flathead help

i have an 8ba that i have been trying to sort out for a year, when i got it, it had been sitting for 20 plus years, its .125 over, adj lifters, isky 400jr and was told it had a merc crank in it, checked the comp and it was 90-95 in all cyls except #3, it was 30, tore it apart to do valve job, pistons were marked .125 lc, measured stroke and it come up 3 3/4, pistons are 1/4 in below deck, did valve job, still 90-95, and #3 is 90-95, at mid throttle, it ran like cam was a tooth off, that checked out ok, also verified it has 400jr in it, change fron electric fuel pump to mech, no change, had carb rebuilt (94), solid core wires, hotter plugs, 2 dirrerent dizzys, both stock, set timing all over the place, new vac adv, moved the float up and down, still runs like ****, judging by the pistons, its had a merc crank in the past, a guy told me it will never run right till i change the crank or pistons, i know 90-95 comp is not much, but think im still over looking something else, how lumpy is a 400jr? is it comparable to a 350 horse 327? this thing idles pretty smooth! i have another 8ba i want to start building for it, but would like to do some cruising in this one while in doing the other motor, ive put about 250 miles on this thing but thats been test runs, help!

 

No way it's going to run correctly (optimum) with the wrong crank. Or get Ford pistons.

 

iT SHOULD BE EASY TO CHANGE PISTONS out of the top on yours considering it doesnt have many miles. Easy fix.

 

Fix it. With a quarter inch of air over the pistons it is pretty much junk...think of this as a cheap engine build! Or swap out the crank...might not cost much more, and a more appealing option!

 

thanks guys, think ill go the piston route as im gonna put a merc crank in the other engine, what are good pistons and rings? ring end gap? what about rod bearings? it holds 25 lbs at idle.

 

Are the old parts good? If the lowest comp cylinder was caused by valves, you might just want to transfer the rings to the new pistons--I suspect those numbers are pretty good for an engine with totally FUBAR compression height...
If pistons look good, I might be interested in them, by the way

 

thanks bruce, will keep you in mind.