Roadrace d24 problems

[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.

[FJ40Jim]

For the folks following along at home, this LeMons car is actually unconstrained by budget. Any terrible car (any cheap watercooled porsche) or terrible engine swap (any diesel) is not sweated on budget by the judges. The $500 rule is more heavily enforced on the Miata/E36/RX7 gang.

After we swapped a TDI into our Mk2 GTI, we were given no penalty in spite of the obvious addition of TDI engine & tranny, inter/oil/fuel coolers, new instruments....

I've also had the (dis)pleasure of piloting a smallblock powered Monza and a supercharged '47 plymouth in LeMons, and those cars also receive no penalty laps in spite of having too much $$ stoopidly invested in the powertrain.

Back on topic: Is the MLS headgasket available for D24 anymore? They seem to be more reliable than fiber gaskets.

[v8volvo]

Jim, good to know that about the rules, have always wondered how strict they are, it makes sense they don't worry about scrutinizing the budget unless you really are testing the limits of reason. Guess it is supposed to be about having fun anyway, not about fighting with the judges...

Would be fun to hear more about your A2 TDI swap, what transmission are you running? 020 or a TDI 02A? Axles? Subframe swap? Maybe we need an off topic section here to talk about other projects that are not powered by D24 engines...

MLS D24/T headgaskets have been NLA in the US for a while although you can still find them on German Ebay and other overseas sources with enough effort. The fiber headgaskets are almost as good though, especially with studs, as long as the engine doesn't get overheated or have other issues:

Most important factors are that the head isn't warped, head and block mating surfaces are flat and clean, torque procedure is carefully observed (including having fastener threads very clean and using the correct special ARP grease in the right places if running studs, so that the nut torque values result in the correct actual clamping force), and camshaft and injection pump timing are set correctly so that peak cylinder pressures stay within design parameters. Boost and fueling need to be kept within reason also. Any sustained visible black smoke at all under full load means very high EGT and head temps and will stress the head, head fasteners, and headgasket excessively and eventually overheat pistons and score the bores. This last piece is a hard reality for a certain percentage of people to understand and accept if the whole reason they bought a diesel was so they could crank up the pump to blow thick black smoke and poison pedestrians, etc, but those folks deserve to suffer some consequences anyway. Of course you also need to measure piston projection and select the correct thickness headgasket.

With all those things done, and with the cooling system kept in sound health at all times, these headgaskets hold up just fine regardless of what material they are, even at much higher than stock power levels (with careful and reasonable timing/fueling settings and head studs). In short I wouldn't worry about using those fiber gaskets if they are a reputable brand in an unopened package and if the supporting factors above are good to go. Some brands of fiber gasket have different designs and appearance for the fire ring, steam holes, etc, but all work equally well. Elring and Reinz gaskets for example are both excellent yet look quite different.

[Dirty Duc]

Jim, you're telling all my secrets!!!1!!1

Seriously, though, if someone else wants to swap a random VW diesel into a 924 I'll lend you the torque-tube clocking tool.

[Dirty Duc]

So, had a younger Arrive and Drive (A&D) to whom I gave incomplete instructions as to how to drive the car (race the car, not the engine). After a couple of stints in which he exhibited little mechanical sympathy (and another driver also brought it back puking up a milkshake), I took it out to see what had changed since my mid-day stint.

It was throwing water all over the windshield! Still started fine. In my experience, if the head gasket is blown, it won't start easily.

"Fine," says I. And we pulled the head. After careful inspection of the head gasket, I finally found two small flaws in the red ring goop. From the oil supply head bolt hole to the water jacket holes. One of my teammates noticed that these small flaws corresponded with flaws in the block. It was cracked between both coolant holes next to the oil supply for the head.

Over the next two hours, at least 20 gearheads offered possible solutions and rehashed the arguments that we had 20 minutes ago. In the end, cleaned everything up and J-B welded the stud into the hole in hopes it would minimize the leakage. I figure the block is mostly junk at this point.

But Sunday, after finally buttoning everything back together and eventually getting the wiring hooked back up, injection timed (ish, .80mm on our measurements seems a little off the power curve), and injection bled (tow it around the paddock until it remembers how to run), it got back on track and finished the race.