So the truck ('58 292, Mallory dizzy) has been running like a dream thanks to everybody here but lately I have noticed a lot more fumes coming out the down draft tube so I decided to do a compression and leak down test to see what was going on, kind of wish I hadn't. The compression was right around 100-110 across the board but I was thinking that my gauge might not be working right because it would jump up to that number and right back down to 0, I never had to release the pressure. Then I did the leakdown test with 80 psi it would drop to around 20 on the cylinder side and my little compressor had a hard time keeping up with the amount of air that was rushing by. Had it at tdc, with the choke closed and accelerator plate wide open, no air cleaner on. It sounds like the air is going passed the rings and or the valves (I know "really narrowing it down") because I can hear it coming out the dipstick I think. My question is, with the numbers could I really have the truck running so nice, it sounds like clockwork? Thanks to all in advance.
Regards,
Cbass (Sebastian)

 

Excessive crankcase fumes equals blow by usually equals worn engine, worn rings at least. Sometimes an old engine seems to run great. The oil getting by the oil rings help seal the compression rings. I would suggest the leak down and compression tests are telling you what you don't want to hear. I've seen them run a long time this way. Many PCV systems have been added to mask the blowby problem.

 

I know exactly what you mean about wishing you didnt have certain information after doing an engine test.

I have a '62 Merc at a mechanic's now. While it is in he is to do an oil pressure check to verify the accuracy of the car's OEM oil pressure gauge. I expect the gauge will turn out ok. BAD!...showing real low oil pressure. Anticipating the poor results i already picked up a little 260 SBF for workover as a replacement.