The GTS clone project that I received in February came with a rebuilt engine that has not been fired. I asked the folks that were involved in the project about the engine's new cam and no one was able to provide details. The engine was delivered as a long block without a water pump and I noticed that the timing cover gasket was separating from the block. Since I needed to replace that gasket I went ahead and pulled the cam, and found it to be a CompCams 32-541-8 hydraulic roller. I am putting it back together and need help confirming that I lined up the timing marks correctly. The position of the crank did not change while doing this. Are the timing marks in the photo aligned correctly?
Replies sorted oldest to newest
If you are trying to install the camshaft 4deg retarded, then yes. If you are trying to install it "straight up" then you need to move the crank sprocket two slots over. This should be verified by consulting the cam card and then degreeing the camshaft to be certain that the cam timing is where the cam manufacturer intended.
Ron
Comp Cams does not mention anything about 4deg retard. Below is from their website for their cam 32-541-8.
Maybe the crank gear is installed on the incorrect notch? The crank keyway is straight up at 12 o'clock. I did not move the position of the crank during disassembly. I could have put the the crank pulley on the wrong notch or some one else could have done the same.
In any case I will use my degree wheel to verify correct installation.
UPC | 036584780274 |
---|---|
Manufacturer | COMP Cams® |
Emissions Code | |
Engine Family | Ford 351C, 351M-400M 8 Cylinder (1970-1983) |
RPM Operating Range | 2,500-6,000 |
Cam Type | Hydraulic Roller |
Camshaft Series | Magnum |
Camshaft Gear Attachment | 1-Bolt |
Usage | Street/Strip |
California Proposition 65 | WARNING: Cancer and Reproductive Harm P65Warnings.ca.gov |
Advertised Intake Duration | 290 |
Advertised Exhaust Duration | 290 |
Intake Duration at .050 Inch Lift | 230 |
Exhaust Duration at .050 Inch Lift | 230 |
Intake Valve Lift | 0.578 |
Exhaust Valve Lift | 0.578 |
Lobe Lift Intake | 0.34 |
Lobe Lift Exhaust | 0.34 |
Lobe Separation | 110 |
Intake Centerline | 106 |
Valve Timing Lift | 0.006 |
Exhaust Close ATDC | 31 |
Intake Open BTDC | 39 |
Exhaust Open BBDC | 79 |
Intake Close ABDC | 71 |
Lifter Style | Hydraulic Roller |
Compcams "on the shelf profiles" typically are cut with 4° advance when installed straight up. That is what I am reading on that cam card.
The criticism is generally that the Ford stock iron heads cannot take advantage of a 110° centerline because of the restrictive exhausts. That's where it is typical to see a 112-113° centerline on the original Ford cams and some current aftermarket cam designs.
I don't think that the 110 hurts anything, there is just no significant advantage to using it and you will get a smoother idle with a 113. It is almost a matter of taste on how you like the engine to feel? Almost.
The low restriction Pantera exhausts help a little but can't fix the bad stock ports unless you go to the old "Pro-stock" exhaust modification. That's kind of pointless in a Pantera unless you are going to drag race it and turn 9,000 rpm with it?
I think that’s what Ron is getting to…. On the lower gear, the keyway engages the 4R notch, vs. the 0 notch, which is 2 notches to the left in your picture.
But you probably already saw that…. So I’ll let the experts take it from here…
Rocky
@rocky posted:I think that’s what Ron is getting to…. On the lower gear, the keyway engages the 4R notch, vs. the 0 notch, which is 2 notches to the left in your picture.
But you probably already saw that…. So I’ll let the experts take it from here…
Rocky
It was not/is not uncommon to mess with that timing to dial in the nature of the engine. Most don't bother. With the power range expected of that cam, just go straight up. It may be advertised as a 290° cam but it is only 230° @ .050.
My experience in taking out some of the advance was a disappointment in the results. If it was a car with an automatic transmission that's a different story. It may pull "a little" harder "off of the line" but you will be looking for another top gear running flat out.
As made, it isn't even close to being radical. It's just going to sound like a spunky stock high performance engine at idle, which is what that profile is intended to do.
It's now clear to me that I was the one who put the gear onto the crank a couple of notches off. Now it looks like the crank keyway is at 12 o'clock and the timing marks are straight up. Do I still need to degree the cam?
Attachments
You don't have to but it probably would be a good idea with everything apart now. This way you will have peace of mind at least.
Unless I'm misremembering, that's not any different than the original timing other than the markings on the crank gear. I believe any advance or retard would have the crank gear 0-degree timing mark aligned with the cam gear timing mark, and the crank keyway would not be straight up but be offset one way or the other by the 2-, 4-, 6-degree advance or retard keyways. Please correct me if I'm wrong. It's been quite a while since I last timed a cam.
The advance is built into the camshaft by Compcams already. Installing it straight up advances it 4 degrees.
You would need to degree it to actually see that.
Probably the most practical change would be to take 4 degrees out of it, so set it to -4 but I'm not sure that it is worth the effort?
I'd talk to Compcams about that first and see what they say. They may have a graph print out that will overlay between the two settings available but I suspect that you are taking some upper rpm's out of the engine that you might like to have?
It might or might not effect the idle as far as idle rpm? That depends on the engine itself, that's why you should talk to the tech adviser.