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

[William Huff <whuff@xxxx>]

If I understand what is going on, he is asking whether to continue with his 
iron heads or wait and purchase the Edelbrock aluminum heads. IMHO, the 
Edelbrock heads would be a waste of time. It is true, they outflow 
everything except maybe the MOPAR stage VI heads and the INDY heads, right 
out of the box. The problem is that one generally needs to make other 
modifications to utilize that extra flow.

The cam profile must change, certainly a lot more lift, and probably a lot 
more duration. Most of the difference in flow comes in the higher valve 
lifts. This means the engine will then be making maximum H.P. and Torque 
at a considerably higher RPM. This is usually to the detriment of the 
lower "off the line" performance of the vehicle, unless the rear end ratio 
is changed, say to a 3.70:1 or a 3.90:1. Try cruising with those ratios, 
you would have 3000 RPM or better at highway speeds. Been there, it isn't 
fun and its tough on the car. Even after all that, if you tried to use 
this new found horsepower with the lower gear ratio from a stop, you would 
find that the rear suspension and rear tires needed modifying to put the 
horses on the ground. My '67 440 GTX is a much lighter car than my 300D, 
but with 4.10:1 gears, any time I floor it and it downshifts below 35-40 
mph, it's smoke city from the street tires. This is with a basically stock 
engine.

The 300s are heavy brutes, they respond to low end torque and 
horsepower. A good RB engine matches this profile with its relatively high 
HP and Torque at lower RPMS. A good RB will probably beat any similarly 
prepared Hemi (392 or 426) for the first half of the quarter mile. That's 
an eighth mile. This is because all the horsepower and torque are 
available one or two thousand RPM lower. Later, when the Hemi (or any high 
RPM engine) begins to make their real horsepower, the story can 
change. Unless on a race track, you would probably never be flooring the 
gas pedal for that long, so play to the engine's strengths.

I have found (following the old Direct Connection Engine buildup 
instructions) that the big block heads respond to minor valve and bowl 
relieving, port matching (intake mainly). Get the Mopar Performance 
porting templates, if you don't have the confidence, get someone to use 
them to open the heads up a little. Use the Mopar purple cam shaft with 
the street hemi/440 magnum specifications and recommended valve springs, 
use around 10:1 compression and premium fuel. This cam will peak around 
5300 -5400 RPM, but will still be making lots of power up to around 
5800. Use a good high rise intake such as the Edelbrock Performer RPM with 
a 750-800 CFM carburetor, Have a knowledgeable person jet and maximize the 
carb for your application. Recurve the distributor to bring the advance in 
a little earlier. Invest in a custom 2 1/2" exhaust system with mufflers 
that flow well. Either use headers or find the HP C body exhaust 
manifolds. Make sure you have the limited slip differential. I think you 
will end up with a nice comfortable 300 that will absolutely surprise many 
a "fast car" from 20 mph to whatever you care to push it to.

Sorry this post is so long, I just got to typing and couldn't stop. Hope 
my thoughts help you come to a good decision that will allow you to invest 
wisely and still retain the enjoyment of the car.

300ly,

Bill Huff