318 Cam

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Plymouth Power

Plymouth Power

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I was wondering what camshaft to go with, I have a 1973 318 all original with less than 70,000 miles on it. It will have a 4bbl on it and I am planning to put it into my Duster it has the (guessing) 2.76 gears in the back, in a (fact) 7.25. I want something that will also be able to keep up with the later addition of a Six-Barrel and an 8.75 with 3.23's or 3.55's haven't decided yet. I want something that will give me power and torque, things like fuel economy and cost don't matter. Thanks for all of your help.
 
So, a bone stock 318 with a 4bbl. is looking for a cam. And also, the same engine is going to get a 6pack intake and 3.55's. Correct?

The first issue is low compresion and the second thing is the heads. Are you doing anything about those two items or will they remain stock?

If there remaining stock, I beileve a good cam to think about is a Comp Cams XE262H with 218 @ 050 duration.

If your adding some head work, bowl porting and a milling for some compresion, Look at the XE268H and add a little stall to it.
 
Plymouth Power said:
I was wondering what camshaft to go with, I have a 1973 318 all original with less than 70,000 miles on it. It will have a 4bbl on it and I am planning to put it into my Duster it has the (guessing) 2.76 gears in the back, in a (fact) 7.25. I want something that will also be able to keep up with the later addition of a Six-Barrel and an 8.75 with 3.23's or 3.55's haven't decided yet. I want something that will give me power and torque, things like fuel economy and cost don't matter. Thanks for all of your help.
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If you are looking to keep the internals and rotating assembly the same and have a gear ratio of 3.23-3.55, you can make use of Comps XE262 or XE268 cam. They will both give good low end torque and make power throughout the rev range. They will work with a stock converter, but the later works best with a 2300+ converter. You will need the matching Comp valvesprings as well. Being that as it stands with the stock bottom end, compression will be around 8.0:1. With that said, it probably isn't a good idea to run a Six pack carb setup without higher compression and cyl head modification. It would drown the motor. If you were to up the compression, I'd go with KB167 pistons (preferrably zero decked) and either install 1.88/1.60 valves in the existing heads, or do the same to 302 casting heads. If that is not in the cards and you want to maintain the stock bottom end, I would search for an LD4B intake or Edelbrock Performer intake and use either a 600 cfm Eddie carb, or 650 Holley.

With the stock rotating assembly, one of the two cams mentioned, 3.23-3.55 gears, and one of the carb and intake setups listed (including headers), mid to high 14s should be easily obtainable with good tuning. This should put you in the 265-290 hp range, roughly 320-330 ft lbs of torque and yield decent mileage.

-Justin
 
MOPARJ said:
With that said, it probably isn't a good idea to run a Six pack carb setup without higher compression and cyl head modification. It would drown the motor.

-Justin
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Justin, I agree it would drown the engine if it was not rejetted. But then again, who puts on a carb, then realizes it is ding dong dag rich and leave it alone? The first thing that happens is the owner gets a jet kit and starts tuning the carbs.

Drowning fixed.

Otherwise, I like what you wrote, Good thoughts on the heads IMO. I have also run the LD4B intake and a 600 Carter and Holley on top. Nice combo indeed!
 
rumblefish360 said:
Justin, I agree it would drown the engine if it was not rejetted. But then again, who puts on a carb, then realizes it is ding dong dag rich and leave it alone? The first thing that happens is the owner gets a jet kit and starts tuning the carbs.

Drowning fixed.

Otherwise, I like what you wrote, Good thoughts on the heads IMO. I have also run the LD4B intake and a 600 Carter and Holley on top. Nice combo indeed!
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Rob,

Agreed on the six pack jetting. Anything can be made to work. I think I was mainly just going on the premise of there being a possibility that not much jetting has been done by the OP in the past.

He could prolly get away with it, especially jetted way down and running a set of heads port matched to the 6 bbl intake that would be needed and with a bit bigger valves installed to make use of that added fuel.
 
I agree. I knew a dude that ran a set up like this. Dang 318 moved very well. He ran a set of seriously milled J heads. I forgot how much he milled off. I think it was .090 or some crazy thing like that. I'm not even sure how far you can go on a head mill.
 
I have a set of 360-J heads with 188/160 valves that I took off of a running 318 if your interested, but you will probably want to have them milled for more compression....some where in the 62cc area would be ideal...
 
Plymouth Power said:
I was wondering what camshaft to go with, I have a 1973 318 all original with less than 70,000 miles on it. It will have a 4bbl on it and I am planning to put it into my Duster it has the (guessing) 2.76 gears in the back, in a (fact) 7.25. I want something that will also be able to keep up with the later addition of a Six-Barrel and an 8.75 with 3.23's or 3.55's haven't decided yet. I want something that will give me power and torque, things like fuel economy and cost don't matter. Thanks for all of your help.
Click to expand...

Of all the things that you mention here, the cam is probably the least expensive and pretty easy to change out later.
When I first put my Duster together it had a 318, 2.76 gears in a 7.25 and the cam I chose was an Edelbrock Performer-Plus # 2177, a very mild cam and have been very happy with it. Decent low end and mileage, but the idle is pretty meek and it was inexpensive. I now have 3.55s in an 8.25 and I'm going to change the cam when I rebuild the engine this fall.

What I'm really trying to say is, that you should choose the best cam for the set up you have now and you'll enjoy driving the car more than if you go with a wilder grind that is not well suited to your gearing, heads or carburetion. Just my $.02.
 
People can scream old technology all they want, You just can't go wrong with Mopar purpleshaft. You can run the 430/450 cam or the 450/455 cam. Both work well in a 318.

I run the 450/455 purple cam in my 318 which has a more noticeable idle than the 430/450. It has a pretty nice chop to it and runs well after we installed it "straight up" .

When using a 340/360 head on a 318, what you gain in flow will be offset by lower compression. To optimize you're setup aim for around 9:1 and get headers. You can shave the heads around forty thousanths a side and then
have you're intake faces of the heads milled to match up so that you can use any intake; rather than shaving an intake that will only be good for one engine.
 
First of all thanks to everyone who helped. Secondly would running the Purple Shaft 474/474, 484/484, or the 509/509 be too aggressive?
 
Plymouth Power said:
First of all thanks to everyone who helped. Secondly would running the Purple Shaft 474/474, 484/484, or the 509/509 be too aggressive?
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yes,i think so.look at the duration @50 and the listed rpm range.it would be a dog down low, have a rough idle ,and crappy driveability.
 
Johnny Dart said:
Some have said running the 340 cam works well in a teen.
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i tried that before,it ran well and had a very nice "stockish " idle.i ended up swapping it out for something with similar specs,just a tighter lsa and it woke it up alot.
 
The cam that I have always used in 318's that works great is the purple shift 471 lift and 289 duration.
 
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