Mopar Muscle Association UK

As you all know I have a daily driver Chrysler Fifth Avenue with a 318 in it. I have been acquiring bits for it to pep it up a bit.

So far I have:

Edelbrock Performer intake (2176)
Holley 600VS carb (4150)
Mopar linkage kit
Dodge Challenger 340 electronic distributor
MSD5 ignition box

This means I've now got the stuff I need for the top of the motor. I will also ditch the air pump, EGR and any other emission rubbish I find. the car will get duals with Wills old Flowmasters and high flow manifolds when I find some.

Thing is now I'm thinking its a shame not to do the cam as well. But this is a daily driver and mileage is important (well, as important as it can be to a guy running a 5120 lb V8 daily driver!)

I will retain the stock A904, converter, lockup and currently have a gay 2.23 rear (7.25") - see post in driveline topic area...

Should I swap out a performance cam? Does anyone have any recommends for something to wake up the motor a little but keep a stock idle, good vacuum, work with stock converter and highway gears...

or is it a waste of time...

This is the "high compression" version of this engine, makes about 8.9:1 stock. How much CR would I lose going to a 360 head and how much would I get back by using the thin MP head gaskets? As these are the "good" 318 heads I might be best to stick with them?

You sure you have 2.23 gears? I didn't know they made axle gears that high?

Confirm which gears you have, what size rear tyres/wheels you have, and what speed you drive at on the motorway and I will get back to you with a cam tomorrow. You might be better sticking with the 318 heads but I will run some numbers into the desktop dyno and see what happens.

Oh. The casting numbers of both heads might help.

yeah, I was surprised they do gears that high, but I can do about 60 in first! I'll double check 'em. I thought they cam with 2.7 gears (and thats high) but that was apparently only the Diplomats. The Chryslers got taller ones still.

also check out 0-60 11 sec, 1/4 mile 17.35 @ 72.2 - makes me think way tall gearing!

My 0-30 is like 7 seconds then it seems to wake up a bit.

I have 205/75x15 on at the moment, although I'm hoping to swap to 235/65x16 (which is within 2% of the same rolling radius if I remembered the size right)

On the motorway I tend to cruise about 75.

Longer term I want to swap in an A500 with lockup / overdrive and get lower gears.

If you had the common mopar 3.23 (not 2.23) rear gears you could still do 60 in 1st and 75 mph would be about 3200rpm. 2.23 gears would give you a top speed of 200mph. I doubt you would have enough torque to pull away even in 1st either.

One cam does not "fit all" Decide what combo you want the cam for. I can't give you a spec for a load of "might fits".

Just to rub this in a bit (sorry mate but this is for others as well as yourself) you need to decide what you want the car to do first.

You need a target performance goal.

You cannot pick a cam for a combination of parts. You pick the cam and heads FIRST as they determin the spec of all the other parts.

In other words you can't build a house around a carpet. You cut the carpet to fit the house.

depends if you already have the carpet?

I have to use either a stock intake or a Performer as I wish to retain the air con. I have the Holley already as it was ?90 brand new and that formula comes out telling me I only need like 520 CFM anyway.

I don't want the hassle of headers so "performance" exhaust manifolds are the way forward.

I've posted for clarrification on the M Body forum see who knows what on the gears.

From the M Body web site...

Possible Production M-Body Gear Ratios:

2.26:1 This ridiculously high ratio was found in later M-bodies.

2.47:1 This was the most common ratio for 1978-1979.

2.94:1 This was also common. Usually found in police/taxi/fleet cars.

3.23:1 This highly desirable ratio was not so common.

so it looks like I'm with the 2.26 until I can swap out to something else, probably requiring a 8 3/4 rear to do so.

With gears as high as that you need a torque engine. I will look into it.

cheers Dave

OK mate. This is the best I can do for you. There might be truck cams out there giving more torque at lower rpm but I can't find them.

NOTE: I assume that the output of your trans is 1:1 ratio! I just wonder with gears that high.

Your stock 318 has about 8.8:1 compression ratio and put out about 142 factory rated HP yes?

With 2.26:1 rear gears you only have 2200rpm at 75mph.
With gears this high you are never going to want or need any cam making HP up the rpm scale. You need LOW RPM TORQUE to move this baby.

For the same reason the 360 heads will be a waste of time. Your rpm is so low you need small port runners and valves. Going bigger will only slow the airflow and spoil throttle response and economy. Also an overdrive at this point is pointless. Your 1st gear is like the overdrive on my car!!

Now if you did fit lower gears it would be a different story! Then you would want more duration and lift on the cam and those 360 heads too.

But with the current gears just stick in a Hughes Engines cam HEH-0515-AL.

It will give you at least the horsepower and torque in these charts. 240hp @ 4500rpm will make it overtake better in second gear and 307lbs of torque from 3000-3500 rpm will make it economical right up to 120mph!

2.26? that's more than gay! we might have to create a new catagory for gears that high......

Called Gay Goth? Nah! That doesn't fit somehow.

Serious gears them Blue. Theoretical top speeds over 200mph! If only it had the torque to do that at 6500rpm.