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Re: How high a compression on pump gas [Re: cudaman1969] #3004157
01/11/22 02:41 PM
01/11/22 02:41 PM
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Originally Posted by cudaman1969
“chambers softened” Not sure what this means
Probably not applicable to Hemi heads tsk twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: How high a compression on pump gas [Re: Cab_Burge] #3004427
01/12/22 03:54 AM
01/12/22 03:54 AM
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Originally Posted by Cab_Burge
Originally Posted by cudaman1969
“chambers softened” Not sure what this means
Probably not applicable to Hemi heads tsk twocents


Definitely out of the norm for HEMI heads, but was applicable, although an experimental gamble with someone who knew what they were doing. My dad had a well known big name shop in N. Carolina do them. It worked out.
DJ

Re: How high a compression on pump gas [Re: jwb123] #3004472
01/12/22 09:58 AM
01/12/22 09:58 AM
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Originally Posted by jwb123
Performance trends engine program will make a prediction on spark knock and will generate a spark curve to use if knock is predicted, very cheap insurance when designing an engine build. I have built pulling truck engines that had to run on pump gas with 13 to 1 static compression, and it did not detonate.


Kevin at Performance Trends has greatly impressed me.

After buying two Engine Analyzer versions and one Fuel Economy Calculator program
his on the phone support was top notch,
and twice when I mentioned “It would be great if”
he did a software mod at no charge.

Re: How high a compression on pump gas [Re: cudaman1969] #3004517
01/12/22 12:32 PM
01/12/22 12:32 PM
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I have seen the new motorcycle engine's have 11.0 on the the compression, it is all about the volume you have in the engine .

Re: How high a compression on pump gas [Re: B1Frank] #3004538
01/12/22 01:33 PM
01/12/22 01:33 PM
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Originally Posted by B1Frank
I have seen the new motorcycle engine's have 11.0 on the the compression, it is all about the volume you have in the engine .


My new 6.4 Challenger is 10.9


1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim


Re: How high a compression on pump gas [Re: B1Frank] #3004547
01/12/22 01:52 PM
01/12/22 01:52 PM
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Originally Posted by B1Frank
I have seen the new motorcycle engine's have 11.0 on the the compression, it is all about the volume you have in the engine .


Some are 14.0-1


Lots happening for that to work


69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 595rwhp 475rwtq.
Re: How high a compression on pump gas [Re: cudaman1969] #3004571
01/12/22 02:36 PM
01/12/22 02:36 PM
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Chesterfield Twp. Mi.
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Originally Posted by cudaman1969
“chambers softened” Not sure what this means

Anyone?

Re: How high a compression on pump gas [Re: 493_john] #3004590
01/12/22 03:00 PM
01/12/22 03:00 PM
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Originally Posted by 493_john
Originally Posted by cudaman1969
“chambers softened” Not sure what this means

Anyone?


I'm going to go with this, softened means they have been deburred and any sharp edges that could be a hot spot removed.


68 Barracuda Formula S 340
87 "Chrysler" Conquest
Re: How high a compression on pump gas [Re: csk] #3004607
01/12/22 03:34 PM
01/12/22 03:34 PM
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Originally Posted by csk
Originally Posted by B1Frank
I have seen the new motorcycle engine's have 11.0 on the the compression, it is all about the volume you have in the engine .


My new 6.4 Challenger is 10.9



I had one of those same 6.4 SRT8s in my 2011 ram 1500 4 door 4wd but I had more compression, I had eagle heads swapped onto it that are about 10CC smaller, ran great on 91 octane (3000 foot elevation) but would knock if it even sniffed anything lower. I don't remember the exact number but I think it was around 12to1 actual.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: How high a compression on pump gas [Re: 493_john] #3004677
01/12/22 06:32 PM
01/12/22 06:32 PM
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Originally Posted by 493_john
Originally Posted by cudaman1969
“chambers softened” Not sure what this means

Anyone?



Softening the chambers is something that is done usually to nitrous engines to keep from melting pistons. I have never seen it done on a Mopar engine, I have seen the mod on a few Chevy engines. The last one was a big block chevy with raptor heads on a mud racer. Basically they CNC the chamber to give it a taper from the quench to the valves. Reher Morrision did the work.

Re: How high a compression on pump gas [Re: 493_john] #3004740
01/12/22 09:39 PM
01/12/22 09:39 PM
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Originally Posted by 493_john
Originally Posted by cudaman1969
“chambers softened” Not sure what this means

Anyone?


John,

Keep in mind this procedure is mostly done in high performing race engines. In the OP's case it could be purely unnecessary, but has been utilized on HEMI heads. Chamber softening is where the chamber is laid back and cuts out sharp areas that create hot spots and slows the flame travel down. We all know each combustion chamber design will vary with its efficiency, but from talking with Monte he said its great if you can start out with a head that already has efficient chamber design. Removing area's in the chamber will allow heat to soak in and give more area for expansion. Of course quench & chamber shape are important when doing this. Most importantly its finding someone who has a good program and knows what they're doing. This is typically done with nitrous or other power-adder applications, and "some" N/A setups. My current heads chambers are softened by Slawko. There are several dudes who know what they're doing that have programs for Mopar heads. It all comes down to heat. As we know the whole deal in an engine is the overall combination and managing heat. In my conversations with Monte, he stressed emphasis on being all about timing, valve events, combustion efficiency, ability to fill the cylinder, etc. Man that dude is missed.

Wes



"Any fool can know. The point is to understand"

- A. Einstein
Re: How high a compression on pump gas [Re: EvilB1Dart] #3004933
01/13/22 03:03 PM
01/13/22 03:03 PM
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for sure, Monte knew his stuff and is missed by many here !
if a guy were to knock off the sharp edges by hand with sandpaper only, such as around the plug hole, and any other machined defined edges, would that be a waste of time, or just something that couldn't hurt ?
kind of like dressing the sharp edges of the valve reliefs on pistons.
beer

Re: How high a compression on pump gas [Re: EvilB1Dart] #3005020
01/13/22 07:34 PM
01/13/22 07:34 PM
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Originally Posted by EvilB1Dart
Originally Posted by 493_john
Originally Posted by cudaman1969
“chambers softened” Not sure what this means

Anyone?


John,

Keep in mind this procedure is mostly done in high performing race engines. In the OP's case it could be purely unnecessary, but has been utilized on HEMI heads. Chamber softening is where the chamber is laid back and cuts out sharp areas that create hot spots and slows the flame travel down. We all know each combustion chamber design will vary with its efficiency, but from talking with Monte he said its great if you can start out with a head that already has efficient chamber design. Removing area's in the chamber will allow heat to soak in and give more area for expansion. Of course quench & chamber shape are important when doing this. Most importantly its finding someone who has a good program and knows what they're doing. This is typically done with nitrous or other power-adder applications, and "some" N/A setups. My current heads chambers are softened by Slawko. There are several dudes who know what they're doing that have programs for Mopar heads. It all comes down to heat. As we know the whole deal in an engine is the overall combination and managing heat. In my conversations with Monte, he stressed emphasis on being all about timing, valve events, combustion efficiency, ability to fill the cylinder, etc. Man that dude is missed.

Wes



Totally agree and great explanation, but hemi heads dont work like wedge heads..... There is no quench or 360* of quench, depending how you want to look at it. I believe chamber softing isn't supper applicable to a hemi's chamber. Works great on a lot of wedge heads, and have also seen it done on pistons.


Fwiw, ive been 11.3:1 on pump gas and made 986hp with 572 cubes and a indy 1RA head.

As for Best machines theory on compression....... I took a motor out of my racecar and changed pistons and cam. Went from 15:1 to 11.3:1 and made more power. Compression doesn't work the same in hemis.

Re: How high a compression on pump gas [Re: cuda499] #3005031
01/13/22 07:53 PM
01/13/22 07:53 PM
Joined: Mar 2005
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Originally Posted by cuda499
Originally Posted by EvilB1Dart
Originally Posted by 493_john
Originally Posted by cudaman1969
“chambers softened” Not sure what this means

Anyone?


John,

Keep in mind this procedure is mostly done in high performing race engines. In the OP's case it could be purely unnecessary, but has been utilized on HEMI heads. Chamber softening is where the chamber is laid back and cuts out sharp areas that create hot spots and slows the flame travel down. We all know each combustion chamber design will vary with its efficiency, but from talking with Monte he said its great if you can start out with a head that already has efficient chamber design. Removing area's in the chamber will allow heat to soak in and give more area for expansion. Of course quench & chamber shape are important when doing this. Most importantly its finding someone who has a good program and knows what they're doing. This is typically done with nitrous or other power-adder applications, and "some" N/A setups. My current heads chambers are softened by Slawko. There are several dudes who know what they're doing that have programs for Mopar heads. It all comes down to heat. As we know the whole deal in an engine is the overall combination and managing heat. In my conversations with Monte, he stressed emphasis on being all about timing, valve events, combustion efficiency, ability to fill the cylinder, etc. Man that dude is missed.

Wes



Totally agree and great explanation, but hemi heads dont work like wedge heads..... There is no quench or 360* of quench, depending how you want to look at it. I believe chamber softing isn't supper applicable to a hemi's chamber. Works great on a lot of wedge heads, and have also seen it done on pistons.


Fwiw, ive been 11.3:1 on pump gas and made 986hp with 572 cubes and a indy 1RA head.

As for Best machines theory on compression....... I took a motor out of my racecar and changed pistons and cam. Went from 15:1 to 11.3:1 and made more power. Compression doesn't work the same in hemis.



Like to here more details about that 572-1RA deal.

Re: How high a compression on pump gas [Re: cuda499] #3005216
01/14/22 12:01 PM
01/14/22 12:01 PM
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Posts: 1,041
The Great White North
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Originally Posted by cuda499
Originally Posted by EvilB1Dart
Originally Posted by 493_john
Originally Posted by cudaman1969
“chambers softened” Not sure what this means

Anyone?


John,

Keep in mind this procedure is mostly done in high performing race engines. In the OP's case it could be purely unnecessary, but has been utilized on HEMI heads. Chamber softening is where the chamber is laid back and cuts out sharp areas that create hot spots and slows the flame travel down. We all know each combustion chamber design will vary with its efficiency, but from talking with Monte he said its great if you can start out with a head that already has efficient chamber design. Removing area's in the chamber will allow heat to soak in and give more area for expansion. Of course quench & chamber shape are important when doing this. Most importantly its finding someone who has a good program and knows what they're doing. This is typically done with nitrous or other power-adder applications, and "some" N/A setups. My current heads chambers are softened by Slawko. There are several dudes who know what they're doing that have programs for Mopar heads. It all comes down to heat. As we know the whole deal in an engine is the overall combination and managing heat. In my conversations with Monte, he stressed emphasis on being all about timing, valve events, combustion efficiency, ability to fill the cylinder, etc. Man that dude is missed.

Wes



Totally agree and great explanation, but hemi heads dont work like wedge heads..... There is no quench or 360* of quench, depending how you want to look at it. I believe chamber softing isn't supper applicable to a hemi's chamber. Works great on a lot of wedge heads, and have also seen it done on pistons.


Fwiw, ive been 11.3:1 on pump gas and made 986hp with 572 cubes and a indy 1RA head.

As for Best machines theory on compression....... I took a motor out of my racecar and changed pistons and cam. Went from 15:1 to 11.3:1 and made more power. Compression doesn't work the same in hemis.



Thats because high compression requires a very tall dome which inhibits flame travel. J.Rob


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Re: How high a compression on pump gas [Re: RAMM] #3005458
01/15/22 08:12 AM
01/15/22 08:12 AM
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So after all this tech talk, what was the answer?

I have run many engines on the street and at the track too.
Iron/iron, iron/ali, ali/iron there's lots of variables here...

But when folks ask me these days, I just say 10 to 1...

Its safe and its old school, flat top piston closed chamber head. blah

But when it comes to hemi's its a whole new ballgame!

I got a street 'all iron' hemi from a guy a few years back with 13 to 1 pistons, driving it on pump gas.
Yes the pistons were worn, but it seemed to run ok?.
0.008 thousanths clearance in the bores and smoked when hot etc...

He said it ran good, cos its got a RACE camshaft...
Yep it was huge around 700 lift... coffee

''Bleeds OFF all the compression at low RPM's''!

I heard that a lot over the years and maybe its TRUE???

Last edited by Gtxxjon; 01/15/22 08:13 AM.

Carpe diem, quam minimum credula postero, thanx Horace!

There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
Re: How high a compression on pump gas [Re: Gtxxjon] #3006469
01/18/22 11:44 AM
01/18/22 11:44 AM
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Marion, South Carolina [><]
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FWIW...my 575" hemi is right around 11:1 and I run it NA on pump gas. On spray I do run race fuel.


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