Degreeing a Cam, or not.....

[PRH]

I’d pull the rockers off the drivers side, along with the spark plugs on that side, and take the readings off the pushrods instead of at the valve.

If your cam is in 8* or so retarded....... it should be corrected IMO.

There is another thread here where someone is running that same basic cam(XS282S) in a flat top 446, same heads, in a full bodied 66 Coronet 500 with a 10” converter and 3.73’s, and with only a few outings at the track has already run 11.55@117.

 

[Kent mosby]

Exhaust info.
Opening at 54* bbdc closing 18*atdc 18+54+180= 252 duration. spot on the cam card specs.

BUT, 18* should be 10*atdc and 54* should be 62*bbdc

Finally, I measured the Exhaust CL at..030 before and after max lift 43 * bbdc gives 137* plus 77* =214/2=107CL
Again, at.050 145*+71*=216/2= 108CL

Could it be possible that it is 8* off? both intake and exhaust say so. Any other verifications that I can do?

The 116 for intake and 108 for exhaust do give me 112 lobe separation. AND in case anyone is thinking about it??? I know enough that the intake is the one coming from the EFI and the exhaust is going to the header, It just seems that the numbers are backwards.

I am perplexed and figure that more work is on the way. I look forward to it.

 

[RustyRatRod]

Yeah, it can be that far off. I've seen a few that far and farther. It's not real uncommon. I would absolute verify the heck out of it, though. I wish we were local, I'd come give you a hand with it. We could screw it up together. LOL

Remember, if you decide to take readings off the pushrod side, you're now reading lobe lift, not gross lift at the valve.

 

[oldkimmer]

And now u see why that it is so important to always check timing events every time a cam is installed. Kim

 

[Bewy]

Being a single pattern cam, this is an easy way to check the adv/ret of the cam. Get #1 or #6 cyl on overlap @ TDC, ie both valves open. Put a straight edge across the prods of the cyl being checked. If the cam is advanced [ ie, ICL is a lower number than the LSA ], then the int prod will be higher; and vice/versa. Swap prods in case the lengths are different. When I say 'higher', that is referencing off the crank centre line.
Couple of things to note. This test is not as accurate as putting the straight edge across the lifters. And the difference in height is very slight, about 0.030" or less. The point is though that if the int lifter [ or prod ] is higher than the exh, then the cam is advanced. The accuracy of this tests depends on the accuracy of finding TDC.

 

[Kent mosby]

Yeah, it can be that far off. I've seen a few that far and farther. It's not real uncommon. I would absolute verify the heck out of it, though. I wish we were local, I'd come give you a hand with it. We could screw it up together. LOL

Remember, if you decide to take readings off the pushrod side, you're now reading lobe lift, not gross lift at the valve.

Thanks for the offer. I checked and double checked and to me the numbers all point to retarded 8* or so. I will continue checking as I break it down. I will remove the rockers and do a check directly on the pushrods. If I find the same results, out with the cam and start over. a couple weekends ought to do it. I will do it correctly this time.

 

[RustyRatRod]

Thanks for the offer. I checked and double checked and to me the numbers all point to retarded 8* or so. I will continue checking as I break it down. I will remove the rockers and do a check directly on the pushrods. If I find the same results, out with the cam and start over. a couple weekends ought to do it. I will do it correctly this time.

If you end up verifying that 100%, that will definitely be worth correcting.

 

[George Jets]

Being a single pattern cam, this is an easy way to check the adv/ret of the cam. Get #1 or #6 cyl on overlap @ TDC, ie both valves open. Put a straight edge across the prods of the cyl being checked. If the cam is advanced [ ie, ICL is a lower number than the LSA ], then the int prod will be higher; and vice/versa. Swap prods in case the lengths are different. When I say 'higher', that is referencing off the crank centre line.
Couple of things to note. This test is not as accurate as putting the straight edge across the lifters. And the difference in height is very slight, about 0.030" or less. The point is though that if the int lifter [ or prod ] is higher than the exh, then the cam is advanced. The accuracy of this tests depends on the accuracy of finding TDC.

I like this simple test a lot, if the intake pushrod at TDC is higher than the exhaust pushrod (at overlap) then the camshaft is advanced.

If straight edge is level at intake and exhaust, then all is good.

Thanks

 

[RustyRatRod]

I like this simple test a lot, if the intake pushrod at TDC is higher than the exhaust pushrod (at overlap) then the camshaft is advanced.

If straight edge is level at intake and exhaust, then all is good.

Thanks

No, because most cam cards want the cam advanced.

 

[George Jets]

No, because most cam cards want the cam advanced.

OK, have to take that into account then.

Turn the crank to the cam card advance recommended * , like if it is 4* then turn the crank to 4* BTDC. Then the pushrods will be level at overlap if the cam timing is set properly.

Easy . . .

 

[RustyRatRod]

OK, have to take that into account then.

Turn the crank to the cam card advance recommended * , like if it is 4* then turn the crank to 4* BTDC. Then the pushrods will be leve at overlap if the cam timing is set properly.

Easy . . .

That sounds about right. I prefer the degree wheel to the level. LOL

 

[George Jets]

That sounds about right. I prefer the degree wheel to the level. LOL

Yes

At least it gives a person a clue as to what is going on without a lot of effort.

 

[Kent mosby]

Being a single pattern cam, this is an easy way to check the adv/ret of the cam. Get #1 or #6 cyl on overlap @ TDC, ie both valves open. Put a straight edge across the prods of the cyl being checked. If the cam is advanced [ ie, ICL is a lower number than the LSA ], then the int prod will be higher; and vice/versa. Swap prods in case the lengths are different. When I say 'higher', that is referencing off the crank centre line.
Couple of things to note. This test is not as accurate as putting the straight edge across the lifters. And the difference in height is very slight, about 0.030" or less. The point is though that if the int lifter [ or prod ] is higher than the exh, then the cam is advanced. The accuracy of this tests depends on the accuracy of finding TDC.

I don't understand this perfectly. But let me see if my logic is sound. I suspect that the cam is retarded. If the pushrod height of the intake is higher than the exhaust, then the cam is advanced.....as it should be. If the exhaust is higher than the intake, then the cam is retarded. This will double check my measurements. Correct? I may have just repeated what you said but I wanted to be sure.

 

[PRH]

Being a single pattern cam.....

It’s not a single pattern cam.

 

[RustyRatRod]

Surely we have a member in Kent's area that knows degree wheels and can stop by and give him a hand if he needs it.

 

[PRH]

Frankly, it seems like he understands what’s going on, and what the numbers mean.
If the results repeat when checked at the pushrods, then it’s time to pull the front cover.
(If they don’t, then it’s a procedural error)

 

[Kent mosby]

Frankly, it seems like he understands what’s going on, and what the numbers mean.
If the results repeat when checked at the pushrods, then it’s time to pull the front cover.
(If they don’t, then it’s a procedural error)

Yep. I will check before pulling it out.

 

[cookietruck]

Yeah, Kent seems to have a good grasp on what's going on. He is just trying to make sure something is probably off before he pulls the front of the motor apart.
Seems he might be 4* retarded from straight up and 8* retarded from what the cam card is asking for on the installed center line...

 

[Dale Davies]

Well, I am an idiot engine builder. I built my 512 RB from scratch. Fresh block, completely new rotating assembly, new cam, lifter,,,,,everything. But, when I assembled it I measured everything and it all went together smoothly. What I did not do was degree the cam. I now know that was a big no no. How could I be so dumb? As I look back on the results of the build, I see a big motor that sounds great but underperforms on the racetrack. I have gone 12.3 seconds in the quarter mile but on paper I should be much better. I know that there are other factors but I look back on the lack of degreeing the cam as a possible source of frustration. The cam was built by Ken of Oregon cams. The specs are.

244/252 @ .050”, 282/290 adv, .516”/.537” lift(1.5:1 rocker), 112 sep, .016”/.018” lash

This is a very good street/strip grind that should make power from 2200/6400 or so. Will need a 3000+ converter and will work well with your compression ratio. Normally I would put this on a 110 lobe separation but with the nitrous and fuel injection I think 112 to 114 would work better.

Is there any way to correct this without pulling the entire front of the motor off?? This is a. what would you do if you bought the car and knew this was the situation?? The racetrack in Spokane will open sometime in the future and I hope to race it again there. I may also consider a new cam without the nitrous accommodation. Something more aggressive.

What would you do? I know that I was stupid. Go ahead and remind me, or not.

I am not a cam expert, but there is much more to installing a cam than the cam card and degreeing it. My recommendation is to read David Vizzard's How to Build Horsepower, and watch his Youtube videos. His 50 years experience and an obscene number of dyno runs testing has given him unique knowledge of what really works and what probably does not.
Heads, compression ratio, intake system and exhaust system all have an affect. LCA and whether the cam is installed " straight up", advanced or redarded all affect dynamic compression as compared to static or theoretical compression.

 

[Dale Davies]

Not alot of lift for so many cubes. I'm not cam guru thou, just first impression.

Looks older technology but easier on the springs.

 

[George Jets]

I don't understand this perfectly. But let me see if my logic is sound. I suspect that the cam is retarded. If the pushrod height of the intake is higher than the exhaust, then the cam is advanced.....as it should be. If the exhaust is higher than the intake, then the cam is retarded. This will double check my measurements. Correct? I may have just repeated what you said but I wanted to be sure.

Here are a few pics on how you measure valve timing events off the pushrods. Engine still in the car, heads on, rockers off, intake manifold on.

Can make up some pushrod caps so you have a big flat target for your dial indicator.

Some 5 1/6" brake line fittings to use as bushings in the heads to keep the pushrods on center that won't drop through the head. (small block setup pictured here)

Can use the straight edge trick on top of the pushrod hats when cylinder is on overlap at TDC, or whatever the advance degree number is recommended by cam mfg.

Pushrod caps bolts, drill out to a few ths larger than pushrods.

There you go, have fun.

Creative Minds at Work

☆☆☆☆☆

 

[Kent mosby]

Before taking stuff apart maybe run a compression test first because it's relatively quick and easy. With your low-10 SCR and that cam I'd call it good if it cranks close to the 170-180ish neighborhood? Now if it cranks140s-150s then yeah maybe it's off and wants to be advanced a bit more. Otherwise...the cam's IC isn't your problem.
It could very well need more detailed tuning, BUT since you're judging it on track E.T. I kinda think it's gonna take some more camshaft to get you where you want to be...good luck!

Cylinder 1 was 152 I will check the others this weekend

 

[fishmens67]

Surely we have a member in Kent's area that knows degree wheels and can stop by and give him a hand if he needs it.

Del is just a few miles away in CDA. He could ask him.

 

[beanhead]

Cylinder 1 was 152 I will check the others this weekend

I know there's lots of variables that will influence a cranking test reading but that does seem just a bit low with your build. If it were me, I'd want to investigate the cam timing further....which it looks like you've been busy doing.
If your readings are close it appears your intake is closing quite a bit later than the card recommendation...you will feel 5-6 degrees IMO. Gonna get you where you want at the track? Don't know.. Looks like you're well-motivated though, keep on it you'll get it fingered out!

 

[Bewy]

Kent,
Post #113. The procedure I posted was for a single pattern cam. For some reason I thought you were using a SP cam. But it is a dual pattern, so it won't work. Sorry for the confusion.