Carb tuning

[gmebey]

Well now that I have eliminated all low hanging fruit, per se, I’m ready for the next big challenge in the learning curve.

After cleaning up the worn-out front end, shot tranny, wrong power steering pump, worn out distributor…. I’m now working on improving engine performance. In a past post I mentioned that I have a square bore intake with a spread board carburetor (Edelbrock 1902), the intake casting numbers are 3927184.

The past owner didn’t realize this combination of carburetor and intake would force the secondaries closed. I was able to correct the secondaries from not opening by adding an adaptor.

So now when the secondaries open the power goes flat and seems to ping.

Where do I start on this challenge?

[davepl]

Pick a carb you want to learn about. You likely have what used to be known as the Carter AFB. Nothing wrong with it, just not sure how easy it is to find a book on them, but here's one:

Rebuild & Powertune Carter/Edelbrock...
Then READ the book. Cover to cover. Then go back to the start of the book and start your process with your carb.

When doing anything with it, take a lot of pictures. Like for every part you take out, showing orientation and order of disassembly. Trust me when I say that what looks obvious when disassembling it will be hazy when it's time to go back together...

[n33k0]

Originally Posted by davepl

When doing anything with it, take a lot of pictures. Like for every part you take out, showing orientation and order of disassembly. Trust me when I say that what looks obvious when disassembling it will be hazy when it's time to go back together...

Or you get everything back together and have some spare parts lying around that weren't there before

I still have a lot to learn, but I was under the impression that pinging was affected by timing

[geezer#99]

Pinging can be caused by a lean carb too.
Maybe his secondaries air valve isn't opening enough.
BTW The eddy 1902 is edelbrocks version of the quadrajet. Same thing but with a few refinements.
Here's some info.
http://www.edelbrock.com/automotive/.../1000/1904.pdf

[BMERDOC]

Here is a couple of things to read. Remember to base line the carb first and make sure everything functions like it should (clean fuel filter, Throttle plates open completely using the gas pedal, correct fuel pressure, no air leaks, etc). You should at least have a vacuum and rpm gauge to monitor your changes.


http://www.edelbrock.com/automotive/.../1000/1904.pdf

http://www.florida4x4.com/tech/quadrajet/

[BCOWANWHEELS]

Back off the timming a couple degrees and pinging will stop. Its because of todays bad gas

[GASoline71]

That SBC intake is a spread bore Q-jet intake just like the spread bore Q-jet Replacement carb you have on there... I'm confused to why you needed an adapter?

Gary

[BMERDOC]

I Googled it. Its definitely a spread bore.

[BCOWANWHEELS]

Those sure are great low end hi-torque manifiolds. Gm hit a homer with them. SAME WITH THE Q-JET CARBS

[87Skier]

Check out the link below, it's a bunch of common problems with quadrajets but a lot of it should cross.

http://www.digitalcorvettes.com/foru...ad.php?t=88376

I'd start by changing the fuel filter, ensuring the secondary flap is adjusted correctly and checking total timing.