smoking on decel....

[don lemelin]

hello all, new to the forum and need a little advice.
I'm going to do a wet/dry comp test but until then some of your thoughts would be appreciated.
I've got a 64 roadster with 300hp original motor. Mileage is a little over 61k and the motor has not been apart.
Car runs well, fast and doesn't smoke at start up or during acceleration.
but.. on decel especially on a long down hill it'll smoke pretty bad.
spoke with one mechanic and he says rings for sure but I'm suspect as it runs too well... any thoughts? could it be just seals or sticky oil rings? If it's the oil control rings can something like seafoam free them up? any other possible causes I'm missing?? thanks in advance.
Don

 

[gmjunkie]

hello all, new to the forum and need a little advice.
I'm going to do a wet/dry comp test but until then some of your thoughts would be appreciated.
I've got a 64 roadster with 300hp original motor. Mileage is a little over 61k and the motor has not been apart.
Car runs well, fast and doesn't smoke at start up or during acceleration.
but.. on decel especially on a long down hill it'll smoke pretty bad.
spoke with one mechanic and he says rings for sure but I'm suspect as it runs too well... any thoughts? could it be just seals or sticky oil rings? If it's the oil control rings can something like seafoam free them up? any other possible causes I'm missing?? thanks in advance.
Don

Stuck Rings,Valve Seals,Wore Valve Guides,Intake Manifold needs re-torqued,Crankcase Ventilation plugged, Could be any of several things!! If it has set around allot,Dump 1/2 Qt of ATF in the oil warm it up good and drive it a day or two, then change to Oil and Filter and see if it clears up!!Might just be stuck rings from setting!

 

[BigJimZ16]

Decel is high vacuum time, possible PCV issue??? Valve guides are a definate possibility. Agree with junkie... too many possible issues, some real diagnosis is in order. I think that I would check compression (wet and dry).

 

[2X4's 60]

Your symptoms are classic indictors of valve guide problems. It could be that they are worn or possibly the little O-rings have dried up and fallen off. The wet-dry compression test will tell you for sure.

Jim

 

[JohnZ]

A compression test is a useful indicator, but a leakdown test will show you exactly where the leakage is (rings or valves).

 

[wallyknoch]

A compression test is a useful indicator, but a leakdown test will show you exactly where the leakage is (rings or valves).

Most logical reply, and if it passes the leak down then valve seals would be the next possible problem. Otherwise the other replys have it covered....

 

[G Winter]

If it ONLY smokes on deceleration , I would go with worn valve guides and/or dried out valve seals.
Those chevy V8s use only an O ring on the valves which came real close to contact with the guide. This sheds the oil so it don't go down the guide.
There used to be seals available to cure this. This is done without removing the heads.On one of my own of that era (in that era)I found umbrella seals for a Dodge that fit over the valve and cleared the OD of the valve guide. Worked perfectly.

Glenn

 

[2X4's 60]

Glenn,

Do you remember what year & engine size those Dodge umbrella seals were for?

Jim

 

[G Winter]

This was pre 1980 so had to be in the 60s or 70s .
Been so long I can't remember.
Will do some thinking on it.

Glenn

 

[G Winter]

In the 60s and 70s weren't the Dodge heads in each engine style pretty much the same? Should be able to narrow it down if you can find a supplier ,,, maybe a dealer that has some on hand and check dimensions .


Glenn

 

[gmjunkie]

Try These!!
Advance Auto Parts___

I personally like these!! Any time I have to change out Valve Seals,these are what I use!! Well worth the few extra Bucks!!

TRW and Sealed Power both make this type for SB and BB Chevy!!
They be Good Mon!!

 

[G Winter]

Try These!!
Advance Auto Parts___

I personally like these!! Any time I have to change out Valve Seals,these are what I use!! Well worth the few extra Bucks!!

TRW and Sealed Power both make this type for SB and BB Chevy!!
They be Good Mon!!

They require machining the guide boss?

Glenn

 

[gmjunkie]

They require machining the guide boss?

Glenn

I've never had to with the TRW's!!
I just found out that sealed power made them looking for a photo to swipe!!:L
The TRW's look a little different at the bottom,they have a wider spring,I just couldn't find a photo of a TRW!

 

[DINO1970]

A classic Gen I SB Chevy

An easier diagnosis might be to put a vacuum gauge on it and taken it for a drive at the highest value you can achieve (probably 50-55 mph) Have someone follow you and check the exhaust. If you have a steady blue smoke screen like a four pipe destroyer, its the valve guides and seals. Usually its both. Cars that have these few miles on an engine this old get a lot of cold starts with very little residual oil in the guides. Its punishing on them. And of course the little O rings seals at the top of the valve will crack with age no matter how few miles you have on it. I took my 66 Impala from Boston to L.A. in 1974 coming back from the Navy. I had a case of motor oil in the trunk. When I had a high speed of advance, say 70-75, oil comsumption went down. When it was 55, like driving through Ohio (the cop said: "The absolute speed limit in Ohio is 55", and I said yes sir), oil comsumption went way up. Its the guides and seals. Ultimately, you do overhaul the heads with bronze guides and PC style seals, and enjoy the clean exhaust! I love those roadsters. I drove one during the Summer of Love '67, ya gotta love em. Take good care of it.

hello all, new to the forum and need a little advice.
I'm going to do a wet/dry comp test but until then some of your thoughts would be appreciated.
I've got a 64 roadster with 300hp original motor. Mileage is a little over 61k and the motor has not been apart.
Car runs well, fast and doesn't smoke at start up or during acceleration.
but.. on decel especially on a long down hill it'll smoke pretty bad.
spoke with one mechanic and he says rings for sure but I'm suspect as it runs too well... any thoughts? could it be just seals or sticky oil rings? If it's the oil control rings can something like seafoam free them up? any other possible causes I'm missing?? thanks in advance.
Don

 

[Tom Bryant]

You can get the umbrella seals for a Chevy from NAPA. Changing the seals is a quick and easy job and just might cure the problem without any major engine disassembly.

Standard replacement umbrella seals.



Positive seals requiring machining.

Tom