Incipient detonation

[Louie The Lot Lizard]

I've been trying to post a pic of a friends clone, no lap completed.
The chamber and piston look fine, no spalling.
The mixture was awful lean.
The copper shim gasket blew adjacent to the spark plug, (hence my diagnosis of detonation).
He was running enough compression to need a starter, (won't tell me).
The cooling fin is blown thru and the block was cut. I will send a picture as soon as I figure out how.
It looks like a "Fire ring" or a Cometic shim or multi layer gasket is needed.
Just thought I'd share this.

 

[OzFab]

Can you post another pic or two from different angles? I think I see the issue but, it's not the best pic...

 

[Louie The Lot Lizard]

Here is a better picture

 

[Louie The Lot Lizard]

Found out some more stuff.
He was running a lot of advance (maybe as much as 32 degrees) and mighty tall gears. He hasn't told me what cam but I think it was a "Black Mamba", not sure though. But it was something similar anyway.
Just goes to show you though, if yer gonna run this wild stuff ya gotta wind 'em up.
I think its interesting that no damage occurred in the chamber, but the plasma cut the dickens out of the head OUTSIDE of the gasket. Again, not one lap was completed.

 

[fowler]

Who is this bloke

Wants to fix his stuff
But won't give u any info

Really if u ( or anyone on here) wants to give advice then we need to get all the info

Id say
He had way too much advance
Way too lean
Way too much heat

It's a testiment that it even started
And it didn't melt the piston

Copper has a very high melting point

Heat transfer though to the ally
Then once the gasket failed the compression gases blew the soft ally away with ease

It is interesting that the failure occurred there

 

[88nightrider]

It is interesting that the failure occurred there

The engine block and cylinder head might not have been 100% flat for a perfect seal

 

[Louie The Lot Lizard]

The guy is a member of a club that is racing these things and doesn't want every body else in the club to know his "secrets"and is doing his own work, I just happened to be there and took these pics. He did have a head gasket issue last season, so your dx that the mating surfaces were probably not quite true is on mark. I am trying to learn as much as I can about these things before I jump in with both feet. I want to build a dyno, thought I could use a kart chassis, axle and all. I will post it when and if it happens.

 

[88nightrider]

I want to build a dyno, thought I could use a kart chassis, axle and all. I will post it when and if it happens.

IDK if you might be able to scale this up
http://www.sci-spot.com/Mechanical/dyno.htm

 

[Louie The Lot Lizard]

Thanks nightrider, I downloaded that and will have something to study tonight, looks neat
Off the subject, but I just looked at a rod that one of the club members was using. Its an ARC billet, really long, like 3.695", used with a Wiseco low drag piston. He had just freshened the motor with a new cam (something like an NR 274) and it refused to start, when he finally got it started it sounded like crap. He tore it down and found the rod with a longitudinal crack from the pin end extending halfway down the beam! Man, those rods are tough, that's hard to do! Another of our guys who really knows motors thought that a spiraloc had came out of the pin and let it go to one side, putting a side load on the rod. The spiraloc was missing but I think it came out secondary to the main problem. The main problem I think, is again, running higher compression without higher numerical gearing with too much spark advance and too darned lean. He had already discarded the bearing inserts, but I looked at the big end of the rod and the top half had really been taking a licking, while the cap looked good. From what I can remember of "Motor101" the highest g forces are supposed to be at TDC, stressing the cap and bolts. Incidentally the cylinder wall was OK.
I've been trying to convince these guys that if they are going to cam a motor into the 7's that they need to run it there, not 4500 RPM. Meanwhile the one guy who knows what he is doing is spanking there rear ends but good with a 4500 RPM motor.