Carb issues, just chime in.

[lyrikz]

chevy 454 with edlebrock q-jet intake. Decent size cam in it.

So, i tried to run a quadrajet that i had. Can not get it to idle. the guy working on the car has years and years on these things. there is some corrosiion building up in it and thinks that some of the fuel passages may be getting clogged. The vehicle just can not maintain a normal idle. It will idle fine, then not, then normal again.

Tore it all apart. Everything looks good and we blew everything out.
im going to get a new carb. this one is 30 years old.

I was going to get a Edlebrock 1813 or 1413. Then i read that edlebrocks are awful and go with holley. Im lost. Any suggestions????

[oldgold70c10]

Get the book by Cliff Ruggles and rebuild & re-tune the Q-jet. Seriously. All of my Q-jets are at least 30 years old, they've been rebuilt, and they run great. I wouldn't go back with an Edelbrock if I was paid to.

[lyrikz]

Originally Posted by oldgold70c10

Get the book by Cliff Ruggles and rebuild & re-tune the Q-jet. Seriously. All of my Q-jets are at least 30 years old, they've been rebuilt, and they run great. I wouldn't go back with an Edelbrock if I was paid to.

Its been rebuilt, retuned twice already. By people who have experience with these things. Is edlebrock that bad??? I see them on everything.

[biggestjohn]

What are the cam specs? How much vacuum is the engine pulling at idle?

[lyrikz]

Originally Posted by biggestjohn

What are the cam specs? How much vacuum is the engine pulling at idle?

Cam specs
Gross valve lift intake= .552 exhaust .555

Duration at .050 230 intake 236 exhaust.

Vacuum is within specs

[a_barth]

I have run a few Edelbrocks and have been happy with them, easy to tune and decent performance but...

I have pretty well settled to using Q-jets on everything because they really are a good carb when built and tuned properly. There are a number of online references that can help with the tuning process. My key question is whether the q-jet you are using is made for a big-block or not. Every q-jet that left the factory was specific to the motor it left with and that is usually the best place to start tuning for performance increases from. It is much more difficult to tune a carb for a 307 to a built big-block than one for a big-block.

[biggestjohn]

Originally Posted by lyrikz

Cam specs
Gross valve lift intake= .552 exhaust .555

Duration at .050 230 intake 236 exhaust.

Vacuum is within specs

With that much duration, your not going to get a low RPM smooth idle. I assume that the statment of "Vacuum is within specs" equals that you don't know. You have a big cam, get used to it, Its not going to idle like a stocker no matter what any of the guessers say.

[slikside]

Originally Posted by oldgold70c10

Get the book by Cliff Ruggles and rebuild & re-tune the Q-jet. Seriously. All of my Q-jets are at least 30 years old, they've been rebuilt, and they run great. I wouldn't go back with an Edelbrock if I was paid to.

If you are really interested in seeing if you can get that q-jet fine tuned, I strongly recommend Cliff's book as well.

I knew next to nothing about q-jet's (or any other carbs, for that matter), and this book lays it all out. Tore mine completely apart, and rebuilt with one of his kits (also had the primary throttle shaft rebushed....made all the difference in the world. I got it right the first time because of that book!

[lyrikz]

Originally Posted by slikside

If you are really interested in seeing if you can get that q-jet fine tuned, I strongly recommend Cliff's book as well.

I knew next to nothing about q-jet's (or any other carbs, for that matter), and this book lays it all out. Tore mine completely apart, and rebuilt with one of his kits (also had the primary throttle shaft rebushed....made all the difference in the world. I got it right the first time because of that book!

On order...

[lyrikz]

Bringing this back. Have some questions.

Driven the truck about 3-4 times. Idles good, starts good. Accelerates OK. It feels like it spits a bit under hard acceleration. Very hard to explain.

So i want to get it tuned. I would like to do it myself. I understand basic engine concepts. Timing, vacuum, and all that.. But i have never really messed with the acceleration portion of it. Or different jet sizes.

Without having wide band o2 sensor on the truck, how do you tell if you are rich or lean during accleration. Right now the truck goes pretty dang good, but if your doing like 30 and romp on it, it goes but you can tell its just not right. Very hard to explain what its doing. Almost feels like its missing a tiny bit under hard acceleration.

[MusicMan70]

"Its been rebuilt, retuned twice already. By people who have experience with these things. Is edlebrock that bad??? I see them on everything."

Well I guess even some experienced folks have trouble time from time. Glad it works for you now! I've rebuilt a few and it's been more hit than miss. I have had to go back in, an redo again what I did before, because I'm still learning about the Quads'. Glad it's running fine. Now you can play with the Quadrajet knowing you have a solid back-up.

[lyrikz]

Originally Posted by MusicMan70

"Its been rebuilt, retuned twice already. By people who have experience with these things. Is edlebrock that bad??? I see them on everything."

Well I guess even some experienced folks have trouble time from time. Glad it works for you now! I've rebuilt a few and it's been more hit than miss. I have had to go back in, an redo again what I did before, because I'm still learning about the Quads'. Glad it's running fine. Now you can play with the Quadrajet knowing you have a solid back-up.

I have no plans getting rid of the quad. I do want to try some of those tips to get this idling correctly. The edlebrock is on point. Thottle response is still immediate but there is just SOOO much more go right off the bat.

[geezer#99]

I'd leave the carb alone. Concentrate on the timing now.
What's your initial timing?
Vacuum advance hooked up where?
Do you have a Timing tape or dial back to zero timing light?

[lyrikz]

Originally Posted by geezer#99

I'd leave the carb alone. Concentrate on the timing now.
What's your initial timing?
Vacuum advance hooked up where?
Do you have a Timing tape or dial back to zero timing light?

I will check my timing again.

I have both timing lights. Just the standard blink light and an expensive dial electric one.

Vacuum is hooked up to... let me get a picture.



Its hooked up to manifold vacuum port.

timing is 14 at idle. then 32 ish at 3000 rpms. Thats what the timing was with the OLD carb. i put the new carb on and didnt readjust the timing. Didnt think that was necessary.

One side note. I have this SMALL ass air filter. When i take that off, the truck runs COMPLETELY different. Is that normal with an air filter??? The air filter is like 5 inches round, if that. Runs better without the air filter but still not right.



Let me know what to do next.

[geezer#99]

Could be air cleaner related. Starving for air with a small filter. Try a test run with it on and off and see what that does.
One more thought. I've never had success tuning a motor in the winter.
And your timing curve. Quick or slow from idle to 3000rpm's.

[lyrikz]

Originally Posted by geezer#99

Could be air cleaner related. Starving for air with a small filter. Try a test run with it on and off and see what that does.
One more thought. I've never had success tuning a motor in the winter.
And your timing curve. Quick or slow from idle to 3000rpm's.

SOrry geez, i dont know what that means... When i rev and hold at 3000 it reads 32 ish...

With the air cleaner off, it does run better. Just doesnt seem right. As for winter tune.. When it was warmer on when i installed the carb, it ran alot better but would still cut out on power. It felt lean...

When i get home, im going to take off air filter. Check timing/idle. Drive it till its warm, then get on it and report back.

[70STOVEBOLT]

The vacuum advance line should be hooked to the timed vacuum port. The manifold vacuum port will pull vacuum all the time, so you are advancing your timing slightly even at idle.

[lyrikz]

Originally Posted by 70STOVEBOLT

The vacuum advance line should be hooked to the timed vacuum port. The manifold vacuum port will pull vacuum all the time, so you are advancing your timing slightly even at idle.

Man, i have researched this topic OVER and OVER and OVER. I read this huge article that the reason they went to timed vacuum was emission reasons and manifold vacuum is fine.

I dont know. I mean, i got guys on here that say manifold, a few techs that say manifold. A few that say timed. ahhaa. Im damn lost with that.

[geezer#99]

When you say your timing is 32 degrees at 3000rpm does that mean with vacuum degrees added on.
A quick curve is timing comes up real fast right after idle and slow curve means timing comes up slowly up to when your timing is all in.
Ported or manifold. Every motor is different. You gotta experiment.

[lyrikz]

Originally Posted by geezer#99

When you say your timing is 32 degrees at 3000rpm does that mean with vacuum degrees added on.
A quick curve is timing comes up real fast right after idle and slow curve means timing comes up slowly up to when your timing is all in.
Ported or manifold. Every motor is different. You gotta experiment.

Geez, i couldnt really answer that. I was to busy paying attention to the rpm then checked timing. I couldnt tell how fast it went up...

[Cannonball1]

Have you tried adjusting the accelerator pump linkage to give you a little more juice when you hit it? If it's like my old Carter AFB (they look the same), move the linkage one hole inward toward the pump. This will give it a little more gas through the boosters when you stomp it. If that fixes it your good. If it makes it worse, go one hole out from the original hole.

[lyrikz]

Originally Posted by Cannonball1

Have you tried adjusting the accelerator pump linkage to give you a little more juice when you hit it? If it's like my old Carter AFB (they look the same), move the linkage one hole inward toward the pump. This will give it a little more gas through the boosters when you stomp it. If that fixes it your good. If it makes it worse, go one hole out from the original hole.

I noticed that was a very easy thing to try. Once i verify timing, remove that air intake, i will try switching that and see if it gets worse or better and chime in.

[DANTIP]

Did the Q-Jet ever have a throttle-shaft bushing kit put in it?

[lyrikz]

Originally Posted by DANTIP

Did the Q-Jet ever have a throttle-shaft bushing kit put in it?

The quadrajet had corroision in EVERY hidden crack. SOaked it, blew it out, and i was continually getting pieces of junk coming out. So i bought a new one.

I also kept the quadrajet and bought a book on how to rebuild it. Mine has all new stuff and is setup right, i just need to get the passages cleaned somehow. THe soaking didnt seem to do it.

[story2tell]

Take a look at a couple of articles on this Corvette site (http://lbfun.com/Corvette/Tech/vettetech.html) scroll down the page to "timing and vacuum advance." The article "Vacuum Advance Principles and Application" by Duke Williams and one by John Hinckley, "Advanced Curves" will explain vacuum advance, timing, and ported vs manifold vacuum. Big Blocks with big cams typically have lower vacuum than stock and usually need to have a different vacuum advance can installed. These two articles helped solve my problems.