One of the problems I've had with tuning my engine, is that I've never really been 100% positive what it really is. It was built by AR Racing in Sumerduck, VA, and I never received the build sheet or the dyno sheet for it, as was promised. I'm sure it never saw a dyno, regardless...

The cam spec he gave me was .575 lift and .248 Duration @ 050. This is in a 454 bored .60 over (468). This was a year after the engine was built that he finally sent me that spec, and the cam just seems more radical than that. I base this on absolutely nothing.

Is there a way I can identify my cam without pulling off the timing cover? If not, I'm going to have to pull the timing cover and timing gear and look at the headstamp on the cam. On a small block, you have to pull the pan before you can pull the timing cover, can a timing cover be removed and reliably resealed on the big block without pulling the pan?


In any case, I'm starting to get back into this car after letting it sit for a couple of years, so I'm going to start with the carb setup, I'm probably jetted too lean. I got hit with an unexpected expense today, so my EFI plans will probably have to wait till next year.

 

Pull off the driver's side valve cover, setup a dial indicator at a stable point on the #1 intake valve retainer parallel to the valve stem and where it won't interfere with the rocker, and zero the dial with the valve closed. Rotate the crank (by hand) and note the max lift. For duration, install a degreed tape on your harmonic balancer (if you have or don't mind purchasing a spark plug type piston stop, I'd take the time to verify TDC) and slowly, but steadily, rotate the crank until the intake valve has opened to 0.050" lift. Note the degrees BTDC. Continue to rotate the crank past max lift until the valve is back at 0.050" lift on the way to closing, and note the degrees ABDC. Repeat the process on the exhaust valve, noting the degrees at which 0.050" is reached BBDC and ATDC.

To calculate duration from the above readings, add the intake opening BTDC and closing ABDC degrees, plus 180 and you'll have intake duration at 0.050". Likewise, add the exhaust opening BBDC and closing ATDC, plus 180 and you'll have exhaust duration at 0.050".

Now, to calculate lobe center angles, take 1/2 the intake duration minus intake opening BTDC and you have the intake lobe center angle (ILCA). Then take 1/2 the exhaust duration minus exhaust closing ATDC for exhaust lobe center angle.

To arrive at lobe separation angle (LSA), just add the intake and exhaust lobe center angles and divide by two. Advance equals LSA minus ILCA.

Unless I messed up due to sleep deprivation, that ought to yield sufficient info to extrapolate what cam you have with a little research, but note that the accuracy of your readings depends on the accuracy of your work and the tools you use. Hope that helps.

 

I do have a Mitutoyo dial indicator and a magnetic base and holder for it. I could give that a shot. I am a bit confused, how do I put the tip of the indicator on the stem without interfering with the rocker? I'm running roller rockers.

It almost sounds like it would be less work to pull the timing cover. I'm changing the water pump anyways .

 

What you want to do is find a good spot on the retainer adjacent to the stem where you can setup parallel to the valve...

This process can keep one form having to dig all the way into the cam, but if the pump's coming off anyway I'd agree that it's not going to save you nearly as much trouble, tho. If you're only interested in knowing lift, you could skip the more cumbersome steps of determining the timing info.

 

Yeah, I think I'm just going to pull of the timing cover. Any thoughts on pulling it off without pulling the pan?

 

I might advise pulling the intake rocker and setting the dial indicator up on the tip of the pushrod. The published .050" timing numbers may be at .050" TAPPET lift and zero lash rather than net valve lift and it will be easy to avoid any rocker arm geometry and hydraulic lifter bleed down issues that way. You can download free degree wheels from the net if you do not have one and are on a tight budget.

Just a thought.

-MArk.

 

For anyone following along, if you chose to measure at the push rod, keep in mind you'll get lobe lift and not valve lift numbers.



Bump for any good ideas on timing cover...

 

I'm not sure about the big blocks, but with a small block, you can take the first 2 or 3 oil pan bolts completely out and then just loosen the others a bit and drop the front of the pan down(about 1 1/2 inch or so) far enough to take the timing cover off. But be really careful not to damage the gasket or the front seal or it will leak.

 

The big block timing cover is different than the small block timing cover. The front two bolts on the pan actually screw into a lip on the bottom of the timing cover instead of the block.

I know it's possible to remove it separately, I just wasn't sure of the prospect of actually resealing it properly doing it this way.