Roadrace d24 problems

[Dirty Duc]

This is the d24 into a Porsche 924 swap.

Over the summer, tried to work on blow by issue (pretty significant) with rings and pistons (and rod bearings since I was in there). Got to the track and chased other unrelated issues for a while, then finally got out in the afternoon. Engine sounded a little advanced, but I drove a couple of laps anyway to shake it down. Brought it back in to check fluids, etc. And it seemed fine. Took it back out, and after half a lap it was starting to drag the pistons, so I shut it off and waited for a tow.

Eventually realized the head was warped beyond use, but the spare wasn't together enough to swap in the time remaining (as we'd robbed the shims to set valve clearance on the installed NA head). Head gasket was gone as evidenced by compression (bubbles) in the coolant under cranking and hard starting.

Back at home, swap to the spare d24t head and new fiber head gasket. Forgot to use ARP lube on head studs, and didn't realize it until someone had stepped on the packet, but were short on time so loaded it up and towed to the next race. Drove alright, but non-engine problems sidelined us for a while again. Got those sorted, and noticed a serious milkshake problem in the coolant (water only). But it runs and starts fine.

So, given all that background, is it likely I have leftover oil in the coolant passages or should I do yet another head gasket? Or is there some difference in oil and coolant passages between the heads that needs resolved?

Speaking of, I bought three head gaskets from Rock Auto, and two match the old fiber gasket, one is different with different holes and built in rubber o-rings. Thoughts?