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School me on Open Chamber VS Closed #921933 02/06/11 12:23 AM 02/06/11 12:23 AM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	I know that closed chamber heads usually give you the compression and quench that you need/want. But mainly my question is, what is the point of running an open chamber head? It seems to me a closed chamber will do everything you want, so why ever use an open chamber? For example, I can see using it in a later 70's model car where they used lower compression ratios to run on lower octane gas etc....but why were they using them on performance cars in the 60's? Why use them today?

Re: School me on Open Chamber VS Closed [Re: JoesMopar] #921934 02/06/11 12:29 AM 02/06/11 12:29 AM
Joined: Jan 2007 Posts: 7,664 IN A ahy master
ahy master A Joined: Jan 2007 Posts: 7,664 IN	One reason may be they are not too sensitive to manufacturing variation. Quench depends on precise tolerences. If you can't control deck height very well, for example, the open chamber design is more forgiving. MOPAR block machining in the late 60's/70's wasn't the best. I believe the open camber head was also part of the emission reduction strategy of the day. Lower NOX perhaps.

Re: School me on Open Chamber VS Closed [Re: ahy] #921935 02/06/11 01:02 AM 02/06/11 01:02 AM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Quote: I believe the open camber head was part of the emission reduction strategy of the day. Lower NOX perhaps. live every 24 hour block of time like it's your last day on earth

Re: School me on Open Chamber VS Closed [Re: RapidRobert] #921936 02/06/11 01:14 AM 02/06/11 01:14 AM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	But I thought a closed chamber would reduce emmissions more because of the more complete combustion?

Re: School me on Open Chamber VS Closed [Re: JoesMopar] #921937 02/06/11 02:22 AM 02/06/11 02:22 AM
Joined: Mar 2005 Posts: 7,052 Madera, CA. MowP4rsn master
MowP4rsn master Joined: Mar 2005 Posts: 7,052 Madera, CA.	Quote: But I thought a closed chamber would reduce emmissions more because of the more complete combustion? NOx is the result of high combustion temperature, so having less quench could help towards reducing that.

Re: School me on Open Chamber VS Closed [Re: MowP4rsn] #921938 02/06/11 03:17 AM 02/06/11 03:17 AM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	I see, that makes sense. I didn't think they worried about that in the 60's though. So basically the point to open chambered heads is strictly emissions and nothing performance orientated whatsoever.

Re: School me on Open Chamber VS Closed [Re: JoesMopar] #921939 02/06/11 10:26 AM 02/06/11 10:26 AM
Joined: Jan 2003 Posts: 75,012 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,012 U.S.S.A.	Quote: I see, that makes sense. I didn't think they worried about that in the 60's though. So basically the point to open chambered heads is strictly emissions and nothing performance orientated whatsoever. EXACTLY , but yes they started to worry about that stuff in the 60's , califorina cars were the first to have air pumps in the late 60's

Re: School me on Open Chamber VS Closed [Re: JohnRR] #921940 02/06/11 12:50 PM 02/06/11 12:50 PM
Joined: May 2009 Posts: 508 Cincinnati, Ohio S superbeedave mopar
superbeedave mopar S Joined: May 2009 Posts: 508 Cincinnati, Ohio	So with that being said, The 10.1-1 compression that was advertised in 69 & 70 on the 383,440's with the 906 heads really wasn't true? More like 9.5-1. Would this be a true fact?

Re: School me on Open Chamber VS Closed [Re: superbeedave] #921941 02/06/11 12:54 PM 02/06/11 12:54 PM
Joined: Aug 2003 Posts: 11,179 Atco NJ DJVCuda I Live Here
DJVCuda I Live Here Joined: Aug 2003 Posts: 11,179 Atco NJ	i measured 8.8:1 on an original 383 magnum motor we pulled out for rebuild.

Re: School me on Open Chamber VS Closed [Re: DJVCuda] #921942 02/06/11 01:11 PM 02/06/11 01:11 PM
Joined: May 2009 Posts: 508 Cincinnati, Ohio S superbeedave mopar
superbeedave mopar S Joined: May 2009 Posts: 508 Cincinnati, Ohio	Could you imagine that back in 69 you bought a Superbee with a 383 magnum and you were under the impression that it was a true 10.1 engine only to find out it really was 9.0. They probably wouldn't have sold as many as they did!

Re: School me on Open Chamber VS Closed [Re: superbeedave] #921943 02/06/11 01:40 PM 02/06/11 01:40 PM
Joined: Jan 2003 Posts: 75,012 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,012 U.S.S.A.	Quote: So with that being said, The 10.1-1 compression that was advertised in 69 & 70 on the 383,440's with the 906 heads really wasn't true? More like 9.5-1. Would this be a true fact? I can't say for 70 because the piston CH changed but the 68-69 383 HP is about 9.2 as delivered , piston is .0025 in the hole , head is 90 - 92 CC, yes Chrysler OVER RATED compression ratios on the 383 and I am sure others

Re: School me on Open Chamber VS Closed [Re: JohnRR] #921944 02/06/11 10:17 PM 02/06/11 10:17 PM
Joined: Apr 2003 Posts: 1,324 Western Pa joewhite440 pro stock
joewhite440 pro stock Joined: Apr 2003 Posts: 1,324 Western Pa	Actually the 69 383Hp engines had a Positive deck. In other words the piston actually was above the block deck surface. I do not have my book in here but I believe the 67 440HP Pistons with the 915 closed chamber heads were at a lower deck than the 1969 and 70 440's with the open chamber heads. I am sure someone will chime in with the numbers. The deck differences is what kept the compression up on the 68/69/70 engines with the open chambered heads. if you punch the numbers into a Compression Calculator (Bore,Stroke, Head volume CC, +/- Effective Dome CC, Deck Clearance, Compressed Gasket thickness, number of cylinders). You will see the factory numbers are real close.

Re: School me on Open Chamber VS Closed [Re: superbeedave] #921945 02/06/11 10:44 PM 02/06/11 10:44 PM
Joined: Feb 2009 Posts: 1,274 Ontario.Canada C can.al pro stock
can.al pro stock C Joined: Feb 2009 Posts: 1,274 Ontario.Canada	..Was the manufacturers rating an NHRA limit? i.e a 383 could be built to 10:1 for competition. i think 10.5 340's were really around 9.5 if you do the math?

Re: School me on Open Chamber VS Closed [Re: JohnRR] #921946 02/07/11 12:19 AM 02/07/11 12:19 AM
Joined: Mar 2005 Posts: 7,052 Madera, CA. MowP4rsn master
MowP4rsn master Joined: Mar 2005 Posts: 7,052 Madera, CA.	Quote: Quote: I see, that makes sense. I didn't think they worried about that in the 60's though. So basically the point to open chambered heads is strictly emissions and nothing performance orientated whatsoever. EXACTLY , but yes they started to worry about that stuff in the 60's , California cars were the first to have air pumps in the late 60's But NOT MOPARs sold in California, only the GM and Ford brands.

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