Coolant Leak 2

[XfireZ51]

Jerry,

Here's a couple of pics with your gaskets on the plenum. I thought it was a pretty good fit from the start. Was able to get car running today and it ran pretty well. Idle was smoother than previous.

[GOLDCYLON]

Dom are you still having a leak? Jerrys gasket coverage looks pretty good to me? :dontknow:

[XfireZ51]

Dom are you still having a leak? Jerrys gasket coverage looks pretty good to me? :dontknow:

GC,

Yeah. I had installed my WB O2 and decided to go see what AFR looked like at WOT. Got on it at the on-ramp in second. When I got off the throttle, got smoke out the back so I immediately shut motor off and coasted to access road. Got it home and pulled plenum finding both
#3 and #4 primary runners with coolant in them. Leak is from the
IH/Head interface. I had used gaskets from Flatout Racing. This is the second set to have gone bad. Its as if the coolant burrows through the gasket to the runner. I had used a .060" gasket and first time used .030". This time I got gaskets from Jerry based on Haibeck's rec.
I promised Jerry I'd post pics of his gasket alignment which was very good as you can see. I did trim the IH gasket but the plenum was pretty much spot on. Jerry's have a rubber binding to them, while the FOs are paper impregnated with silicone. Jerry explained that the thicker gasket exposes a greater crosssection of the gasket to the coolant stream, and that's where the gasket is weakest. I've checked for warpage etc. Not an issue.
Took it out yesterday and everything was fine. Motor ran well and it seemed to idle smoother than it had before but that may be because minute amounts of coolant were getting into cylinders before. However,
oil looks clean and plugs had not shown any sign of being "washed" until
this last incident.

[A26B]

Dominic,

Thanks for posting the pics. The second picture looks like the port on the left of the coolant passage is a tad too close to the coolant passage, but can't tell for sure.

Since I started working on the gaskets, I have now come to understand better where the use of CNC with correct dimensions, has an application in porting. By performing a short counterbore, it orients the port exactly where it should be, rather than simply enlarging an existing port "where it is." I've check fit gaskets to different engines and noticed some significant core shift which occurs in manufacturing. This is an area which received attention in the later, 405 hp engines, along with alignment dowel sleeves to accurately orient the injector housings.

The conditions where you "got the smoke" creates the highest differential pressure across the gasket between the coolant passage & the adjacent port(s). Vacuum is greatest when the throttle is closed at rpm & coolant pressure at max system limit through the bypass/radiator. Say 16psi to 20" vacuum?

Please keep us posted & thanks for the pictures. Sure hope it holds up for you.

Jerry

[GOLDCYLON]

Jerry thanks for doing what you do to keep these gaskets available in the ZR-1 community. Also the R&D on the new projects. Im currently running with your plenum gaskets and WP gaskets at the moment. :thumbsup:

[XfireZ51]

Jerry,

Its actually the port on the right (Primary #3)that runs into problems. Primary #4 is the corresponding runner on the Passenger side. In trimming the gaskets, I left extra material on both of these and in aligning the gaskets, I tried to make sure the coolant passage was flush with the gasket rather than have an "overhang" into the coolant passage. Some of the exposed deck you see is due to the angle of the picture itself. Looking straight down into the runner, its very close.
I spoke to a friend of mine who owns a repair shop and has run Super Stock for years using Mopars. He suggested spraying the gasket with a
Permatex Copper Hi Tack Gasket Fixative if I continue to have a problem.
You are absolutely right about the high vacuum condition that precipitates sucking the coolant into the runner. In fact, during some scans, I can see MAP values down around 16-18kPa, so its about 24-25" Hg I believe during hard decel. Pete looked at my IH the other day and thought there is plenty of meat on the IH between the coolant passage and the runner.
Now all of this started once I installed my Magnaflow exhaust in July. This system includes an integrated Xpipe. It may simply be coincidence.
Prior to that, the gasket I had on there had lasted from the time I assembled the motor after completing my porting ( March 08). I drove down to BG and back, ran the drags twice etc. One week after the Magnaflow install, I started getting smoke. At first I thought it was the plenum, but then with =Jeff= help, we saw the coolant leak at the IH using a pressure tester. So I tried a thicker gasket. They lasted about
2 months.
Well now I'll keep my fingers crossed. :pray