I am looking at replacing my 4 barrel carb on my OHC6 and am wondering what all you guys would recommend. Should I stay with a Q-jet or switch to a Holly carb and what size is best for a stock engine. A friend of mine says to go with a Holly because the jets can be changed to any size. I told him I would check here first.
Thanks for any advice. AL

Maybe the one you have can be refurbished? Look at recarbco, or there are probably others. That's where I got my Qjet with a core exchange. Are you having problems with yours?

aftermarket carbs can be adjusted to your engine and the upgrades you've done a lot easier than the quad

If the vacuum of your engine (the driving force behind the calibration of any carburetor) is anywhere close to the stock figure; the ORIGINAL Q-Jet is by far the best bet for this engine. I cannot think of anything that would come close on a street-driven vehicle.

If this engine is race only, then you might consider an aftermarket carburetor. If so, remember that your manifold is set up for a "spread-bore" design. This means that to use the original manifold, you MUST use a spread-bore to replace the original carburetor. The adapters simply do not work, period.

Jon.

I'll second Jon's recommendation for the original Q-jet for your stock engine. Even if you make some changes to the engine, the Q-jet will still be much closer than a generic Holley or Carter.
As far as jets go, you can get a kit for the Q-jet that contains all the parts reasonably needed to tune your carb.

I'll 3rd that!
i mean, ummm,
i think you should definitely get a holley...
and give me the old ohc6 q-jet, fuel line, and linkage. you wont need that stuff anymore anyway, as you will be hand crafting it to fit.

i have a v8 q-jet on my ohc6 right now, tuned to work adequately. still wish i had an OHC6 carb. i had a clifford intake and 390 holley on there for a little while, but never got the fit quite right.

Thanks for all the replies. My car is a street car only.I take it to car shows where poeple are fascinated by the engine I have. The Q-jet that is on is not the original. The guy who sold me the car last september also gave me the spare engine(in pieces now)and two Q-jets. The one looks like the original.I took it into this one shop and after two weeks they told me that they couldn't get parts for it.The Q-jet that is on there now sucks gas with 0 performance. From a dead stop it sputters before going up slowly.At 50kpm it goes but it doesn't feel like a 4 barrell(like 2 only). I've been told it might be the wrong size carb for the engine.

Al - parts are readily available for all Q-Jets up through the 1974 model; as long as you have the carburetor identification number.

Jon.

Thanks Jon for that info. I was thinking of taking that carb else where already too.Just to get a second opinion. There is no tag on the carb though. I'm guessing that anyone who works with carbs will be able to figure out what it is?
AL

With an OHC-6 Sprint, you want a properly calibrated carburetor set up FOR THAT ENGINE (displacement, carburetor, compression ratio, camshaft). Try Primatech Motorsports and see if they have any OHC carbs on hand.

The OHC carb is very similar to, but not identical to, the V-8 carb.

Thanks Vikki. I was also on EZboard and saw your write up there. That Napa carb kit that you spoke of (CRB 25194A)would that work for mine as well if it is the original carb? By the way I also like the name change.
AL

The OHC uses a different base than the V-8 Q-Jet. We can mod a V-8 base to work on an OHC. I'll let you know how that works out.

We have one spare 68 4-Bbl right now.

The CRB 25194A kit is for a 1-Bbl. carb, the Rochester BV. The BV was used only on California emissions 1-Bbl. motors.

NAPA part number CRB 25365 is the 4-Bbl kit part number for the Q-Jet.

NAPA 4MV Kit

Thanks P.M.I. USA for you help. I sent you a pm with a few questions. Thanks again for your help
AL

There are several different carburetor rebuilding kits, depending on the carburetor number for the OHC Q-Jet. One kit does not fit all!

Jon.

OK ,I went out to the garage and brought the carb in.There are only two numbers on it
7032720 and RP29865
There is no tag. These are numbers on the carb. Do they mean anything? If there is anything else I need to look for let me know cause I have the carb here on the desk next to me.
AL

Al - from these numbers, we can tell that you have a 1966 casting. The casting was machined a dozen different ways, to be used on a number of different engines, including the 1966 Pontiac 230 CID OHC Sprint.

The original tag was round about the size of a dime, and pressed into a depression on the throttle linkage size of the bowl (center section).

The 1966 was the worst of the Q-Jets used by Pontiac, as these still had the funky internal dashpot that would bind after it acquired some wear; and the still funkier "umbrella" fuel valve that didn't work. Any good carburetor rebuilder will replace this valve with a conventional style when rebuilding the carburetor.

There are no other identifying numbers on this carburetor, if the tag has been removed. To positively identify it, one first looks at the throttle arm (the Pontiacs differ from the others); and then disassemble the carb and check the airbleeds, restrictors, etc. and compare these calibrations to the calibrations for the various units.

Sorry to be the bearer of bad news.

Jon.

Not to take this thread off track, but Jon, what are the symptoms if the fuel valve is malfunctioning on the '66? Mine appears not to have been rebuilt (36,000 miles) and the carb works adequately but just not quite like new.

Yellowbird - the umbrella style does not adequately shut off the fuel; causing at best too much fuel in the bowl and a rich mixture; at worst, gas all over the intake.

Most of them were replaced in the field within a few months of new.

Jon.

This car is mechanically pristine. I do see a bit of fuel seepage above the body which stains/moistens the intake around the carb, which is why I wondered. If I have to open it, what should I look for with the dashpot?

Vikki, I would can the jesus clip, the wire clip between the needle seat and the float. I have looked and looked and asked and asked, but I have never found any information about anyone else having problems with the clip. Then again, I was into my carb at least 50 times before I noticed the problem. (The problem was that the clip caused the needle seat to sit caddywampus in the sleeve of the seat, not allowing the needle to seat, and the problem was intermittent. The previous repairs were done by revving the dog crap out of the engine or a couple of wot runs.)

Al, let's do a quick troubleshoot of your carb, and it doesn't cost a dime. (Well, with gas prices, I guess it might cost a dime.) The symptom you describe is a textbook example of a failed accelerator pump.

Before you even get out a wrench, check the accelerator pump's operation. This failure is the biggest failure in quads,a nd it's a normal failure.

With the breather off and pressure on the fuel, meaning just after cranking/running the engine. If it's closed, hold the primary butterfly open. Hit the throttle, and you should see 2 distinct squirts of gas. (Based on feel alone, I can hit the throttle linkage by hand and tell whether or not the fuel acceleartor pump discharges gas.)

If you get just a dibble, broken squirts, or nothing, the accelerator pump is toast. Also, your freind and mechanic didn't offer accurate information. IF you're mechanic says that parts are not avaiblble, s/he may have never worked on a car with a carb. There are many primary jet sizes for the quad, and the secondaires are altered by changine meetering rods and hangers.

Vikki - the problem (if one exists) with the internal dashpot is wear in the dashpot cylinder. The vertical movement of the dashpot tends to wear the cylinder in the carburetor housing, thus allowing the dashpot piston to move sideways, and eventually bind.

The umbrella style fuel valve does not have a clip.

Amervo - with no disrepect intended, removal of the clip from the fuel valve is not a good idea. The placement of the clips is quite confusing. Some are designed to be placed behind the bar on the float arm, some in front of the bar on the float arm, but I am unaware of any which are to be placed in either of the 2 slots in the float arm which one would think is the proper spot! With the carburetor on the bench, install the fuel valve with the clip; and then with a string looped under the toe of the float, move the float from fully opened to fully closed observing the action of the valve. If the valve binds, place it on the other side of the bar, and repeat the test.

Removing the clip from a passenger vehicle driven daily will probably not be a problem. However removing the clip from a non-passenger vehicle or a passenger vehicle which is not driven daily may result in the valve sticking in the seat, thus preventing fuel from entering the carburetor.

Al - while I disagree with Amervo's diagnosis that the accelerator pump is the problem (based on the fact you are also having problems at 50 MPH when the accelerator pump should not need to be functional); the test that Amervo suggested should always be done when having this type of problem, as it positively will prove either the accelerator pump is good or bad. And Amervo may be correct. Neopreme accelerator pumps fail more frequently on vehicles which are infrequently driven; as the neopreme, having one been in gasoline, tends to turn hard if removed from gasoline. Todays very volatile fuel will evaporate from the bowl, thus allowing the accelerator pump to turn hard, and fail. When replacing an accelerator pump, use a leather pump if possible.

I especially agree with Amervo's comment about the mechanic. It is much easier to say "parts are not available" than to say "I don't know how to work on this item". You can always determine what the mechanic meant by asking if he will do the work if YOU supply the parts.

Jon.

Thanks everyone for your help. I will try Amervo's advise with the carb that is on the car and see if I am getting the two squirts. As for the carb on my desk, I guess I can't hurt it any more if I open it up and see what's up inside,right? Also I remembered today while at work that the carb on the engine doesn't even have a tag on it. So a guess that means I can't do anything with that one either if it needs a rebuild. Which could mean I'm back to my first question which the answer from you all is staying with the Q-jet.Now what size will be best? This is to be a winter project as my son and I still have three more car shows to go to before the car goes up on blocks for winter.So far we are the only car with this engine and enjoy showing it
AL