Scalpel

iTrader: (4)

Well, got the heads off my brother's SS (he did a mechanical overrev and had no compression on the third cylinder on each side and poor compression everywhere else) and we see some rather prominent eyelash marks in the pistons.

What do we do? Should we file them and with what do we file them with? If there are tiny shards of metal sticking up from the eyelash marks (about 1/8" deep) these could become heated to glowing when the new heads are put on and cause preignition.

I pulled all of the valves and none of them show any signs of warpage or being bent. What does this mean since I was getting zero compression in a few cylinders? Are the pistons fucked?

Any and all help is greatly appreciated.

I'm just glad we have air tools.

Red2000SS

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by NastyC5:
<strong>Well, got the heads off my brother's SS (he did a mechanical overrev and had no compression on the third cylinder on each side and poor compression everywhere else) and we see some rather prominent eyelash marks in the pistons.

What do we do? Should we file them and with what do we file them with? If there are tiny shards of metal sticking up from the eyelash marks (about 1/8" deep) these could become heated to glowing when the new heads are put on and cause preignition.

I pulled all of the valves and none of them show any signs of warpage or being bent. What does this mean since I was getting zero compression in a few cylinders? Are the pistons fucked?

Any and all help is greatly appreciated.

I'm just glad we have air tools.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Zero compression is very bad!!! This means that you bent some valves so they are not properly seating, or you blew a hole in your piston <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> Either option is not good <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> My bet if you have eyelash marks on the pistons and zero compression is you bent some valves, although you seem to not think they are bent. Eyelash marks on your pistons means your valves hit your pistons at a high rate of speed. This is not good for your valves or pistions!!!, but you already know that.

It sounds to me like bent valves, but if you pulled the heads you should be able to check for holes blown throw the pistons.

Good luck...

Scalpel

iTrader: (4)

No holes are in the pistons just eyelash marks from where the intake valves smacked them pretty good. What can I file these grooves down with? Are the pistons ok? thanks.

Ebbsnflows

iTrader: (15)

Like you said...You need to get rid of the sharp edges on the pistons. Those edges will retain heat and result in detonation. Just use a Low # sandpaper to clean them up a bit...they don't have to be perfectly smooth, but the smoother the better.

Regarding the bent valves. You need to have a machine shop test them. Just because they don't "appear" to be bent with the naked eye, doesn't mean they're not. All it takes is a slight imperfection to result in loss of compression.

BTW...How bad were the Pushrods? Mangled or just Bent to hell? <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

BADZ

iTrader: (5)

Replace valves period!!!!

NB99Z

iTrader: (9)

I have a set of brand new stock valves that I would let go for $50. If you are interested shoot me a e-mail. I will throw in new stock springs also.

Kevin

Scalpel

iTrader: (4)

Thanks for the offers on the parts, fellas but I already have a set of new heads with new valves, etc ready to bolt on. I just wanted to make sure that we'd be fine by sanding down the rough spots.

Ebbs, so just sanding them down should do it, correct? That'll debur them and prevent hot spots.

Well, we'll get some sandpaper and smooth them out. Then we're gonna slap the new ones on. Should have an update later this afternoon.

ross

Remember, these pistons are relatively "strong" compaired to the valves. If the valves put witness markes on the pistions then I'd bet that there was contact between the rod bearings and the rod journals on the crank, which could have damaged the bearings. What do u guys think?

I know this stuff isn't cheep, nor is it easy to do, but I should wouldn't put that motor back together without new pistions and an inspection of all the bottom end bearings.

Think of those witness marks this way. Not only are they hot spots for detenation, but now they are stress risers which weaken the pistion and eventually could lead to totally failure of the pistion.

I know this isn't the news u were hopping for, but I think it's best to do it right instead of wondering when the bottom end is going to fall out.

Sorry about your brothers luck <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

Scalpel

iTrader: (4)

ross,
This has been brought to my attention by Visceral. I totally agree that he probably did damage some of the rod bearings. When we drained the oil nothing suspicious came out so he didn't muck them up too bad however he DEFINATELY weakened them. To be honest, I don't care if they go out. It's his fault and this is all I'm doing at the moment for it. I'll slap these new ones on so it'll at least run. If it throws a rod down the road then it's in his hands. Again, I appreciate the insight <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Anyone have any suggestions on the type of sandpaper?

BADZ

iTrader: (5)

The same situation happend to me and all we did was just get the sandpaper and like you said just smooth out the scar's. I did bend valves though and had to replace them...

Good Luck...

BluVette

A sharp gasket scraper can be used to remove any aluminum burs sticking up. As for sandpaper, 220 or 320 grit aluminum oxide to smooth out the area. Use a small block of flat wood to back up the sandpaper to help keep the sanded area flat. It is better to start out with finer sandpaper and then go to coarser sandpaper if needed.

Most important, use a shop vac (vacuum cleaner) to keep the top of the piston clean during the repair. You don't want to get any abrasive between the piston and the cylinder bore, as this will scratch the cylinder when you start the engine.

NoGo

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by BluVette:
<strong>
Most important, use a shop vac (vacuum cleaner) to keep the top of the piston clean during the repair. You don't want to get any abrasive between the piston and the cylinder bore, as this will scratch the cylinder when you start the engine.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Ditto on this one. Make sure that you are actively removing what you are sanding off. I didn't, thought that I cleaned it good enough, and now I have some serious cylindar wall scratches on 6&8.

Good luck <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Mike at Boost Performance.co.uk

Hi, I would put a ring of grease around the bore, bring the piston to tdc and then file the piston smooth followed by some sanding using a block of wood to keep things flat. Hoover out the muck or use a greasy rag. When you move the piston down the bore you can remove the grease which will have prevented any dirt getting to the rings. Carbon will soon cover the piston crown. As for the heads you can check for valve seal by filling the ports with parraffin and seeing if it 'leaks away' overnight. I strongly suspect you have bent some valves. Don't forget to take a look at the guides. IMHO I doubt that the shells have been damaged. The oil film can withstand tonnes of compression.

Scalpel

iTrader: (4)

Thanks for the info, Mike. I already knew I had bent valves that's why I replaced them with a complete set of new heads, valves and springs from ValveGod. All is well! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />