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removing pistons from a severely rusted cylinders.

80' 427

80' 427

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The truck my grandpa and I restored in high school has been sitting since his death. After getting it out last year for my wedding I found the head cracked. I have been looking for a GMC 302 for years and finally found one. It has been sitting a long time and the cylinders are horrible. My machines say it can be fixed if I get it apart. Any one have a way to remove the horrible rust? Muratic acid? Kroil and leave it sit? I will have to sleeve one cylinder but being it will go 100 over the rest should be fine.
 
Fill with oil and let soak for awhile and then use WOODEN block to pound it out.
 
What about some of that stuff you can buy now that removes rust. I think wd40 makes some and there's another brand too. I used it on my heads and it removed quite a bit. Idk how well it will work on thicker rust though.
 
Fill the cylinder with a 50/50 mix of acetone and ATF. Drink beers and wait days. Make a wooden "plug" 1/4 inch smaller than the cylinder to smash on with a BFH while someone with a breaker bar and long cheater pipe try and turn the motor over (turning in a direction that will move the piston down.) Use the hardest hard wood to for the wooden plug, pine is a waste of time.
 
We soaked a few badly seized antique car engines in the hot tank at the auto machine shop...worked,a few hours later we were able to tap the pistons out with a block of wood..we had Oakite in the hot tank,nasty stuff..it will dissolve aluminum in a few hours and you have to keep watch on the parts!..

The electrolosis method is effective--I dont know if the pistons will get eroded by the "battery" effect though...

At the junkyard we got one stiff old Packard engine free by hooking up the heater hoses on its engine to our yard trucks heater hoses and letting it run a good hour--after the engine was as warm as it was going to get,we pulled the plugs and put ATF in the cylinders and then gently rocked the crank back and forth with a breaker bar on the bolt in the harmonic balancer..it worked!!..got it to turn 3 complete revolutions,then the starter was able to spin it over..it actually ran decent after we got it to start...


An old timer I know uses a grease gun to free up stuck small engines he restores..he takes a non-fouler thing that screws into the spark plug hole,brazes in a grease fitting,and pumps it full of grease--this only works if the piston is NOT at bottom dead center though..
 
The pistons can dissolve I am getting new forged ones. These holes are bad like 30 years outside.
 
to do the heat method if you have a salamander / torpedo heater set it up in front of the engine and let her run . lots of heat in the block that way also . my buddy and I did this with my 14ff we welded the tubes on the center . used a temp gun and sure as sheet it got nice and warm real quick .

I freeded up a Yamaha three wheeler engine like this one time . been dunked in a river and kid didn't tell day for 3 days by then frozen . the atc sat for over 3 years like that . I got it free in hr or so and running just fine. no smoke and every time I rode the atc it would be running in 1/2 pull of the cord.
 
If I remember right, I did this to my 455. Pulled the crank, soaked it in pb blaster and gently beat on it with a hammer and a 2x4. Back and forth. I would work each cylinder then soak it again and try again the next day.
 
Mark1968 said:
If I remember right, I did this to my 455. Pulled the crank, soaked it in pb blaster and gently beat on it with a hammer and a 2x4. Back and forth. I would work each cylinder then soak it again and try again the next day.
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I did this and it worked fine. The coke did nothing and was a waste of time. PB was the best
 
Does this block have any special meaning to you? If not, junk the block or sell it to someone with an old 69 Z28. Pull the crank, knock the pistons out so you can get the rods if they are GM "pink" rods. If they aren't pink just leave them. They are no better than other large journal rods. Get yourself a good 350 block, (dime a dozen) and build your 302 off that. If you get a late block you can get an adapter that will let you run the old crank in a one piece seal block. Use your old 202 heads off the 302 and have a good motor for a lot less than fixing that block. There is nothing special about the 302 block except the numbers stamped on the front. You may be surprised how much the Camero crowd may give you for it.
 
hmmm..when I read GMC 302,I assumed a straight six from the 50's they used a lot in drag cars and street rods back in the day...not the 69 Camaro only V8 !..:dunno:
 
diesel4me said:
hmmm..when I read GMC 302,I assumed a straight six from the 50's they used a lot in drag cars and street rods back in the day...not the 69 Camaro only V8 !..:dunno:
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I bet you're right. I forgot about that motor. I never think about old whimpy engines. My train of thought stops at small V8s! So, on that note, disregard my last post. Fix that block.
 
The 302 GMC wasn't a wimpy six,it had a long stroke and was quite a contender back in the days before V8's became popular on race tracks..

I think it was the largest cubic inch straigh six GM used in light duty trucks...they were used in step vans and panel trucks for delivery mostly..

The later 292's were pretty hard to beat in later years even after tbe V8's came along..


Another decent heavy duty truck engine often overlooked are the 305 and 351 V6's used in larger trucks like C60's and busses..GM put them in some 1/2 and 3/4 ton trucks from 1963 to 1972...only 2wd I think though,never seen one in a 4x4 factory..
 
I 2nd, 3rd even 4th the PB Blaster. Look for it in a gallon can (comes in rectangle not paint can) might make it easier. Ive also used marvel mystery oil and even all-in-one oil as well. But with PB in the shop I use it!
 
It is a I6 GMC. It will only be about 240 HP but that will be plenty.
 
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