Laust Pedersen

A couple of weeks ago I was out racing at Streets of Willow in +100F weather and the car was running fine (apart from the usual brake problems) until I noticed that the engine was getting hot. I slowed down for a lap to cool down, but the temperature kept rising, so I pitted. When opening the hood I noticed that the fans were not on and after a short while I opened the expansion tank and saw that it was empty, but no water underneath the car. After pouring some water in the cooling system it was clear that there was a big leak, since water was gushing out over the bell housing. It turned out to be a blown hose to the heater valve, which is very inaccessible. When starting up the engine it was running on 3 cylinders and sounded strange. After pouring more water in it I discovered that it was spitting come of it out the exhaust, which unfortunately is the usual clue for a blown headgasket.

Later when testing the water injection I discovered that the water filter was clogged to the extent that no water flowed, so that may have been what started the problem. With high rpm (noisy engine) and a helmet I did not hear any detonation and fortunately I caught it early enough so only the headgasket and a hose was damaged by the event. Apparently the cooling system is not designed the combustion pressure from 25 psi of boost .

Danno has been kind enough to help taking the engine apart (and fortunately promised to help putting it back together again) and in the process I discovered that it had a bent #2 connecting rod, which based on the piston wear pattern, must have happened before my ownership. Oddly the dreaded #2 rod bearing looked very good, except for a twisted wear pattern (caused by the bent rod) on the bottom shell. All the cylinders look OK although #2 has a few scratches, but not to bad.

I am looking at this as a Darwinistic approach to car improvement, the weaker parts die and get re-engineered as I increase the power. Fortunately the 951 is really well engineered (except for serviceability). In addition to replacing the needed standard parts, here are some of my planned “tricks”:

1) Multilayer Steel headgasket (MLSHG)
2) Thermal coat on the piston crown
3) Low friction coat on the piston skirt (High Performance coatings assured me that they got a new, better and harder friction coating)
4) Total Seal gapless top ring. I sent a ring set to Total Seal to be modified.
5) Thermal coating on cross over pipe. Cleaner, but probably less effective than my current heat wrap.
6) I intended to install a modified K26-6 turbo with sleeved exhaust outlet to reduce the clearance from .060” to .030”, thermal coated almost all components, a step diameter change on the intake of the compressor to minimize boundary effects, an aerodynamic nut and new seals and bearings (I am very curious about the effects, which I believe are earlier and faster spool-up). However I am taking up the challenge of reaching 300 WHP with the standard K26-6, by leaving my old turbo in place and just for the heck of it install an electric water pump that actually works.

I/we should be finished in less than two weeks. If the far “feels good” I’ll look for a dyno.

Laust Pedersen

Here is the typical weak point namely the relatively short distance between the combustion chamber and a water channel. The fire rings on the headgasket (WFHG) are only very thin steel wrapped around the periphery of the cylinder bore and the corrugated steel that hold the fibers does not have much transverse strength and is further weakened by corrosion from the coolant. My WFHG is about 10k miles and 2 years old. You can also see the imprint from the steel O-ring, which would have made more sense if also applied to the cylinder. The fire ring is also broken up inward, which I think is from coolant seeping in during cool-down and boiling from the hot combustion.

Laust Pedersen

The combustion pressure was apparently too much for this coolant hose (near the “bunny-ear” thermostat).

Laust Pedersen

Here Danno is showing (off?) how easy it is to disconnect the cross-over pipe from the turbo using the right tools (in this case a crooked articulated-head ratchet) without removing the brake booster heat shield.

Laust Pedersen

Here is my setup for measuring the (intake and exhaust) runners ability to hold vacuum. This gives a very good picture of the combined valve- and valve-guide sealing. I measured how much the vacuum dropped in 30 seconds from 20 inHg. The worst result was to 6 psi and 2nd worst to 13 psi; in essence my valves and guides are sealed very well, considering two revolutions at idle takes 0.13 seconds.

jsonnen

Thats one reason why I'm hesitant of relying on water injection to combat detonation, if anything go's wrong with the set-up( run out of water-pump failure - no flow-etc) then your screwed.Its one more system that could lead to engine failure and IMO not worth the risk. Just my 0.02 cents hope I didn't offend you Laust cause I have a ton of respect for you.

Tom M'Guinn

What's that thing Danno is wrenching on? It looks like a turbo, only smaller. Just kidding, sorry about your HG. If you are going to blow a water pipe and HG, you might as well do it with gusto like that!

I wonder if a big oil cooler might help your temps?

Ahmet

May be a good idea to install a level/pressure gauge in the coolant tank so if the level goes down in the future due to a leak, no consequent failure has to happen. Ditto for the water injection system.
Ahmet

jwl

Are you going to flush your cooling system? That turbo water pipe sure looks rusty IMO.

Duke

That's what I call a blown hose!
Good luck with the rebuild.

KLR

Wow, that hose really blew! Is your clutch OK? I've always heard that when that hose or the heater valve goes, you typically get a ton of coolant dumped into the flywheel inspection hole.

nine51

I just popped my HG yesterday.
I'm looking for a source for the Cometic HG or which ever MLSHG you're going to use.

thanks
Jay

Laust Pedersen

Nine51, I am getting it through GURU Racing (Danno) and believe it is a Cometic gasket. It has a number of design features that gives me confidence in its durability.

jsonnen and others, don’t let my incidence hold you back from a well designed water injection system. Once you have it, it is addictive in the power potential it can release from the engine. My error was using a much too small filter combined with overconfidence in how well I had cleaned the water tank. Next I’ll be using a much larger transparent filter so it is easy to visually monitor its condition.

Tom McGuinn, I too think substituting the puny oil cooler with a bigger one is a big advantage, since the oil pressure was dangerously low at idle after a racing session, but one thing at a time. However the rod bearings looked surprisingly healthy … including #2.

Ahmet, a better safety feature would be a boost controller bypass valve triggered by low water pressure (when the system is on).

jwl, the rust is at a few pipe endings only. I think that some of the PO’s were using tap water, since I also see quite a few calcium deposits.

KLR, I “limped along” for maybe ½ a mile and the clutch felt good, but let’s see when I get it started up again.

And thanks to the well-wishers.

hosrom_951

Laust, just a question regarding those bunny ears, which one of the pong connect to the throttle body? my older thermo switch had a red mark on one of the pongs, now the difference bwteen the two is that one is straight and one is bent (a bit). Which ones goes where?

nine51

thanks
I gotta contact danno anyway I want to get 65# injectors while i got stuff apart. speaking of which, i just saw today that i split the same hose you did. What a PITA to get to that was. Can we bypass that, I really don't feel like trying to put it back on.

jay