Subject: Re: 1990 L98 rebuild by rklessdriver on 2012/11/5 20:04:08
Quote:
Matatk wrote: Quote:
red90 wrote:
Why do ya'll think the # 7 cylinder is always the problem? Did GM ever acknowlege the problem and correct things?
From what I've read, #7 and #8 run hotter because the way the coolant flows through the system and it gets to those last. Could it also be due to the fact that the block is against the fire wall and has less heat dissipation? Or timing/spark related?
On the stock L98 gaskets you'll see a blocked port on the back of the intake ports for those cylinders. I guess GM thought if they restricted the flow there, the coolant would remain longer and cool better?
I've also read that GM finally addressed the head gasket issue at the end of the L98 run, around 1991, and the ZZ3 crate motors use the revised head gasket. But I can't find any proof/tsb/etc on this.
Matthew
Cyl 7&8 get water last in the **block** but that dosen't have anything to do with it....
The real heat for the cooling system is in the cyl heads (combustion chamber), not the block... If heat was the real problem, then cyl 1&2 would be blowing, since they are the last to cool...
In the bigger picture.... Don't forget about the 2 exhaust valves situated right next to each other in cyls 3&5 and 4&6..... That is some real heat and can be a real problem on some racing engines.... which we mitigate with external cooling lines.
Around cyl 7&8 is where the coolant is forced up to the cyl heads... that is the point of greatest restriction and water pressure..... also when you shut the engine off, water drains back to that point and coolant system sediment settles there... That is where corrosion comes into play....
Most head gasket failures on L98's, I've seen are a product of corrosion, due to a lack of cooling system maintenance. A little corrosion there, couple with the higer water pressure is why I think most all head gaskets fail in that area. Will
