Deposit on top of pistons

[tx5117]

OK, been a lurker for a while and now have a question. Q'jet cratered on my 72 Blazer. Put a new kit in it and got a wild hair and decided to rebuild top end of engine. Blazer is a dog and needs a lot of work, shocker...huh? Painted the valve covers and pulled the heads to take to a machine shop. Noticed a black deposit on top of the pistons. Deposit is gummy but not to thick. Doesn't cover entire top of piston. Cylinder walls look good. Should I be concerned with the deposit on the pistons and what do I use to clean it off. Don't want to srew it up more. Thanks.

[bigvinnie]

sounds like you've been running a bit rich recently, or not getting complete combustion for one reason or another... you didn't say how many miles are on the motor... in any case, if it's gummy, you can use a solvent to wipe it off (something like berryman's chemtool or maybe paint thinner).... get each piston to the top of the bore... blow each one clean with compressed air, then move on to the next one...

It's usually a hard deposit that you have to use a wire brush or wire wheel on a drill to remove, not sure why it would be gummy...

cover the rest of the motor so you don't get gunk in there while you're doing this...

[tx5117]

Thanks bigvinnie,
I looked at the plugs and they are in the same condition, hopefully a new kit in the carb. will help.

[mrein3]

I always spray gasket remover on top of the pistons and wipe that and the carbon off with a rag. Before you put the head back on blow each cylinder out with a good shot of air.

Of course change your oil when you button everything back up in case any solvent gets in the engine.

It is kind of funny. I finally bought the 3M Roloc attachment for my 1/4" angle grinder to clean off gasket surfaces. After I got the head off my Escort, cleaned up the surfaces with the grinder, and got the head to the machine shop I went back home and THEN got out the gasket remover to clean the top of the pistons. That Roloc deal is the best thing since sliced bread. No more gasket remover and hours of scraping.

[Ed ke6bnl]

Originally posted by mrein3
I always spray gasket remover on top of the pistons and wipe that and the carbon off with a rag. Before you put the head back on blow each cylinder out with a good shot of air.

Of course change your oil when you button everything back up in case any solvent gets in the engine.

It is kind of funny. I finally bought the 3M Roloc attachment for my 1/4" angle grinder to clean off gasket surfaces. After I got the head off my Escort, cleaned up the surfaces with the grinder, and got the head to the machine shop I went back home and THEN got out the gasket remover to clean the top of the pistons. That Roloc deal is the best thing since sliced bread. No more gasket remover and hours of scraping.

I picked up a few boxes fo the rotoloc scouring pad type discs and we went through about 3 for two heads and and intake and the valves for this v8 engine looked so nice and clean when we were done. Ed ke6bnl So. Calif.

[sakohntr]

Attention all gearheads. DO NOT USE the rotolocs on a short block deck. There is a bulletin out not to use the abrasive rotolocs to remove gasket material that is still adhering. The small abrasive particles fall off while using them and fall inside. They wreak havoc on bearings and other metallic surfaces (just like there supposed to). I have seen engines fail after having a headjob done. Unless the part is removed from the car, or you can completely (100%) prevent the particles from going where they are not supposed, do not use on assembled motors. This item is a lifesaver and a killer if not used properly. good luck

[oldsub86]

My machine shop said I shouldn't use them either. They were concerned with the amount of metal that gets removed. They say they have seen parts ruined by using these things. I personally wondered if you could do much harm to a cast block or heads. Aluminum parts I could see. I am much more careful with it now but I still use it as it is easy and does a real nice job.

Thought I would add another thought. They also said they don't like to see people use a ridge reamer. They said that you will usually need to bore and hone anyway, so you don't need to worry about the ridge. It won't matter if you hurt the pistons if you are going to toss them anyway. Makes sense I guess.

[lngbed71]

Use a hotter range spark plug, high octane fuel, and burn those deposits with a few rpm's. My 2 cents

[Ed ke6bnl]

Originally posted by sakohntr
Attention all gearheads. DO NOT USE the rotolocs on a short block deck. There is a bulletin out not to use the abrasive rotolocs to remove gasket material that is still adhering. The small abrasive particles fall off while using them and fall inside. They wreak havoc on bearings and other metallic surfaces (just like there supposed to). I have seen engines fail after having a headjob done. Unless the part is removed from the car, or you can completely (100%) prevent the particles from going where they are not supposed, do not use on assembled motors. This item is a lifesaver and a killer if not used properly. good luck

Thanks for the information that makes perfect sense, the motor I used it on will nerver see any service to speak of. The heads were off but the block was exsposed and I can see that it could easily cause some major problems. Ed ke6bnl So. Calif.

[mrein3]

I sure have a lot of hard miles on my truck since I used the Roloc pads on the block surfaces. Of course I put rags in the valley and cleaned up everything good when I was done.

Another thing to do to clean things up is change your oil BEFORE you start it up again when assembled. Then change it again, both oil and filter, about 100 miles later. That was SOP for me even before I used the Roloc system.

I've got close to 2000 miles on the head job I did on my Escort last month. Over half of its miles are at 70+ mph driving to work and back. I just checked my log and my truck has 15,500 miles on it since I did the heads cleaning the block surface with the Roloc pads. Most of those miles are pulling my boat.

Just like any other tool, use it right.

Now only if the rear main seal on my truck didn't leak so bad...