My 81 has never run properly. Got a new chip and that helped. But I pulled the carb thinking I was going to rebuild it only to find out that the QJet is number 17070839 (on the side, in a circle, and under the word GM and RP) which doesn't come up as a Vette carb. Best I can tell its a Cadillac carb but it's hard to find solid info on it.

Also there's another number on the top of the carb 17070635 right beside the word RP (near the ECM connector)

http://imgur.com/a/xjcwO

Anyone know for sure what it's from? Is this two different carbs put together?

Is it going to work with my Vette even if I rebuild it? I think I read the QJets for 81 Vettes are supposed to be 1705 or 1708 carbs but I dont know what the difference is from my 1707.

 

Those arent the carb numbers youre looking for.
On the drivers side of the carb stamped vertically on the flange outside of the rear venturi is where you'll find the number.
If you dont know what you're doing on a CCC carb you can screw it up pretty quick

 

the original carb numbers are below, cannt find anything related to vette on your current number
4 speed trani 17081217
auto calif. 17081218
auto other 17081228

 

What he said.
You are looking at casting numbers. I made the same mistake.

 

Thank you. It is in indeed a 17081218 which is correct for a CA Vette.

Im trying to stay close to stock but Ive taken off the pollution control hoses and air pump. Will the CA version still work ok or should I be looking for the 49 state carb?

 

Yeah I think I counted a dozen different numbers on it. Confusing as hell.

 

You'll be fine, as long as the carb is in or near original calibration.

 

It should be. I don't see any drilled out covers on it.
I also managed to find an OTC 3485 monitor 85 on eBay for 40 bucks which should help me set it up. Not sure how it works but it comes with the manual.

 

Those electronic feedback carbs where hard to make run when they were new ....That being said there are adjustments that can be done to compensate for certain drivability problems. Can you describe the problem with the drivability.

 

It starts great, idles well although not quite totally smooth. But midrange acceleration is poor, like it's fuel starved. Just kind of bogs when you try to accelerate but *occasionally* its fine. But if you punch it, it pulls pretty good at wide open throttle.

It won't keep steady at cruise, it surges - always seems like its cutting in and out a bit, as if someone were turning and on and off a cylinder. Sometimes, but rarely backfires too which I'm guessing is indicating a lean condition.

Have been through a few fixes with the carb already. First was finding the chip was dead so I got a new HyperTech chip. Then discovered the accelerator pump spray was only happening on one side. Fixed that, then found the fuel mixture solenoid wasn't 'jumping' up and down like it should, so we got it unstuck and now you can hear it clicking properly. Then there was a base gasket leak that improved everything when we tightened down the carb and I finally replaced the gasket the other day and that smoothed out the idle considerably. There seems to be good vacuum and I did a vacuum leak test using propane and a plastic hose around the carb with no sign of rpm change so I think we've got that one covered. Not sure what else to do.

I have also wondered if the fuel pump isnt failing and thats why she doesnt keep up during acceleration, but then why does it seem to kick in at WOT?

 

Ok a couple of quick checks first .....If your EGR valve is still connected disconnect the vacumm hose and plug it then test drive it . EGR surge at mid throttle was a big problem for ALL feed back carb systems . The spring in the diaphragm gets weak and the valve open too far diluting the air fuel charge with too much exhaust during cruise . WOT vac falls off and the valve closes making it run better. If that makes no difference you need to make sure that the timing is set properly . My AllData info system only goes back to 1982 so if I am wrong I am sorry . You should disconnect the 4 wire timing connecter at the dist CEL should flash set timing 8 deg man 6 deg auto at an idle. Also these engines are prone to vibration dampener slippage so you may have to verify TDC # 1 cyl is correct on the timing pointer . Let me know how this stuff goes for you. Checking the mixture control dwell would be next but with out a scan tool can be hard but not impossible.

 

You can also do a search on 'E4ME' on the forum for good advice. should help with the surging issue you describe.

 

Have to double check but Im pretty sure I plugged the EGR valve when I took off all the other pollution control lines.

Timing, uh, could be an issue. It was at 8 degrees but last year I read in this forum about guys advancing it to 14. I tried it and it seemed to run much better but maybe now that some other gremlins are worked out I need to set it back.

Have never checked the vibration dampener but given the improvement by advancing to 14 degrees, maybe it has slipped. So how do you test TDC? A wire in through the spark plug hole?

Getting the OTC 3485 should make checking the dwell pretty easy.

The car is in a storage garage at the moment and I won't be there for a few weeks, but will remember to check your advice when I am. Thanks! Its not that I can't replace the darn E4ME, it's that I've already chased down enough of her demons that I want to beat this problem. THEN I can pull the beast, put it in storage and put in the crate engine that she deserves lol.

 

Checking The TDC can be tricky on a corvette . Pull #1 plug install a compression gauge hose without the gauge . Disable the ignition system . with your thumb over the hose have someone TAP the starter till to feel the compression blow your thumb off the end of the hose. OK you found the compression stroke now the hard part you need to get a wratchet on the crank nut and turn the eng normal direction of rotation while to have something in the cyl to tell you when the piston is at the top of its stroke . I use long wooden Q tip rods . NEVER PUT A SCREWDRIVER IN THE HOLE !!!!!!! Once you determine TDC you can check it against the timing pointer