Stopping the knock: Lower compression and ported heads...

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A few more.
 

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The valve cover baffle.
 

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Lunati cam card.

The lift numbers are based on a 1.5 rocker ratio. I have 1.6 rockers.
 

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To recap:

Bore size: 4.35 .
Stroke: 4.15.
Head chamber: 84 ccs
Head gasket bore: 4.410
Head gasket thickness: .039
Piston @ TDC: .017 below deck
Piston valve notch: 6 ccs
These numbers give me a 10.7 ratio according to the online CR calculators that I have tried.
The dynamic comes in at 8.09 according to another source.
Does quench make up for increased cylinder pressure and a jump in the dynamic ratio? The .027 Cometic puts me at .044 quench but puts my dynamic at almost 8.3. Since my cranking #s were already above 190, how could quench save me if the cranking comp goes to 195 or 200?
 
OldmanRick said:
Wow man, i've been nudging some guys to push the envelope a little more on their limited use "hot rod's", but this one really has me thinking.

Thanks for posting your numbers. :thumbrig:

I assumed you have the Lunati with 316/326 advertised duration. Looking at the XE285HL and the 509, it's hard to comprehend that the cranking compression/knock tolerance could be worse with the Lunati?

Grasping at straws here, But is there any way that cam was misground or mismarked?

Keep us informed. This could be a learning experience for some of us.

Good Luck, Rick
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I was surprised to find that the engine detonated more with the Lunati than with the other cams. Yes, the cam I have IS the 316/326 solid.
Mis marked? Here are the numbers on the end of the cam:
 

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Sorta hard to read.
 

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What did the chambers look like? Did they have carbon buildup too? Carbon buildup makes the chambers smaller which can aid in detonation. It also retains heat which can promote detonation and preignition.
 
RustyRatRod said:
What did the chambers look like? Did they have carbon buildup too? Carbon buildup makes the chambers smaller which can aid in detonation. It also retains heat which can promote detonation and preignition.
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you got too much clearance in your squish area! get it down to about .040---------------------------:coffee2:---bob
 
The chambers were pretty clean as far as any buildup. They were discolored but the rough finish of the aluminum was still present. All the exhaust valves were a light tan color. The quench pads aren't very large, maybe about 15% of the chamber? You can tell where the pistons are the cleanest at the tops, thats where the quench pads are.
 
Since there seems to be no physical signs of detonation, what else could it be? What else makes a knocking noise that goes away with higher octane fuel?
This one boggles the mind. Most people say my CR shouldn't knock, but I heard something. Now if the parts don't show any evidence of detonation, what the heck do I do now?
 
I am talking about evidence of clean burn where you do have a little quench going on.
 
I thought the same thing.
I am not married to any one "fix". If the thicker gaskets work, I'm cool with that. If the thinner ones work, I'm okay there too.
One of the most frustrating things for me is when I do a teardown and can't find any obvious problems. I read before that on a detonating engine, you'll see speckled deposits on the spark plugs. I didn't see any of that either. If what I was hearing was NOT detonation, what was happening? The LH header was close to the steering chuck and may have touched a few times, but I doubt that would have gone away when I was burning the 110 fuel.
 
**** if I know. You've never bothered to post videos with good audio. It would totally suck nasty balls if what you were hearing was something else.
 
I still have no clue at this point. I have to think that the carbon that showed up was from rattling the pistons and breaking the ring seal. That 190ish cranking number has to play a role in this somewhere, but I still don't know why it's that big. I can't help but thinking about your predicament, but I have no remedy for it. :banghead:
 
i run 11.25 with 205psi cp on pump 93 360 with j heads, quench cools the combustion chamber i would run a gasket that is around .025 to no more than .030. round off all sharp edges on the piston and head chamber, have to run a plug that is at least two or 3 steps colder, obvious stuff like heat crossover blocked, fuel cool, jetting correct, no oil in combustion chamber, should only need around 34 total with good quench.black specks mean detonation usually, also if plug ceramic is yellow that means cyl temp is rising very quickly.
 
Frankenduster said:
Since there seems to be no physical signs of detonation, what else could it be? What else makes a knocking noise that goes away with higher octane fuel?
This one boggles the mind. Most people say my CR shouldn't knock, but I heard something. Now if the parts don't show any evidence of detonation, what the heck do I do now?
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Piston slap.
 
That's true-he said the sound he interpreted at detonation never subsided until he mixed in 110 octane...don't recall the ratio, but he stated it was scary fast when he was able to stay in it with no fear of detonation.
 
txstang84 said:
That's true-he said the sound he interpreted at detonation never subsided until he mixed in 110 octane...don't recall the ratio, but he stated it was scary fast when he was able to stay in it with no fear of detonation.
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its a bummer we couldn't get and EGT and AFR curves, i think that would tell us everything thing...
 
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