compression leakdown test #s 275 cosworth

[john olson]

Hi
I have an old 3l(I think) 275 Blackmax cosworth motor,1992 0r 3 vintage.THe serial number sticker is missing. I want to do a compression test and leakdown test on it in the spring to see where I am at with this motor.

Can anyone give me the following info, as I have never done the tests but have access to the equipment.

-What the proper readings should be and in what range
-Proper sequence to do the compression check
-Proper sequence to do a leakdown test
-And any other info that will help me in determining what condition the motor is in before I go any further with it.

Any help much appreciated

Thanks
John

[Capt.Insane-o]

Warm the motor up. Compression should be around 125 with a fully charged battery. Leakdown less than 10% is ideal.

They are a 3.4 liter and not a high rpm motor. propping it for 53-5600 max will keep it happy. Parts are very scarce.

A nice running motor actually. A lot of people tried to make them do what they were'nt designed for and they earned a bad rap.

[Reaction1]

I have a couple of Cosworth 275s and have not had any troubles other than lower unit problems. I just picked up a counter rotating lower at this place called Superior Outbards, in Ft, Myers, FL, that has all kinds of spares for outboards. They have a couple of 3.4 Mercury 275s, so when you need parts, you know who's got them. 239-267-6722. Good Luck!