Re: Iron Head Compression Limit
[Re: R/T1968R/T]
#914292
01/26/11 10:56 AM
01/26/11 10:56 AM
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Joined: Mar 2007
Posts: 9,336
South-Central (Sebring), FL
Commando1
master
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master
Joined: Mar 2007
Posts: 9,336
South-Central (Sebring), FL
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My iron head BB is running a 10.25 C.R. and I have no knock with 93 octane but I had to keep the timing is conservative. Because of the conservative timing, the distributor advance also had to be adjusted accordingly. Which is OK because the cam is kinda torquey, which required....  It's all tied together.  You might want to shim up the head gaskets to lower your C.R. a tad with that cam. But, then again, what the heck do I know?
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Re: Iron Head Compression Limit
[Re: Commando1]
#914293
01/26/11 11:14 AM
01/26/11 11:14 AM
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Joined: Jan 2006
Posts: 587
IL . usa
cjs69mope
mopar
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mopar
Joined: Jan 2006
Posts: 587
IL . usa
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if you really have .o42 quench i would say you will be OK at 34 deg total timing but i would definitely not try to lower it by shimming any thing .
because a 9.1 compression motor no quench will ping more than a 10.5 to one motor with tight quench this is a FACT .
quench is like octane the more you can get the better as long as the motor has clearance .
1969 Dodge Charger
1969 Dodge Superbee
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Re: Iron Head Compression Limit
[Re: cjs69mope]
#914294
01/26/11 11:35 AM
01/26/11 11:35 AM
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Joined: Oct 2003
Posts: 3,698
NE Oklahoma
Von
master
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master
Joined: Oct 2003
Posts: 3,698
NE Oklahoma
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You should be OK. Emphasis on the should part. Im at 10.6 to 1, open chamber heads, but my cam is quite a bit bigger than yours. 259@050, on a 108. On a hot, humid day it will ping with the timing any faster than 33-34. I just run it at 32 and dont have any problems.
72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72.
Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.
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Re: Iron Head Compression Limit
[Re: cjs69mope]
#914295
01/26/11 11:39 AM
01/26/11 11:39 AM
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Joined: Oct 2003
Posts: 3,698
NE Oklahoma
Von
master
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master
Joined: Oct 2003
Posts: 3,698
NE Oklahoma
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Quote:
if you really have .o42 quench i would say you will be OK at 34 deg total timing but i would definitely not try to lower it by shimming any thing .
because a 9.1 compression motor no quench will ping more than a 10.5 to one motor with tight quench this is a FACT .
quench is like octane the more you can get the better as long as the motor has clearance .
Camshaft design plays a HUGE role in detonation, or lack there of. As I said above, my current motor is 10.6 to 1 with about .140 quench, give or take. Cool, cold weather you can run as much total as you want on pump fuel. Hot and humid you need to pull it back to 32ish total. All on pump fuel.
BTW, I talked to 2 guys at Ross pistons who definetly dont think that the quench/detonation issue is fact.........
72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72.
Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.
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Re: Iron Head Compression Limit
[Re: R/T1968R/T]
#914296
01/26/11 05:59 PM
01/26/11 05:59 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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You'll most likely have to be conservative on the timing curve which hurts you alot. Advancing the cam will up the cyl psi & make it more likely to ping so no on that and may want to experiment & actually retard it so you can run a good curve. Any ping you can hear is TOO much
live every 24 hour block of time like it's your last day on earth
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Re: Iron Head Compression Limit
[Re: RapidRobert]
#914297
01/26/11 07:41 PM
01/26/11 07:41 PM
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Joined: Jan 2006
Posts: 587
IL . usa
cjs69mope
mopar
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mopar
Joined: Jan 2006
Posts: 587
IL . usa
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".140 quench " I don't think I would call that quench , anything more than .040 starts to loose the benefit pretty quick go to the KB website and read about the benefit of a quench dome piston design .
1969 Dodge Charger
1969 Dodge Superbee
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Re: Iron Head Compression Limit
[Re: R/T1968R/T]
#914298
01/26/11 09:48 PM
01/26/11 09:48 PM
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Joined: Feb 2005
Posts: 4,314
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,314
Prospect, PA
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Quote:
because a 9.1 compression motor no quench will ping more than a 10.5 to one motor with tight quench this is a FACT .
Really. Please supply the data for that fact.
Anyways - I think that you are at the edge and it could go either way. My 10.3 motor, with a smaller cam than what you're planning, was not even close. It rattled like crazy, and there was nothing reasonable I could do to stop it. This was at about 1000 ft above MSL. Mine would blow about 195 psi on the gauge. I also had a tall gear, heavy car and a tight converter, all which make it worse. Install the cam straight-up and tighten the intake lash will help.
Personally, I'd try it, understanding that I might have go back in.
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Re: Iron Head Compression Limit
[Re: R/T1968R/T]
#914299
01/26/11 10:20 PM
01/26/11 10:20 PM
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Joined: Feb 2007
Posts: 2,315
MOPAR HEADQUARTERS IN ALDEN NY
hemigod426
top fuel
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top fuel
Joined: Feb 2007
Posts: 2,315
MOPAR HEADQUARTERS IN ALDEN NY
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you would need something like the 557 m/p cam with 10 degrees more duration than the small 528 241vs251 dur@50.,will blow off some more static comp dynamically.msd box for sure puts in 3 sparks instead of 1 up to 3,000 rpm the ping city zone 0-3k,the right fuel mixture cant have fat girl rich carbs, piston design plays in as well less sharp edges the better,for not holding heat,ceramic coat tops of them for sure.when testing pump gas comp limit, 915 head is the way to go for sure,closed chamber wedge heads have perfect quench area and cause blow down/cross turbilence to cool the head piston area on every tdc fire. if piston flat has proper quench. thats why proper quench can make a 10.4 comp motor run like 9.4 on 93 octane. a .060 in the hole motor can ping on 93 @ 9.4. follow these steps and you can make it work for sure
MOPAR OR NO CAR
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Re: Iron Head Compression Limit
[Re: cjs69mope]
#914302
01/26/11 11:41 PM
01/26/11 11:41 PM
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Joined: Oct 2003
Posts: 3,698
NE Oklahoma
Von
master
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master
Joined: Oct 2003
Posts: 3,698
NE Oklahoma
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Quote:
".140 quench " I don't think I would call that quench , anything more than .040 starts to loose the benefit pretty quick go to the KB website and read about the benefit of a quench dome piston design .
Ya, I know .140 isnt quench. I was being funny...
FWIW, my cam is on a 108 and in at 101.5. Neither of which are good for controlling/stopping detonation...But, it works......
72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72.
Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.
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Re: Iron Head Compression Limit
[Re: R/T1968R/T]
#914306
01/27/11 04:26 PM
01/27/11 04:26 PM
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Joined: Feb 2007
Posts: 2,315
MOPAR HEADQUARTERS IN ALDEN NY
hemigod426
top fuel
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top fuel
Joined: Feb 2007
Posts: 2,315
MOPAR HEADQUARTERS IN ALDEN NY
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Quote:
Im using SRP flat top pistons, they are .022 below deck. steel shim head gasket, .019-.020. Quench appears to be near perfect. The car is a 68 Charger, 4 speed , dana. I have a choice of many gears from 3.55s all the way to 4:88s. Im in a catch 22 position, I want to run HP exhaust manifolds and I think about 242 duration @.50 would be pushing it with the manifolds (According to AndyF and his tests).More cam might kill the bottom end! 
dont believe everything you read,those tests were with 1973 400 manifolds,and unported also. i have custom ground solid cam for fast class type car hp manifolds/powerbrakes 550/540 lift 112lsa that i dont need now. had close combo 440 like yours 40 over 440 ross flat tops/big valve 915s,all stock trim. now went of the deep end 500 inch 440 with roller cam 602/603 lift252/257 duration@50 114lsa still gunna run manifolds and power disc 
MOPAR OR NO CAR
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