to simply put an electric choke on my Q-jet, or is that a major hassle?

- GoldOlds

 

I'm running a Performer RPM with the original QJet and it also had a divorced choke. Just go to a junk yard and yank the electric choke off a later model QJet. Run an IGN hot wire (from the windshield washer works great).

70Wcars is a QJet builder. PM him and he'll set you up.

C.J.

 

Q jets are great, but as was said, they are a pain in the ****. Frankly I'm gonna keep mine, there are many things you can do for performance. If it's a computer controlled, then you can only mess with the secondaries, but even at that, it's plenty of flow.