Cam up my 318, help me chose!

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henrikolsson

henrikolsson

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Hello eveyone!

I need help on a Cam choise. Im drivning a -73 Duster, with a 318 stolen from a 85 van, it got the stock cam in it. Oderwise its 302 heads, Performer intake, Holley 650 vac carb, Accel coil, Tti headers and a 2,5 double exhaust. Behind it sits a 727 and a 8.25 with 2.76 gears...? I plan to change gears to 3.55 and a sure grip. Also maybe a higher stall converter. Im thinking about a Hughes Whiplash or a Comp extreme energy of som sort. Im quite lost about camchafts, and the car is quite a dog. please help me choose right one. //Henrik
 
I had the magnum 270 hydraulic cam in my little 318 before I stroked it. It did sound cool, you could sure tell there was a cam in it. Performance wise I never raced it but seem to move my dart around pretty good. I had 355 gears, 600 edle carb, 318 heads ported with larger 1.88 intake valves and headers at the time. I liked it.
 
FWIW, I run the Comp HE268 in my teen with 3.55's. I need to change the converter yet, but won't do that until I rebuild the trans.

It doesn't run bad IMO.
 
Before I answer your question, I have a few.


What is the tire size on what size rim.
Is this the size you will end up with when your done?
If not, what will you end up with?

what is the power band you want for the car.
At what rpm so you want to cruise at?
In general, what is the build for?
Example; street, hot street, street strip?

What is the compression ratio of the engine?

Once you decide on a cam, you'll need a converter (probably) and gears. I also suggest wider tires for the increased power.
 
If the car is a dog as you say now, changing just the cam will make it worse.
 
4spdcuda66 said:
Will you elaborate please? What are the rest of the factors at play here? Thanks.
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When you increase the cam size, the duration goes up. The power band moves up in RPM with a bigger cam. He already has the BEST cam for his combination now. The stock cam. There's not another cam that will likely improve bottom end torque with the rest of his combo. What I would do would be to work from the rear forward, starting with a decent gear FIRST. That way, there's less disappointment and with each change there will be power he can FEEL.
 
henrikolsson said:
Thank's but arent those camshafts supposed to live in a bigblock?
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Correct ,and apologies on my part. This is what I should have posted.:
http://www.google.com/url?sa=t&sour...eMTRyJfhNCmMGoSCPw7zLAA&bvm=bv.76802529,d.cGU
However a few number of posts here related to adding torque multiplication through a rear gear change,possibly a converter swap. I see, you have a bunch of aftermarket goodies added. Have you even bothered to tune, what you have yet? Timing curve(initial,2500-3000)/ carburetor float level/idle mixture/accelerator pump/ jetting ? These need to be done /revised every time you change the combination. Have you done any,or do you want to just add a cam?
 
Henrik, there is lots of good info above that I agree with. You really need to decide if and when you will go to the 3.55's, as that makes a huge difference in cam choice with a mild low compression engine like you have. A month or two, I'd say go ahead and cam up now.....but if it's just a "wish list" item that may take a year or two, I'd leave well enough alone for now and just tune the timing and the Holley to get the best out of it that you can.
 
The 3:55s is not on my wish list, it's on my to do do list, i hope to change gears this winter as the cam change. I'm running 235-45-17 but when the rear is wornd out it's going to be a little wider.
I thougt the smartest thing is to fine tune after the cam change. The car is running fine, but not as performance oriented as i wish.
 
I agree with RustyRatRod. But I want to know what he considers a "dog". Is it because he raced a 12 second car and got smoked? EVERY car needs to be compared as follows: what is it doing with what it is equipped to do. In other words, his combo isn't a 12 second combo, or 13 second combo. So what IS he considering a dog??? I happened to have the exact same '85 engine, with 302 heads, ALL STOCK (even exhaust manifolds) except a 4bbl, with auto and 2.94's. I can roll along 10 mph and just "mash" it and it will break the 245/60R14 loose. Without power breaking it, it will smoke the tire and lay a 40 ft. black mark. I think as my car sits, it is low 15's. So, even though low 15's may be a "dog", I don't think my car is a dog because it is doing everything that it is suppose to do (and more than what most expect from it). So, I ask the question, why, to him, is it a dog???? What is he looking for in his ride?? If he wants an 11 second street car, Ummmmm, I guess we have a lot of things to talk about.... :)
 
rumblefish360 said:
Before I answer your question, I have a few.what will you end up with?what is the power band you want for the car.At what rpm so you want to cruise at?In general, what is the build for?Example; street, hot street, street strip? QUOTE]

Exactly, what is the mission, or your goal?????
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You are on track with the gears. If you want a little more useable RPM I would go with a 340 replacement or equivalent. You may "wonder" if it would run a little better with a bigger cam but you will know it's a "dog" with too much cam and money down the hole...
 
Well, 318willrun´s description of his engin/car setup got me thinking...I can't lay any rubber behind me, maybe my car is overcammed as it sits... it´s about 11-12 seconds to 100km/h and really slow from a start, but it pulls quite good to 6000 or above. I bought the car with the setup as it is, and the previous owner told me that it is the stock cam... any good tips to check that without tearing everything apart?
Also my goal with the car is a street/hot street car for recreation and fun.
Thanks for all the input, all discussion with you makes me learn a lot!
 
100 k is a little over 60 mph. A 12 second 0-60 time is pretty slow. You need steeper gears first. Then you can cam it up a little and it will do you some good.
 
henrikolsson said:
Well, 318willrun´s description of his engin/car setup got me thinking...I can't lay any rubber behind me, maybe my car is overcammed as it sits... it´s about 11-12 seconds to 100km/h and really slow from a start, but it pulls quite good to 6000 or above. I bought the car with the setup as it is, and the previous owner told me that it is the stock cam... any good tips to check that without tearing everything apart? Also my goal with the car is a street/hot street car for recreation and fun. Thanks for all the input, all discussion with you makes me learn a lot!
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You can take the valve covers off and measure lift with a dial indicator. Add in a degree wheel or timing tape, and a solid lifter, and you can get a pretty idea of the cam specs.

Really slow from the start suggests to me a look at the initial timing. Check the whole curve while you're at it though.

As far as cam, do the math on the tire diameter plus gear ratio to figure out what rpms you will want torque. driving on the street to 100 Kph is going to be different than winding out to a 100 mph.
 
Rusty is right. Gears would be my first choice also.
-Camshaft selection is pretty much married to compression, and stock 318s dont have much of it. If you cam it up without a corresponding C/R change, you will trade away a bunch of bottom end torque for a very little bit of top end power. But since you have 2.76s, you barely get into the powerband at 60mph, and because of the torque loss,it takes forever to get there.
-And spinning one of two tires, however far, is hardly grounds for bragging.
 
Have you done a compression and leak down test yet?
Think about it the motor is 30 years old, and it has most likely wore one vehicle out before it was installed in your car.
 
AJ/FormS said:
Rusty is right. Gears would be my first choice also. -Camshaft selection is pretty much married to compression, and stock 318s dont have much of it. If you cam it up without a corresponding C/R change, you will trade away a bunch of bottom end torque for a very little bit of top end power. But since you have 2.76s, you barely get into the powerband at 60mph, and because of the torque loss,it takes forever to get there. -And spinning one of two tires, however far, is hardly grounds for bragging.
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WHO bragged about spinning one tire?? If your referring to my post, I wasn't bragging, simply made a statement that's fact. If you read my entire post, it is about doing good with what you have. One has to compare apples to apples. I was also implying that one has to have a performance level that they would "be happy" at when building a motor. My point within my point was also that your car needs to be achieving what it should before moving on. For example, if something is severely wrong now, yes gears would help. But that's a false improvement. Get the issues fixed now so you can get the full benefit of the whole package, gears, stall, engine.
 
I would do gears first, before any more engine mods. Its possible that sometime during its life that a performance cam could have been added.
 
Ok, you have convinced me. I am going to change gears to 3:55 or 3:91 first. I will try to mesure the cam to check if it could be someting non stock. What are the stock specs on a -85 van in a 318 camshaft?
 
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