2.4T Compression 80 x 6 - ok?

[porschecab]

I know compression on 2.7, 3.0, and 3.2 motors, but unclear as to what a 1973 2.4T motor should be. The one available to me reads 80 across the board before putting carbs on. Is this acceptable?

[Rot 911]

Should be closer to 120, but maybe their gauge reads different. Or it could be an engine that is shot and needs a rebuild.

[Mr9146]

Does it run?

How does it run?

Has it been sitting idle for a long time?

When was the last time it ran?

If it runs and sounds decent, put a few miles on it and then adjust the valves. You may get a different reading.

[porschecab]

Yes, it does run. Sat for about 5 years. Run well? That I don't know. Thoughts?

[BK911]

80 is very low. My lawnmower is more than that. I would do a leakdown just to verify. If the 80 is accurate I would expect a leakdown to be over 20% and be VERY close to rebuild time.

My bet is closed throttle plates giving a low compression test.

[Tyson Schmidt]

Did you do the test with the throttle wide open?

With individual throttle bodies you have to have the throttle wide open to get a proper reading. And a fresh battery too.

[Hladun]

Compression Test Pressures

[larrym]

way too low

- culprits can be bad rings, not enuf pump strokes (6 needed ), closed throttle, weak cranking, or (unlikely) universally and equally leaking valves - a leakdown will tell a story , cold or otherwise

my 2.7 8.5 CR pumps 165 with solex cams - cool block - OAT = 85 at 2800 altitude (readings 2 weeks ago)

I had that engine dyno'd today - it makes 125 rear wheel HP and flat 112 torque curve from 2800 to 6500 rpm with webers and stock distributor curve

[BK911]

Larry I agree with everything you said. But more importantly, I LOVE your signature.

The older I get, the better I was. Just classic!!

[larrym]

Bruce Anderson writes in Performance Handbook 2 that a good 911 engine will show 130-170 psi

our guru Wayne Dempsy's book has a complete procedure outlined on page 14 and uses 150 as an example reading