79 3.0 compression question

IMR-Merlin · 07-11-2015, 11:44 AM

Looking through the Bentley. I can't find the info. Anyone know what compression should be on a 79 SC 3.0?

I'm getting 168-175 cold for pressures.

It looks like someone freshened It up recently too.

Thanks

Brendon.

Flat6pac · 07-11-2015, 01:22 PM

You're in the ball park, not too long from freshened up.
Bruce

IMR-Merlin · 07-11-2015, 03:04 PM

Thanks Bruce.

All the writing is on the wall. I found one of the PO's of the car and he told me that when he sold the car it was tired and that the new owner "blew it up" then had it rebuilt.

In my work today I noted a bunch of new lines and hardware. Not proof, but definitely looks like there was someone in there.

So as I dug deeper I found new oil return tubes, new oil return line from the scavenge side of to the oil tank, then the gem was finding brand new cylinder studs! Take all this and the fact that it has Carrera tensioners.... it at looks like a freshen up.

Now if I could only figure out the idle issue. I can't get it to set and be consistent.

On warm up, it sits at 2k, I can turn the idle screw all the way in and it won't go any lower even after the engine warms up. Then I can let it sit for 15 min and then the idle is 900 RPM or it won't even hold idle.

Flat6pac · 07-11-2015, 04:53 PM

You have to check your fuel pressures to know where it is. There is a graph for the warm up regulator performance.
Ascertain the pressures and you can set the enrichment until you can balance the idle at the throttle body.
Make sure there is a good seal in the oil tank.
Bruce

IMR-Merlin · 07-11-2015, 05:36 PM

I am borowing gauges tomorrow. I am leaning toward a faulty DV or AAR

fred cook · fred cook's Garage

Quote:

Originally Posted by IMR-Merlin

I am borowing gauges tomorrow. I am leaning toward a faulty DV or AAR

Sounds to me that the +12v connector either is not properly plugged into the socket, is not getting voltage, or, the heater coil in the AAR may be bad. You can pull the AAR and put it in the freezer for a few minutes to make sure that it is opening all the way. Then, use a heat gun to see if it is closing properly. Check for +12v with a volt-ohm meter. Good luck!