mr gtx
Active Member
lets say if you have zero deck height and .039 gasket what is your quench difference between a closed or open chamber head. both would be .039 quench the difference would be the compression ratio not the quench.
440 TNT rebuild
- Thread starter Jakub Varga
- Start date
mr gtx
Active Member
pin height is 1.991 for 65-67 so the most it could be is .091 in the hole. the 1967 engines I tore apart were at 75-85 thousand in the hole. block is supposed to be 10.725 height mine were all a little shorter. after 67 the pin height changed to 2.03 because of the open chambered heads I would think.
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mr gtx
Active Member
close chamber heads are the way to go if you want the right deck height and compression. otherwise you would need dome pistons or step pistons and they are not the best for flame travel and combustion. never seen or heard of a 516 or 915 head at .070 cc. average 79-80 cc
Jakub Varga
New Member
Assuming using L2355F30 with 2.061 CH and head gasket from Source with .051 compressed thickness to get the quench of .040 the deck has to be milled .032. Seems to me like it is too much milling? Is there another option besides custom made pistons? Thinner soft gaskets for aluminum heads? Thanks!
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mr gtx
Active Member
why are you using a .051 head gasket ?
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You can use steel shim gasket as the factory or MLS makes thin gaskets. They cost a bit more than the standard felpro rebuilder gaskets, but it gives you the abuility to choose your compression ratio.
mr gtx
Active Member
no figures are in stone. every block even side to side or from front to back, pin height and rod lengths vary.
fury fan
Old Man with a Hat
There's no quench pad on an open chamber head?
My understanding of quench is the 'smash distance' between piston top and the mating cyl head surface.
That combustion charge volume gets pushed with extreme energy toward the spark plug, mixing it well into a smaller area for reduced flame travel distance, and preventing 'distant' hotspots that cause detonation.
So with an OC head the quench distance would then be to the surface of the combustion chamber which is ~1/8" deep?
10.725 - 1.99 for the piston CH (67_300_Convertible's piston) - 6.76 rod -1.875 (1/2 stroke) = .10"
I don't have any data on block height variation, so I use the factory spec. It's all academic until the block is machined and measured anyway.
But yes, if they run a little shorter and his also got decked, your .075 is probably correct to actual.
Yes, a step or dome is necessary for quench on an OC head, agreed on not as good as zero deck and a closed-chamber head.
IIRC the Mopar books said -516s were 70cc, everything I've read real-life agrees they are ~80cc.
He's planning on Stealth heads now, I've not yet read any recommendations to use a steel shim with those. ???
If you have info I haven't heard, I'd like to read it and learn something.
But if he builds a zero-deck assembly, the .039" std FelPro is a good combination?
Yes, but when doing pre-build plans, you gotta start with something. Better to start with what it's supposed to be until you learn otherwise?
But pin heights shouldn't be off in modern aftermarket pistons, if they are their machining equipment and/or QC requirements are off. Better to buy better pistons?
In your experience, what block deck height would be more generally correct to start with?
mr gtx
Active Member
I apologize. you are right after looking back one of my blocks was 10.725. pistons could be as much as 91 thousand in the hole. I had blocks 10.723 and 10.723 and 10.724 and that was with one 413 cubic inch engine and 440 that I have done I can recall. I was talking about factory stock pin heights that vary. think about it if the piston is .080 in the hole the combustion is happening in the bore and head. if the piston is at zero deck height then the combustion is happening in the cylinder head and not down in the bore no matter what cylinder head or piston top you have. PS most call the stock pin height 1.99 but are 1.991 so a lot of some differences in figures change measurements slightly
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Just to add this... I have driven @mr gtx s Newport with that engine in it and it's impressive. Pulls hard in that heavy car.
For Stealth aluminium head you would use an MLS gasket.
mr gtx
Active Member
don't forget only 2.94 gears. LOL
fury fan
Old Man with a Hat
No apology necessary.
Thanks for deck heights you've measured, good to know factory specs are close.
Agreed on location that combustion is happening with a down-hole piston. But the it seems there's something to be gained from closed-chamber heads, as I've seen a number of 'modern' (like mid-90s and newer) that have quench areas, sometimes small ones that seem to be 'aiming' or something. IIRC I've seen one that had 2 small ones, each about the size of a nickel or so.
Jakub Varga
New Member
On 440source website they are stating that Comp cam .477/.480 (CL21-223-4) uses single valve spring but CompCams states double spring (911-16) are needed. Therefore, I would lean towards ordering double spring Stealth heads that already have needed 10 degree retainers, but there is difference in spring pressures too:
Comp double spring (911-16) has 309lbs open pressure and 122lbs closed pressure.
Double Spring Stealth heads have 374lbs open pressure and 130lbs closed pressure.
What do you recommend? Is the pressure difference negligible?
Thank you very much.
Comp double spring (911-16) has 309lbs open pressure and 122lbs closed pressure.
Double Spring Stealth heads have 374lbs open pressure and 130lbs closed pressure.
What do you recommend? Is the pressure difference negligible?
Thank you very much.
fury fan
Old Man with a Hat
The higher the open pressure, the more likely to wear the cam lobes.
Is another 65lbs significant? I don't know.
But I wouldn't run any stiffer a spring than necessary, certainly not any stiffer than the cam calls for.
There might be a different single-coil spring to hit near that 309lb requirement. I'd keep looking to see what's out there.
Is another 65lbs significant? I don't know.
But I wouldn't run any stiffer a spring than necessary, certainly not any stiffer than the cam calls for.
There might be a different single-coil spring to hit near that 309lb requirement. I'd keep looking to see what's out there.
mr gtx
Active Member
comp 911-16 are not really double springs. they have a damper just like the factory put in their higher performance engines. 911 should be all you need unless you're running a solid roller cam.
Frank Odenthal
Member
911-16 are fine for cams below .500 lobe Lift.
925-16 is the comp cams double spring.
I beliefe 440Source is using a different Brand Double spring with similar ratio, But higher max lobe lift capability.
925-16 is the comp cams double spring.
I beliefe 440Source is using a different Brand Double spring with similar ratio, But higher max lobe lift capability.
mr gtx
Active Member
I have no problem with 911 and 520 lift and 6000 rpms. 925 too little 111 lbs seat pressure and too much open at 388 lbs
Frank Odenthal
Member
Are you Running .520 Lift with a flat tappet or Roller cam ?
mr gtx
Active Member
flat hyd with 1.6 roller tip rockers. best shift point about 5300-5500 rpms. The cam has 488 lift intake and exhaust with 1.5 rockers with my 1.6 rockers brings it to 520 lift
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