Leak Down Test for 454's

[MikeP]

Well...An engine is an engine; there is no difference between a marine 454 and an auto 454 as far as the function is concerned - they both carbon up in exactly the same way given the same circumstances.

I agree with the idea that if there is no perceived problem, why go looking for one? But baseline data (compression/leakdown, etc) is always a good thing...

 

[krush]

Well, the environment of a car engine and a boat/airplane engine are completely different...that is unless u drive your car up a steep mountain forever.

 

[MikeP]

True, a gas boat engine normally runs at much higher load for extended periods than does a car engine. This just means that they wear out in a far lower number of operating hours. By the same token, boat gas engines are generally rated at lower HP levels than their auto equivalents to help the wear index. But the engine wear process is exactly the same; the wear symptoms are exactly the same, and the diagnostics/repair is exactly the same. You just will be doing it more often for the same number of operating hours.

 

[67hat34c]

How about this idea. Attach baloons to the breather on the valve covers on both engines and run at same rpms, see how fast they inflate. if one is significantly faster then there may be a problem.

No idea what the block pressure should be, guess i could rig somehting to put a low pressure gauge into the breather and block the other one off. compare the 2 engines that way.

4 blade props are done and she comes out in a couple of weeks so will post results once it has been splashed. out for about a week for bottom job and prop change. Going to Cape Marina so I will have to hang with Wild Bill, Roger Helms and Todd Howard.

 

[captddis]

Before you pull your hair out, wait on the props. There is a good chance that is it. I sent you a PM about the recons.
A few months ago I had a cust with a 34 with Cummins, he wanted the injectors pulled etc. They were all hitting strong, I said lets go for a ride first. Ex temp, boost etc were all good. Had the props scanned and reconditioned and tuned. He picked up 1 1/2 knots and rpm even on both. The props looked perfect to the eye, but the scan told different. It does not take much.

 

[Maynard Rupp]

did vacuum check a while back but did not have any specs to compare it to.

idle vacuum, acceleration etc.

Maynard do you have this info?

Mike, Seafoam is something most on this site swear by. poured directly down carb throat. Have also used ATF in the past. Would guess it may work better on cleaning the intake valves.

May pull heads but dont want to if I can help it. Why break a perfectly good seal.

Think we will wait and see when I change the props.

I really don't have any data about the value of a vacuum gage as a test tool. On airplanes we do set the power with a manifold preasure gage which is nothing more than a vacuum gage re-labeled. I do swear by Sea Foam and I am not a fan of additives or snake oil. The only other thing I like is Marvel Mystery Oil.

 

[krush]

I think the MAP gauge is damped heavily so it doesn't bounce around in a plane.

A vacuum gauge is a very useful tool for a good mechanic. I can't believe you've never used one.