--- Begin Message ---
- From: "Frederick Joslin" <fljoslin@xxxxxxxx>
- Date: Fri, 22 Feb 2008 15:26:09 +0000
Rodger:
I do not believe that any stock 413 powered Imperial came with the larger volume open chamber heads. Your original heads probably have a volume in the low 70's cc (for example 72 cubic centimeteres) and the 452 heads have a volume in the mid 80s cc. I think that you will lose about 1 unit of compression (drop from 10:1 to 9:1 for example).
I have read letters in Mopar magazines about people who have done this type of a head swap in pre 68 C-body cars with less than stellar results. You do get a little more flow through the engine, but lose compression which is the basis of torque and especially important for the real beasts of the road.
If your engine is really tight and you are really running 10:1 compression, then dropping a little compression may help avoid predetonation and you may be able to advance the timing a little. This with a little better air flow would probably make performance changes a bit of a wash switching heads.
However, if your engine is tired and already running lower compression, any drop is going to hurt.
If you do not have predetonation issues now, I would suggest having your current heads (or similar) rebuilt with all new valves and springs using the larger exhaust valves and getting bronze valve guides and hardened valve seats installed. A little porting on the exhaust side may help after you cut the big holes for the larger valves. If you do this you will have heads more or less equivalent to the "highly" valued 915 heads which will last forever and which will be original to your car.
I did this head work (minus bronze guides) on a 383 powered 66 Newport with 516 heads and things definately did improve, but I also added a dual exhaust at the same time so I cannot separate the two factors. The car was much more fun to drive after the head re-build/exhaust addition than before. You could actually hear the car wheezing before the work and certainly not after.
Good luck.
----- Original Message -----
From: TomC
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: RE: IML: 1967 440 and trans {big valve heads}
Date: Thu, 21 Feb 2008 21:46:13 -0800
Rodger,
The different year 413?s had different head castings ? see below. These different castings had differences in chamber volumes.
If we assume that your head is an open chamber then the advantage gained with a 452 head is a larger exhaust valve/port and hardened exhaust seats.
As far as a performance advantage, I am not sure it would be noticeable in an Imperial. In high RPM operation, the 452 would be of some advantage.
Depending on which heads you have, it might be more beneficial to have a valve job done and have the exhaust seat swapped out for a hardened seat. You could also have the larger 1.74 exhaust valves installed.
Casting numbers:
http://www.mymopar.com/headcastnumb.htm
Tom
From: mailing-list-owner@xxxxxxxxxxxxxxxx [mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of RODGER D. REDDISH
Sent: Thursday, February 21, 2008 8:58 PM
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: Re: IML: 1967 440 and trans {big valve heads}
The 1963-65 413's are all at 10 plus on the compression ratio's.
----- Original Message -----
Sent: Thursday, February 21, 2008 10:30 PM
Subject: RE: IML: 1967 440 and trans {big valve heads}
Rodger,
What year/compression ratio 413 do you have?
Tom
I have been thinking of swapping for a pair of the late issued heads that have the casting number ending with 452 and put them on my 413 powered Imperial. As of now the heads are the first series six bolt valve cover design. Is there an plus for doing this ( what does B-Jackson have to do with me ) ???
----- Original Message -----
Sent: Thursday, February 21, 2008 9:20 PM
Subject: RE: IML: 1967 440 and trans {big valve heads}
There is very little difference between the 516 heads and the 915 heads that you cannot get from installing the larger exhaust valves with hardened seats into the 516 heads and doing a little porting.
The 516 heads found on just about every 383, 361, 413 and 440 from 1964-1967 have the same quench design as the 915 heads.
On most of these heads you would probably need to install new exhaust valves (1.72" are cheaper than 1.60") and should probably go to the hardened valve seats for unleaded gas so it is pretty much a wash between the very plentifully and cheap 516 heads and the very rare and expensive 915 heads.
----- Original Message -----
From: TomC
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: RE: IML: 1967 440 and trans {big valve heads}
Date: Thu, 21 Feb 2008 18:21:53 -0800
Hello All,
It is true that the 915 heads do not have the best valve size and port areas. However, and this is a big however, it has been discovered over the years that detonation is not only a factor of compression ratio, but also something called the quench area. And the 915 heads have one of the best quench areas of big block heads, due to their closed chamber design. Please see the articles linked below.
http://www.moparmusclemagazine.com/techarticles/mopp_060800_mopar_max_wedge_cylinder_heads/factory_parts.html
http://www.moparts.com/Tech/Archive/motor/15.html
If anyone would like to trade their 915's for open chamber heads, I would be happy to acquire them.
Tom
From: mailing-list-owner@xxxxxxxxxxxxxxxx [mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of Bob
Sent: Thursday, February 21, 2008 5:37 PM
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: Re: IML: 1967 440 and trans {big valve heads}
I was going by word of mouth. Glad theres people out there who know their stuff. I learned something today. I always enjoy reading info like that. Helps for future refrence. Thanks for the effort.
----- Original Message -----
Sent: Thursday, February 21, 2008 7:20 PM
Subject: Re: IML: 1967 440 and trans {big valve heads}
915 heads don't do an Imperial owner any good except for bragging rights, and the pain may not be worth it. We're talking about a compression ratio greater than 10:1, requiring great care to avoid preignition and/or detonation with today's pig slop gasoline. In addition, the larger valve sizes are of negligible benefit at an Imperial's normal RPM range (below 4000). Even racers know the 915 heads don't flow as well at high RPM as the later heads that came with larger valves. This engine combo is best suited for somebody trying to do a correct restoration of a car that came with it from the factory. Those of us who like to drive our cars a lot need later open-chamber heads. Compression ratio is lower, the valves are larger -- paint them Mopar turquoise and only an expert can tell from the outside that they're not year correct for your car.
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Fred Joslin
Fred Joslin
--- End Message ---
