Fwd: Re: [Chrysler300] alum head or current heads- reasked

[William Huff <whuff@xxxx>]

Hi again,

Just a couple of more thoughts on the subject to add to the good advice 
from Steve. After looking inside my 300D, and my non-letter (gasp!) '70 
300, I sort of thought that the C bodies probably have pretty good hood to 
carburetor clearance. When I used the Performer RPM in my GTX, clearance 
was a slight problem, to avoid rubbing the hood, I use a Summit low profile 
foam type air cleaner.

I can tell you that from installing the Performer RPM manifold and having 
the Holley 750 worked over by the Carb Shop, I was astounded at the seat of 
the pants increase in acceleration from those two changes alone. I agree, 
vacuum secondaries are a must. I wasn't sure car had ram manifolds or not, 
or if the gentleman had intended to stay with them if they did, but for 
performance on the street, I would certainly use vacuum secondaries and 
have the carburetor(s) worked over by a competent performance person.

The reason I didn't mention the Xtreme energy or the Hughs dual pattern cam 
is that I have read that valve-piston clearances can become a problem with 
OEM pistons as the lift approaches .500". The advantage of having the 
quicker opening and closing is to get more lift without increasing duration 
markedly. The purple cam hemi resto cam is in the .467 lift range, I believe.

Steve, I am interested in the fact that the B body manifolds fit the C 
body. I have the engine and tranny out of the '70, and since it originally 
was a 350 HP 400 cid engine, the manifolds were the crummy log type. I had 
some HP manifolds from a '68 B body, but finally got a HP C body driver 
side manifold for a premium price on eBay. Since the driver side manifold 
for the B body exits at the very rear of the manifold, where the C body 
exits from between cylinders 5 & 7, I didn't think the B manifold would 
fit. It is impossible to tell until the engine is ready to go back 
in. Were there any interference problems fitting them in?

I certainly agree about the mufflers, the thrill of that big roar following 
you around can diminish very quickly. However, I believe, based on some 
testing done in some of the Mopar mags that even with cast iron exhaust 
manifolds, the larger free flowing exhaust can yield real performance 
benefits. At the very least, I would ensure that the tailpipes were the 
same diameter as the exhaust pipes, which are probably 2 3/8". There are 
some mufflers that flow very well and are not that loud, I can't locate my 
reference on that right now. Also, making sure the tail pipe ends protrude 
well beyond the body can reduce the chance of reverberation and 
resonance. Turning the tips down also reduces reflected sound.

Dick Landy (of drag racing fame) writes a column in one of the Mopar mags, 
and I have seen several instances where he has recommended milling the 
heads to get approximately 10:1 compression on street engines when the 
cheaper pistons with lower compression heights were used for a 
rebuild. Admittedly, this is not for everyone, but for the performance 
minded. As you know, unless you cc the head and cylinder volumes, you 
really don't know what compression ratio you have, just guessing. My GTX 
still has the factory 10.5:1 pistons in it, and it runs great on pump gas, 
but I must add that the high gear ratio of 4.10:1 means the engine is 
seldom heavily loaded. With a large heavy car and a low gear ratio you may 
well be right in using a little less than 10:1.

Amen to using gauges and looking at them often.

Bill Huff


> > Excellent response, Bill. Your recommendations conform very closely to the
> > specs on the 413 in my 300L (and may I also compliment you on your use of
> > real sentences, with capital letters too!).
> >
> > A few comments I would add:
> >
> > -Be careful with hood clearance with the Performer RPM intake. I used the
> > regular Performer intake for that reason (although I didn't check the
> > clearance on the RPM).
> > -With an auto transmission, I recommend a carb with vacuum secondaries. Then
> > you can just mash the pedal off the line without any bogging.
> > -I used a Holley "Street Avenger" 670 CFM on my 413. On a 440 a 750 CFM is
> > probably plenty big unless you are going with a really big cam which would
> > be a mistake for the street.
> > -Think about using one of the latest design cams such as Comp Cams Xtreme
> > Energy. They open & close the valves more quickly so you can use a shorter
> > duration cam & get bigger-cam flow.
> > -You can't get off-the-shelf headers to fit a C-body (at least not a '65).
> > Custom is expensive. I swapped my stock exhaust manifolds for those off a
> > 440 6-pack which flow better. If you are using stock exhaust manifolds, a 2
> > 1/2" exhaust is redundant since the stock manifolds are restrictive. In that
> > case I would use 2 1/4" pipes. Also the smaller pipes will reduce your
> > exhaust sound level.
> > -Get quiet mufflers. I first tried Flowmasters and they were way too loud!
> > With a breathed-on big block, big pipes and a C-body you can get a lot of
> > reverberation in the passenger compartment, especially when you lift off the
> > throttle.
> > -Install a 160 degree thermostat and make sure your cooling system is up to
> > snuff. This gives a little more room to advance the timing.
> > -I would keep the compression ratio around 9.5:1 with iron heads and a
> > medium size cam. Then you can still add some timing and run on pump premium
> > gas 92 octane. At 10:1 compression you'll probably have to back off on
> > timing and/or use octane boost additive.
> > -Install oil pressure and temperature gauges under the dash. Don't risk all
> > that money in the motor on idiot lights.
> >
> > Steve Galezowski
> > 1965 300L