924Board.org

[TroyDest]

Hey Rick,

So, so sorry. Your 931 sounded like it was one of the best ones out there. Not to throw salt in your wounds but, once you get your motor apart, what do your pistons look like? I've been admiring your anti-detonation solution for a while now. From the looks of your pistons and combustion chambers, how does the system seem to have worked? Do you think the extra boost contributed to your demise?

Whatever the case may be, I hope to see you in the forum again soon with your 931. I'm looking forward to your experiences with a 931 rebuild and your modifications.

-Troy

[Rick MacLaren]

That's a really good question. And I'm not too sensitive about it. The answer is yes and no.

The piston chambers, head lower surface, plugs and pistons show zero (0) signs of detonation. The piston in #1 chamber had a piece sheared off. It seems to have hit the spark plug. Moreover, the piece of piston that broke off banged itself around the head and piston. If you can imagine a surface of metal that looks like it's been hit numerous times with a hammer and screwdriver, then that image is pretty close to what the head surface (where the explosions happen) looked like. Very messy. The head is toast.

Three hypotheses present themselves:

1. The rod bearing wore down leaving a gap between the rod sleeve and the crank, thus the piston extended into the combustion chamber hitting the spark plug. Extra boost and power made this situation more impossible as time wore on and I continued to drive the living crap out of it.

2. The mechanic putting the timing belt and cam on the car neglected to consider that it was an interference head (doh!) and started the car. Difficult to prove or establish.

3. The cam, a USED one from another 931 of mine, and USED tappets, were installed. Perhaps this made for a poor situation wherein things around the head clunked around. I dunno. I would, next time, use ONLY NEW PARTS.

The alcohol system was quite useful. On hot days I used it, on cold ones I didn't. But I think the extra boost contributed to making the engine run faster, though not hotter. Still, it was another stress. And as racers know, increased speed equals increased stress on the engine parts and this equals increased maintenance.

_________________
1980 Porsche 931 In hospital...
1979 Porsche 924 Tweaked.

[ This Message was edited by: Rick MacLaren on 2001-11-21 08:01 ]

[Nick Neves]

Hey Dwak,
sorry if I'm getting a little off subject, but i was curious if you ever installed that air damn i sold you a while back. If so, I'd love to see how it turned out. BTW, about those spare engines that you have laying around, I'm in the market for a turbo head, the combustion camber on one of my cylinders looks like it's been blasted by buckshot. I actually pulled a sliver of metal from the surface, and guess what, it stuck to a magnet. hmmm. My pistons look alright, though, and there's absolutely no scoring on my cylinder walls. Although i wouldn't mind installing 8.5 comp pistons in if some one wanted to sell em to me cheep. let me know.
nick><>

[wdb]

another option
http://www.atkengines.com/catalog/porsche.htm

[dwak]

Hi Nick,
All I've done with the air dam so far is clamp it temporarily in place on one of the cars but it looks good. I'm just waiting for some more house deposits so I can waste more money on cars and abscond to Mexico with Ricks dowry money.
Sorry but I'm keeping and grabbing all the 2 litre engines I can.