'77 85hp - Update and confusion

[jimmbo]

Re: '77 85hp - Update and confusion

Re: '77 85hp - Update and confusion

Dhadley, you beat me about the thicker gasket.

 

[h_lankford]

Re: '77 85hp - Update and confusion

Re: '77 85hp - Update and confusion

just to be devils advocate:

you said the bores are in spec.

you said the pistons and rings rings look shiny and the rings are still springy....but.....

how do you know the rings are still in spec without taking them out? If you saw a widened ring gap that might give you a clue to worn rings, but the ring gap should not be visible looking through the port when installed correctly.

seems like lack of seating might be more likely if the 90 lbs really is a problem.

Leak down test ? (but the head needs to be back on)

 

[iwombat]

Re: '77 85hp - Update and confusion

Re: '77 85hp - Update and confusion

I measured the bore with a bore gage, and it's within tolerance for the standard size pistons.

This whole adventure into the cylinders started out on kind of a lark.

See, the reason I dove into it in the first place was the poor idle. I attributed that to clogged low-speed jets so I removed the carbs for a rebuild. All the while I knew the compression was in the 90-range and that may be looking at a rebuild in the next year or two. Then I figured hell I'm most of the way there why not go ahead and ring it while I'm in there. (I'm weird that way)

Priced out the ring job - too pricey for a "just because" so I figured I'd do an invasive cleaning and free up any sticky rings and take out what carbon I could - head gasket and inspection covers are cheap and easy.

If it was coked up and looked like it'd been around the block a few times I would have buttoned it back up right there and thought nothing of 90psi and been pretty happy about it. But, a motor with the kind of measurements I'm getting I figured 100psi at least if not 120psi or so. Now, I'm just trying to figure out why it's not. Not because I'm crazy about getting it up to some mythical number, but because I'm simply curious.

What do these motors normally get freshly rebuilt anyway?

Now that I've beat it to death, it's already back together and the carbs go on tomorrow. I'll run it just like it is, and it'll run just fine I'm sure. I'm still puzzled at what I'm seeing though.