long crank puff of blue

[geezer]

Experiencing long crank and blue smoke on hot start.

If the restart occurs within approx. 10 minutes, starts fine no smoke but problem if left for a longer period.
Once it fires it runs smooth & strong. Replaced OEM injectors with RC's 2 years ago.

Has anyone else experienced this? have any knowledge on this issue.?

Thanks:

[tccrab]

Originally Posted by geezer

Experiencing long crank and blue smoke on hot start.

If the restart occurs within approx. 10 minutes, starts fine no smoke but problem if left for a longer period.
Once it fires it runs smooth & strong. Replaced OEM injectors with RC's 2 years ago.

Has anyone else experienced this? have any knowledge on this issue.?

Thanks:

Need more info to perform accurate arm chair diagnosis.

What year Z?
How many miles?
Mods?

Fairly common for '90s as they have no valve seals on exhaust valves.

TomC
"Crabs

[geezer]

'90 - 25000 mi.- completely original.( except RC inj.) No smoke on hard acceleration --smoke & long crank on hot restart after shutdown time of more than 10-15 minutes.

[Pete]

Sounds normal to me.

1990 ZR-1's do not have exhaust valves seals so they had the common small block chevy issues, smoke at start up.

It's also common for LT5 for long crank start up,just make sure you crank her till she starts.

Pete

[geezer]

Since it's a one owner car for 20 yrs. & I have never had this problem until recently I felt it was not normal. Consenus so far is that it is normal due to lack of exhaust seals so maybe I have to live with it but if seals are the issue why no smoke on hard acceleration (WOT)?
Only on hot shutdown restart

Thanks to Tom & Pete for their input.

[tccrab]

Originally Posted by geezer

Since it's a one owner car for 20 yrs. & I have never had this problem until recently I felt it was not normal. Consenus so far is that it is normal due top lack of exhaust seals so maybe I have to live with it but if seals are the issue why no smoke on hard acceleration (WOT)?
Only on hot shutdown restart

Thanks to Tom & Pete for their input.

Oil tends to pool on the outside edge of the heads where the exhaust valves are. Small amounts of this hot oil sneaks past the valves and seeps into the combustion chamber.
When the engine is new the tolerance are too tight to allow oil to seep past, however as the engine wears those tolerances loosen up and oil sneaks past.
I've read that it's possible to machine the heads and add valve seals to cure that little puff of smoke.
However, it would mean taking the heads off and all that entails.
Seems like a pretty big expense for a fairly minor issue.

The other option is to sell the '90 and buy a '93-95 with the 405hp engine that has valve seals.
Again, a pretty drastic solution to a minor problem.



TomC
"Crabs

[bobbyhi]

Originally Posted by geezer

Since it's a one owner car for 20 yrs. & I have never had this problem until recently I felt it was not normal. Consenus so far is that it is normal due top lack of exhaust seals so maybe I have to live with it but if seals are the issue why no smoke on hard acceleration (WOT)?
Only on hot shutdown restart

Thanks to Tom & Pete for their input.

My '90 with 72K does smoke at hard acceleration and down shifting at high revs.