[jhein]

I had to take the one I was running off for repairs as I mentioned in another thread. It had some fairly significant problems but ran surprisingly well.

Now I have another 7040263 on there that came from Quadrajet Power. It's freshly rebuilt and was calibrated for my motor. I don't know exactly what jets and rods are in it, or exactly what other mods, if any, were done.

When I installed it, I adjusted the idle mixture using a vacuum gauge with no problems. It starts great, hot or cold. Idles nice. Exhaust doesn't smell too gassy.

But there are a couple problems. First, I noticed from the first drive that it ran fine on the primaries, but when I went to WOT, it seems lazy.It just doesn't pull at all like it did with the other carb. Second, I did a fuel mileage check with the other carb just because I was curious. I got 15 mpg cruising at 65-70 mph. Now, one of the problems that carb had was that one of the primary jet tips was bent and wasn't functioning, so I had one jet wide open all the time. So I figured I'd get better mileage with the new carb. Doing the same test, 65-70mph, I got 11.3 mpg. So I'm wondering what gives? Could it be that much different just from jets and rods? Also, why would it be a dog at WOT?

[george kujanski]

I'd say secondary throttles not opening correctly or the air valve not functioning correctly, as a first guess. If the choke linkage is not correct, it will block the secondary throttles from opening. This lockout exists to prevent secondary ops until engine is warm.

George

[77 TRASHCAN]

Hein,
You need Cliffs book.

[Quad]

Originally Posted by 77 TRASHCAN

Hein,
You need Cliffs book.

could not have said it better

[jhein]

Originally Posted by george kujanski

I'd say secondary throttles not opening correctly or the air valve not functioning correctly, as a first guess. If the choke linkage is not correct, it will block the secondary throttles from opening. This lockout exists to prevent secondary ops until engine is warm.

George

The choke seems to be working properly. The choke valve is about 1/4" open when cold. It's fully open when warm. The secondary air valve moves freely with no vacuum applied to the pull off. So I think that's all working as it should. But even if that was amiss, it wouldn't explain the problem with such a seemingly rich condition on the primaries.

[Kenth]

"Now I have another 7040263 on there that came from Quadrajet Power. It's freshly rebuilt and was calibrated for my motor. I don't know exactly what jets and rods are in it, or exactly what other mods, if any, were done."

Carb needs to be opened and checked. Guessing wont help.

[steve25]

Once the motor is fully warmed up lock out the choke and take a full throttle blast, does the motor respond better?

[jhein]

[QUOTE=Kenth;6510189
Carb needs to be opened and checked. Guessing wont help.[/QUOTE]

Yep. That's what I'll be doing later this morning.

[unruhjonny]

the secondary butterfly spring tension could be off;

Originally Posted by jhein

... I noticed from the first drive that it ran fine on the primaries, but when I went to WOT, it seems lazy.

Do the secondaries kick in as they should, or is there a delay?

The 263 was set up a bit leaner than the 273 on the primary side of things - so you could be seeing diminished mileage because the rebuilder richened it up a bit.

I have never played with the idle circuit(?) - which requires some enlarging of passages - hopefully your builder didn't do this...

It feeling doggy could be from either too lean (not enough fuel), or too rich (too much fuel - but if that secondary spring tension is too loose, then it might not be closed while you're cruising (it should be), and be drawing fuel on the secondary side too...
I have seen many rebuilders remove the secondary lock out - which is silly, because if it's set up properly, it has a legitimate job to do.

My first thought is that your diminished mileage might have you running a bit rich - which would require you look into what the jetting and needles are.

Some 1970 OEM jetting combinations are (jets - needles - sec rods):
'262: 72 - 43 - BE
'263: 71 - 44 - CC
'264: 70 - 41 - BP
'267: 71 - 42 - CC
'268: 71 - 42 - CC
'270: 70 - 39 - CC
'273: 70 - 39 - CC

[jhein]

Originally Posted by unruhjonny

the secondary butterfly spring tension could be off;



Do the secondaries kick in as they should, or is there a delay?

The 263 was set up a bit leaner than the 273 on the primary side of things - so you could be seeing diminished mileage because the rebuilder richened it up a bit.

I have never played with the idle circuit(?) - which requires some enlarging of passages - hopefully your builder didn't do this...

It feeling doggy could be from either too lean (not enough fuel), or too rich (too much fuel - but if that secondary spring tension is too loose, then it might not be closed while you're cruising (it should be), and be drawing fuel on the secondary side too...
I have seen many rebuilders remove the secondary lock out - which is silly, because if it's set up properly, it has a legitimate job to do.

My first thought is that your diminished mileage might have you running a bit rich - which would require you look into what the jetting and needles are.

Some 1970 OEM jetting combinations are (jets - needles - sec rods):
'262: 72 - 43 - BE
'263: 71 - 44 - CC
'264: 70 - 41 - BP
'267: 71 - 42 - CC
'268: 71 - 42 - CC
'270: 70 - 39 - CC
'273: 70 - 39 - CC

It's supposed to have 73 jets, 42B primary rods and AX secondary rods.

Yeah, I guess the secondary air door could be too loose. I'll check that too.

Thanks.

[srmmmm]

Quadrajet Power did the restoration on my Q-Jet that came from a 1971 Buick GS455 Stage-I. It was updated to a Stage-II and jetted up from the configuration I used running on a 350, to the 413 cu in of my stroked 350 block. They nailed the primary side perfectly, but the secondaries were running 15% too rich (bsfc at .555) on the dyno, and they weren't opening smoothly at all. We swapped out hangers and secondary rods for about a 10% improvement, but later determined the air valve spring wasn't in the best condition and seemed to be binding.

Overall, I still think they had done a good job of the initial set up on the carb. The engine started on the second spin up on the dyno with the carb straight out of the box and we never had to make any other adjustments for starting or idle quality.

[jhein]

OK, so here's what I found.

I'll cut right to the chase. The secondary air valve tensioner parts were installed but not adjusted at all. It's as if they got installed and then he got distracted and forgot to adjust. The spring was not contacting the rod on the shaft at all. Totally loose.

I decided since I had it off to just disassemble and inspect everything. I'm a quadrajet novice but I didn't find anything else obviously wrong.

I have 73 jets, 42B primary and CC secondary rods with a I (capital i, not L, I think) hanger.

So I adjusted the air valve tension to 3/4 turn past contact with the shaft. That's per the Quadrajet Power video.

I'm not sure if that could account for all the problems I had but it seems like it could.

I'll put it back together after lunch. Hopefully that will fix it.

Thanks for the help.

[65 Lamnas]

Originally Posted by jhein

OK, so here's what I found.

I'll cut right to the chase. The secondary air valve tensioner parts were installed but not adjusted at all. It's as if they got installed and then he got distracted and forgot to adjust. The spring was not contacting the rod on the shaft at all. Totally loose.

I decided since I had it off to just disassemble and inspect everything. I'm a quadrajet novice but I didn't fund anything else wrong.

I have 73 jets, 42B primary and CC secondary rods with a I (capital i, not L, I think) hanger.

So I adjusted the air valve tension to 3/4 turn past contact with the shaft. That's per the Quadrajet Power video.

I'm not sure if that could account for all the problems I had but it seems like it could.

I'll put it back together after lunch. Hopefully that will fix it.

Thanks for the help.

Take a look at the secondary cam...replacements are white. Old ones will be a reddish-brown color and can be worn and loose on the shaft. Also, it doesn't hurt to put a little dab of grease on the rod that contacts the air valve spring. Make sure the dashpot has a "timed" release.

[jhein]

Originally Posted by 65 Lamnas

Take a look at the secondary cam...replacements are white. Old ones will be a reddish-brown color and can be worn and loose on the shaft. Also, it doesn't hurt to put a little dab of grease on the rod that contacts the air valve spring. Make sure the dashpot has a "timed" release.

The cam is white and looks new.. Yes, I can see that a little grease on that shaft will help. How do I check for the timed release? Pull off the vacuum line while running and see if it releases slow or fast??

[65 Lamnas]

Yeppers. Maybe drive it and test it first….if it releases too quickly, you’ll have a bog.

[jhein]

The first picture is the pulloff I have on the QJP carb now. The second one is another that I have that came from Cliff. The metal one with the two ports, I assume that the second port is to allow for the timed release? The Cliff part is also supposed to be made for timed release. I'm inclined to switch to the Cliff part. That's what I had on the other carb and it worked great. Also, I assume with the metal one with the two ports, one is left open, not capped.

[65 Lamnas]

Originally Posted by jhein

The first picture is the pulloff I have on the QJP carb now. The second one is another that I have that came from Cliff. The metal one with the two ports, I assume that the second port is to allow for the timed release? The Cliff part is also supposed to be made for timed release. I'm inclined to switch to the Cliff part. That's what I had on the other carb and it worked great. Also, I assume with the metal one with the two ports, one is left open, not capped.

Cliff's CPOs are made to his spec and correctly timed. Try your carb "as is" and see if it's satisfactory...if not, switch to Cliff's plastic one if it'll fit..

[jhein]

Originally Posted by 65 Lamnas

Cliff's CPOs are made to his spec and correctly timed. Try your carb "as is" and see if it's satisfactory...if not, switch to Cliff's plastic one if it'll fit..

So am I correct that the second nipple on the CPO is left open?

[Bruce Meyer]

Originally Posted by jhein

So am I correct that the second nipple on the CPO is left open?

That other nipple goes to this gizmo here that mounts to the inner fender

[Kenth]

Originally Posted by Bruce Meyer

That other nipple goes to this gizmo here that mounts to the inner fender

Only on non-Ram Air vehicles. 7040263 is a non-RamAir carb. If used on a RamAir car, cap the nipple not used or the p-o will not work as intended.