Bead blasting and fitting pistons

1970Thunderbird · Oct 9, 2011

Hey all,

I just got my block back from the machinist and I'm ready to start putting her back together. While I was visiting with him, he suggested I sand or bead blast the exhaust side of the block, including the water jacket cover, to remove the carbon deposits. What do you guys think? I'm a bit worried about doing this, as it's aluminum, and I don't want to etch or mar anything.

Also, the bolts on the crankshaft end of the piston connecting rod face into the block, meaning they are only torque-able while they are outside of the block. So this means I have to fit all four pistons at once. Do you have any tips for how to do this? Also, will standard ring compressors from Autozone work?

Also, the machinist recommended thoroughly washing the block with soap and water to get all the machining grit out. Any extra steps I should take to ensure the block is completely clean before fitting the pistons?

Any tips you have would be greatly appreciated.

As always, you have my deepest thanks

MercMan82 · Oct 9, 2011

Re: Bead blasting and fitting pistons

take a look at my post. Just got done doing a rebuild myself. I would sand blast it or bead blast it. Wont hurt anything but make it look better. Afterwards you need to get a stiff bristle brush and some dishwashing liquid and clean the cylinders really good then dry them by wiping them with cloth. Rub the inside of the cylinders with 2 cycle oil to lube them up. Factory manual warns against using automotive ring compressors. It is too hard to see where exactly the gap in the ring is while you compress them and can easily break them. I used my fingers to compress and wiggled the piston back and forth making sure the ring gaps were in the right place, working the piston down slowly. Had all 6 pistons in in about 45 minutes. That included measuring all the rings gap in the cylinder for each piston. The key is patience and don't force them.

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

MercMan,

Thanks for the post. I, too, heard that all the pistons have to go in at once. The fact that you were able to do that with a 1150 gives me hope for my 800.

Overall, how difficult would you say it is to attach the connecting rods to the crankshaft once all the pistons are in? I was told I absolutely had to take it to a mechanic to do it, and the ones I've spoken to will only do it if they can reassemble the whole thing. And thank the Lord the crank end bearings have a cage!

Also, what blasting material would you recommend? The machinist mentioned using soda, though he couldn't be more specific than that.

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

Also, MercMan, what did you do, if anything, to your reed valves? Since I have mine completely torn down, I figured they ought to get a once-over, as well.

MercMan82 · Oct 10, 2011

Re: Bead blasting and fitting pistons

Attaching the rod bolts wasn't hard at all except for the last one in which I think my anxiousness got the best of me and I kept dropping the bearings

.

As for the sand blasting material I'd use sand. The idea is just to knock off as much dirt and corrosion as possible to make it easier when you clean up the sealing surfaces.

I blew off the reed halves pretty good but didn't disassemble them. Checked and adjusted the reed stop height and that's about it.

MercMan82 · Oct 10, 2011

Re: Bead blasting and fitting pistons

Btw, what's your sn, or year and hp so we can know how yours is configured.

Fishing Dude too · Oct 10, 2011

Re: Bead blasting and fitting pistons

I would use somthing othere than bead, thinkking cob material, could see if find a auto machine shop with a lie wash maching.

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

It's a 1978 Mercury 800. Inline four.

I was lucky in that the machinist agreed to clean the old gaskets off the surfaces. They're very clean. The only area I'd need to blast is inside the exhaust side of the motor. There's a water jacket cover in there that is coated in carbon build-up

Fishing Dude too · Oct 10, 2011

Re: Bead blasting and fitting pistons

Have bead blasted alum blow molds you will get it eveywhere will be a big cleaning job.

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

Well, I do have a blast cabinet, so I'm not worried about the clean-up. Most concerned about keeping the block from getting pitted.

Fishing Dude too · Oct 10, 2011

Re: Bead blasting and fitting pistons

Could try chem clean or somthing simular, blasting would be my last choice. Use a small brush to scub ports

MercMan82 · Oct 10, 2011

Re: Bead blasting and fitting pistons

I think your just splitting hairs then. If you have to replace the water jacket gasket then by all means but if it's just for looks, nobodies gonna see it and unless there is a substantial amount that absolutely needs it then I wouldn't bother.

MercMan82 · Oct 10, 2011

Re: Bead blasting and fitting pistons

Btw, that aluminum is a cast and it's more durable than you think.

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

MercMan,

Perhaps I am splitting hairs. I do have that tendency. I figured I'd give the block a thorough going through, as it's already torn apart. Another reason I thought about doing this is to ensure there's no chance of either overheating, or blocking exhaust from flowing freely.

MercMan82 · Oct 10, 2011

Re: Bead blasting and fitting pistons

Then focus on the water passage ways and make sure there's no blockages anywhere. Exhaust isn't the concern, it's proper cooling. Also, make sure your carbs and fuel pumps are cleaned. Did you buy a gasket kit for your motor?

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

Yep, got the full gasket kit. Replaced one carb gasket set already.

Over all, I think everything will turn out fine, but I want to cover all of my bases, as I want it to run a long time before I have to take it down again.

MercMan82 · Oct 10, 2011

Re: Bead blasting and fitting pistons

I understand. Plus, it will ensure that you don't have to tear it back apart for whatever reason. Good luck to ya!

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

Thanks. If you can think of any thing I should know, anything, please let me know. It's my first rebuild I want to ensure I do it properly.

MercMan82 · Oct 10, 2011

Re: Bead blasting and fitting pistons

I'm sure others more qualified than I have something to say here

1970Thunderbird · Oct 10, 2011

Re: Bead blasting and fitting pistons

I've been messing around with the crankshaft. Did your mains (the center one and the two with the reeds) move around? Mine slide around, and I want to make sure that's normal. I think it is, as they have retainer pins in the bottom. Also, should the connecting rods have wiggle? Mine do. Figured I go ahead and replace the bearings in those as well.

Bead blasting and fitting pistons

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