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906 heads question
#1593830
03/16/14 01:31 PM
03/16/14 01:31 PM
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Joined: Feb 2009
Posts: 1,706
Nebraska
70VcodeCoronetRT
OP
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OP
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Nebraska
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OK, after doing a little research on compression and 906 heads I'm a little confused. I've read that anything over 9.5-1 compression with the 906s will lead to detonation due to the lack of quench. Even the Smothers Supertune video says they tried everything (Even high octane fuel) to get a 906 headed motor to stop detonating.
So how did the Six pack motors live from the factory with 10.5-1 compression? What am I missing here? And would a domed piston work better than a flat top with a 906 head?
I'm wanting to run 10.5-1 compression with 906 heads. But want to do it right. And without detonation if possible. Thanks in advance
Last edited by 4406forPOWER; 03/16/14 01:32 PM.
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Re: 906 heads question
[Re: 70VcodeCoronetRT]
#1593835
03/16/14 06:10 PM
03/16/14 06:10 PM
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Joined: Feb 2005
Posts: 4,324
Prospect, PA
BSB67
master
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master
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Prospect, PA
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Quote:
1) I've read that anything over 9.5-1 compression with the 906s will lead to detonation due to the lack of quench. Even the Smothers Supertune video says they tried everything (Even high octane fuel) to get a 906 headed motor to stop detonating.
2) So how did the Six pack motors live from the factory with 10.5-1 compression? What am I missing here? And would a domed piston work better than a flat top with a 906 head?
3) I'm wanting to run 10.5-1 compression with 906 heads. But want to do it right. And without detonation if possible. Thanks in advance
1) Depends on the cam you will be using,
2)They really were not 10.5:1 CR and the available pump gas octane at the time was over 100, although the rating system was different, and
3) It will be very difficult to do.
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Re: 906 heads question
[Re: 70VcodeCoronetRT]
#1593836
03/17/14 12:39 PM
03/17/14 12:39 PM
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Joined: Jan 2003
Posts: 75,125
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JohnRR
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Quote:
OK, after doing a little research on compression and 906 heads I'm a little confused. I've read that anything over 9.5-1 compression with the 906s will lead to detonation due to the lack of quench. Even the Smothers Supertune video says they tried everything (Even high octane fuel) to get a 906 headed motor to stop detonating.
So how did the Six pack motors live from the factory with 10.5-1 compression? What am I missing here? And would a domed piston work better than a flat top with a 906 head?
I'm wanting to run 10.5-1 compression with 906 heads. But want to do it right. And without detonation if possible. Thanks in advance
First off factory ADVERTISED compression ratios were always INFLATED , Chrysler may have been the biggest Liar , 383HP in 68/69 rated at 10.0 . actual was more like 9.2.
You can do it but you didn't specifiy what gas , if you run RACE gas you'll be fine .
Seriously there is ZERO reason to run 906's unless you are building for a certain race class , the open chambers and the fact that they flow like BLEEP without huge $$ in porting makes them relegated to door stop duty
Build for quench with an alum closed chamber head or spend lots of $$$ and time making equal quench pads and custom reverse dome pistons. I put 50hrs into equalizing a set of 452's , good thing I did it for FREE .
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Re: 906 heads question
[Re: JohnRR]
#1593837
03/17/14 03:12 PM
03/17/14 03:12 PM
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Joined: Aug 2007
Posts: 1,271
Vista, California
67Satty
pro stock
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pro stock
Joined: Aug 2007
Posts: 1,271
Vista, California
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This is the part where someone always says for the same amount of money you put into your 906s, you could just buy some Stealth heads.
Wrong. For the same amount of money your Stealth heads will not have a good valve job, good locks and retainers, and springs matched to your cam.
If you build your motor with the TRW 2355 "6 pack" pistons and your 906s, the compression will be more like 9.5:1 tops and will run fine on 91 octane even with no quench.
Will the aftermarket aluminum heads flow a lot more at .600 lift? Yes, but will you be using a cam with that much lift to take full advantage of them?
Also, what are your performance goals? Ten second quarter miles? Then yeah, you'll want the aftermarket heads. 12 second range? Don't sweat it, even my unported 452 that flow even less than 906s have gotten me there.
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Re: 906 heads question
[Re: 67Satty]
#1593838
03/17/14 04:16 PM
03/17/14 04:16 PM
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Joined: Nov 2005
Posts: 15,119
85086
moparpollack
Lil Herman
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Lil Herman
Joined: Nov 2005
Posts: 15,119
85086
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Quote:
This is the part where someone always says for the same amount of money you put into your 906s, you could just buy some Stealth heads.
Wrong. For the same amount of money your Stealth heads will not have a good valve job, good locks and retainers, and springs matched to your cam.
If you build your motor with the TRW 2355 "6 pack" pistons and your 906s, the compression will be more like 9.5:1 tops and will run fine on 91 octane even with no quench.
Will the aftermarket aluminum heads flow a lot more at .600 lift? Yes, but will you be using a cam with that much lift to take full advantage of them?
Also, what are your performance goals? Ten second quarter miles? Then yeah, you'll want the aftermarket heads. 12 second range? Don't sweat it, even my unported 452 that flow even less than 906s have gotten me there.
Did John ever say stealths?  he did say aluminum heads but didn't specify.
John you are making us ASSuME here.
56 Plaza 63 D100 step side 67 Coronet, 68 Roadrunner, 69 Super Bees, 69 Coronet 500 convertible, 70 Roadrunner Post, 79 D150 360, and a severe case of Mopar a,d,d
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Re: 906 heads question
[Re: moparpollack]
#1593839
03/17/14 05:05 PM
03/17/14 05:05 PM
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Joined: Jan 2003
Posts: 75,125
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JohnRR
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Quote:
Quote:
This is the part where someone always says for the same amount of money you put into your 906s, you could just buy some Stealth heads.
Wrong. For the same amount of money your Stealth heads will not have a good valve job, good locks and retainers, and springs matched to your cam.
If you build your motor with the TRW 2355 "6 pack" pistons and your 906s, the compression will be more like 9.5:1 tops and will run fine on 91 octane even with no quench.
Will the aftermarket aluminum heads flow a lot more at .600 lift? Yes, but will you be using a cam with that much lift to take full advantage of them?
Also, what are your performance goals? Ten second quarter miles? Then yeah, you'll want the aftermarket heads. 12 second range? Don't sweat it, even my unported 452 that flow even less than 906s have gotten me there.
Did John ever say stealths? he did say aluminum heads but didn't specify.
John you are making us ASSuME here.
I didn't chose a specific head because I didn't want to start a pee pee contest with the sword swallowers
One can choose whatever head they want and have them looked over , let their wallet decide for them , which is what drives most purchases.
A stock 906 flows about 220 at .450-.500 lift , even the overinflated cfm rating, off shore, ebrock copy is 40cfm better , that's HP .
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Re: 906 heads question
[Re: 70VcodeCoronetRT]
#1593841
03/18/14 11:20 AM
03/18/14 11:20 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
This build is on a factory Six Pack motor. And I want to use the factory 906 heads. This is going to be a Mr. Six Pack cam build. So basically a stock build. I might just end up going with a flattop 0 deck setup with 9.5-1 compression. This is suppose to be ok with 906 heads and no quench. But it will be down a little on HP.
Your still gonna have a head gasket so thats your
quench
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Re: 906 heads question
[Re: MR_P_BODY]
#1593842
03/18/14 12:01 PM
03/18/14 12:01 PM
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Joined: Jan 2003
Posts: 75,125
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JohnRR
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Quote:
Quote:
This build is on a factory Six Pack motor. And I want to use the factory 906 heads. This is going to be a Mr. Six Pack cam build. So basically a stock build. I might just end up going with a flattop 0 deck setup with 9.5-1 compression. This is suppose to be ok with 906 heads and no quench. But it will be down a little on HP.
Your still gonna have a head gasket so thats your
quench
Not with an open chamber head he won't any quench unless he has a custom piston made.
Here is a piston I had made to have quench and keep the compression in the 9.5 range with an open chamber head.
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Re: 906 heads question
[Re: 70VcodeCoronetRT]
#1593843
03/18/14 12:07 PM
03/18/14 12:07 PM
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Joined: Jan 2003
Posts: 75,125
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JohnRR
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Quote:
This build is on a factory Six Pack motor. And I want to use the factory 906 heads. This is going to be a Mr. Six Pack cam build. So basically a stock build. I might just end up going with a flattop 0 deck setup with 9.5-1 compression. This is suppose to be ok with 906 heads and no quench. But it will be down a little on HP.
what makes you think the compression ratio you are saying you are going to build to is any different than the factory ? I just ran the numbers with what would have been the way an original 70 44 6pk rolled out the door of Chrysler and it would have been 9.55:1 .
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Re: 906 heads question
[Re: JohnRR]
#1593844
03/18/14 02:16 PM
03/18/14 02:16 PM
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Joined: Feb 2009
Posts: 1,706
Nebraska
70VcodeCoronetRT
OP
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Nebraska
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I was just going by the 10.5-1 that was advertised by Chrysler. I didn't realize those were bogus numbers. Bob (Mr. Six pack told me to expect around 450 horse at 9.5-1 And 475 with 11.0-1. So of course I would like to get closer to the 11.0-1.  But if I'm going to have detonation issues with the 906s. I guess I'll go with the 9.5-1. Nice custom Diamonds JohnRR  What was the compressed thickness of the head gasket on the factory 70 440 6 pack? .022?
Last edited by 4406forPOWER; 03/18/14 02:19 PM.
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Re: 906 heads question
[Re: 70VcodeCoronetRT]
#1593845
03/18/14 03:45 PM
03/18/14 03:45 PM
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JohnRR
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Quote:
I was just going by the 10.5-1 that was advertised by Chrysler. I didn't realize those were bogus numbers. Bob (Mr. Six pack told me to expect around 450 horse at 9.5-1 And 475 with 11.0-1. So of course I would like to get closer to the 11.0-1. But if I'm going to have detonation issues with the 906s. I guess I'll go with the 9.5-1. Nice custom Diamonds JohnRR
What was the compressed thickness of the head gasket on the factory 70 440 6 pack? .022?
thanks , that piston is in member rtman's 440 with 452's that started life as Paul Rossi street fighters that have been massaged more by Dwayne Porter aka fast68plymouth ... nevermind the 50hrs I put into them equalizing the chamber depth and size in a Bridgeport.
The steel shim gaskets are .021 , the 440 6 pk piston would be .021 in the hole on a blueprint deck , they usually ran taller. , 906's are typically 90cc. Factory advertised ratio being bogus is typical for Chrysler during the muscle car era .
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Re: 906 heads question
[Re: 70VcodeCoronetRT]
#1593851
03/19/14 05:15 PM
03/19/14 05:15 PM
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Joined: Jan 2003
Posts: 75,125
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JohnRR
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Quote:
Maybe I'm better off just using Stealth heads? Better quench, flow a bit better and can run a bit higher compression. What do you guys think? I still want to use my factory cast iron intake though.
You would be better off with a closed chamber head or a piston like I posted above at minimum. Stealths would be better than 906's flow wise for sure , don't plan on running them out of the box, I'd swap that iron intake for an alum one , that iron intake is a boat anchor ... painted it will look just like the iron one .
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Re: 906 heads question
[Re: JohnRR]
#1593855
03/20/14 05:58 AM
03/20/14 05:58 AM
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Joined: May 2008
Posts: 5,399
Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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Quote:
Quote:
Quote:
This build is on a factory Six Pack motor. And I want to use the factory 906 heads. This is going to be a Mr. Six Pack cam build. So basically a stock build. I might just end up going with a flattop 0 deck setup with 9.5-1 compression. This is suppose to be ok with 906 heads and no quench. But it will be down a little on HP.
Your still gonna have a head gasket so thats your
quench
Not with an open chamber head he won't any quench unless he has a custom piston made.
Here is a piston I had made to have quench and keep the compression in the 9.5 range with an open chamber head.
Those are nice looking pistons!
The Stealth and Edelbrock RPM heads are "closed chamber", but the flat quench area is not that large. Custom pistons like these would get you almost the same quench area. The Victor, and B1 heads have much larger closed (quench) area.
The advertised compression ratio was way off. If you check the real compression ratio of the high compression 440's they were never 10:1 compression.
If you need the engine to look stock, use the 906 heads and put money and hours into them if you want them to flow like inexpensive aftermarket heads.
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Re: 906 heads question
[Re: Thumperdart]
#1593856
03/20/14 03:08 PM
03/20/14 03:08 PM
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Joined: Jan 2003
Posts: 75,125
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JohnRR
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The alum. would be better but now the stock intake could be the restriction or choke point............... 
Not really , F.A.S.T. racers have gone well into the 11's with one.
Didn`t realize he had the 6-pac set up...........
Pretty sure Ed Cook went 10.9X ... Intake work ??
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Re: 906 heads question
[Re: 451Mopar]
#1593857
03/20/14 03:11 PM
03/20/14 03:11 PM
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Joined: Jan 2003
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JohnRR
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Quote:
The Stealth and Edelbrock RPM heads are "closed chamber", but the flat quench area is not that large. Custom pistons like these would get you almost the same quench area. The Victor, and B1 heads have much larger closed (quench) area.
I have a pair of the 383/440 replacement alum heads , Stage VI's with the stock port location instead of raised , they have a nice heart shaped combustion chamber like a Stage VI and they sort of look like a stock head on the outside , I was thinking of machining the tapped core plug on one end of the head that would be seen for a std. freeze plug.
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Re: 906 heads question
[Re: lewtot184]
#1593858
03/20/14 03:14 PM
03/20/14 03:14 PM
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JohnRR
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stock type rebuild? '906 heads? just do a kb184 and be done with it. keep it simple.
I was going that route before having that piston made , it's a horrible piston choice , the step is way to short, unless you don't mind not have proper quench distance. If you don't care then there is no need to use that piston.
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