Top-End

[c.o.]

I'm all set to reassemle a top-end on my '48. When I pulled it apart to swap out the heads I had found some grooves in the bores (some of you may have heard me ramble about this already).



The front and back of both the pistons looked like this....



Anyway when I stopped at the machine shop to get my cylinders today the machinist said he really had to grind away at the barrels to get to .010" over. The pistons that I pulled out were standard but the cylinder bores weren't. He thought it was possibly due to a manufacturer error (aftermarket barrels). So... I'm thinking whoever initially put this together must have trusted that he ordered a new set of jugs and standard pistons and could just fire it together. This engine was set up too tight!!! I know you engine guys know to check things but for somebody that's just putting together something in their backyard I would advise that you check your tolerances prior to assembly. Especially if it's shiney new bought parts!!!!!

Long story short.... I'm starting over....

[RicD]

WASH and wash and wash again!! Use as hot awater as you can and Dawn dish soap and wash the bores until you can push a dry white t-shirt through the bore and it comes out white. That may mean washing the bore a dozen times or more. If you leave the grit it will wearout or score soon Wash the pistos also. that is the best info I can give.

[c.o.]

WASH and wash and wash again!! Use as hot awater as you can and Dawn dish soap and wash the bores until you can push a dry white t-shirt through the bore and it comes out white. That may mean washing the bore a dozen times or more. If you leave the grit it will wearout or score soon Wash the pistos also. that is the best info I can give.

Believe me they will be sparkling clean before I start buttoning things up... Thanks for the input!

[BigLakeBob]

Cory, How is the cross-hatch in the cylinders? From the photos they don't look right. I think, someone will know more than me here, but shouldn't they be an 'even to each other' approx. 30* off horizontal and consistent throughout the length of the bore. I'm pretty sure this is critical for proper oil flow, staying there for the piston lubrication-but still draining off the walls as needed. Bob AMCA#6738

[c.o.]

Bob!!! Here's another shot... I don't know the fella that did the boring has been building engines for a lot of years now. I had hoped he knew his stuff. If something is glaringly obvious somebody please speak up!

[T. Cotten]

Cory!

Pics are deceiving, so here's some basics to look for:

Ideally, the crosshatch could cross at a bit wider angle; 60 or 30, depending on how you look at the axis.
But angle is by no means the most critical concern.

Modern rings do not seat.
They are already round.
And if the coating is worn from their edges, they are worn out.
(As per Hastings.)

So a "plateau finish" is desired.

That is where the bore is roughed out with coarse stones to within a little more than a thou of final bore size.
Then a medium stone takes the top off of the mill profile, and a fine stone takes it to size.
This leaves three depths of crosshatch.

A final finish is usually provided by an impregnated abrasive nylon brush set for the honing head, although Scotchbrite on a drill seems to do as well.
After cleansing, you should be able to draw a cotton ball up the bore without pulling fibers.

Caveat: This was state-of-the-art for the late 80's, and I haven't been keeping up lately!

....Cotten

[c.o.]

Cotten!!!

Thanks for the reply. Pictures are indeed deceiving. Especially at the angles I've managed to capture with the camera. I'm going to give these a good cleaning, put it back together and hope for the best!!!!

[kg993]

I want to add to washing the cyl. bores. Imediatly after washing EACH cyl. (Dawn is also what I use) wipe water out with a lightly oiled lint free cloth (gun cloth/WD40). Then spray WD in the bore and wipe out with another moisture free cloth. If there is anything left the oil wil bring it out. The first pass may bring out some red (rust) but that seems to be normal.
I keep the cloths clean and in ziplock bags, never lay them on a un-clean surface and make sure my hands are clean before the final washings.

[kg993]

One more thing that wasn't mentioned is to clean out the passages for oiling and return, honing grit will set up like cement and oil will break it loose and run it back through the motor.
Two more, clean ring compressor and atmosphere.

[c.o.]

I want to add to washing the cyl. bores. Imediatly after washing EACH cyl. (Dawn is also what I use) wipe water out with a lightly oiled lint free cloth (gun cloth/WD40). Then spray WD in the bore and wipe out with another moisture free cloth. If there is anything left the oil wil bring it out. The first pass may bring out some red (rust) but that seems to be normal.
I keep the cloths clean and in ziplock bags, never lay them on a un-clean surface and make sure my hands are clean before the final washings.

One more thing that wasn't mentioned is to clean out the passages for oiling and return, honing grit will set up like cement and oil will break it loose and run it back through the motor.
Two more, clean ring compressor and atmosphere.

Thank-you for taking the time to run through what you do on re-assembly. I will make sure everything is spotless prior to assembly!

[gary.h]

no worries about the jugs cory,gregs been keeping shovels,pans,flatties ect,ect rebuilt for some time now ive never had any issues with his hone jobs.glad to see things getting ready to go back together.

[c.o.]

Gary, thanks for the good opinion on Greg's work. I've heard a lot about him from a wide variety of folks and if I get it buttoned up properly I think all will be well.