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914World.com _ 914World Garage _ Testing a motor: what should I do.

Posted by: Cevan Jun 12 2008, 09:22 AM

I have recently come to purchase another 914 with a 2.0 motor. I am contemplating doing an engine swap, replacing my 76 hp 1.8 with a 95 hp 2.0. I originally wanted to build a 2056 (still do) but then this car came along. The car allegedly has 72,000 miles on it. I don't have much history on the car other than the fact that the PO bought the car in 2000 and the inspection sticker on the windshield is from 1994.

I want to assess the health of the motor and see if it makes sense to do the swap. What is the best way to do this? Leakdown test? Compression test? The motor does run, and I should be able to drive the car up and down my driveway (it's long) to warm it up.

Posted by: Racer Chris Jun 12 2008, 10:01 AM

Leakdown test.

Posted by: SLITS Jun 12 2008, 10:07 AM

Make sure the valves are adjusted correctly.

Do a quick compression test for a quick evaluation then do a leakdown for a final evaluation.

The leakdown, as RC said, is the absolute best.


Posted by: Cevan Jun 12 2008, 10:09 AM

I have neither tool, so can I just get a leakdown tester or should I get both? I've read that you should have a way to prevent the motor from spinning so that once you pressurize the chamber, it doesn't turn the motor over. How is this done?


Hey Chris, can I get a tour of your place sometime??

Posted by: SLITS Jun 12 2008, 10:17 AM

QUOTE(Cevan @ Jun 12 2008, 09:09 AM) *

I have neither tool, so can I just get a leakdown tester or should I get both? I've read that you should have a way to prevent the motor from spinning so that once you pressurize the chamber, it doesn't turn the motor over. How is this done?


Hey Chris, can I get a tour of your place sometime??


If it's on dead exact TDC on the cylinder, it won't generally turn over. That said, it is hard to get exact TDC (timing marks are approximate) so you have to lock it somehow ... wrench on the fan hub bolt head or on the alt pulley nut (and holding the fan belt) are about the only choices you have with the engine in the car.

That's why I said a quick and dirty compression test first.

Posted by: brer Jun 12 2008, 10:19 AM

sounds like a good topic for a "write up".

How to inspect and assess a motor in/out of a vehicle.

Posted by: SLITS Jun 12 2008, 10:26 AM

A further note on Leak Down Testing came from the Pelican 911 Engine Rebuilding forum .... If the numbers are bad, try turning the engine a degree or so each side of the TDC "mark". If the numbers improve, you were not at true TDC anyway.

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