69 340 Cmshaft Decision ?

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cecil4speed

cecil4speed

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Ok guys here is what I need help with. What I have now.
69 340 engine, 4speed, 3.55 limited slip 235x60x14 (25")tires in a 68 DartGTS
Chrome box Mopar HEI, Accel HO coil, no vacuum advance hookup, 8mm wires, MSD Soft Touch rev limiter set at 6,000, stock valve train, eng was rebuilt before I purchased the car, I have found out that it was not bored but the cam that was installed took away bottom end torque, it pulls half decent midrage up. I have purchased a thermoquad from demonsizzler, but I have not received it yet and it will be going on an oem cast intake, heat crossovers will be left open, manual choke, and I will be hooking vacuum advance back up.
What I want do do with the car. Daily driver, so gas mileage is an issue. I want a choppy big cam sound, good bottom end and midrange torque. When I cut that thermoquad open, I want this thing to go foolish. I mean tire screaching performance. I will learn to index the cam in. With bottom end torque like this, will it hurt me if I want to go to the track every once in a while, because I do want to race later on. I want to go to roller gear later on. Maybe I should just go back to a stock 68 4speed cam or Purple shaft. Can you guys tell me what I need for a cam or is it not possible to get what I want ? Any help would be greatly appreciated. Thanks.
 
QUOTE: I want a choppy big cam sound, good bottom end and midrange torque. When I cut that thermoquad open, I want this thing to go foolish.

cecil, the statement above is kind of self defeating. :) Getting a "choppy big cam sound" along with "good bottom end" are opposite ends of the cam spectrum. The choppy big cam sound comes from a big cam, which usually means you have too much cam for the engine. This puts your power in the mid to upper RPM range, thus negating the good bottom end. When choosing a cam, you need to take in to consideration the end use of the vehicle, as well as compression ration, induction system, exhaust system, tranny/converter, or standard tranny, and final gear ratio. The quickest way to turn a good running engine into a dog on the street is to over cam it. Stay conservative in order to make the drive enjoyable. try to keep it in the 268/272 duration and 474/484 lift area. Contact the cam manufacturers with your exact specs and they will point you in the right direction. Good luck.
 
You really can't have the best of both worlds....... You want big power and sound along with daily drivability and milage.

Note... (you can have that I guess but not from a simple cam swap on your combo)

This is a classic situation in the hobby.

What you need to do first is form a plan and decide what you REALLY want.

What ET would satisfy you?

What MPG do you want or need?

For example..... for me 10 MPG is fine, but my car has only seen 2500 miles in 29 years.

If you want 15-17 on the highway the advise we give you will be totally diferent from what we would give if you wanted 9-12.

How many miles a year will you drive it? Again.... We will tell you one thing if you will be driving it 2000 miles and another thing if you drive it 15,000 miles.

Sit down and come up with what you really want. MPGs, Miles you will drive the car per-year, 1/4 mile time.....

What is "going foolish" for you? For some mid to low 14s will satisfy that feeling of power.... For others its 11s or lower....
 
From my experience over the years I have learned that I will be happy with a 14-14 car.

If it runs mid 14s and can pull off 14 mpgs on the highway it will make a happy daily driver for me.
 
There are better more modern cams then the old 340 cam although I do have one in my 318 and I like it, it probably leaves 25 HP on the table over something more modern that would give similar millage. Something like a comp XE 262 or slightly bigger comes to mind. Also since you are running a 4 speed why not swap that out for an OD unit and cut down you revs on the highway. I bet with good tuning and an overdrive you could approach 20 mpg with your 340, and still run 14 second ET's. My old 70 roadrunner stock with a 3310 holley and good tuning could get almost 17 on the highway at 55 mph. It ran low 14's with a 3.23 gear and the crappy street tires of the day.
 
IMO, the XE262H (1300 - 5600 rpm) would be the better mileage getter with a edge on torque and a XE268 (1600 - 5800 rpm) would more likely knock out another 30 or so HP with less mileage. It is also just a slight bit bigger than a OE 340 cam shaft via duration @ .050 numbers.
The 268 should have you in the low 14's.

Both cams are ground on a 110 centerline and will have a "Chop" to the idle.
 
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