How much blowby is okay? I am looking at purchasing a low mileage (46K) 87 Chevy 1 ton truck from a government auction site. The 6.2 diesel "whistles" when I take the cap off of the oil filler neck (not sure of correct nomenclature, but it is the tube into which you would add oil, just behind the radiator). I have heard that some blowby is normal, due to high compression ratios. Any help is appreciated

'Whistling' is probably cam gear driving inj pump gear noise, and some double-link roller-type timing chain noise.


Should be little bowby with hot engine coolant temperature, around 180 ~ 200deg.


Put oil filler cap back on, pull dipstick, see how much vapor from the dipstick tube.