Degreeing question

[ledslinger29]

So i'm in the process of putting my 170 back together, and I'm degreeing the cam. I thought i had it all figured out, but putting teading into application almost always leaves me with more questions. I've attached a picture of my cam card below.

My first question is, what exactly does it mean when it says to degree intake lobe to 110? Is that for me or the tech that ground the cam?
Second, i am off about ten degrees on all openings and closings, as an example, my exhaust lobe hits .050 lift at 46 BBDC instead of 36, and closes at -22 ATDC instead of -12. I have the billet adjustable timing chain set set at 0, what is the appropriate correction?

 

[bubba22349]

Here is an excellent video by the site member "echo1955" from severial years back it covers cam degreeing very well and may help you to better understand the process. See below link, good luck

https://m.youtube.com/watch?v=zj-GA494SJQ

 

[cr_bobcat]

When I installed my adjustable gear set, I ended up 10* off too. I had it installed off by 1 gear tooth. Pay very close attention to the pictures in the directions. At first glance it looks like the dots are supposed align but they really don't. There is a slight offset.

 

[pmuller9]

My first question is, what exactly does it mean when it says to degree intake lobe to 110? Is that for me or the tech that ground the cam?

That is for you. It means that if the cam timing is correct the center of the intake lobe (Max Lift point) is at 110* ATDC.
You can check this point by going .050" down from max lift on both sides of the intake lobe and find the halfway point in between.
I use this to verify the timing set by using the .050" lift points specified on the cam card like you are doing now.

Second, i am off about ten degrees on all openings and closings, as an example, my exhaust lobe hits .050 lift at 46 BBDC instead of 36, and closes at -22 ATDC instead of -12. I have the billet adjustable timing chain set set at 0, what is the appropriate correction?

How did you zero the degree wheel?

 

[ledslinger29]

Thanks guys, I love those echo 1955 videos, well done and with a little class to top it off. I had watched that one a while back, it was very much worth watching again, that might have cleared me up some. I'll go check those instructions for the gear set too, as I set the dots to line up perfectly. I used the piston stop method at first, but my bridge was aluminum and had a little flex in it, so I set the depth gauge on the center of the piston head and got it lined up properly and fine tuned my TDC like that. I understand the 110 intake thing now, if I'm doing this wrong the way I think I am, max lift should be at 100 or 120 right now.

 

[pmuller9]

I'll go check those instructions for the gear set too, as I set the dots to line up perfectly. I used the piston stop method at first, but my bridge was aluminum and had a little flex in it, so I set the depth gauge on the center of the piston head and got it lined up properly and fine tuned my TDC like that. I understand the 110 intake thing now, if I'm doing this wrong the way I think I am, max lift should be at 100 or 120 right now.

If you want to double check the degree wheel TDC, the piston should be .050" down from TDC @ 13 degrees before and after TDC.
Be sure to come into the BTDC position turning the crank clockwise and into the ATDC counter clockwise.

If you still find the cam as being 10 degrees advanced then use the 8 degree retard keyway on the crank gear and see how close it is to being right.

 

[Econoline]

To dbl check your method, search degree by the centerline method, when that looks good and repeatable you can check the valve events @ .050" method.

 

[pmuller9]

To dbl check your method, search degree by the centerline method, when that looks good and repeatable you can check the valve events @ .050" method.

If the cam lobe is not symmetrical there may be a difference between the centerline method and using the opening and closing .050" points.
Not a big deal and even if there is a few degrees difference the comparison between the two methods will still show if you are close or making a big error somehow.
The halfway point between the opening and closing .050" readings is the one that counts.

 

[ledslinger29]

So I re-established my TDC, set the timing to the -8 degree keyway, and heres what I've got:
Intake opening -10.5 BTDC
Intake closing 28 ABDC
Exhaust opening 35 BBDC
Exhaust closing -13 ATDC

Card calls for
Intake opening -13 BTDC
Intake closing 27 ABDC
Exhaust opening 36 BBDC
Exhaust closing -12 ATDC

Intake hits max lobe lift at 110, stays there for a few degrees, then starts coming back down. What do you guys think?

 

[Econoline]

It sounds like you are maybe a tooth off, which would be 7 degrees @ the crank, iirc. If you were a tooth off and used 8 degree slot that would explain why you are close but off by a degree or so.

 

[wsa111]

Sounds like you are a tooth off. Who is the camshaft grinder??
I bought a camshaft from Erson & the camshaft was 10 degrees off. They did not index the shaft properly before grinding. I sent it back for a refund.
In reality even if you advance the cam 2 degrees the timing chain probably stretches about that much so you are really running it straight up in operation.
I shoot for 3-4 degrees @ when you figure the load placed on the chain from the distributor running the oil pump you will end up with 1-2 degrees real advance.
Clay Smith, Schneider, Crane, Isky & Comp cams are usually on the money. Remember Comp cams already advances most of there cams 4 degrees. Most of the others are ground straight up.
Take your time & get it right, even if you have to consult local professional assistance.

 

[ledslinger29]

My max lobe lift seems to be dead on, and all my other checks are 1 degree off except for intake open, which 2.5 off, wouldn't moving it s tooth set me 6 degrees off in the other direction? Or are you saying that i seem to be a tooth off because i had to use the -8 degree keyway? It's a schneider cam, BTW

 

[Econoline]

I had the same experience with Erson, along with base circle run out. My Schneider cam came in right on

 

[Econoline]

If you are a tooth off +7 and you use the -8 key way you'll be -1 off theoretically

 

[pmuller9]

If you do the math
Intake Center: [(180-10.5) + 28]/2 +10.5 = 109.25 ATDC
Exhaust Center [(180-13) + 35]/2 + 13 = 114 BTDC

The intake lobe center is advanced 0.75 degrees.
The exhaust lobe center is spot on.

Doesn't the crank gear have 19 teeth.
If so then moving the crank one tooth makes a 19 degree change.

 

[ledslinger29]

I think Seth is talking about cam gear teeth. The max lobe lift currently hits at 110, and lingers for 4 or 5 degrees before falling off.

 

[pmuller9]

When you check the top of the lobe for center, you come down .050" on both sides from the lobe top and find the center point between those two readings.

 

[ledslinger29]

With the -8 degree keyway being used, and using the .050 over under max lift method, the intake lobe maxes out a little above 109.

 

[pmuller9]

With the -8 degree keyway being used, and using the .050 over under max lift method, the intake lobe maxes out a little above 109.

The .050" opening and closing readings you took earlier showed the intake lobe center at 109.25* ATDC which seems to be verified by the max lift reading you just took.
You cannot get any closer with what you have and as pointed out earlier with chain stretch it will be right on.
I would call it good.

 

[drag-200stang]

A reminder, do not use the oil slinger!