Smoke at startup

[rossgn49u]

Considering trading my Duster for this car


https://austin.craigslist.org/cto/d/1990-zr1-corvette/6577312081.html


Seller mentioned car needed to be driven as it smokes a little on startup. I would hope not rings with only 52k miles. What are the potential issues, if any, I could be looking at with "a little" smoke at startup?


Thanks in advance

[Ccmano]

Smoke at startup is not unusual for a 90. They do not have valve stem seals. Highly unlikely rings are an issue, very rare to see ring issues even at very high miles. Worse case the lower injector housing seals are leaking. A relatively easy fix. As me how I know. Price is a bit high for a 52k mile 90’. Looks very clean, but without a detailed service history I wouldn’t bid over $17k for that car. Good luck.
H
:cheers:

[oricale]

Concur!..very common for 90's[emoji6]

Sent from my SM-G955U using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[ZR2]

I have recently purchased a 94 for less and think you can get one in the high teens with less mileage, but......I do get it. Just remember . .....you have the money and they want it.

[rossgn49u]

Id say the value of the car Im trading is $17k-$18k. I found where the seller purchased the car for $16.5k at Leake auction this Spring. He has since replaced injectors.

[tommy]

I have the same symptom in my 1990, i was afraid when i saw it first time, but now I know that 1990 do not have valve stem seals and i`m calm :)

[Paul Workman]

If ever you have the heads of you 90 off for porting, or whatever, Marc Haibeck can retro-cut the grooves needed in the valve guides to accept valve stem seals. It also reduces oil consumption a good bit as well.:icon_thum

[Hib Halverson]

My belief is that smoke on start up, if it's very noticeable and happens regularly, is not normal, even for a '90.

While it is true that all the engines built prior to MY91 lacked exhaust valve stem seals and that contributes to higher oil consumption than with the 91-95 engines which had exhaust valve seals–and that oil use is constant, somewhat more than engines with "unsealed" exhaust guides–but they are unlikely to "smoke bad," unless there is some guide wear or some other mechanical problem.

Sometimes smoke on start up can be due to leaking injectors.

Also, smoke on start up could be coolant smoke and indicative of a head cracked around an exhaust port.

It depends on the type of smoke, white, blue or brown/black, and what it smells like

In any event, with 52,000-mi on the odometer and regular smoke on start up, you're looking at eventual repair cost.

[Paul Workman]

My belief is that smoke on start up, if it's very noticeable and happens regularly, is not normal, even for a '90.

While it is true that all the engines built prior to MY91 lacked exhaust valve stem seals and that contributes to higher oil consumption than with the 91-95 engines which had exhaust valve seals–and that oil use is constant, somewhat more than engines with "unsealed" exhaust guides–but they are unlikely to "smoke bad," unless there is some guide wear or some other mechanical problem.

Sometimes smoke on start up can be due to leaking injectors.

Also, smoke on start up could be coolant smoke and indicative of a head cracked around an exhaust port.

It depends on the type of smoke, white, blue or brown/black, and what it smells like

In any event, with 52,000-mi on the odometer and regular smoke on start up, you're looking at eventual repair cost.

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...

[rossgn49u]

Thanks Paul. Guy quit communicating, so maybe a blessing in disguise.

[Hib Halverson]

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]

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!":p

[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.