427 S.O. smoke

[Dwight]

I did a compression check today on the 427. At 100 psi I had 10% to 13% loss on each cylinders. So the rings are good and the valves are seated. Maybe a valve seal or oil ring problem? I think we are going to replace the seals and put it together and drive it this summer.

Dwight Frye algunruner@aol.com

[Dwight]

here is what I found in the #2 cylinder.

Question: does it need to be sleeved or just honed and new rings?

Dwight

[RICK LAKE]

Dwight You have a couple of choises. Those 2 lines looks like the rings where not finished properly and caused the grooves. Unless something got sucked into the motor and wedged into the ring land and piston. If the block is stock, Have your machinist home out the cylinders and buy a set of custom pistons. 5- 10 thousands over. This way you can rebuild the block about 4 times before the walls get thin if this is a 427 block. You can do the same with a 428 block. It's cheaper to get custom pistons than buy a new block or sleeve it. I have .015 over size pistons for my spare 428 motor. I don't like running the bores past .030" over. The only way I do this, is to add block filler. JMO Rick L. Ps in the old days the over size numbers where .005", .015", .017" .025" .030" This gives you an idea on fixing the motor Rick. Ps shoot the installer if the rings caused the grooves. He didn't smooth the ends. Poor assembly work.

[Dwight]

Rick,
The motor is bored .040" over. Wisco made the piston for the last rebuild, about 15,000 miles ago. I had a friend who owns a "old time" parts store that rebuild motors drop by and look at it yesterday. He said it look like carbon or some type of trash had got on top of the piston and cut the grooves. Maybe the motor was cranked and rev'ed up while it was cold. Anyway I'm going to pull the motor out of Mike's Cobra and get ready for a rebuild. This Cobra will not make it to the London Cobra Show this year but Mike is going with us. We always need Co-pilots.

Rick, what do you think about his cam specs? This is a street Cobra only, no racing but of course he needs respect at the red light


Dwight

[vettestr]

Dwight,
Very hard to determine how go/bod the scratch is over the net but there may be hope. Before you can tell if it is a (go or no go) on a re-ring option you will need some hard numbers or measurements. Granted any cylinder wall defect is not ideal but as a racer for many years I have been in your shoes before and seen woorse looking clean up fine.

Double check all the spec's of this cylinder to see where you are at now and what the clearances are now. Hone the cylinder just to the point of an acceptable cross hatch for the rings and measure the new bore diameter. You have a few thou to play with here on an engine with this little wear so see if you are still in the window. You and a good machinist can determine if you are within the +/- limits or not.

Just because you can see a small remaining scratch after a clean up hone does not condemn the engine but it may clean up easier than you think. I would be checking the pistons' ring lands closely and the rings end gap for sure. It may not be ideal but you have limited options. You would be amazed at how loose some of the old race engines were set up or run and RAN WELL. Get the expertise of an old machinist to give you a second opinion. I am hoping it works out for ya. Jeff C