2.7 compression

[tassie targa 76]

G'Day All

just did a cold compression test of my 2.7

i dont have much history on the car other than it has been rebuilt some time in the past

i runs well revs well no smoke seems generally good all round

im about to remove the engine and transmission and everything else for a full body restore thats where my money is going at this stage

anyway back to cold compression i got approx 100psi + - 5 across all 6

not sure if this means a top end pull down any thoughts

Regards Michael

[Flat6pac]

First off, it apears you have the wrong coil in place. With a CD box, you require a Bosch 001.
When you warm up and seal you should have 145# or slightly better. The 100# cold with the +/-5 is good all around for cold as there is enough compression for ignition.
Bruce

[tassie targa 76]

yes i have been told about the coil i will be replacing the ignition system during overhaul.

are you suggesting that simply by bringing up to operating temp an increase of up to 45psi

i was also told that doing a cold compression test with kj intact reduces the air flow therefore reducing overall outcome.

does that sound right

regards michael

[911pcars]

Originally Posted by Flat6pac

First off, it apears you have the wrong coil in place. With a CD box, you require a Bosch 001.
When you warm up and seal you should have 145# or slightly better. The 100# cold with the +/-5 is good all around for cold as there is enough compression for ignition.
Bruce

Could be the cranking speed is lower than normal or the engine is tired (worn rings).
Squirt a teaspoon of oil into each cylinder and retest. If the compression increases close to normal, I'd suspect the rings.

Sherwood

[larrym]

my 2.7 with 8.5 CR pumps 150 cold (6 bumps) - and hits 75 on the first bump at 60*F

my 2.8 with 10.5 CR pumped 175 with 75 on first bump at 70*F

.

[tassie targa 76]

i suspect a set of ring are in order hopefully not much else as all my money is going on body at this stage

[tom1394racing]

Make sure you have the throttle fully open when doing the compression test.

A closed or partially closed throttle will depress the readings.