Competition Head sealing methods - what's not been used yet?

[GO 4LO]

Thanks, bmoeller. That's good news. Where do you buy an ether setup like that? Is that just something that one of the tractor puller shops would carry, or is it more commercially available to farmers and such?



So now that we can start our 12:1 engine that's pushing 200 psi, how can we keep the head on, guys?



Are there any formulas out there that allow you to say something like: If you can run 100 psi on a 15. 5:1 engine, then xxx psi should be okay on a 12:1 engine. ????



Thanks again, everyone.

Chris

 

[CumminFast]

my guess would be 10:1 compression, 14mm kit, and o-ringing and you will Never have trouble w/ boost.

 

[F8LDOSE]

Cometics are reuseable? Last time i removed the head on my KRP/ Fontana motor the head gasket was in no shape to be reused.

 

[Forrest Nearing]

well, they're re-usable if the head has to come off for some reason OTHER than a blown head gasket! LOL!



my buddy has re-used his twice... once for a refresh on the bottom end, and another for a cyl head swap... still kickin' in his 9 sec bottle car.



Forrest

 

[HoleshotHolset]

That's good news... I thought they all were automatic setups...



10:1 compression + lots of fuel = awfully smoky startup/idle.



Matt

 

[GO 4LO]

So what does everyone think max boost would be without blowing head gaskets every run on a 10:1 setup with firerings and 14mm studs, assuming the rest of the engine holds up?



150 psi? 200? 250?





Chris

 

[SSeifert]

I spoke to Cometics tech dude, he said drop off a block and head and they might get to it in about a year. He told me that they have had a ford diesel block and head in there for 9 months and no one has touched it yet. he said the red tape kills them from new low run projects.

 

[CumminFast]

I would say according to the speculative theory of bull$h!t that it would blow at 179. 7 lbs of boost.

 

[cumminspwr01]

If somebody did go to Cometic and get them to make a gasket how much of a gain would it be over our regular options? Can anybody guess at a ballpark figure?

 

[GO 4LO]

Originally posted by SSeifert

I spoke to Cometics tech dude, he said drop off a block and head and they might get to it in about a year. He told me that they have had a ford diesel block and head in there for 9 months and no one has touched it yet. he said the red tape kills them from new low run projects.

When you spoke with them, did you happen to ask if getting a group buy together could speed them up? If they had an order for 100 to start off with, would they get on it quicker?

Chris

 

[Turbo Tim 1]

So pardon my ignorance but let's say you have a stock cylinder / piston setup at 17:1 compression and you're making 80 psig of boost that would make a cylinder pressure of 1609. 9 psia, right? So now just for the sake of argument lets say you have 10:1 compression and your boost is 146. 29 psig giving you a 1609. 9 psia cylinder pressure. What is the advantage of having the higher boost numbers and lower compression ratio? I know that they lower compression ratios on gassers when they put on blowers and such because they have to to get them to run on pump gas. Why would we do this on a diesel? Don't hurt me too bad!

 

[Forrest Nearing]

more oxygen molecules.



Forrest

 

[Forrest Nearing]

sorry, more specificly, you're increasing the VOLUME available in the combustion chamber... same cylinder pressure, you're just sorta making it "bigger"



Forrest

 

[GO 4LO]

When you drop the compression ratio, the negative power difference is smaller in magnitude than the positive power difference you will realize due to the increased boost you can now run.



The formula is:



New hp =





(old hp)*(1 - 2. 5/(new cr))

(1 - 2. 5/(old cr))





So dropping from 17:1 down to 10:1, using your example above, means you'll only lose 14% of your N/A power, but this will allow an extra 60 psi of boost without exceeding the previous cylinder pressure.



Someone correct me if I'm wrong, but I believe this 14% drop occurs only at the N/A level, at which the Cummins might be putting out, what, 110 hp? I don't believe it's 14% of your final overall power.

Chris

 

[GO 4LO]

Originally posted by Forrest Nearing

sorry, more specificly, you're increasing the VOLUME available in the combustion chamber... same cylinder pressure, you're just sorta making it "bigger"



Forrest

Do you mean the cylinder pressure ends up the same after the increased boost or that it stays the same regardless of compression ratio?





It would seem that if you dropped the CR (whether through milling out the combustion chamber, dished pistons, thicker headgasket, or whatever) that the cylinder pressure would have to drop (same amount of air, less volume), wouldn't it? Just trying to understand...

Chris

 

[Forrest Nearing]

cylinder pressure remains the same based on his calculations...



80psi @ 17:1 compression vs. 146. 29psi @ 10:1 compression



BUT, you've got a LOT more oxygen in there w/ 146. 29psi than w/ 80.



and yes, the power loss w/ lower compression is only realized at NA and lower boost ranges, but power is made by fuel,air, and heat. doesn't matter what kind of mechanical compression ratio you've got, it's the EFFECTIVE compression ratio (factored by that beautiful thing we call BOOST ) that burns the fuel and pushes down on that piston



Forrest

 

[GO 4LO]

Ah, okay, I understand. Thanks.

Chris

 

[GO 4LO]

One more additional question - is there a way to factor nitrous into the cylinder pressure equation? Something like CR * (boost+14. 696 + nitrous flow or volume?)



Chris

 

[Forrest Nearing]

there is a way, but it's over my head! LOL!



Forrest

 

[Turbo Tim 1]

Thanks Forrest and GO 4LO, I should've figured it out on my own but I was having a mental block.

BUT, you've got a LOT more oxygen in there w/ 146. 29psi than w/ 80.

As soon as you said that I knew exactly what you were talking about. Thanks