[73XR-7owner]

I have a "CJ Camshaft" in my engine (351C-4V.) I have read here a couple of times that the cam is a critical element in horsepower production. Can anyone tell me what a "CJ" camshaft is and whether there might be a better one?

 

[ChadInman]

There's always a better cam shaft! typically "CJ" means Cobra Jet, though I can't say that that is what it means in this case. Remember the whole "flow in and out" thing that was talked about before. This is the cam's job, so yes it is a critical hp factor. - Chad

 

[73XR-7owner]

Chad, if you'll bear with me here...

Somewhere on here, I read a post about the different 351's that were made. I remember the C, the W, and the CJ. I assume the CJ is the Cobra Jet you refer to. I'm sure that's the cam in mine, put in when it was converted to 4V.

But were all CJ's 4-barrel? If so, what was the difference between the 351C-4V and the 351CJ?

Now, about cams: I understand the relation between the cam and the inflow and outflow, but I don't understand how you can put in a different camshaft than was made for the engine. Wouldn't that throw off the timing more than you could adjust for?

Last question (promise): Where would I look for a better cam and how do I know what will work?

 

[fordsnharleys]

351 cj

I have a Merc. Muscle cars book that explains that in a certain year, I forget which,( I cannot find the book at the moment), but I remember reading that during cleveland production, when cougar sales where declining mercury was looking for something to attract buyers, I believe it was 1973, not sure though. They renamed the cleveland to the 351 cobra jet to attract more buyers. however this engine actually had five horsepower less than the previous clevelands due to emissions devices. I will bet that the cj cam is just the stock cam that came with the motor, and with today's cam technologies, there are MUCH better cams out there. and it is true, a cam is the biggest performance booster available, except for supercharging of course.
Justin

 

[ChadInman]

Ok thankfully someone found alittle on the whole cobra jet thing becuase I wasn't sure... As far as timing goes the cam controls almost all aspects of it. Because the gear on the cam turns the gear on the distributer your engine can always fire in sink with what is going into it. - this means accurate timing. It's pretty card to get cleveland parts.. Summit or jegs probably seels a few cams for a cleveland engine. The only thing is, you should get a cam with a mild lift if the rest of your engine is without performance mods. If the lift is too big you'll drowned/choke your engine... and this is where heads come into play. - Chad

 

[73XR-7owner]

i wish there was a hole-digging smilie on here...

because i'm in is getting way over my head!

what do you mean by "if the rest of your engine is without performance mods?" mods like what? as i have posted before, this is basically the modifications that have been made: "The 2v to 4v conversion Cleveland was professionally rebuilt to run unleaded (premium) gas, was balanced, blueprinted,equipped with forged flattop pistons, a CJ cam, Holley, Edelbrock intake etc." also the rear end was changed to a 3.00 traction lock.

what mods would require something more than a "mild lift?" (i am assuming that a "mild lift" isn't going to generate as much power as whatever more lift would be called.)

 

[modifiedmark]

Chad & 73XR7, I see you guys need help in understanding the cam timing vrs ign timing thing. I dont explain it very well but let me take a stab at it, and someone else hopefully will come behind me and do it better. Cam timing is the relationship of the cam to the crankshaft. Manufactures of aftermarket cams will give you specs on where the cam is to be in relationship to the crankshaft. The procedure for doing this is usally refered to as degreeing the cam and is used to advance or retard the cam in realation to the cam running slightly ahead or behind the rotation of the crankshaft. Advancing the cam will make the intake valve open sooner in relation to the pistons TDC (top dead center) while at the same time will also close the exhaust valve sooner. Redarding the cam will as you can see will do everything just opposite.

Ignition timing is something in itself and is not realted to cam timing at all. Ignition timing is just used for setting how far BTC (before top dead center of the piston on compression stroke) the spark plug will fire. You can turn the camshaft ahead or behind all you want and you can still set the dist for whatever Ign timing you want. All you have to do is turn the dist.

Understand? Someone else can take over now!! mm

 

[Cougrrcj]

OK, here we go yet again...

Clevelands...

A 351C-2V (70-74 engine code 'H') has flat top cast pistons, open chamber (low compression) heads with small ports and small valves. All 'H' code Clevelands have two bolt main caps.

A 351C-4V (70-early 71 engine code 'M') as flat top cast pistons, closed chamber (high compression) heads with big ports and big valves. All 'M' code Clevelands have two bolt main caps.

A 351C-4V (late 71-74 engine code 'Q') has dished cast pistons, open chamber (low compression) heads with large ports. 71-72 heads have large valves, 73-74 have small valves. All 'Q' code Clevelands have four bolt main caps.

Then we have the 71 Boss 351 and 72 351HO, but these were not installed in Cougars, they were Mustang-only items. A Boss had a mechanical lifter camshaft, forged 'pop-up' or domed pistons, high compression heads with large ports and an adjustable valvetrain. The HO had flat top forged pistons, a mechanical lifter camshaft, Low compression heads and an adjustable valvtrain. Boss and HO blocks have four bolt main caps.

OK, Camshafts...

Hydraulic camshafts
351C-2V 'H' All .407/.407
351C-4V 'M' 70-71 .427/.427
351C-4V 'Q' 72-74 .480/.490
Mechanical lift camshafts
351C Boss 'R' 71 .477/.477
351C HO 'R' 72 .491/.491

Unfortunately, my book doesn't go in to the camshaft timing or duration figures. I do know, however, that the 'Q' code camshaft was ground 4 degrees retarded to help with emissions. If you advance it back to where it should be, you get a real screaming motor! (on 429-460s they retarded the camshaft with a different timing chain set. Put the early timing set on and it will really wake up those beasts!)