Last seaon i noticed the boat lost like 5 mph and a couple people told me it sounded like a miss,, well i just done my leak down on all cylinders both motors and all was 5 to 7 % except # 3 was 50 % leak down, coming out exhaust port, pulled head will see tomorrow the problem when i pull the valve, just did the heads all new valves and springs last winter and only put 16 hours on the motors past summer. i also noticed alot more rust in the # 5 exhaust port than the other ports and some rust build up on my lifter valley pan, i had alot of milky chit in my breather hoses and oil caps last year as well, but nothing in the oil on the dipstick,, I did go to a crane 741 cam shafts with my gill exhaust w/ long tails i wonder if i was getting reversion and need different exhaust. never had these problems in 5 years till i redone top end last winter.

The Gils were about 10 years old. I would pressure check the manifolds and inspect the cylinder dividers below the riser for hairline cracks.

This set is only 2 years old i sold my old set last winter and bought a set that was 1 year old last winter, still using my same tails.

Reversion I'm guessing....

Rick,

With the leak down that bad I think you have to ask yourself which issue came first reversion/water leak or the valve wasn't lapped in when the valve job was done or done improperly.

Not common to do but did you do a leakdown after you assembled the motor last year? I went to the dyno with new heads/cam etc. and made miserable HP. Just happened to to a leak down and found 40% leakage in an intake valve which fixed the issue. The machine shop must have made an error even though they wouldn't admit it.

Wouldn't a big air leak on a exhaust valve cause reversion?

BTW, you're right, that is your 5 mph.

After pulling heads off we found many indications of reversion, the ehaust vave seat had to be touched up quit a bit due to reversion to get it to seat again. yes i did a leak down last year after all work was done and all was good, 1st couple time out the boat went 87 mph into the rev limiter and then was down to 81mph and rpm was way dawn as well. both motors show indication of reversion in the exact same places, never an issue till putting in the bigger cams, what exhaust would you guys recommend now with out going dry to the tip becaust that will be to loud where i boat, thunderstruck what exhaust and cam are you running.

I would go with CMI E-Tops. That's what I've been running with ZERO reversion issues since 2006!

Dave

Dave what cam are you running.

Thanks Rick

Crane 168741 with 1.7 ratio rockers on the exhaust and 1.8 on the intake.

Dave