I would like to share an experience I had on an engine build recently. It was a carbureted Gen VI HP500. We rebuilt the engine and added new Dart Pro 1 heads, custom cam and Whipple supercharger. The engine ran great on the dyno and in the boat. However after a few minutes running we got water in the oil. We pulled the engine apart and cleaned it up, checked all the gasket matches and such and reassembled. We swapped the headers out because they were questionable. Still got water in the oil. So, back apart the engine comes. This time we pressure tested everything to find the leak.

Here’s the final resolution. The Dart heads did not adequately cover the cooling ports in 2 places (Dart does state these heads will work on a gen. VI block). There was not enough gasket crush and as water pressure built at high speed it forced water through. Apparently this particular block had a slight amount of core shift that caused the problem. At best there is about .150” of crush. In our case it was none. I spent a lot of time on the phone with Dart. Didn’t really get any answers. They did say that a few engine builders had indeed had this problem. The solution is to weld additional material to the head and machine it. This is what we did and cured the problem. I just wanted to get this information out there to possibly prevent anyone else from having these issues. Personally, I won’t use Dart heads on a gen. VI block anymore. I’m attaching a photo. I used layout dye and clamped the head to the block. You can clearly see where the water port mismatch is.

i have these heads on 540 dart block . will i have that problem???

Bob,
Thanks for the "heads up" .... one more thing to put in the memory banks to try to remember when building an engine Just curious, which gaskets were you using ?

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Thanks for the tip. That must have drove you nuts!

Agreed, also did they say that they are better suited for a Mark 4 block or is this something to look out for on all? Thanks for the heads up.

We were using the fel pro 17048 gasket. I thought about trying other gaskets but I don't think it would have mattered. There was no "crush". Fel pro says you need at least .170" crush to be within spec. I believe the problem is only Gen VI blocks, and not all of them. This water ports on this block were shifted by about .200" the best I could tell. But that means it would be marginal even if there wasn't core shift.

Bob

Thanks bob I just found the same problem on the motor i'm building for a friend.

what he said

Bob,
Don't you just hate finding out stuff the hard way. I know I do. The only good thing is that the ones you find the hard, and expensive way, you never forget. I know that I have several things in the back of my head that cost me a bunch of money that I will never forget. Thanks for the heads up. I have done more Dart heads on Gen VI blocks than I care to remember and have never had that problem. I hate to think I got that lucky. You can bet I will be checking that in the future. I don't really use many Gen VI blocks anymore, but I do use a few. I can't believe it didn't leak on the dyno. I guess it just didn't have any water pressure. It doesn't look like it sealed at all. Looks like there is a gap at the top where it wasn't sealing at all.
Eddie

Me too, they are called X-wives.