redoldsman

Ralph, when the weather worms up (hopefully next week) I a m going to try your method. Too bad somebody didn't make a little gadget to measure the pressure it takes to open the dampers. It would be pretty simple.

Thanks

cutlassefi

You’re kinda right. You said too much air. I guess that’s right in relation to it not being able to deliver the right amount of fuel vs the amount of incoming air.
A lot of people try to set them to open quickly, but as mentioned it can really be more beneficial at times to slow that down significantly.
For the record I’m not a Qjet fan by any stretch. I’ve had a dozen or so on my Dyno from various builders and none were right out of the box. Plus any change in fuel pressure alters the fuel curve. Again not a fan. The newer stuff from Quick Fuel etc is so much easier to tune and so much more consistent it’s not even a fair comparison.
And once the new carbs from Edelbrock are out, you’ll be able to get an even flatter fuel curve.

redoldsman

Mark, are you talking about the AVS carbs from Edelbrock? Of course nobody has any in stock and it would probably be March before I could get one which would not be a problem. They get really good reviews.

OLDSter Ralph

Glenn, I found the procedure to get close enough. Back when I was racing, I could adjust them by "feel" (pressure to open the Secondary Air Valve). I think its spelled out in the CSM also. I think you are close, but "something" is just not quite right. Maybe double check the accelerator pump piston. Otherwise, maybe Kenneth's memory will offer something.

cutlassefi

Nope, their new performance carbs aimed at the Holley HP and XP line. 4 air bleeds per hole and a bunch of other improvements over the traditional Holley design. Nice piece.

redoldsman

I found the one you are talking about that looks like a Holley. I think that would be more carb than I need for a stock 1975 Olds 455 smog motor.

NTXOlds

Thanks for pointing this out. I had missed the news.

Here is a nice write-up on it, assuming this is the one.

https://www.chevyhardcore.com/featur...ech-4150-ever/

olds 307 and 403

Cool to hear about another carb option. Cliff actually adds a restriction to the pull off on his high performance pull off. Most new ones have none at all, he says it is a PIA to add. A slower pull might be all you need.

cutlassefi

Yep that’s it.
Op- I understand it would be overkill for your application. It was just a pointt of reference and an FYI.

redoldsman

Ralph I looked in my FSM and found the procedure. Should have already done this but who needs any stinking directions (I do). You are spot on with the procedure but it calls for a 3/4 turn after contact of the air valves. The carb overhaul kit said hold the air valves closed and tighten the spring until it made contact with the pin in the shaft and then tighten it 3/4 turn and lock it down with the set screw. Same thing just different wording. We are supposed to have some days back up in the 60's this week so I will give it a shot. I will pull the carb again so I can put it on the bench and be more accurate. Cliff Ruggles book arrived today. Man there is a lot in that book. If this doesn't work I will probably replace it with an Edelbrock.

OLDSter Ralph

Glad you double checked. I stand corrected, my memory must be slipping. Ruggles book is a lot to digest. Good luck.

redoldsman

All the Quadrajets don't adjust the same. The 350 in 1975 adjusted 1/2 turn after contact.

Vintage Chief

Agree. Both the 7041250 & 7041251 (1971 model year) I set at 1.5 turns CW initially. I think I stated that in Post #24?

Fun71

Oh boy, from what I have read that will mean you start at zero with carb tuning. Not only will you get to adjust the secondary operation, but you'll need to work on the primary and secondary jetting as well.

Vintage Chief

How come you're taking the carb off. The screw adjustments are done with the carb mounted. At least that's how I do it & it works perfectly. Unscrew the Allen set screw, turn the flat head screw CCW until there is freedom of movement of the secondaries. Push/Hold the secondaries down with minimal force with your finger until they just touch the throttle body opening then tighten the flat head screw until you can just barely feel the secondaries touching the throttle body. It's at that point I turn the flat head screw 1.5 turns, then lock down the Allen screw and take it for a run. If you're too tight you have no secondaries. Come back same procedure, turn it CCW 1/4 turn, take for another run. Repeat until the secondaries open and you feel your head getting thrown back.

Fun71

X2 on what Norm said. No need to remove the carb to perform these adjustments. I’ve done this many times and never removed the carb.
You do need a spot where you can go WOT to make the adjustments without getting into trouble. Those are stories for a different time.

redoldsman

Norm, I am keenly aware how this thing adjusts. I looked at the sheet that came with my carb kit and none of the adjustments are 1 1/2 turns. This is for a 75-77 carb and includes Buicks, Chevy's, Pontiac, Cadillacs and of course Oldsmobiles. The only adjustments are 1/2 for the 350 & 400 and 3/4 turns for the 455's. They are all over the board for the other models and range from 1/2 to 1 full turn. Your 71 may be different and if it works that is all that counts. I think when I get this thing right I will be able to feel my head move backwards and see my gas gauge moving. Thanks.

Vintage Chief

In my description I should have said more accurately the air valve doors (?) or the air paddles (?) as opposed to the secondaries (?). I should probably have said the air horn instead of the throttle body since the air paddles reside above the throttle body on the air horn. I'm pretty darn sure Glenn knows what I'm talking about though.

redoldsman

The Edelbrock probably won't happen because I am going to get the one on the car or the one on the bench to work. I am glad my sledge hammer is in the storage shed and not in the garage. Thanks for all the help guys.

Vintage Chief

Well, Glenn, I'm just reading your thread and basing my predictions on things you've already stated and some things others have stated. The deal with the spring being way too tight, is it the correct spring, was it wound too tight, is it the exact type spring - there ARE some deltas here. You stated the cam was fine. A sprung spring and an incorrectly sized spring can influence your rod travel and seating characteristics which could then impart a delta on your air doors for rod movement. Just trying to think this through. I replace both the cam and the springs with those in the kits when I rebuild. Those springs don't seem like much but they are. You'll get it & good luck man.

cutlassefi

What are you going to do about WOT and part throttle? Buy a wideband or don’t even bother wasting your time.

redoldsman

Mark, maybe I am ignorant but I am not following you.

cutlassefi

Simple. You seem concerned about how to set the idle mixture screws but there’s way more to carb tuning than that. A good wideband is second to none for tuning, even the idle.

redoldsman

I never mentioned anything about setting the idle mixture screws. Yes, I am aware there is a lot more to tuning a carb like jets, metering rods and all the external adjustments. I am not putting this thing on a dyno and watching the power band. It is just a stock 455.

cutlassefi

I understand. However I guess you’re missing my point. Best of luck.

sysmg

I found that after I set it to the factory Air Valve Wrap settings, you could benefit by making some fine adjustments. Loosen the spring 1/8 of a turn at a time and see if there is any improvement. If the car starts to bog, turn it back 1/8th turn tighter. You can also try going the other way (making tighter than factory) if you think it's opening too soon (or bogging on low RPM full throttle).

redoldsman

I am claiming Victory guys. I went out this afternoon and took the air cleaner off and was going to adjust the air valves with the carb on the car. When I first pushed the valves open they were binding. What the heck. So off the carb comes and goes to the bench. I will shorten this down because we have all read too much about it anyway. First off I have the spring on the air valves too tight. Then the second culprit was the cam that the shaft goes through that opens the secondary metering rods. This thing is not metal but some kind of phenolic material with a build up circle on each side of the hole to keep it in the center. The part that rides on top of this little cam would slip in between the cam and the carb body and cause the binding. In addition to the carb I took off the car I had another one and took the cam out of it and used it. Then I put it back together and set the spring tension at 3/4 turn after it contacted the pin in the shaft. No bog on the floor from a dead start or after the car is rolling and is floored and it downshifts. It could probably be fine tuned a little more but trust me it is good for the time being. This thing has kicked my butt but I won. I have done several quadrajets over the years but none as difficult as this one. Thanks for all you help and suggestions guys. That is what make this a great website.

Vintage Chief

NTXOlds

Congratulations, Glenn!

OLDSter Ralph

Glenn, its great you found that "little thing" that was the problem and fixed it. Congratulations. What you found will also help others in the future, thank you.

redoldsman

Thanks Guys. I know more about quadrajets than I ever wanted to. I really didn't use the book but it is a great book and I am going to keep it and put it in my car stuff library. I will be glad to scan pages out of it and post on here if anybody needs help.

Fun71

Congratulations and two thumbs up for the win! Take a victory lap!

(At WOT of course).

Koda

I have both Ruggles's book and the other guy's, that are both quite good.

Dynoking

Put it in the bathroom and read it while on the throne.