gmviso

I got this 77 Vette, (350-180HP, Auto, AC) about 2 weeks ago.

It has 136K miles and is in pretty decent shape cosmetically. Looks like one repaint.

The offer I made took into account that I would be doing some repairs to it, and have.

It was initially running rough, so I gave it a tune up (Distrib Cap, Rotor, Plugs - all AC Delco). While I was changing the plugs I discovered the real reason it had been running rough -- the number 6 plug wire was not attached. Never the less I completed the tune up. Oh I also changed the fuel filter.

It ran great.

I didn't change the wires because they looked like brand new 8MM Accel brand (I think). I did notice that a couple of the wires had been touching the exhaust manifolds though and had started burning the insulation. (I have purchase but not yet installed new Delco Wires.)

I took it out on the highway and went 80MPH. It ran great, but when I got home I discovered that there was oil leaking from the Rocker cover gaskets. I tightened the 4 bolts per cover. They were real loose. Oh I should mention that the previous owner had the car 13 years, but for the last 6 it did not leave the garage much. (The car is all painted up, engine and frame, although the frame should have been cleaned before the paint was applied.)

Now for the problem.

5 days after the tune up, I took it out and started noticing that above 40MPH it might run well or it might start lugging and the engine RPMs would drop. Letting up and reapplying the accelerator would fix that.
This repeated itself the following day. In fact it actually stalled one time. I was able to restart it after a couple of minutes and limp home.
I figured it was a weak fuel pump (mechanical) so yesterday I changed it out. Didn't fix the problem.

Also it started being difficult to start after sitting over night at about the same time. Another post shows how to seal some carb ports with epoxy so I guess I may have to do that. Could this be a factor in my problem?

I expected that an ignition problem would have just shut the engine off, bu I am now wondering whether it is the ignition coil or module?

I guess I also need to get out and dust off my timing light and check timing and advance.

Observations:
1) We have been having a heat wave here in the Midwest which I believe started about the time my problem started.
2) As mentioned in another post my engine compartment temps are unbearably hot, but from the replies to that post I guess that's to be expected.

So what do you guys think?

Thanks in advance -- George

1971_CorVette

the problem is obviously either in the fuel delivery, or ignition system, My guess would be a coil. Mine went once and started doing the same thing, but only on the highway, it would surge, then die, surge then die, But was good when i wasnt on the highway so long as i was not running it hard. I wne nuts with this problem first concentrating on the carb and fuel system. Screwed everything up, then about 3 weeks later, changed the coil with one that i had laying around, and boom the thing ran beautiful. But i had to readjust the carb and everything. to get it back to where it was. hope my story helped.

rcastor426

if the car sat for a while there is probably a ton of rust and other crap that has fallen into the tank. your fuel filter is probably clogged again. i dealt with this alot on a car that had sat for a while. It will get you mad as hell.

tony449777

When the car loses power, does it do it smoothly and still run smoothly? Or does it start to run roughly or miss. The answer to those questions will definately help determine whether it is fuel delivery or ignition. Im ruling out the possibility that its not getting air, Anyway it could be electrical but im leaning more towards fuel delivery. Sounds kinda like a leaning issue, excessive heat could cause the fuel to vaporize before it gets where it needs to be(vapor lock) but unless the fuel delivery has been changed from the factory i doubt thats the prob.

gmviso

It loses power smoothly. Fuel delivery looks stock, with one possible exception. The solid fuel supply and return lines from the tank end above the fuel pump on the frame which I think is correct. The return line then changes to a rubber hose and goes directly to the fuel pump. However the supply line transitions to rubber, then goes through another piece of rigid line (which looks after market) which passes down through a hole in the frame and then transitions again to rubber and finally to the pump. This morning I looked at an exploded view of a GM parts manual and it looks like this is incorrect. The parts manual shows rubber straight to the fuel pump.

Is this maybe the problem? Am I getting vapor lock because of that short piece of solid line?

(By the way I replaced all the rubber hose when I changed the pump.)

Thanks,

gmviso

I will definately pull the "new" fuel filter and inspect/replace.

Thanks

Boofers

Before you do any carb work you should verify your ignition system is 100% first. Check that your mechanical advance springs back freely, just take the cap off and turn it by hand, sometimes they get sticky and just need a bit of light oil or WD40.

Go ahead and change them, just to rule out the possibility that there are problems with the wires on the car.

It sounds to me like your carb needs some attention. Could be a low float level, accelerator pump problem, or it could just be gummed up from sitting so long.

If the previous owner did some 'creative carb tuning' that could be a problem. In that case the best thing to do is to get the carb back to factory specs.

If you decide to buy a whole new carb remember that out of the box new carbs still will require some tuning adjustments.

Go to this site and click the link that says "Quadrajet Troubleshooting Excellent info from Lars - zipped" There you will find the greatest QJet troubleshooting writeup ever written.

http://wiki.corvettefaq.com/index.php?title=Intake

Hopefully your problem is something simple, good luck & let us know how it goes.

gmviso

First of all a hearty THANKYOU to all for you suggestions.

Secondly I hope you guys are kind to me as I bear my soul to the real cause of my problem.

Per rcastor426 (see quote below) I decided to get a new fuel filter. As soon as I pulled off the fuel inlet filter nut I saw the problem quite clearly.

I had installed the other filter backwards. argh.....

"I have seen the enemy and it is I."

Now, I'm really not an idiot, and hopefully others can benefit from my mistake.

The most amazing thing to me is that the fuel pump was strong enough to push the filter back away from the inlet enough to squeeze fuel past the filter.

Well, live and learn.

Boofers

Good news that it was nothing major

Rockn-Roll

Yeah...that would mean that the filter had less surface area exposed to the flow. Keep watching your oil level and especially the oil color. If it starts to get black then replace it immediately...don't wait for mileage or whatever. After sitting for a long time and not getting enough TLC there could be some sludge in the oil pan that will loosen and get washed out with several fresh oil changes.

Keep us posted...and get us some pictures of your vette!

fugawi

if i had a nickel for every time i did something like that, i'd have a big pile of nickels