'Puff' on start up! valve seals need replacing....

[Jwernatl]

Guys I have a new to me '87 V10 4wd 350 - When I start up after sitting a few hours I get a small puff of oil smoke out the exhaust - when sitting overnight, it's a little bigger puff.

I can do this. - And I will -= but, any tips, recommendations? tool list? should I use compressed air to keep valves up? Should i replace the springs? retainers and all that? Truck runs great other than that.

So far, I've completed a total tune up (ALLfluids, plugs, wires, distributor, cap, rotor, etc etc and I did swap the original TBI for a HOLLY TBI replacement unit -

any advice on the valve seals?

 

[yevgenievich]

Piston at tdc and nylon rope works. But compressed air is a better option. A good spring compressor tool makes the job a lot easier. Everything stock should be no need to replace the springs etc...

Also be prepared to make a decision on what to do if you find wore out valve guides.

 

[Matt69olds]

Nylon rope is the best way in my opinion. No worries about power failure, air hose burst, or any other compressed air catastrophe

 

[yevgenievich]

Nylon rope is the best way in my opinion. No worries about power failure, air hose burst, or any other compressed air catastrophe

I use rope method, but air does make it a bit easier and if piston at tdc valve not going far

 

[John Nes]

Piston at tdc and nylon rope works. But compressed air is a better option. A good spring compressor tool makes the job a lot easier. Everything stock should be no need to replace the springs etc...

Also be prepared to make a decision on what to do if you find wore out valve guides.

Valve guides or rings. Worn ring in my 87’s case.
Per the wizard mechanic at the shops recommendation, been trying a bottle of ‘engine restore’, so far it hadn’t helped any blowby but it hadn’t gotten worse either

 

[Jwernatl]

Also be prepared to make a decision on what to do if you find wore out valve guides.

If it were a valve guide' wouldnt the compressed air bled through? And wouldnt it burn oil all the time?

Or how would i know guide vs seat vs seal?

 

[Jwernatl]

Valve guides or rings. Worn ring in my 87’s case.
Per the wizard mechanic at the shops recommendation, been trying a bottle of ‘engine restore’, so far it hadn’t helped any blowby but it hadn’t gotten worse either

Lile b4- if it were a ring it would smoke mor often than only a puff at startup.

 

[John Nes]

Lile b4- if it were a ring it would smoke mor often than only a puff at startup.

Oh absolutely. First noticed it at start up. Now if I’m stuck at a light for longer than I’d like, it’ll make a larger plume upon acceleration. Isn’t constantly billowing, just when it sits for a prolonged idle. After 220k miles on the original motor and that’s literally the only thing wrong with the truck, I can totally manage that till I drop something else in there

 

[John Nes]

If it were a valve guide' wouldnt the compressed air bled through? And wouldnt it burn oil all the time?

Or how would i know guide vs seat vs seal?

Just do a compression test. That’ll help

 

[yevgenievich]

If it were a valve guide' wouldnt the compressed air bled through? And wouldnt it burn oil all the time?

Or how would i know guide vs seat vs seal?

Seals are probably bad due to age. Valve guides will be easy to tell because valve stem will be loose with side to side motion. For rings and valve seat check would do a leak down test. Puff of smoke on start up is usually oil running down the valve stem either due to seals or guides/seals. If guides are wore, heads have to come off to fix it or can just stick new seals and let it be until next time.

 

[Craig 85]

If it makes you feel better, they did this when they were fairly new too. I had an '87 K20 with a 350 I bought in 1989. I get rid of it before it had 50K miles in 1991. It did the same thing after sitting overnight.

 

[80BrownK10]

No wonder I would change or mess with anything from just a small puff of smoke

 

[Octane]

Over 150k on engine guarantee some excess wear on at least 1or more guides.That 1950s technology valve seal tech G.M. uses has always been a smoke puffer engine on startups.I've spent most of 40 years ignoring it.lol

 

[Bextreme04]

When the valve guides are excessively worn, you will get the valves tilting on the seat and not sealing properly. I just pulled down an engine because the valve guides were so severely worn that I was leaking a massive amount of compression from the intake valve on one cylinder. Its going to be about $400 to get them cleaned, new valve guides, and a valve job. It's a budget build so I'm just going to try and buy a used set of truck heads that have good enough guides to lap the valves and send it. I found a low mile set for about $40-60 locally that I'm going to go look at this weekend. For reference I ran a compression test on all 8 cylinders and had 125-150 psi on 7 cylinders. 8th cylinder was at 90psi.

I removed the valve from the compression tester hose, loosened up the intake and exhaust rocker and put 70psi into the cylinder and you could hear the air dumping out the intake valve only. Sometimes you can do that and whack on the valve with a rubber mallet to see if it is just crud blocking the valve from sealing properly. In my case the guide looked like an egg at the top and was obviously toast. The hammer trick didn't help at all with sealing either.

 

[Catbox]

I bought this jobby for the very reason you have stated.
Puff on startup and it won't pass DEQ emissions anymore.
New valve seals are on the bench and just need to installed.

I have not tested it thus far, but it looks simple enough and is priced pretty good for the average home mechanic.

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