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blkgt50
07-20-2004, 12:27 PM
What is good compression on any 5.0 motor?
dave bandt
07-20-2004, 04:09 PM
Please elaborate. Are you referring to cranking compression because you are checking it with a cylinder pressure gauge? Or are you looking for a number to design a combination around?
blkgt50
07-20-2004, 07:46 PM
Sorry! I have been looking for a motor and the places that I have been looking at have been giving me the comperssion numbers that they get from the motor. I have been given numbers from as low as 135 to high numbers of 170, most are 155-160.
bobtodd
07-20-2004, 08:15 PM
On my motor I have seen anywhere from 160 to 170 I think. It's been awhile since I've done it though.
blkgt50
07-20-2004, 08:49 PM
I guess that's good. I just don't want to get a motor that has a bad compression. Thanks
dave bandt
07-21-2004, 07:43 AM
Cranking pressure (compression) and static compression are two totally different animals. The camshaft plays a major role in determining what pressure you see on the gauge when you check the cranking compression....overlap bleeds off cylinder pressure and effects the reading. The main thing to look at is the variation between the 8 holes. If they are within 5-10% the motor is fine. If not then it is cause for concern.
blkgt50
07-21-2004, 09:35 AM
Thanks. do you think that 135-140 is to low of a compression for a motor? I would say so but what do I know, that's why i'm here.
BP Convt
07-21-2004, 10:37 AM
Thanks. do you think that 135-140 is to low of a compression for a motor? I would say so but what do I know, that's why i'm here.
Are you buying a used engine or are you building a new engine? 135-140 is good for a used stock 302 in my opinion. Main thing mentioned previously is that all cylinders are consistent. If its a used engine your checking, I prefer using leak down gauge rather than a standard compression guage.

If you building or buying a new engine combo, then I would spec the compression and cam profile around dynamic compression, not static.

BP
blkgt50
07-21-2004, 11:59 AM
I have a cobra motor that I have on hole while I find out what's right and what's not. The motor is coming out of a 95 cobra and going into a 92 gt. I'm sure that the motor will bolt right up but do I need anything else? The compression on this motor was 155-160.