Arctic White 91 RS

This is long but I have to give the details to fix the problems. I apologize for posting a vette problem here, but I know a lot more folks on ThirdGen can anywhere else.

Car idles very poorlly when in Drive.

Car has never idled really well, I've had for 17 years and 4 rebuilds of carb to fix the problem. The guy that had it before me rebuilt the carb once also. In 1983 it would idle when the car was in Drive and act like it was about to stall out. In 1984 I had a Isky Mega Cam installed single pattern .470 lift and 270 degree at 0 according to Isky. Idle got a little worse but not much. In 1985 the idle got bad it would die idling at a stop light unless you held the brake and gave it a little gas or shifted to neutral.

Over the next few years the idle problem got worse and each rebuild would say "idles that way cause of the cam". Isky said the cam should idle fairly well and not die when sitting at stop lights.

Car was stored from 1990 until 1998. Idle problem was never solved. I was out of the car thing cause I got married and it wasn't the right time for it, ten years later wife is kinda ok with the car thing again.

In 1998 Carb was rebuilt again, and the problem was the same or worse than ever. I called Isky up again, described the problem, they said it need a performance advance kit. Got that installed (Mr. Gasket) for about 2 days the car seemed fixed, then it got as bad as before, then worse. When I asked the local mechanics they were "sorry it's not stock can't help you" or "I don't work on corvettes" for the most part. In other words, the problem would be too time consuming to figure out.

Over the last few months, the idle has gotten worse, car had a tune up, plugs, wires, coil, points, fuel filter, air filter, timing checked and reset, carb tweaked. Then the car had a round of power surges, press the gas petal and the car po-go'd, accelerate hard cut out accelerate hard cut out. Ended up replacing the gas tank cause it was rusty and fuel line. Pogo went away, then a month later pogo returned. I replaced the fuel filter, (car has one at carb and one in line). Pogo went away again for the most part. Idle problem same.

Two weeks ago, I found a Dyno service near by. Tested the car. 160 horse power rear wheels ( 350, cam, headers Turbo 400) That was terrible!!!

Dyno guy said the ignition system almost didn't register on his computer. He mess with it to get it too read. He managed to the hp to 175. The graph was unreadable over 4000 rpm cause the points were shaking causing misfires and ignition system wasn't make a good voltage. He moved the distrubiter about 1 inch (turning) and it didn't do anything. He shook his head and was like,"I've never see that before!" He twisted some screws on the Q-Jet and basically they didn't do a whole lot. He was amazed the adjustments on carb didn't seem to do anything. Finally, he hit a combo that worked and the car idled right for about 1 minute, then it started acting up again. When he finished it was a little better.

Told me I needed a new carb and new ingition system. At when at Wide Open Throttle the Secondarys barely open. The engine pulled 30 inchs on the vacuum gauge. Dyno guy said that was proof the car should be able to idle with the Isky cam it's got. O2 sensor show the car was rich at idle. However at high RPM it was leaned out to 16.5 to 1....way too lean. In fact it leaned out too much too fast. Messing with the carb didn't change how fast it leaned out in any meaningful way was about 16.0 to 1. I checked the fuel pressure it was 6-7 pounds when trying to crank.

I did the cranking compression test. I realize I screwed it up, after reviewing an engine building book. I blocked the choke open but not the primaries and secondaries on the carb. I know this would have made some difference.

Here the data. Each was test 3 times. All plugs looked black and rich except 4 and 6 they were tan/brown and looked about right.

Engine has Mobile 1 5w-30 in it, could this thinner oil effect the test? Should I test test with 10w-30?

Cylinder 1

85 low 100max,

Cylinder 2
could not get the attached treaded in cause the A/C bracket was so tight.

Cylinder 3
65low 95max

Cylinder 4
65low 85max

Cylinder 5
65low 120max

Cylinder 6
80low 90max

Cylinder 7
90low 120max

Cylinder 8
105 low 110max

That looks pretty bad to me cause some vary by more than 25% (85peak and 120 peak 29percent variance!!!)

I did find carbon in the rotor cap and scraped some of that off.

I also found the glass insulator part of plug in cylinder 3 was broken.

The plug gaps were between 30 and 45. Which is pretty bad. I regapped all to 35 because the two cylinders that were gapped at 35 looked the best they were a light brown color. The other 6 plugs looked more black than brown. The engine has R44T's in it.

Car idled better at first. Even idled in drive for about 2 minutes. Took it for a drive. It stalled at the stop sign just like it has been. However it did seem just a tad better than it was.

Comments?

Suggestions?

Does this 350 need a rebuild for top performance?

LilJay

I had a qjet on my car for a while, and it did alot of the weird things that you are describing. I rebuilt it several times and didnt really help, it would seem to act ok for a while then go back to ****. I think the problem may be an internal vaccum leak. Qjets are bad about this. If the internal housing has a crack in it, the varinces of engine speed and vaccum levels can change the fuel mixture. When i had this problem, i didnt know very much about cars. I was running and oldsmobile at the time, and converted to roller rockers cause i thought that i wasnt getting my vavles adjusted right(if any knows anything about olds you understand, i still love those engines)after spending lots of money, i bolted on a carter. The damn thing ran perfect. My suggestion is to bolt on a different carb and see how it does. This may and may not be your problem, good luck. lil jay

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Wide Open Till You See God.....Then Brake

battyice

Sounds like you have a few things going on here. Ignition problems, carb problems, and low compression. I would address things in that order. Get yourself an HEI distributor (you can find them on ebay for <$75), some decent plugs and wires, and a timing light. If your carb has been apart that many times, who knows what is inside it. May have mismatched components, improper assembly, etc. I think it would be in your best interest to get a different carburetor and start from there.

It is impossible to diagnose carb problems if your ignition system isn't working correctly. Once you have a nice hot spark and the correct amount of advance, you can start tuning the carb.

Your compression numbers seem low, but the car should still run and idle once you fix the issues mentioned above.

trumps2000

iTrader: (2)

I'd have to agree with BATTYICE, ditch the points and go HEI. Can't do anything with the carb if the ignition isn't up to snuff. I'm assuming this is an nonCC Qjet?

With the compression test did you let the motor turn over several times? When I tested mine I didn't at first and it lowered my readings. Also when testing compression you should have the motor warmed up too. Those readings are kind of spread out and low, but I guess your cam could cause that. I only have 8.5:1 CR and measured 145-150. I'd retest just to be sure.

five7kid

iTrader: (14)

And it was only 7 years ago. . .

trumps2000

iTrader: (2)

HAHA I didn't even realize, maybe I shouldn't post late night