Motor has been in the machine shop for 6 months and after putting it back together, we put the motor pluggeg into an electric motor to do a compression test and the results were 150 in all cylinders. (remembering that pistons were taken out to install forged rods but the rings weren´t removed. If we start the engine will this numbers bump up to normal or should i forget about it and buy new piston rings???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vtibrazil &raquo;</TD></TR><TR><TD CLASS="quote">Motor has been in the machine shop for 6 months and after putting it back together, we put the motor pluggeg into an electric motor to do a compression test and the results were 150 in all cylinders. (remembering that pistons were taken out to install forged rods but the rings weren´t removed. If we start the engine will this numbers bump up to normal or should i forget about it and buy new piston rings???</TD></TR></TABLE>

wel, it depends on what u want out of it, a motor thats gonna be strong and healthy with it's full potencial powers? or a motor that's just gonna start and run without the full potencial?

 

Well basically it is my wifes car she doesn´t need full power, but the car has to be working 100% no smoke out of the exaust etc. I don´t want to be bruning oil etc. just has to be functioning 85-90%! She doesn´t race I think

 

Was the engine dead cold when you did this? Throttle open?

A good sign is that all your cylinders were even.

 

well we put the car working for half an hour on the electric motor but without the head so I wasn´t totally cold. But since it had no combustion at all no fuel no spark when we put the head on and measured it was let say close to normal temperature but not cold. We wamted to move all the rotating assembly before turning the motor on since we are using a new rod and bearings and crankshaft

 

Same problem here, 150 Psi accross.

Car dont smoke, runs well. but i think its not performing to 100%..

I recommend fixing this problem, as the engine is not yet mounted...

 

with some running i figured those numbers would go up a bit maybe to 170 or so.

 

your rings have not seated, you shouldnt be doing a compression test anyway untill youve reached around 500 miles..

this has been covered alot.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbociv910 &raquo;</TD></TR><TR><TD CLASS="quote">your rings have not seated, you shouldnt be doing a compression test anyway untill youve reached around 500 miles..

this has been covered alot.</TD></TR></TABLE>

Not only that, but did your engine have any oil in it when you did the test? if not that would result in low numbers. Oil in the engine helps the rings seal.

 

Yes I know that but the thing is that for some reason the engine wouldn´t start so we had to plug into a electric machine so that the rings would move. That is the only reason I did the test just out of curiosity.

 

So the compression test was done on a cold engine using an electric motor, right? Was the throttle fully open when the compression test was done?

Well, if the compression is at 150psi all across with a cold engine I say it's fine. Recheck the compression when the engine is at operating temp (190-210 degree F) with all spark plugs out and throttle wide open, the result should be higher. But, remember there are factors that comes to play with compression test they include temperature, valve lash, condition of the cam to name a few.