Cam degreeing question on my first motor rebuild

[paul25g]

Ok, this is where I need some clarification. What exactly do you mean by jump one tooth forward?

Both the crank timing gear and the cam timing gear only have one keyway.

And is it correct that what needs to happen is for the Intake Centerline of 114.5* to be advanced as near to the Lobe separation of 106.375* as possible? And an intake centerline advanced from 106.375 (smaller number than 106.375) is preferable to an intake centerline retarded from 106.375 (larger number than 106.375).

Sorry, like I said earlier, this is my first rebuild...thanks for bearing with me!

 

[MPGmustang]

visualize this in head...

if you were able to keep everything on, and only move (rotate in running direction) the cam gear forward (where the tooth fits into the next chain link) without the chain or crank moving, you jump one tooth on the cam gear...

I don't know how to explain it otherwise lol bubba wanna help?

 

[paul25g]

Gotcha, so the cam and cam gear gets turned clockwise (advanced) to jump one tooth in the timing chain while keeping the chain, crank and crank gear in place.

Then I assume I need to measure everything again and see where I'm at (how many degrees that advanced it)?

After all this is said and done, and I'm as close as I can get....does this do anything to the ignition timing later on down the road?

 

[paul25g]

Bubba,

Standard single timing chain set from an engine rebuild kit.

 

[MPGmustang]

ONLY 1 gear moves not both gears, yes everything else doesnt' move... the cam (and cam gear) moves 1/2 the distance than the crank moves, so if it moves 10* (example) then that's 5*(example) on the crank... where u want 6+...

 

[paul25g]

Right, just the cam gear and cam.

 

[paul25g]

MPG,

Thanks a ton for all your help!

Can you confirm this for me:

Is it correct that what needs to happen is for the Intake Centerline of 114.5* to be advanced as near to the Lobe separation of 106.375* as possible? And an intake centerline advanced from 106.375 (smaller number than 106.375) is preferable to an intake centerline retarded from 106.375 (larger number than 106.375).

So ONLY the cam and cam gear gets turned clockwise (advanced) to jump one tooth in the timing chain while keeping the chain, crank and crank gear in place.

Then I need to measure everything again and see where I'm at (how many degrees that advanced it)?

After all this is said and done, and I'm as close as I can get....does this do anything to the ignition timing later on down the road?

Again, many thanks!

 

[MPGmustang]

sorry our posts are pileing up on each other... I started reading and mis read then re-read and it's already changed from what I thought I read... lol


I don't know how far 1 tooth will go, on my chian set it moved it like 6-8* I don't remember, you will have to re-measure EVERYthing again. it how it works...

the ignition timing is competely separate, it does NOT depend on cam timing... I thought the same thing but I'm running 15* advanced in ignition timing for winter and 8* for summer. but it gets hot here in AZ.

 

[paul25g]

Outstanding....think I'm seeing the light at the end of the tunnel!

I'll give it a shot over the weekend and see what I come up with.

I'll give an update when I get some results....hope this thread will be a help to others in the future!

 

[MPGmustang]

correct, you want your intake centerline as close as possible to 106 or less...

even now I'm still not sure if this is all correct, maybe someone else can help chime in with explaining it all... I can show ya but I can't find any good videos on youtube to measure duration.

Okay I think I've have been wrong in cam position. but the duration is correct...
watch this video.... I'll try to explain what you see... oh and mute the guy, you won't want to listen to him... lol
http://www.youtube.com/watch?v=_FLRAYhhKu4

@ 3 seconds he passed TDC (key point fo reference)
@ 25 seconds he reached .050 lift opening @ 178* (counting from TDC should never be more than 180*)
@ 42 seconds he reached .050 lift closing @ 82* (counting from TDC should never be more than 180*)
82+178=260* duration @ .050 lift (260* druation sounds correct but I don't think his intake lobe is posistioned @ 130* lol that sounds 'off' by alot!)

I really wish I had an engine to play with on degree'n... hopefully more will chime in...

 

[MPGmustang]

Aside from calculating using the duration at .050 method, here's what I came up with using the centerline method:

Intake centerline measured :70.5 + 158.5 = 229/2=114.5

Exhaust centerline measured :141.5 + 54 = 195.5/2=97.75

Lobe separation would be 114.5 + 97.75 = 212.25/2=106.125

Intake centerline of 114.5 - Lobe separation of 106.125 means that it is retarded by 8.375*.

Does this make sense using the centerline method?

This looks correct for finding your centerline

 

[paul25g]

I hope this doesn't sound stupid, but just to clarify, what exactly is the goal of degreeing the cam? Is the point to get the cam events to happen as close to the manufacturer's specs listed on the cam card as possible in relation to crank location? This is where I'm confused .

I'm pretty confident I've done all the measurements correctly, now I need to know what to do with this info.

Cam card calls for Intake lobe center to be 111*
My measurements using the centerline method shows 114.5*
This would mean my cam's intake centerline is 3.5* retarded from the cam card.

Cam card calls for Exhaust lobe center to be 102*
My measurements using the centerline method shows 97.75*
This would mean my cam's exhaust centerline is 4.25* retarded from the cam card.

Cam card calls for Intake valve open at .050 to be 22* After Top Center
My measurements using the .050 method shows 24.5* After Top Center
This would mean my cam's intake valve is opening 2.5* retarded from the cam card.

Cam card calls for Intake valve close at .050 to be 20* After Bottom Center
My measurements using the .050 method shows 25* After Bottom Center
This would mean my cam's intake valve is closing 5* retarded from the cam card.

Cam card calls for Exhaust valve open at .050 to be 11* Before Bottom Center
My measurements using the .050 method shows 7* Before Bottom Center
This would mean my cam's exhaust valve is opening 4* retarded from the cam card.

Cam card calls for Exhaust valve close at .050 to be 13* Before Top Center
My measurements using the .050 method shows 9* Before Top Center
This would mean my cam's exhaust valve is closing 4* retarded from the cam card.

Based on the measurements above and looking at the degree wheel, I have an Intake duration of 180.5* and and exhaust duration of 178*. Cam card calls for 178* duration for both.

Based on the measurements above and looking at the degree wheel, I have an overlap of 32*. According to the cam card, it should have 31* of overlap.

I understand that this is one retarded cam....just not sure what to do about it. I know I'll need to advance the cam in one of several methods (jumping a tooth on the timing chain, using an offset key, etc)...but what I really need to know is what is my target.

Thanks again guys for helping me sort this out!

Paul

 

[CNC-Dude]

Paul, its easy to feel overwhelmed when looking at all those numbers and trying to make sense out of it. But basically, the goal of degreeing the cam is to make sure it is installed in the correct orientation as the manufacturer has specified on his cam card. Because of manufacturing tolerances in all the componenets involved you have to be able to compensate for these tolerances to correct or adjust the readings. You have a keyway in the crank snout, camshaft, a keyway machined in the timing set on both gears, or dowel pin, plus the cam lobes themself that can all be off by some slight amount but still be in spec for production quota. In a perfect world all of these parts would be perfectly machined and all the cam numbers you are seeing would be perfectly aligned with your readings. One problem with taking the time to check all of these specs is you start to find how imperfect they really are and become even more confused. The main spec that is the most important is the intake centerline, especially if you are using the Centerline Method to degree your cam. The rest of the numbers, you are just confirming they are close to being what is on the cam card and not way out in left field. You wont be able to "skip a tooth" on your timing set, that will advance/retard the cam way too much. A degree bushing or offset keyway will be the only way to correct this unless you have a multi-keyway timing set, which you said you do not have. Just focus on your intake centerline number of 111°as being your target, and get that as close to that as you can. Its not uncommon for engine builders to even run most street engines with a little more advance, so even if you wound up with it installed at 110° or 109° would be better. Also remember that there is never any stupid questions, only stupid answers, so always ask if you have doubts about anything. Just think of advancing the cam as having the same effect as advancing your timing. Advancing your timing just one degree you might not see or notice that much of a difference, but 3 or 4 degrees you definately will see a dramatic change in how the engine operates, especially at the lower end of the RPM range where you do most of your street driving.

 

[paul25g]

PERFECT!!!

Thanks so much CNC, it makes total sense now, I really appreciate all your help!

I was just confused before on whether the point was to get the intake centerline as close to the lobe separation number as possible or as close to the intake centerline listed on the cam card.

I've read that the .050 intake/exhaust opening/closing events are more accurate measures than the centerline method, but this is just a standard rebuild for a weekend driver. So that being said, I'll do what I can to get my intake centerline as close as possible (and perhaps a tad advanced) than what the cam card calls for and live with that.

Really appreciate everyone's help!

Paul

 

[paul25g]

Got the Mr. Gasket offset key in and after a little filing, got everything put back together. Took me from a 114.5* CL to a 110.5* CL......advertised CL was 111* so I'm good to go. Thanks again guys for all the help!

Paul

 

[Frankenstang]

Hello Paul,
Congrats on getting it sorted out Sounds like the offset key worked out pretty well in your situation.

Any chance you can post a pic with the offset key installed for those curious (like myself) to see a stock timing set in stalled with an offset key?
EDIT: If you haven't buttoned everthing up already.
Thanks in advance!

 

[paul25g]

Sorry Frankenstang....already buttoned up... I should have taken a picture

The offset key for the timing gear was 0.750" long. I filed the bottom a little to get it to sit down in the crank groove and made sure the offset was in the right direction, then I pushed the timing gear on. I made note of how far the offset key stuck out from the timing gear and then removed it and cut it off so it was flush with the face of the timing gear. Then I measured from the face of the timing gear, out to the end of the keyway and cut the stock key down to fit this length. Then just set the remainder of the stock key into the crank groove and installed the balancer....worked great!

Mr. Gasket provides a 2* offset key and a 4* offset key for the inline 6.

 

[Frankenstang]

No sweat Paul, and thanks for the follow up on fitment details. This is all helpful info. Sounds like you did a thorough job of ensuring a tight fit and proper degreeing with the offset key. Look forward to hearing how it runs. Good luck