Detonation

Anyone had issues with detonation to the point where it will beat up spark plugs every 1 or 2 runs.
One run 2 plugs broke off just above the hex head and blew the wires right out of the tubes and 2 plugs on the other side pushed the centre electrode 1/8 inch up inside the porcelain ,
Will no ground wires on the cylinder heads cause this on a blown alcohol application,
Thanks Bruce

 

Earth the cylinder heads across to each other , and then down to the frame/chassis. No or little earth WILL crack plugs and drop cylinders. It will be fine in the pits on a warm up and even in a burnout probably but under load on the run it will drop cylinders straight away

 

We suggest you go one step further and ground from there to negative side of coil. We just go head to head to coil.

 

Dumb question, could you just have a bad batch of plugs by chance? Do you have any other signs or indicators to suggest that you actually had "detonation"?

 

Dnt think its the plugs, I pulled the plugs from the final on sunday, these plugs were new for the final round, #1,5, 2&6 have the centre post pushed up about .050 inside the porcelain, Same cylinders every time , 2 runs at the most, these are out of the same box of plugs I used last year with no issues,
Im starting to think its not detonation but more likely a misfire, The first pass it will run good to the end, second pass will start popping around 1000 ft and that's the way the plugs come out. Only change since last year is a new set of MSD wires,
Got me stumped,

 

What's your firing order, 18436572 or something else? Crossfire perhaps? How old is your cap?

 

double swap, cap is still last years.

 

We had oil in the plastic plug tube and arced out the plug, cracked the porcelain and burnt the tube. We spray electrical cleaner in the tubes now and haven't had any issues since.

 

Did you replace the wires because you were having issues, or just regular maintenance? If you still have the old wires you could always put them back on and see if the problem goes away.

 

Changed the wires just as maintenance , I dug out the old wires , still all together with the cap so they are going on.

 

If you have egt;s pull rod bearings for hottest cylinder or one for cylinder with bad plug.If you are hammering the bearing out then you know its detonation if not then I would look at ignition or different type plug.

 

Hmmm. So the cap is different now too in your new combo, since the old wires are "still" connected to the old cap? I tend to think what you have described so far is either crossfire due to a more favorable current path, or crossfire due to bad plug leads. What you are describing is not "detonation". What you are describing is a sudden pressure spike way beyond detonation. More like compression ignition. Have you any evidence of pushed gaskets, or actual detonation?

 

Checked the brgs today and # 1 is the worst, Pounded the top about .020 , Took out pistons and #1 pin end is oval,,
Ran new grounds from heads to chassis to coil, Changed mag, coil, points box, crank trigger and harness, wires and grid, Also removed the kill switch and going to use the 12 volt switch for the grid as my kill,
Keeping fingers crossed.

 

Thanks Mike
I have rerouted the the crank trigger harness away from the coil wire, I did have the 2 loosely zip tied together, Also ran the harness to the grid totally separate from all other wiring. Moved the crank trigger ground from the motor plate to the chassis stud.

 

Hi Will
I took a good look at the pistons , everything looks good , Put in a new set of rods..