Was going to be a qjet rebuild, now Holley vs. Edelbrock

["Cadillac Kid" Greg Surfas 15364]

Justin,
Like Roy said, you have the hard part done, the correct throttle linkage and attachment (to the carb) as well as the kick down switch.  You can use any Cadillac (because of the attachment to the linkage) carb. There is nothing sacred about using a '67 unless you are going for absolute authenticity, and any one that uses a divorced choke (through '73) will work.  Broadens the scope of your search a bit.
Last resort, get a complete core from a Cadillac "re-cycler" and send it to one of the reputable re-builders.  I have used Jet performance in CA with a great deal of success for all applications from stock to full performance.
Greg Surfas

[JVA]

I talked on the phone with Jet yesterday for a while, and the guy there largely echoed everything you just said... the linkage is the hard part, after that they can build mostly any Quadrajet into the right Quadrajet.

Earlier today I bought two carbs off ebay - someone listed a '67 Quadrajet that "needs a rebuild" and there was a '68 "was rebuilt, low mileage." I'm going to give the '68 a whirl, and send what I've got and/or the '67 over to Jet if it doesn't work out. I'll be in SoCal sometime in the next month or two anyway, so perhaps I can just plan a trip by to drop 'em off.

I really appreciate all the help guys - I'll follow up in a week or so with the results from the '68 bolt-on.

[JVA]

Nothing is ever easy, right?

Got both the ~'67 and the ~'68 carb in today. The '67 has the same base plate as the carb on the car, so that's positive. The '68 does not. In fact, the base plate on the '68 won't clear the intake manifold in any sort of useful way, so that means at least swapping base plates. No problem, I have two.

However, I am still left with a couple questions:

1. The carb on the car has a vacuum port over on the choke side that is currently the distributor vacuum advance. Neither of the new carbs do. Does anyone know the location of the *proper* port for the vacuum advance on a '67 or '68 Quadrajet?

2. The fast idle linkage - the thing that started this whole situation - is quite different on the '68 than *either* the new '67 or the carb on the car. Does anyone happen to know whether the fast idle cam should match the carburetor OR the base plate? The new '67 carb has an intact cam so no matter what I am not screwed, however what I would like to avoid is getting stuck where I am again when the 45 year old plastic fast idle cam breaks again...

I will try and post some pictures of the situation tomorrow, but I'm hoping these are easy questions for someone who knows qjets better than I do.

Thanks!

[JVA]

Just wanna say BAH. The carb from the '68 is from a mid '70s Chevy truck. Again.

[R Schroeder]

Justin, when I said get another carb, I meant for you to rebuild the one you bought.
You might run into problems if you switch bases ,because of internal vacuum lines,and etc. You would need to check that very carefully by looking at the gasket on the carb, vs the gasket on the carb your taking parts from.
If you have a COMPLETE  carb that fits, just rebuild it. Use the one on the car until you get a nice one.
I'm sort of lost as to the fact that one bolts on, and the other doesn't.

The best place to pick up vacuum for the vacuum advance is off the intake manifold.Any ports on the engine.

Not being there makes it hard to make any sort of call on this.

[JVA]

Yeah, I realize not having this stuff in hand makes it difficult to have a real dialog about. Folks complain a lot about the black box nature of fuel injection, but at least with that stuff it pretty much fits or it doesn't.

I was not confident in getting my current setup rebuilt... Obviously it ran the car, but I have zero confidence that it's doing so optimally. Additionally, nobody I talked to would commit to getting the fast idle cam replaced because they couldn't tell me what the original one looked like. It was always "give us several hundred dollars, and hopefully it works out." That didn't seem like good spending to me, that's why I bought some more Q-Jets for comparison.

The parts that I now have are:

o 2 throttle bodies from - most likely - a 1967 Fleetwood with a 429. Both look the same. One was on the car, one is just purchased from Ebay with a carb
o 1 throttle body from - most likely - a 1971 something with a 472. The fast idle cam, throttle linkage, and choke linkage is quite different from the other two. The choke or fast idle linkage interferes with the intake manifold, so it's totally unworkable.
o 1 Q-jet from a ~1970 Chevy pickup. This was what was on the car. The choke was unhappy (but livable), and the fast idle cam completely failed.
o 1 Q-jet from a ~1975 Chevy pickup. This was supposed to be from the '71 something, but clearly isn't.
o 1 Q-jet from - most likely - a 1967 Fleetwood. I can't find a part number on it! This is from Ebay. It's really dirty and the throttle linkage is slightly bent, but it appears complete otherwise.

I left the "'67 from ebay" intact and put it in a box. It will eventually get rebuilt. I reasonably believe it's fully correct.

I swapped my '67 throttle body from my ~1970 Q-Jet onto the ~1975 Q-Jet. Everything appears to work properly - the throttle linkage operates the butterflies smoothly, the choke linkage behaves itself, the fast idle cam interacts with the linkage properly. Mechanically, it's sound.

As you note, the gasket is the sticking point. I don't really understand the interaction of air paths between throttle body and carb. The gaskets that came off my ~70 carb and the new ~75 carb are different, that's for sure. Subtly different, but different. What's interesting (to me) is that neither "matches" the carb *or* throttle body - both have offset or blocked ports here & there, so without more knowledge of Q-jets in general it's impossible to make a determination. What I do know is that quadrajetparts.com does NOT carry the gasket that came with the ~75 carb, but they do carry the gasket for my ~70 carb. So I ordered one.

I will post some pictures. At this point, I don't expect to learn anything further, but at least some details will be immortalized on the internet.


Edit: What I ordered from quadrajet parts is:

1" x 5/8"-18 - Short Inlet Fitting (the ~75 carb has the later 1" inlet)
Air Cleaner Gasket
Divorced Choke Thermostat
Quadrajet Base Gasket, .062" Thick - OEM # 1486564
Quadrajet Steel Shim Heat Shield, .015" Thick
Quadrajet Throttle Body Gasket, OEM # 7038142
Short Paper Carburetor Fuel Filter with check valve

This is the throttle body gasket - it's an exact match for the gasket that was between my '67 throttle body and the ~'70 carb:



This is the gasket that most closely matches what was between the ~'71 throttle body and the ~'75 carb:



There are very subtly different. On that second gasket, the one I have does not have the little notches in the top outer edge, and has one or two fewer holes at the bottom left. Mine is similar, but not identical. Carbs are black magic I tell you!

[R Schroeder]

Yep, you got my head spinning now.
Sounds like there multiplying right before your eyes.

[JVA]

Tell me about it! It took me two years to fully figure out the eight or so different carbs that Ford put on their pre-smog inline sixes, but at least a Holley 1940 is pretty much a Holley 1940... with these Q-Jets, GM made the basic thing for so long and used it on so many applications I don't know how *anyone* keeps this stuff straight. I sold my '84 Trans Am because I literally could not understand the carburetor. Now, here I am again! Q-Jets are SO NICE when they work, but I can really see why people dump them. *Such* a hassle!

At this point, I'm going to try it and see what happens. I just need to know which vacuum port on the ~'75 carb should run the distributor vacuum advance.

[JVA]

Okay, here are images of all three carbs and their related parts that I now have.

In each picture, the left part is from my '70 carb+'67 tb, the middle is the '67 carb+tb I ebayed, and the right is the '75 carb+'71 tb.

All three from the top. They're all pretty similar from this angle, though you can clear see the extra plastic diagphragm thingy on the true '67 carb.


From the bottom. Some clear visual differenes in the layout.


Choke side. The two on the left have the same '67 linkage. The '71 on the right is clearly different.


The three throttle body to carb body gaskets. No real similarities. I have no idea.


Throttle bodies. The two on the left are the same, which is expected since they're from a '67. The '71 is quite different.


Throttle linkages. The two on the left are the same, which is expected since they're from a '67. The '71 is quite different.


Fast idle linkages. The two on the left are the same, which is expected since they're from a '67. The '71 is quite different. It oddly interferes with the intake manifold on the car.


Below are extremely high res versions of these images, in case it's helpful:

http://www.sacsaabs.org/sacsaabs.org/fleetwoodcarb/fleetwood_carb_top.JPG
http://www.sacsaabs.org/sacsaabs.org/fleetwoodcarb/fleetwood_carb_bottom.JPG
http://www.sacsaabs.org/sacsaabs.org/fleetwoodcarb/fleetwood_carb_choke.JPG
http://www.sacsaabs.org/sacsaabs.org/fleetwoodcarb/fleetwood_tb_gasket.JPG
http://www.sacsaabs.org/sacsaabs.org/fleetwoodcarb/fleetwood_tb_top.JPG
http://www.sacsaabs.org/sacsaabs.org/fleetwoodcarb/fleetwood_tb_linkage.JPG
http://www.sacsaabs.org/sacsaabs.org/fleetwoodcarb/fleetwood_tb_fastidle.JPG

So, I have no idea, but now everyone can have no idea with me.

[R Schroeder]

Well, here is what I'm going to say at this point.

You can find the number of the carb that fits your car, or see if one of those is complete and use it at CARBUETOR EXCHANGE for a core replacement.

http://carburetorexchange.com/docs/rochestercarburetors.php

For a 1967.

http://carburetorexchange.com/plp/search.php?year=1967&man_id=3&man_model_id=52

You could find all the info on rebuilding one. These are very easy to rebuild, IF you have all the info in front of you. The Cadillac repair manual I found to be the best for doing this. Gives you the most accurate info.

The white THINGY on the carb is a choke pull off. It opens the choke a set distance once the car starts. I have never seen one that points down like that. Maybe someone reversed the linkage.
Again a manual for the car and that carb would be the best thing at this point.

The numbers for the carbs are stamped either on the back left , on the secondary housing rib. They are noted with a small round tag on the front left side up front, or they have a tag or stamping on top on the right front .

Good luck
Roy

[JVA]

Ah, so that's what a choke pulloff does. I am still coming up to speed on all of this, so I really appreciate your help.

I am going to continue with Plan A - which is put the '75 carb on my '67 throttle - and see what happens. Maybe good things!

I'm also going to send out the complete '67 somewhere (probably Jet) for a rebuild. I just want to clean it up a little and try and find the number on it to be sure it's what I think it is.

[blue68deville]

The diaphragm on the rear of the 67 carb is for the idle-up function. It increases the idle speed when the a/c compressor is engaged and the car is in park/neutral.
The vacuum break/choke pull-off is low on the front pass side, should tee in to the vac port on that side of the carb. It is a full mainfold vac source. It will slightly open the choke when the eng starts, keeps it from bogging down due to a rich condition.
The vacuum advance should come off the vac port on the front driver's side, just above the idle mixture screw. It should correspond to a port in the throttle area, right above where the butterfly edge rests when at idle position. That makes it ported vacuum, it won't provide a vac signal untill the throttle is slightly opened.

I've had old cars with Holleys and Edelbrocks, tuned them well, and I can say that I've never had any that ran as well as my 68 does with the Q-jet. I've shelved an EFI conversion since I rebuilt it, it runs so well I can't justify the expense.

[R Schroeder]

Beg to differ with you, but the front vacuum is connected to the secondary part of the carb. It keeps the door closed on the carb until you have full throttle, then vacuum drops to allow the door to open , for the secondaries.

The middle carb has the rear vacuum break. On most of the newer carbs this is the choke pull off.
I'm not familiar with the 67 carb, as to the function of that piece on that carb, but on all of them that I know, its the choke pull off.
If it is for what you say it is, then how would it be controlled during none use of the air conditioner.
On my 78 there is an electrical solenoid that pops out for a faster idle when air is on. This is on the drivers side of the carb.
Again, I'm not sure how the 67 is set up, but something doesn't sound right here.
So, please let me know if I'm wrong about this carb.
Roy

[blue68deville]

You're right about the later carbs, I've had a couple of those on other GM stuff.
The early ones are set up like I posted earlier. That's how my 68 is, there is a white striped vacuum line from the climate control vac harness that connects to that rear diaphragm. It has a link rod that ties in to the primary throttle shaft on the r side.
The front diaphragm is the choke pull off and it has a long linkage rod that ties in with the secondary flaps (on top) to limit their travel (and consequently the secondary metering rods). Since it's tied in to full manifold vacuum it uses that signal to adjust the secondary mixture.
That long linkage has a bend in the middle that presses on part of the choke linkage to provide pull off also.

[R Schroeder]

Wow, that's one crazy set up on there.
Thanks for the reply.
I have never seen one like that.
Interesting.
Roy

[blue68deville]

That's funny, I think of the later Q-jets as being weird. I've always tried to stay pre-70 since I'm more familiar with the old 4MV divorced choke coil models.

[R Schroeder]

I guess its all in what your use to.
Great to learn something.
Thanks Roy

[JVA]

Thought I would follow up on this...

What blue68deville about the vacuum diaphragm definitely seems to be true, as I've got a white-striped vacuum line hanging around on the cowl with a screw in it that would reach it perfectly. I suspect it was capped when whomever replaced the stock carb with the Chevy carb that was on it when I got it.

Last week I got all the parts in from quadrajetparts.com and put the ~'75 carb on my '67 base plate. I'm still totally unsure of exactly how the base gaskets are chosen. I do have several qjet books, but none of them go into the painful detail I'm looking for - they all assume you've got a functional configuration and are looking to tune or rebuild or modify. I chose the gasket that matches the ~'75 carb - figured it was as good a place as any to start. If something turns out to be wonky, I still have the gasket that matches the previous ~'70 carb to try.

I got it together Wednesday night, only to find the car wouldn't crank at all. In fast, nothing electrical worked. After an hour of cursing+troubleshooting I found that the battery ground cable had failed at the chassis over the winter. Struck me as very strange since that cable is less than two years old, but whatever. I happened to have a spare battery ground from a 1990 Saab 900 (no joke!) which worked *beautifully* so that's on the car for now. Heh.

It took a bit of cranking to get fuel back up to the carb, but as soon as there was gas in the bowl it fired *right* up. Started faster and easier than it's *ever* started. Settled immediately into a very high idle - like 1400rpm. I backed off the throttle stop as far as it would go and got the idle down to about 1000rpm. Since my old fast idle cam was hosed I have no idea what fast idle speed should be on this motor, but regular idle was previously about 700rpm in neutral, which ended up being ~640 in drive. I don't know if fast idle is good for +300rpm or not, but it seems plausible.

I'd spent so much time on the ground cable it was getting dark by now, and a 429 with a 3" exhaust and an open hood at 1000rpm is VERY loud in the garage so I shut it back down. I'll play with it some more this weekend and see where I get. Mixture could still be off, and honestly I've never checked the ignition timing so both of those are up in the air as well. I assume I can start it back up and manually knock the fast idle cam out of position to see what that looks like, then decide if I need to do anything else.