Healthy 2.7 Compression and Leakdown Numbers??

[Middieman]

Seeking advice on what are acceptable numbers or the range for compression and leak-down test for a US-spec 2.7 in stock form and Carerra-spec?

Thanks

[afterburn 549]

It is all going to depend on your static C/R.
So if you can be with in 10% of your highest and lowest you are in the park, the closer the better of course.

[Walt Fricke]

Both these tests are relative. You are looking for leakdowns which stand out from their fellows, and you want to listen to each one to see where it is leaking. There is no standard leakdown device, either, so that factors in. However, 0-5 is pretty good. I think above 12 starts to get suspect.

On Compression, I've never been able to get numbers which correlate with the CR. Again, what you really learn is if one hole stands out from the others (usually much lower)? Altitude plays into this. I don't seem, at 5,000 feet, to see the nice high numbers people report. I also tend to forget to open the throttle butterfly when doing this. 1135 +/- 5 across the board maybe?

What do you mean by Carrera spec? The Euro 3.0 Carreras came out in '76 and '77, contemporaneously with the 2.7s. Not imported to US. The US Carrera from '74? 75 also? had the stock US 2.7. The Euro Carrera of that era had MFI and was advertised at 210 HP.

[juanbenae]

Originally Posted by Walt Fricke

Altitude plays into this. I don't seem, at 5,000 feet, to see the nice high numbers people report. I also tend to forget to open the throttle butterfly when doing this. 1135 +/- 5 across the board maybe?

I always recognized that at higher elevations the mixture needs to be adjusted as the air thins. id always considered the AFR for combustion to be the driving force there.. but the thinner air contributing to less compression had not ever crossed my mind. makes a ton of sense though. at least mountain air is cooler... thanks for making me think some walt!

can the butterflys seal well enough to skew a leakdown or compression test? seems the volume of the carbs and manifolds would not hinder any positive pressure getting by the intake valve?

lastly, what does the 1135 refer to?