Leakdown test on 4 litre motors?

I believe whoever told you that was misinformed, as I see no potential for the said scenario happening.

 

I doubt you could hurt anything.

 

I did one last year on my 70 Espada and yes it will run backwards if you don't back stop it but the idea that it damage something is a pretty wild ass-ertion. Get yourself one of those ring nut sockets for that "special" front nut first.

Bob S.

 

Please if I could just clearify your wording, it could rotate backwards at most 180 degrees to BDC. It is apparent to most but possibly not all that the engine will never ever rotate more than the said 180 degrees. Therefore it will never run backwards nor for that matter will it ever run forward during a leakdown test.

 

It's this simple. All the plugs are out. You're putting 100-120 PSI in one of the cylinders. Depending upon where that cylinder is in it's rotation cycle it's going to move forward or backwards unless you backstop it which I do with a socket & breaker bar on the front of the accessory shaft. You're suppose to take readings both before, at and after TDC but with the valves fully closed. I don't let the air pressure take the piston to the bottom of the stroke. At least not intentionally. ;>)

Is that any clearer?

Bob S.

 

Yes very much so.