Smoke at startup

[Hib Halverson]

Originally Posted by Paul Workman

Well, other issues not withstanding, the little (blue/oil) smoke issued by my 90 on cold startup disappeared with the installation of exhaust stem seals when added to my heads at approx 50k miles. And, overall consumption was reduced significantly enough to make an unmistakable improvement.

Just sayin...

Note my use of the phrase: "...if it's very noticeable and happens regularly..."

I should have maybe added something like "...more than a little...".

I agree that a little oil smoke on cold starts is indicative of a 90 w/o exhaust valve stem seals and with some miles on the engine.

I've often wondered why Lotus and GM did that. I've also often wondered if the reason that happened.

[Paul Workman]

Originally Posted by Hib Halverson

Note my use of the phrase: "...if it's very noticeable and happens regularly..."

I should have maybe added something like "...more than a little...".

I agree that a little oil smoke on cold starts is indicative of a 90 w/o exhaust valve stem seals and with some miles on the engine.

I've often wondered why Lotus and GM did that. I've also often wondered if the reason that happened.

Excellent point. The fine distinction between the lack of oil seals and symptoms of something more serious is important to make: deserving of avoiding the risk of blowing smoke off as "normal" for a 90 LT5 due to seals when in fact other things should be considered.

So, the description of the lack of oil seals might should be refined to specify:

"At startup" BLUE (oil) smoke appears after the motor was at rest and is more noticeable the longer the motor was at rests up to (say) overnight. However, if smoke of any color persists, and especially under heavy throttle, then more serious issues exist beyond mere valve stem oil seals".

As for why they didn't install the seals on the exhaust stems in the first place, I believe I read it somewhere - sort of tongue-in-cheek, "Oil consumption?? Hey, it's a British thing!"

[Hib Halverson]

I still keep touch with some of the guys I met from Lotus and MerCruiser back in the "old days", and I emailed one of them yesterday.

He told me during development they figured exhaust pressure would keep the oil off the stems when the engine with running but they did not figure on engines with some miles on them starting to leak down the exhaust stems when the engine is stopped. That's why for 91, they added stem seals.

He made the point that when the engines were new or near-new, even without exhaust valve stem seals, they wouldn't puff oil smoke after cold starts. When he said that "engines with some miles on them" didn't necessarily mean "worn" but that worn engines would have a worse problem with that.