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3900 V6 Swap by Joseph Upson

Started on	: 08-07-2007 01:09 PM
Replies	: 201 (19824 views)
Last post by	: diabloroadster on 12-15-2011 09:25 PM

Joseph Upson
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12-15-2011 07:22 PM

quote

Originally posted by fierocarparts:
Updates?

Just received the new F40 to replace the ailing one in the car now. Below are the two links that will cover what happened with the forged build. After more time to think about it and investigating, the engine wound up with a combination of burnt rings in at least one cylinder and possibly a burnt valve as a result of the oil ingestion as can be seen as a hot spot on a few of the intake valves. I thought the reground camshaft didn't have enough duration but considering it has at least 16+ degrees more than the stock cam at 9.8:1 compression it's probably fine for 11.5:1.

I found the real culprit was not just an improper PE AFR but some extremely lean points under boost that I didn't have the datalog table setup to display and didn't catch on the gauge out the corner of my eye given the car ran so aggressively under boost I had to keep my eyes on the road. I was careless and I paid for it. I can't attribute the rod bearing wear to the compression ratio considering my timing was probably still too far advanced, my bearing clearance was on the tight side at around .0018 instead of .0024" and at some point my oil squirters were damaged and after an experiment with 5W20 synthetic I suddenly started having problems with idle oil pressure dropping low enough to trip the light.

The plan is to refresh the engine, install optimum clearance rod bearings, replace the valves and maybe go with a little more duration on the cam. My reluctance with the cam has to do with the fact that even with a weak cylinder and damaged rings the motor still cranked out 33 mpg on the hwy suggesting a fresh motor might have reached as high as 38 mpg considering I under estimated the actual economy over 150 miles to arrive at 33 mpg according to my receipts and the mileage posted on the odometer to make sure I errored on the low side.

The bad knock sensor complicated things also. Hopefully the swap will be completed in January.

http://www.fiero.nl/forum/F...2/HTML/107886-4.html

http://www.fiero.nl/forum/Forum2/HTML/119218.html

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diabloroadster
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12-15-2011 09:25 PM

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I just wanted to thank you for posting up your entire process of failure and success, I gotta hand it to you alot of people would have gave up already. I read every entire page of your swap last night as Im considering purchasing UND_Sioux's 3900 engine swap stuff to put into my Diablo replica. If decide to go with his 3900 it will be turbo'ed like yours, but xmas is getting in the way of making a decision right now...

Looking foward to see your finished project!

Nevermind on the 3900 swap, I see its already sold....

[This message has been edited by diabloroadster (edited 12-15-2011).]

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