.006 is fine and dandy for both intake and exhaust valve opening points, unfortunately the .006 rule does not apply for the closing points, @.006 intake closing the degree wheel is reading 52 ABDC. It should be reading 42 ABDC if the @.006 rule works here.

The dial indicator reads 12/13 ( before valve closes ) thou when the 42 ABDC degree reading is showing.

This reading is approx 6.5 thou away from where it should be?

I check the exhaust and it is the same scenario.

@.006 just as the exhaust valve is opening the degree wheel reads 36 Degrees BBDC just as it should ( using the .006 rule )

Problem is 12 degrees on the degree wheel ( thats when the valve is supposed to be closed according to the FSM ) the dial indicator is still reading 12 thou instead of the expected 6.

A difference again of .006 thou

Both on the closing sides.

Ive searched high and low for an explanation to this and have got a lot of good feedback but no definitive resolution on why I am seeing what I am seeing

I did check all of these things and then some at the time.

Head is off at this point, all disassembled. I am in the middle of doing some head work I.E oversized valves and mild porting/cleaning up/ new hardened exhaust seat ect.

It will go back together sometime soon hopefully but with the super six set-up, better ignition and a different more appropriate cam (for what I want it to do ) that will have a cam card.

It may be one of those mysteries that just will never be solved.

The only thing at this point I am questioning is the condition of the "new " camshaft.

Looking down at it thru the lifter bores it looks brown, really brown on the outer edges. I would expect a cam with only 18 miles on it too be shiny and pretty.

I need to pull it out to have a better look.

Quote: Just a quick check- you are setting yout timing in degrees BTDC, not ATDC, right? That is the kind of mistake I would make (and have made), which is why I ask.......

Maybe clarify on this one just so I am sure we are on the same page.

I think you should try installing one of the old stock cams from one of the two unrebuilt motors you have and see how it works for you. Who knows what the engine builder put in there, or what the cam company provided the builder for a "stock" cam.

When I say set the timing in degree BTDC and not aTDC, I simply mean make sure the timing scale you are using to set your timing has the numbers on the passenger side of the block with the numbers counting down as they get closer clockwise to the 0 or TDC mark. Some timing tabs have up to 10 degrees marked on the ATDC side of the TDC mark and I just wanted to verify that you weren't possibly using the numbers on the ATDC side of th enotor to set your timing.

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Casually looking for a Clifford hyperpak intake for cheap.

Did you ever use these measurements to degree the cam in your brothers van?

I am under the impression that without a standard of measurement there is no way of telling when the timing events shown in the FSM are supposed to occur on the degree wheel.

My search for this standard of measurement is covered briefly in the prior post AKA .006

Actually, you can figure out the cam events on the cam yourself. You already ahave the degree wheel installed, so just note at what degree the intake reaches .006 lift and then at what point it returns to .006 lift. That will give you the intake duration. While the cam is unde the dial gauge, note how high the dial gauge indicates. That gives you the lift.

Now do the same for the exhaust lobe. Then you will have the intake and exhaust durations, lifts, opening and closing points, and from there you can work out the overlap.

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Casually looking for a Clifford hyperpak intake for cheap.

Yes this is how my timing scale is set-up and so yes I have been reading it correctly.

When I timed the cam in my brother's engine I used .050 as the point of measurement for valve events. I was using a custom ground cam at that time.

I have since pulled the custom cam (after the cam locator dowel broke off) and installed a stock 1983 hydraulic cam. I didn't degree the 1983 stock cam. I just slid it in, put on the lifters, turned the key, and let it go.

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Casually looking for a Clifford hyperpak intake for cheap.

Yes in a couple of posts back I showed a map of where I had taken quite a few measurements, unfortunately I am still at a loss for how these coincide with the FSM specs.

FSM Intake opening 6 degrees BTDC.........OK at 6 Degrees BTDC I am on the .006 mark of lift

FSM Intake closing 42 degrees ABDC......Ok at 42 degrees ABDC dial indicator reads .013 of lift still before valve closes.

FSM Exhaust opening 36 degrees BBDC.........Ok at 36 degrees BBDC I am again at the .006 reading on the dial.

FSM Exhaust closes 12 ATDC......At this point when I am at 12 on the degree wheel I am also at .012 on the dial.

I am confused on how do I know that these events are in correct time.

Again that is why I am comparing cams at this point. Dont know what else to do!

I can map them out but proving that events are happening at the correct time is where I am stuck!!

I hope you understand with my ramblings where I am at. Maybe even have a solution?

OK- when you map valve events on a cam, you have to pick a consistent level of valve movement to measure for both the opening and closing events. For example, you are measuring the valve opening events at .006 inches of lift. This is fine. I used .050 inches just so I had some fidge room to account for tool deflection, wobbly bases, general slopiness, etc… However, if you are using .006 inches of lift to determine when the valve begins opening, then you must also use .006 inches of lift to determine when the valve is closed. The intake valve duration will be the number of degrees between when the lobe had moved the lifter .006 up in its bore from its resting point on the cam to the point where the lifter reaches .006 inches from its resting position on the downhill side of the cam lobe.

In other words, you are measuring the opening events fine, but you need to not worry about the lobe height at the factory soecified degree, but you DO need to note where the lobe height equal .006.

In other words, keep rotating the cam until the dial reads .006 again and then note the degree ATDC that the lobe has reached that height again.

It sounds like the builder put in a cam with a little bit longer duration than stock.

Looking at the measurements you took, here is my ballpark guess as to the specs of the cam in your rebuilt motor (using .001 as the valve lift reference point. These numbers will change if .050 lift is used).

Spare engine specs (presumed stock cam)

Intake duration = 284 (19 btdc + 180 + 85 abdc)
intake lift = .251

Exhaust duration = 281 (50bbdc + 180 + 51 atdc)
exhaust lift = .251.5

valve overlap = 70 degrees (51 atdc exhaust closes + 19 btdc intake opens)


"Parts truck engine specs"

intake duration = 278 (19 + 180 + 79)
intake lift = .245

exhaust duration = 308 (50bbdc + 180 + 75abdc)
exhaust lift = .247

valve overlap = 82 degrees (63 atdc + 19 BTDC)


Now lets do the "spare engine" at .050 lift, since that is what lots of aftermakret cam companies use to give their cam specs:

intake duration = 221 (17 + 180 +24)
intake lift + .245

exhaust duration = 202 (15 bbdc + 180 + 7)
exhaust lift = .247

overlap = 23 (7+16)


Do those numbers make sense to you? I hope someone else comes along and checks my math on this. My brain hurts now.

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Casually looking for a Clifford hyperpak intake for cheap.

CRAP! I did the .050 lift umbers wrong. Here they are done right.

"spare engine" at .050 lift:

intake duration = 221 degrees (17 + 180 + 24)
intake lift = .251

exhauist duration = 198 (13 + 180 + 6)
exhaust lift = .2505

overlap = 23 (17 + 6)

I think those are the right numbers...

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Casually looking for a Clifford hyperpak intake for cheap.

I am amazed at how people can keep all these numbers straight in their mind! I just have a pea sized brain I guess.

I look on the cam card and find the "intake lobe center." If it says 108 degrees, I verify top dead center, install the degree wheel and rotate the engine until it reads maximum valve lift. Re-zero my dial indicator and then rotate to .050 on each side of zero on the dial indicator. Write down the readings, add them up and divide by 2. If that reading is 104 for example, that would be 4 degrees advanced. If it is off more than you want then you adjust from there.

I have found several timing sets that were stamped way off. I have had to move the timing chain whole tooth to get them close.

Hope that helps some.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

At this point I still stand on my observation ( and the observation of others ) that I have to know the method that was used to get the FSM numbers I am using to check the cam. Once I find out this and understand that method then I can go about checking the FSM numbers using the same method.

At this point I have not found this information and I am pretty close to throwing in the hat on finding this.

This guy normally has reliable info. http://www.moparaction.com/tech/quest/CAM_PLANS.html

This would seem to confirm. http://sbftech.com/index.php?topic=22953.10;wap2

Thanks for giving me these things to look over. Reed sent me a bunch of stuff via e-mail as well so I have my hands full to get caught up on all of this.