Hello everyone,

Been having some idle problems with the 80 Vette. The problem is most pronounced when the auto trans is in gear; it drops to about 500 RPM, seemingly without regard to how high I set the idle speed on the carb. Creates surging and drivability problems one I press the accelerator.

I took the Vette to a Vette specialist in my local area. He diagnosed the issue as a misfire caused by the need for valve stem seals replacement. I took him the old AC Delco plugs from my recent tune-up, but he said they didn't look fouled out. My understanding is that the valve seals are there to keep oil out of the combustion chamber. He wants to charge $2,000 to replace the seals. I'm going to pick up the car tomorrow morning and bring it home.

My questions are:

1) Does the diagnosis of valve seals replacement match the very low idle in gear issue? I don't remember seeing blue smoke at startup, but I'll check again tomorrow.
2) The next best price I've found locally is about $1,000 for this job. That seems high also. What should I expect to pay from a reputable shop?
3) From looking at online videos of this task, it seems like something I can do at home. Looks like vendors sell kits for this. I have better-than-average mechanical skills. Should I just take on this task myself and put all that saved money down on the UNC/Gonzaga game?

Thanks everyone!

Blaine

 

That diagnosis sounds off to me, but I don't have the car in front of me. If the problem was the same with new plugs as it was with previous ones, I just don't buy it at all.

$2,000 for a valve seal job is absolute madness, and $1,000 isn't much better. I haven't done the job myself, but when the time comes, I would certainly try it myself - some patience and an air compressor are the keys, it appears.

 

I've been out of the game for a long time but when I was in, it used to be blue smoke at start up that goes away soon after was a reason to replace seals. Had to used a pressure regulator to compress cylinder to keep valve up before pressing spring to remove valve spring locks to remove spring and replace dry cracked seals. It used to be a $300 to $400 dollar job at our shop. But like I said. It's been a long time ago.

 

 

That's nuts ! I do my own work and could do that job for less than $50, might spend a whole afternoon on it taking my time. I use rope in the cylinder though. Not totally sure it's a valve seal problem though.

 

are you aware you are supposed to be adjusting your idle speed in gear with the parking brake on and the wheels chocked. You do not adjust the carburetor in park or neutral with an automatic transmission.

 

For $2000.00 you can buy a new set of aluminum heads, intake, and a carb.

 

1. It doesnt sound like a valve seal problem. No smoke, plugs not fouled
2. I would go through resetting the idle first i.e. in gear, take safety precautions
3. If you decide to do the seals go ahead and do them. Its not a big job. You can use rope in the cylinders to keep the valves from dropping down. Read up on it, check YOU TUBE for video

 

if you have average or above skills you have to do the job your self.Its not hard to do .It does take time.the bad part is you will take time to clean everything .you will also change all the plugs and nows a good time to change wires.i would stop by the local auto store and see if you can rent or if they loan tools.I like the spark plug screw in to hold up the valves .they may rent or loan the spring compressor.everything else you may already have.find a buddy whos done it and buy him a few of beers to help.

 

$2000 to do valve seals is a complete ripoff. Find a new mechanic. I can do the job in about four hours. Five with beer.

I also agree that its highly unlikely your problem is in any way related to a valve seal issue. I've seen small blocks with valve seals so old and dried out that most of them had disintegrated and fallen off and the engines ran just fine. Puffed a little blue smoke on startup, and fouled plugs every few thousand miles, but otherwise ran just fine. If you do elect to change the seals yourself, its very doable for a guy with above average mechanical skills. You will need some specialty tools like a spring compressor and something to hold the valves in place while you remove the springs. I use a fitting in the spark plug hole connected to a compressor. Apply about 30 psi to the cylinder while you're removing the springs and replacing the seals.

 

It sounds like a tuning issue.

Open the idle mixture screws 1/2 turn counter clockwise on both sides and see if it gets better.

Raising the idle with no results does sound like a mixture and possible vacuum leak.


Hard to tell without being there...

 

This is a recent development?
I'd check to see if the vacuum advance is still functioning.

 

Update:

Got it back from the shop today. It was a misnomer on my part to say that the valve seals needed replacing. The actual diagnosis was that the valve guides need replacing. They performed a compression test and a leak-down test.

* Compression test found static pressure at 125 across the board.
* Running compression test found pressure varying at 40 to 80 psi.

The $2,000 was to pull both heads, check for warpage, adjust idle speed, ignition timing, valves, clean and adjust spark plugs, disassemble and assemble heads.

I have a couple of new questions:

1) Does it make sense to have this work done to the (likely) original heads?
2) If all that needs doing is the valve guides, can they be done on the car, or do the heads have to be pulled?
3) Does it make more sense to just get new/replacement heads instead and just put them on myself?

I try to remember that I am both the current owner of the car and the custodian of it for a future owner. Doing things right make things best for everyone, both current and future owners alike.

Thanks!
Blaine

 

1. Are you burning oil or notice a lot of blue smoke? If not I dont see a valve guide problem. It would also help knowing how many miles are on the engine?
2. Did you go back and adjust the carburetor the proper way, in gear with parking brake on and wheels chocked? By adjusting I mean both the idle speed screw and both mixture screws.

 

If spending $2,000 I would buy a new set of aluminum heads and bolt them on myself.

 

factory heads are boat anchors.if you are going to pull the heads.put new ones on.If you have the money put aluminum heads on .if you want low dollar you can get double hump heads for a fair price..if you have not done all this before ,you should be honest with your self what you can do .it will cost more to have someone fix it ,if you can only do half the job.

 

Thanks everyone. Good advice here.

I've found a local machine shop that will rebuild the heads for me at a very honest price as long as I bring them there. I am feeling pretty good about my ability to remove them from the car, based on online instructions and tutorial videos I've watched.

Do you have a "best" video or set of written instructions for removing the heads? There are some great videos out there, but they all generally work in time-compressed format.

Thanks!
Blaine

 

http://www.aeroheadracing.com/chevy.html you can get redone heads for $400.00. bolt on more power for maybe less money than reworking your old not very good heads.

 

giving 2000 to a mechanic is like pi$$ing it down the drain. Those are just base numbers that will escalate as more upselling will be proposed. you are not getting value for your dollar.

valve job? special gaskets, carb rebuild, engine timing curve, extra parts not in the estimate.. then there is a great chance for a return to the mechanic due to installation problems or leaks. more gray hair....
2000$ will buy you lots of tools you get to keep for a lifetime, and learning to do it your self will save you many times over during your lifetime. it will also buy you a nice set of bolt on heads ( or will totally refurbish your original heads) and a nice decent rebuilt bolt on carb.

 

Trick Flow heads come with installation instructions, which will apply for any brand.....
Link............https://static.summitracing.com/glob...41b012-m72.pdf