tcolt

I am installing a 2004R transmission in my 1972 Vista Cruiser. I found out that the throttle bracket off a 307 engine will only work with Quadrajet carburettors. The stock carb. on most 1972 Vista Cruisers was a 2 barrel Rochester carb, so now I am thinking of upgrading to a 4 barrel carb before I swap the transmission.

I'm doing the transmission swap mostly to save gas, so is installing a 4 barrel carb. silly? I've heard that it would get about the same gas mileage as my 2 barrel as long as I don't step on the gas pedal hard, but I'd have the extra power if I need or want it. Is this true? What would be the best new or used carb to use that isn't too hard to find? Edelbrock? I'd love to find a stock Q-jet, but I hear they are a bear to set up unless they were already tuned to a 350 rocket engine?...

Thanks, Tom

Erinyes

A properly set-up Quadrajet will usually give better gas mileage than the stock two-barrel, provided you are one of those rare birds that has the self-control to not crush the pedal. The primary venturies are a bit smaller, if I remember correctly. As far as setting one up, it's not too difficult if you are running basically a stock car and not squeezing every drop of performance out of it. The usual issue is finding a useable combination of primary jets and rods, but there is a decent range that will work, and it is possible to find advised combinations for a given engine - Ruggle's book, or the other one that I have buried away somewhere I think has a chart.

tcolt

Thanks. That sounds tempting. Is there a series of car models where I would be most likely to find the correct Quadrajet? Oldsmobile only, I'm guessing?

MDchanic

Just get a QuadraJet from a '72 Olds 350, or set one up like one.

A QJ from a low compression '72 350 is not particularly in demand and should not be hard to find.

- Eric

toymobile

(Just get a QuadraJet from a '72 Olds 350, or set one up like one.)

Did 72 QJ have the right throttle bracket to attach kick down cable??
I have a QJ listed in parts for sale from a 77 that has the right set up for KICK DOWN CABLE, And I think I have the right throttle cable bracket for kick down.

Let me know if I can be of any help, Thanks

Johnny

PS. Just checked and I do not have the right throttle bracket you need, I have 7 QJ brackets but not one for kick down cable.

MDchanic

'72 used a kick-down cable connected to the accelerator pedal, rather than to the carburetor.

The 200R4 uses a TV cable, which may need to be set up slightly differently (I am not an expert on this), so having a carb. that's all set for a kick-down cable may or may not be helpful.

Please note, though, that a '77 carb is jetted for EGR and a catalytic, neither of which is on the '72.

- Eric

hookem horns

Maybe stating the obvious, but you need a 4bbl intake manifold too. Stock from any small block Olds or aftermarket like the Edelbrock Performer 3711/2711. Other little things too like fuel line and the throttle cable bracket, though not sure what is needed for the 200R4.

joe_padavano

As discussed in the O.P.'s other thread on this same topic, the bracket from a 307 car with the 200-4R works on any Olds Qjet intake and will accept the TV cable as well as the throttle cable. Note that a TV cable is NOT a kickdown cable. The functions are different.

tcolt

Thanks for all these great replies! Dane. Nothing is obvious for me :-) In fact, I do have another question about how to recognize a 307 and a 350 Olds when I see one at the wrecking yards. I have run into very few rear wheel drive Olds, Cadillac, Buick, etc. at all, let alone Olds. If I'm lucky, the DOT year sticker is still legible on the door jamb. Is there any way to confirm that I am looking at a 350? And a low compression one at that. What years and models could I use as donors? What were all the differences from the low compression engine vs. the normal or high compression engine? I'm assuming heads, camshaft, distributor, timing?... Is it worth looking for these parts for my engine? Was there a big difference between the performance? I hear the engines were de-tuned for 1972 to run on regular instead of premium, so obviously there would be some necessary power loss ...

tcolt

I just checked Craigslist and there are tons of 4 barrel q-jet carbs. I also just figured out there was no 350 Olds in 1972 with a Quadrajet carb, so I'd have to figure out what engine came closest to a 1972 low compression engine and so far my guess is that a 1975 Olds Cutlass would have been the first year that had a low compression 350 engine with the Q-jet? Does anybody have thoughts on that? Was 1975 before there were any other major changes to the 350 engine like converters and air pumps?

BlackGold

?????

joe_padavano

How exactly did you figure this out?

FYI, the Qjet was the ONLY 4bbl carb used by Oldsmobile from 1966 to 1990.

tcolt

I spoke to a guy named Joe at https://www.carburetorexchange.com/search.php and he and his web-site doesn't list any 4 barrel Q-jet for a 350 engine in 1972. Is he wrong? Were there other similar GM 350cu low compression engines that had a 4 bbl? Sorry, I'm pretty ignorant about all this. I'm new to muscle cars. I've been playing with old BMW and Mercedes for 30 years....

joe_padavano

Let's be charitable and say his data is incomplete...

More to the point, that website only lists the carbs he has available to sell. That is NOT the same as a comprehensive list of every carb Olds used in a specific year.

If you check the factory Chassis Service Manuals or factory parts book for the years 1966-1990, you will get the correct information.

brown7373

I would avoid the "guy named Joe" for any carb work as he doesn't know what he's talking about. As Joe Padavano said, the ONLY 4 bbl used 66-90 was the Quadrajet, and millions of Olds 350, 400 & 455 had them.

tcolt

Joe. He does have the 4 barrel Q-jets, but he is simply saying they were only used on the larger engines. Are you both saying that the q-jet was definitely used on a 1972 350 too? Not just on the 400 and 455 engines? I know people use these carbs on 1972 350 Olds engine too, but my thinking is that I'd prefer to get a carb that was already set-up for a low compression 350 cu in engine, preferably from the factory. Maybe that's asking too much?... Also, would the intake manifold have to come off an Olds engine or would a Chevy manifold be the same?

MDchanic

And he is wrong.


Yes.


YES.


Arrrrgh!





- Eric

tcolt

Ok. Thanks Eric. I take it the pictures were to show me that the Chevy and Olds manifolds are different... :-)

This seems to confirm that a Cutlass (maybe other too) was available with a 350 engine and a 4 barrel carb starting in 1971. I wish I could find out what those carb model numbers were.

https://en.wikipedia.org/wiki/Oldsmobile_Cutlass

Starting in 1975 they had catalytic converters so the carb set-up was probably much different from earlier.

joe_padavano

I'm sorry, but you clearly are NOT getting this.

I'll try to type more slowly...

The ONLY 4bbl carb used by Olds on ANY V8 engine from the 1966 to the 1990 model years was a Quadrajet.

The fact that some yahoo on the interweb doesn't sell them does NOT mean that Olds didn't make them. Hell, you can go to RockAuto or your local auto parts store and buy a rebuilt one. Go to RockAuto.com, look up 1972 Cutlass with a 350 motor, and see what rebuilt carbs are offered. By the way, don't panic when the listing says "Autolite". That's the rebuilder, NOT the original manufacturer.

hookem horns

Tcolt - maybe we need to back up to what you have now, goals, and budget. Then we can give better advice before going into QJet stamping codes. Lots of really smart folks on this site that have steered me right many times.

Now - I assume a stock 1972 VC with a decent running 350 2bbl but bad TH375 based on prior posts. (I guess you are learning it's a completely different animal than a Chevy SB)

Goals - Back on the road as-is? Better gas mileage with a little better performance? Bad-a** "sleeper" wagon?

Budget - Rebuilding the TH375 is probably around $1-2k depending on how much is wrong and if a shop does all the work. Swapping a 200R4, lower geared rear end and 4bbl could easily exceed $4k for a snappier driving car that gets ~17mpg vs. current ~12mpg on the highway. Sky's the limit if you have higher performance aspirations. (All very, very rough estimates on my part)

tcolt

Joe

Maybe a misunderstanding, but I did finally understand that the q-jets were also available on the 1972. Is that what you meant? I'm just trying to figure out where and how to make sure I buy the right q-jet (used or rebuilt). There's no use in buying a carb that's set up for a 455 10.5 motor or cat when I could get one that's in the right ball park for my 8.5CR 350 motor, right? I've been told that they can be a bear to set up right for someone like me, who mostly has experience with mechanical and electronic fuel injection. Also, I don't just have jets and needles and other parts laying around to swap out.
Dane, you summed it up well, except that I'm not worried about the rear axle swap yet. It just seemed like the q-jet swap was a smart thing to do before the 2004R swap, since the two work together so closely. Sorry, if I don't know my *** from my elbow with the intake manifolds either which seems to have caused frustration. Maybe I'm being unrealistic, hoping to find the right parts that were more or less already designed to use on exactly my type of engine. I know they weren't used for more than two or three years on the regular Cutlass and hopefully other Olds engines and for all I know even the intake manifolds might have been different. Maybe it's even easier or better performance-wise to get an Edelbrock manifold, although I'd lean to using period correct factory parts if I can, unless the factory parts are known to be bad choices or the aftermarket would yield a lot more performance at a reasonable cost.

Thanks for all your patience. I hope I'm not wearing it out already. I know, I tend to ask a lot of questions and some of them are very basic to most of you because I have almost no knowledge about American cars (I know, bad American- I was raised overseas...). Also, I'm an engineer, so I like to understand why and how things work and what would be a reasonably good way to go about doing these things.

Thanks again for all your well-meant and very helpful posts so far. This is an awesome group of caring people, if I haven't said it in a while since I joined in February :-)... Tom

Joe. After re-reading your post, maybe you thought I was referring to 4 barrel carbs other than a q-jet. No, I was trying to figure out where to look for a 4 barrel q-jet I should get that would bolt right onto my 350 engine with the least fuss. So far, the closest I found is a new 1975 q-jet for $135 on Craigslist which is tempting, but I think it might not work well because it was set up for an engine with a cat?... (The guy listed the carb number as 17075274, but I'm not sure that is the stamped in number and not just a number of the casting).

joe_padavano

And again, did you ever go to Rockauto.com? If you did, you would have found a rebuilt Qjet for EXACTLY your application. It was rebuilt by Autolite, but it is a Rochester Qjet. P/N is C9202, $190 plus $80 core charge. Not the cheapest option, but the one that will bolt on and work without drama. A 1975 carb will be calibrated for the emissions equipment on that year engine, like EGR and catalytic converter. It will likely not be calibrated correctly for your 1972 motor.

Another option is a rebuilt carb from Sparky's. He's been doing this for decades and is an Olds guy. The factory carb for your application is Rochester #7042250. He's got an original core in stock and can rebuild it.

MDchanic

... Or just put up a Wanted ad on this board. The likelihood is high that a member here has one (or a bucketfull) for a reasonable price, which may or not require a rebuild.

Essentially, and '71 or '72 350 QJ would fill the bill, and one from '68 to '70 would likely work fine, too.

- Eric

tcolt

Thanks Joe and Eric. That's great news. I hadn't checked Rockauto yet. I guess I'm not used to having so many options off the shelf with the European cars that weren't built or survived in as many numbers...

Tom

Here's my classified post: https://classicoldsmobile.com/forums...tml#post857678

MDchanic

Yes, you can get almost any mechanical parts for these cars from your local auto parts store - many are even in stock.

- Eric

tcolt

Joe

I don't know where you found that carb. number for a 1972 Vista cruiser, but what do these numbers tell you that someone is trying to sell in the classifieds?

7041250 NU 2440

Thanks, Tom

toymobile

A 72 carb will not have the throttle linkage you need for the TV cable on your 2004R. The carb I have listed is from a 77 Olds 350 with the right hookup, I'm not trying to get into your head but you have got a lot of feedback from a lot of people, take your time and seek out what will work for you. Good luck.

Johnny

MDchanic

In theory, that number should designate a 1971 Oldsmobile QuadraJet for an automatic transmission car, manufactured on September 1st, 1970.

Interestingly, I can't find the production code "NU" in any of my information, so I cannot say exactly which model and engine that carburetor was made for.

- Eric

joe_padavano

The carb number is stamped on the carb body on the driver's side.

70 = Rochester prefix
4 = 1970s decade (2 would have been 1960s decade)
1 = year (1971 in this case, since it is preceded by a "4")
250 = sequential number for a specific application. Typically the "250" Qjet in a given year was the base Olds carb with AT. These were used on both 350s and 455s, which gives you an idea of the flexibility of the Qjet. Other applications would have used different numbers like 251, 252, etc.

tcolt

Thanks Joe, Eric and Johnny. I'm glad we've had this in-depth discussion questions since a few more things came up. Dane pointed out that an early 70s Q-jet wouldn't yet have the throttle lever to match my 200R4 application, but I spoke to Sparky at Sparky's Carb. Service who said that a later carb. would be difficult to adapt to a non-emissions car and that I'd be better off with the correct carb. and find a later throttle bracket or possibly find an adapter kit.

BTW, it seems like I would need a larger air filter housing than the stock one that fits my 2bbl Rochester for the larger carb. throat. It that right? Does anyone have one and a late 70 or early 80s throttle lever?

Joe, I assume that the Q-jet has to be set-up differently for a 455 and a 350 engine?...

MDchanic

Yes, you need a QuadraJet air cleaner housing instead of a 2-Jet air cleaner housing.

In 1971, according to the Assembly Manual, the 7041250 was the only QJ used for the 350, and was not used on the big blocks, so I will leave it to Joe to detail which QJs were used in both big and small blocks without modification (I believe '68 and '69, and maybe '70, in certain cases).

- Eric

joe_padavano

Yes, in prior years the same '250 carb was used on both big and small blocks. I'm guessing the tightening emissions requirements starting in 1971 led to the different calibrations. The Qjet has far more control over mixture than does lesser carbs, so it is somewhat more capable of adapting to the different engine requirements. The secondary air valves control both airflow and mixture based on engine needs.

As for the TV cable interface, have Sparky swap the primary throttle shaft on that '250 carb with one out of a later core that has the fitting. This is very easy to do during a rebuild and solves this problem.

tcolt

Thanks again Joe and Eric. Is this information you guys have collected over the years or is there a book or web-page?

A guy is selling a bunch of the 4 barrel carbs for parts cheap on ebay, but they are mostly late 70s Corvettes and other GM. I'm guessing their throttle linkages also would work for the TV cable? Although a Corvette probably never used a 2004R...

Tom

tcolt

I already got a factory intake manifold and the correct q-jet off 1972 350 engines. I spent $100 total so far, but I still need an air cleaner... I'm not in a big hurry though. That fuel intake fitting is huge on the Rochester. I'm guessing there is some sort of special hose or pipe that I also need to adapt it to my 2bbl fuel lines....

joe_padavano

If you are looking at the "huge" 1" threads on the front of the Qjet float bowl, then it sounds like you are missing the fuel filter housing. The "special hose or pipe" is the pump-to-carb tube for a Qjet, which is completely different from the one for a 2GC. The repro tube vendors sell them, or you can make your own if you can bend and flare tubing.

tru-blue 442

Tom, Joe nailed the fuel line you need. E-bay, $18.

tcolt

Haha. It's pretty funny to read this old thread and see how much I've learned here. Thanks to all of you for the good answers which pretty much all helped get me to where I am today, a little less than 2 years after I bought my Vista, which I still get as much of a kick out of as I did back then. (I won't even start about the extensive roof repairs I've begun, due to some of the typical light roof rust. They turned out to be less light and more rust than the few blisters originally might have suggested.) I have just installed the "correct" 4-barrel intake and q-jet. I rebuilt the q-jet and now I'm fabricating a simple extension lever that will operate my 200-4R, just as I did with my 2bbl. A year ago, I built myself a nice 200-4R with the help of a lot of research here and on the BuickRegal and other sites and I'm quite happy with it. I'm still having a hard time finding detailed engine pictures to figure out where all the 6 or 7 hose attachments on the Q-jet go to on and around the manifold. The PVC hose I bought has a short 90 degree molded section on one end, but I don't know which end that goes (if any...) Also, how the carburetor return spring goes and brackets for the heater hoses, etc.

Also, I realized that my 1972 Q-jet was missing the yellow cad-plated idle speed solenoid bracket that bolts to the front of the carb. I think the solenoid itself may be the same as on my 2bbl carb?... I bought many of the other missing parts (fuel pipe, throttle cable, carb. mounting bolts and air filter mounting stud) from Inlinetubing (Motor City Muscle Cars) on ebay. Good prices for good reproduction parts... Correct clamps and hoses from PaceCarJeff.

Does anyone have an extra idle speed bracket?.. (I know it's probably just used with air conditioning, but eventually, I'd like to have it all back to ClassicOldsmobile...)

Thanks, Tom

olds 307 and 403

I don't know why a 1976 to 80 carb off a 350 or 403 wasn't suggested, you wouldn't have to fabricate anything. Plus you gain 50 cfm along with some improvements. Although my 76 350 carb had the proper linkage but was missing the kick down stud, most I have seen had them. You did awesome to rebuild one of the harder transmissions out of the gate.

BILL DEMMER

a '76-'80 carb. wasn't suggested because those things were meant to sit on top of a EGR-choked motor, and were calibrated so lean that if they are used on an earlier, higher compression motor without EGR, they will make the engine sound like a popcorn popper, and eventually destroy the motor. xxxx250 carbs. were never used on anything but standard 350's, 251's were the standard big block carb. number. you can add a TVS cable pin to any olds throttle lever, BUT, you have to drill the hole for the pin exactly right, or you run the risk of killing the 200-4r tranny. if you look for a 7041250 or a 7042250, you'll be calibrated close enough for good results. pay attention to the fuel filter inlet type(internal/external sealing) and the threads in the float bowl to make sure they're in good condition. a qj from another gm brand will be calibrated incorrectly for an olds motor.

bill

MDchanic

It sounds like you're doing great, Tom!

Please post some photos of your carb. and your PCV components, and we should be able to tell you what to do.

- Eric