Midrange ping. Considering quench/squish

mark1122 wrote:

Nice work on the cad.

I smell a fellow engineer.....:laugh:

mark1122 wrote:

copper head gaskets are usually the same thickness as the composite. The composite is a better choice for longevity on a street ride. copper tends to leak oil sooner. This is well documented.
Copper is just for ease of disassembly and can be reused.
Been there.
Nice work on the cad.
Did u find that 1 side of the clearance was slightly dif?

I know solid copper head gaskets require the block to be o-ringed with wire for proper cylinder sealing but I have yet to use them. Also, I think it's possible to specify the thickness for the gasket if you deal direct with Cometic. I'll call them on Monday and get their thoughts.

The quench measurements were pretty consistent on this engine. Between 0.050" and 0.055" across all cylinders.

A cam that will bleed off some low rpm pressure might be better. You may just be filling the cylinders to effectively at the particular rpm where the pinging occurs. I think that more overlap is the recipe for fixing this but some of the more knowledgeable cam guys can probably give more specific direction.

By the way, I love that drawing - I have often wondered what the relationship of piston to head looked like in these hemi style heads.

kpier998 wrote:

A cam that will bleed off some low rpm pressure might be better. You may just be filling the cylinders to effectively at the particular rpm where the pinging occurs. I think that more overlap is the recipe for fixing this but some of the more knowledgeable cam guys can probably give more specific direction.

By the way, I love that drawing - I have often wondered what the relationship of piston to head looked like in these hemi style heads.

I agree. Just remember though, that there is a trade off. More duration will move the torque curve upwards. Less bottom end more top.
I lean more towards the Dyna 2000 for this 1. No trade off here, just all around improvements. u also get a rev limiter, and throw away the inaccurate, mechanical advancer.

So I just got off the phone with Mike at Cometic. Good guy. Here's what he said:

Copper head gaskets can be fabricated in various thicknesses from 0.010" to 0.094".

Copper will transfer more heat than fiber from the head to the block.

Wire o-rings are necessary. The block or head can be o-ringed. Has anyone o-ringed the HEAD on a KZ?



mark1122 wrote:

I lean more towards the Dyna 2000 for this 1. No trade off here, just all around improvements. u also get a rev limiter, and throw away the inaccurate, mechanical advancer.

I agree with this. The Dyna 2000 is nice! But I think it's necessary to make this engine more knock resistant regardless.

One thing I didn't mention is that if I'm riding hard on the highway 80mph+ for extended periods, the range where the engine pings will broaden from 4000 to 4500 - 5000. If I slow back down to 60mph the head will cool back down and the pinging will subside. Again, retarding ignition timing helps but definitely reduces power.

Bleeding compression pressure off through cam timing might also help with the ping but that will surely reduce midrange torque. That's sacrilege! Gobs of midrange torque is what makes this thing so fun!

davel wrote "I agree with this. The Dyna 2000 is nice! But I think it's necessary to make this engine more knock resistant regardless."

U think like i think. some may call it excessive, but it just feels right.
True your case,head, and block before ordering a gasket.

it is common to oring bigblock kz's and others. My 1327 was done. any big shop will do it.
are u running APE cyl studs now? u can go to 40ft.lbs. with them. this will reduce your squish a thow or so, by compressing the gaskets a bit more.
a standard composite or copper head gasket it .043".

mark1122 wrote:

True your case,head, and block before ordering a gasket.

Sound advice Mark!

Still running stock studs. Maybe I'll switch them out as well.

mark1122 wrote:

U think like i think. some may call it excessive, but it just feels right.

No compromises...No prisoners!

Lighting the advancer weights will bring on full spark advance on sooner. It's possible you may solve the problem by returning to stock advancer weights. Also, make sure the springs aren't stretched.

hoghaterkaw wrote:

Lighting the advancer weights will bring on full spark advance on sooner.

Heavy weights/light springs = early advance
Light weights/strong springe = late advance

I played with this one for a while. The ignition curve is good and total advance is correct (dyno told me so). Got to reduce squish and get the heat out of the head if possible.

davel wrote:

hoghaterkaw wrote:

Lighting the advancer weights will bring on full spark advance on sooner.

Heavy weights/light springs = early advance
Light weights/strong springe = late advance

I played with this one for a while. The ignition curve is good and total advance is correct (dyno told me so). Got to reduce squish and get the heat out of the head if possible.

My bad your right. Was the head milled?

hoghaterkaw wrote:

Was the head milled?

No. Just lightly cleaned up and verified for flatness during the 1075 install.

www.sudco.com/Diagrams123/exprs3.gif

#90 - try next size down if available

You seem to like to experiment with things, www.rexresearch.com/singh/singh.htm

I've communicated with a guy that performed that modification to a truck engine he uses to tow his race car. He swears it works......

It's one of those deals that people argue about. Seems perfect for KZR......

Taking more material off the head surface is only going to raise cylinder pressure. I highly doubt it's going to help the knock situation.

If you do take the head off, go in there with a die grinder and clean all the slag out of the air passages in the fin area. Sometimes those castings are really bad and the air passages are up to 40% blocked. Every bit helps.

If you can get it in NYC, try fueling up with Sunoco Ultra and see if that helps any.