87 930 rebuild

[Don Cothard]

Here is an article on my recent 87 930 engine rebuild.

http://www.cpa-pca.org/more/articlesindex.html

Don

[beepbeep]

Nice writeup and nice mods. They make sense. I was just puzzled about few details mentioned:

We did not add bigger ports nor polish the heads. We know that the max HP on a CIS is near 500HP and we can achieve this without big boost and without big valves. The bigger the valve and port, the more air in the head. The more air that comes in then has to move out and that means a delay in time in throttle response.

I tought delay time in throttle responce was function of turbo size, intercooler volume and compression ratio. Interesting :-)

We added coated and X-rayed springs. The coatings help keep friction down on the springs.

Spring friction?

By less timing we create the same HP and we reduce the stress on the main bearings, rods, rod bearings and crank. It is a win/win situation.

Well this can be debated, but i tought that dual plugging means faster ignition time due to shorter distance flame-front has to cover, which in turn means in-cylinder pressure will raise faster which means it will beat harder on rods.

The rods also received an oil shedding coating to reduce oil friction and drag.

Mmmmkaaay....oil-shedding coating? :-)

[armandodiaz]

Where did you get that 934 frt bumper? I've been looking for them but all I can find is a two piece.

[Don Cothard]

beepbeep&armandodiaz--I'll have to contact the builder to answer your questions.
Don

[TerryH]

Awesome 930, Don! I was LOL at the NC hammerman as he no doubt had a mechanical engineering degree.

[rick conrath]

Armandodiaz:
I just picked up a 934 front end like that from TRE Motorsports. There was a group of us that did a group buy last year.
Rick
'78 930

[armandodiaz]

Thanks Rick

[dean]

Nice write up and car
Dean

[89turbocabmike]

Nice article Don! Even nicer car! Love that 934 front bumper I can't wait for my rebuild.

[Don Cothard]

Turbo mike
Is yours in proscess now?
Don

[89turbocabmike]

No, unfortunately not Don. I just put in SC cams, but the motor (75K) is tight and it's hard to justify, at this point, a complete tear-down. I've begun collecting parts though. Picked up a set of heads which I'm having Ollie's twin-plug and rebuild. Haven't decided on P&Cs yet but I'm leaning toward the 3.4L 8:1 LN Engineering "nickies". I'm going to EFI but I'm still researching whose system to use. A few people I know are in the EFI process, some with the Pat Williams type system, some using DTA or megasquirt. I'm waiting to see their results. I just finished a complete suspension overhaul and I'll add another oil-cooler and upgrade my a/c system this spring. Everything will be ready for the increased power. Ideally I'm hoping to come across a good core motor to build-up and swap over-night, how did you sleep while Stephen had your car? It looks like you got just what you wanted, I'm looking for a similar outcome. As this is a daily driver I'd really like to build an engine that is strong at .8 bar, I plan on driving this car a long time Congrats on the great transformation!

ps. Interested to see how Eric Hood's car turns out!

[lukeh]

How did you get the extra fuel you needed to safely get to 475 hp? Was it the newer fuel head mod I've read about?

That is the engine I would love some day.

[Don Cothard]

Yes--the fuel head was modified by Stephen.
Don

[Don Cothard]

Turbomike,
It was the longest 4 months especially doing it during the summer. But it was running so bad I had to do something. I was lucky in that I had just bought a 99 996 so I have the comfort of a/c when I need it and the raw power of the 930 there so differant to drive, I do enjoy both. Good luck with your rebuild. Wisk I had the skill to do that.
Don