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?

[v8volvo]

Hard to say on the question of oil in the coolant, that's always a guessing game. It can take a while to get all the oil out if it makes its way into the cooling system. When I have dealt with one of those situations after a leaking headgasket or oil cooler it's taken a few flushes over a period of multiple weeks, and sometimes I add a little bit of gentle dish soap (just regular liquid soap, not dishwasher detergent) to help break down the oil. Even after all that and multiple flushes you might still see a little residue from time to time. It's hard to get it all at once as the oil wants to cling to the inside of rubber hoses, insides of the rad and heater core, etc.

If it doesn't seem like the amount of oil is increasing, and you don't see other symptoms of headgasket trouble (loss of coolant, overheating under load, etc), then I would try another flush or two and see if you can get the oil out. But if it seems like there's more and more oil in the cooling system, or the engine is losing oil faster than usual, or any other signs of HG trouble, then you might still have more work to do.

Kudos for what you're doing, it's fun to hear about one of these engines getting used this way. Sometimes it seems as if you might have easier paths available to keep your car reliable, though, other than tearing it down time after time. Do you own the correct tools for setting camshaft and injection pump timing? As one example, if timing is too far advanced it will quickly destroy headgaskets, damage pistons, and cause other harm much like the problems you described that recently sidelined the car. These engines don't usually require as much or as frequent major internal work as you seem to have to do, particularly the bottom ends are normally extremely durable and strong, and with head studs and a healthy cooling system, HG and head trouble is also more or less avoidable. What about taking a shot at doing it slowly and by the book before your next event? Might keep the car on the track longer and be more driving and less wrenching.

If you're constrained by the budget rules of chumpcar/lemons (forget which one this is running in) for buying the expensive special tools, I'm sure folks on here would contribute to your cause by loaning what they have.

[Dirty Duc]

v8volvo: Thanks for the kind words. At times this seems an odd windmill to be tilting at.

I have been accumulating the proper tools and information, unfortunately in this case I left the most important one (the metric dial indicator) at home nearly 700 miles away. This is a Lemons car, so tools don't count toward rules budget (just actual budget).

I started with an unknown engine, and then we ran it in an unknown state for some time (3 races?) while it was "fine."

At the race before the pistons and rings (Buttonwillow 2018), the blowby was causing a visible fog above the idling engine (open breather, no recirculating into the intake). It also liked to put all the oil onto the outside of the engine in quite spectacular fashion. Hence the decision for a light refresh. Pistons and rod bearings just because I was in there anyway and it seemed prudent to replace them given the amount of work to do rings.

I probably should have sent the engine to the machine shop, but ran out of time. One of the bores had suffered some significant trauma in the past and should have led to an overbore.

It's encouraging to hear that oil can linger in the coolant passages. We'll work on that this weekend. I was thinking dish soap and running it, glad to hear I'm not alone.

Another source of unreliability is the human factor. It's not just me driving the car, and I fund some of this by renting out seat time (generally referred to as Arrive and Drive in the niche) to decidedly non-professional drivers. So instructions are sometimes not followed, and sometimes there are racing incidents (unrelated to the engine) and sometimes there are car problems unrelated to the engine.

For example, we were initially sidelined for hours at Buttonwillow 2019 to replace vent hoses on the fuel tank. The ones from 1984 had turned to some sort of crumbly hard substance that wasn't at all fluid proof anymore. The fuel tank on a 924 sits above the transaxle (because, as near as I can tell, they were designed to be disposable and assembled upside-down), necessitating some significant disassembly.

Then we spent much of Saturday at Houston 2019 (a month and a half later) chasing fuel leaks that were related to the work done to fix the fuel tank and head. Someone had wrestled the filler neck with pliers and damaged the cap sealing surface, injector leak-off lines had come asunder and were spraying fuel everywhere, etc. Then the wheel bearings failed and undid the spindle nut on the left rear and the wheel (and drum) fell off.

It's just racing. Stuff happens and you fix it, hopefully quick enough to get back out on the track. The extra head gaskets are talismans. One never needs the parts one has on hand.

[v8volvo]

I have used that talisman technique a few times too on long road trips, bringing along the specific spare parts that I particularly hope to not need. It does seem to work pretty well. I have sometimes brought a spare starter motor if I take a long journey in a car with an automatic transmission, a spare IP belt, spare set of injector delivery pipes, etc. Usually does result in warding off the need for a repair, but every now and then I have had some kind of spare on board and then actually ended up having to use it. Not sure which situation is better. But it is of course almost always the case that the part you do need is the one you don't have.

The injector return hoses really make a mess when they leak and the 3.5mm fuel rated line can be hard to find in a hurry. Had to use vacuum hose a couple times but that doesn't work for long. Anymore, I always keep a spare length on board in the glove box if I'm going further than across town. I have also found that those little hoses really don't like to be removed and then reinstalled, for whatever reason seems they always leak pretty soon afterwards if reused. I consider them as single-use parts at this point.

[Dirty Duc]

Yeah, I have a spare set of injector lines and two extra pumps I take along with the usual wheel bearings and other car-specific things.

The fuel injector leak-off lines made a huge mess under the hood, but an hour of racing with the leaking fuel cap had put a bunch of fuel in the unibody frame rail on the right side, so it was everywhere... in the passenger compartment, dripping on the floor, generally looking terrifying, etc.

The next race for this beastie is at the end of February in my neck of the woods here in Arizona.

I washed out the engine and radiator today, other than a new leak in the likely 36 year old radiator hose no drama. Some more platform-related stuff this weekend and I will call it race-ready barring the hoses and valve-cover gaskets and the like.

I haven't really fired it up since the mad thrash at the last race looking for axle stubs and wheel bearing parts, so I was pleasantly surprised today when it turned out the rings seated nicely and it no longer spews gases out of the breather. The engine fired up from it's cold-soaked state at 40-50 degrees F with little drama (two attempts, glow plugs for a 10 count each attempt) and no throttle.

[Dirty Duc]

So, I just found one of the older headgaskets that either came with the engine or was one that I put on first (it's two notches, but I seem to remember only having been able to find one notches), and it has yet a different pattern of holes and sealing surfaces.

All fiber gaskets, at least 3 variants.