Paul Workman
10-22-2011, 10:34 AM
As I indicated a couple weeks ago, I had a coolant leak cut short my drag racing day...Bummer. It turned out that water pressure breached the #3 primary IH runner, made a weeee bit too thin during my porting project, almost 3 years ago.
My rev limiter was bumped to 7600 rpm, which I suspect indirectly resulted in the water pressure sufficient to cause the breach... I was in the water box at the strip at the Crown Point Corvette Challenge day and the rpm flashed past the shift light and against the new rev limit before I could react in time. (Lots of power or slow reactions...I'll go with "power":p) Thinking back, I may have had signs of the beginning of a leak, but set it aside as something else.
In talking to Marc Haibeck after the fact, we hypothesized that the momentary increase in rpm raised the coolant pressure above the threshold of that thin spot, and it split. Then, while bumping the sift light going down the track, the dam broke, and my LT5 got a real steam cleaning, I can tell ya! In any case, there was a hole about 5mm x 2mm in the IH runner as result. The good news is it was in an easy place to get to - from the water side of the breach, so there was less chance of the weld leaking when the runner was restored to it's original shape.
Changing the subject...
http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZR-1008.jpg
The large radius side of the IH runner needs some more material removed so as to remove the slight oblique angle at the IH/head junction...see it?? It shouldn't take but a couple hours to blend the radius of the runner to eliminate the angle, resulting in a smooth transition into the heads. To a lesser extent, the same goes for the short radius junction too.
I'll have more pix later as things progress...
P.
My rev limiter was bumped to 7600 rpm, which I suspect indirectly resulted in the water pressure sufficient to cause the breach... I was in the water box at the strip at the Crown Point Corvette Challenge day and the rpm flashed past the shift light and against the new rev limit before I could react in time. (Lots of power or slow reactions...I'll go with "power":p) Thinking back, I may have had signs of the beginning of a leak, but set it aside as something else.
In talking to Marc Haibeck after the fact, we hypothesized that the momentary increase in rpm raised the coolant pressure above the threshold of that thin spot, and it split. Then, while bumping the sift light going down the track, the dam broke, and my LT5 got a real steam cleaning, I can tell ya! In any case, there was a hole about 5mm x 2mm in the IH runner as result. The good news is it was in an easy place to get to - from the water side of the breach, so there was less chance of the weld leaking when the runner was restored to it's original shape.
Changing the subject...
http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZR-1008.jpg
The large radius side of the IH runner needs some more material removed so as to remove the slight oblique angle at the IH/head junction...see it?? It shouldn't take but a couple hours to blend the radius of the runner to eliminate the angle, resulting in a smooth transition into the heads. To a lesser extent, the same goes for the short radius junction too.
I'll have more pix later as things progress...
P.