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View Full Version : Degree specs when using adjustable cam gears-TIII



turbovanmanČ
08-16-2007, 02:35 PM
I have found nothing here, anyone have them then I can also put them in an FAQ. Just bought some adjustable cam gears for the van, :thumb:

86Shelby
08-16-2007, 03:46 PM
All 4 valves for cylinder #1 should be closed at TDCc. Close enough? ;)


Ok, here's the figures I had stored away, not sure if they are the stock ones though.
Intake: 121 ATDC
Exhaust: 104 BTDC

turbovanmanČ
08-16-2007, 04:24 PM
Thanks, I think, :eyebrows:

I know there posted on TD but I don't go there anymore.

iTurbo
08-16-2007, 04:31 PM
All 4 valves for cylinder #1 should be closed at TDCc. Close enough? ;)


Ok, here's the figures I had stored away, not sure if they are the stock ones though.
Intake: 121 ATDC
Exhaust: 104 BTDC

Yep, those are the stock centerlines. You will be glad you got the adjustable gears because my stock gears were WAY off!

turbovanmanČ
08-16-2007, 04:41 PM
Yep, those are the stock centerlines. You will be glad you got the adjustable gears because my stock gears were WAY off!

Cindy gave me a deal on some red ones she had kicking around. Perfect for my red themed engine bay, :p

So those numbers are with the crank at TDC?

iTurbo
08-16-2007, 05:08 PM
Not sure what you mean, but the crank will be at 121' ATDC with the intake valves at max lift and the crank is at 104' BTDC with the exhaust valves at max lift. Man I need some coffee.

turbovanmanČ
08-16-2007, 05:51 PM
Not sure what you mean, but the crank will be at 121' ATDC with the intake valves at max lift and the crank is at 104' BTDC with the exhaust valves at max lift. Man I need some coffee.

Ok, gotcha. Now I need some coffee, ;)

iTurbo
08-16-2007, 06:17 PM
Keep in mind that max lift occurs over a number of degrees on the wheel, so you'll need to read the degree wheel before/after max lift and divide by two to get the true centerline. For example, I read the degree wheel at .020" before/after max lift and then double check using .030 and .040 before/after max lift just to be sure my readings are consistent. Hope this makes sense! Once you do it and visualize the process yourself with everything in front of you it really is pretty easy. For me, the most difficult part was setting up the degree wheel and dial indicator correctly.

turbovanmanČ
08-16-2007, 06:21 PM
Thanks, I have read about it but never done it personally. This will be my first time actually doing it.

turbovanmanČ
09-20-2007, 01:29 AM
Man, this is hard to do, engine is so hard to turn over, :(


Ok, done. Intake took along time just to be sure but exhaust took 5 mins, I cheated. Intake is out 2 deg, ex 3 deg or 1 line and 1.5 lines.

I did the intake then put it at TDC, I checked the alignment hole at the intake sprocket, it was bang on, drill bit slid thru. Checked the exhaust, off. So aligned it then checked it, bang on, opens at 104 deg. :thumb:

Xtrempickup
09-21-2007, 06:42 AM
sounds like fun I think I will have to prepare to put my stage 1 cams in and the gears, but I dont think I can do the centerlining without help and i have to see if my friend has the dial indicator

turbovanmanČ
09-21-2007, 02:40 PM
I am soooooo glad I did it on an engine stand.


BTW, after removing the timing belt to fix my sticky cam, the factory marks aren't bang on, the intake is off a little bit but the exhaust, you can slide a drill bit thru easily.

iTurbo
09-21-2007, 04:00 PM
Ya doing it on an engine stand would be a lot easier. It's not so bad doing it in the car (or van in your case) but it's a little tougher to read the wheel and turning over the engine about a million times gets old real quick!

I checked the centerlines when I initially got my Spirit R/T running with the stock cam gears. IIRC, the exhaust was sitting at 99' BTDC and intake was at 124' ATDC, so both were retarded. I don't think it was off a tooth either, because if it was, it would have been way more off than that. I'm now using the centerlines LWP suggested for my stage I cams (108'/118').

Turbo3Iroc
09-22-2007, 01:12 AM
BTW, after removing the timing belt to fix my sticky cam, the factory marks aren't bang on, the intake is off a little bit but the exhaust, you can slide a drill bit thru easily.


Simon, this is why you degree the sprockets. The cams or sprockets aren't off, the belt is. You could re-tension that same belt and come up with totally different numbers. This is why it's useless to use the cam offset keys.

Kelly

turbovanmanČ
09-22-2007, 03:21 AM
Simon, this is why you degree the sprockets. The cams or sprockets aren't off, the belt is. You could re-tension that same belt and come up with totally different numbers. This is why it's useless to use the cam offset keys.

Kelly


Well I rechecked it after I put the belt back on and they were still in spec. Interesting about the belt theory though.

Directconnection
09-22-2007, 01:56 PM
Re-check it after breaking it in and I would guess it will give slightly different readings due to belt stretch.

iTurbo
09-22-2007, 09:57 PM
That is one reason the sprockets are so nice. You don't have to mess with the belt tension at all. I also would not be surprised to see the centerlines change a little as the belt gets some miles on it.

MOPAR2YA
09-26-2007, 02:07 AM
Before I got the adj gears, I chassed my tail for 2 days trying offset keys...And the belt tension will throw the cams out.

BTW. iTurbo, did you get your issues figured out?

iTurbo
09-26-2007, 06:01 AM
BTW. iTurbo, did you get your issues figured out?

Hello Wallace, to answer your question: yes and no. On the one hand the car has been VERY reliable, probably the most reliable TM I have ever owned yet. I have most every issue worked out but some things are still mysterious. I haven't been able to get more than ~12 in/hg vacuum at idle, and the power band doesn't start until about 3000 RPM. From 3k RPM to redline the car hauls! Below 3k RPM the car is very sluggish and throttle response is a little wierd. It is difficult to take off from a red light without lugging the engine or riding the clutch or major fanfare. For in town driving, it can be a bear. Add to the fact that I have a 3.50 final drive ratio so that makes it a little worse in that respect as well. And did I mention I live at ~4500ft elevation!

So it very well could be that nothing is wrong and it is simply the combination of parts that I put into the car; mostly between the cams (shifting power upwards) and the lower final drive (making it a bit tougher stay in the power band around town). It has taken some getting used to for sure. It is a very different kind of 'fast' than my other cars. The torque curve feels a lot different but the R/T pulls hard to redline and can really stretch it's legs. I have to admit I'm surprised no one else with the LWP stage I cams says anything about adverse driveability or low RPM performance. Some times I think something else might be wrong but I just can't find it...the car is just lazy down low and that is all there is to it. Modify driving accordingly;)

I probably would experiment with it more but have been busy with my TIII SL project. That car is going to be 2.5L mostly because of my experience with the Spirit R/T so far.

turbovanmanČ
09-26-2007, 12:50 PM
Before I got the adj gears, I chassed my tail for 2 days trying offset keys...And the belt tension will throw the cams out.

BTW. iTurbo, did you get your issues figured out?

I couldn't even imagine using offset keys, that would take hours, :mecry:

Jeremy, maybe take it to a dyno and play with advancing the intake and exhaust cams or ???? to see if you can lower the powerband or just tweak it 2 degs one cam at a time and see what happens?

iTurbo
09-26-2007, 02:57 PM
I've messed with the cam timing a lot. I've finally come to the conclusion that it isn't going to fix the low end. Advancing the cams helped, but generally if I moved too far from the LWP centerlines it would only give me even less idle vacuum and just didn't seem to help all that much.

I wonder if maybe I need a recal at this point? I have a hunch the car is running leaner than it should during cruise and light accel. The car gets wonderful gas mileage and it's not difficult to get over 400 miles per tank in town. The stock turbo seems to spool up just fine. You can hear that sucker spin up just touching the gas!! But if you look at the narrow-band A/F gauge at idle/cruise, it looks crazy. It 'bounces' (sorta) but not like my other cars. The sweeping movement is so fast it is mostly a strobe affect. The only time I have ever seen an A/F gauge behave like this is when my other cars are in the process of running out of gas while driving. No problem at WOT though.

Currently the car has stock cal, MP +20s, 3" exhaust, LWP cams, ported exhaust manifold, A568 w/3.50, OBX, and a few other little things. I've messed with the base pressure a lot too and I have it at ~45 psi fuel pressure. Didn't seem to run any different with stock injectors though, except less fuel at WOT. I still haven't had the boost above about 10 psi!

CaptMoe
04-26-2011, 02:24 PM
All 4 valves for cylinder #1 should be closed at TDCc. Close enough? ;)


Ok, here's the figures I had stored away, not sure if they are the stock ones though.
Intake: 121 ATDC
Exhaust: 104 BTDC

bump...

turbovanmanČ
04-26-2011, 05:30 PM
What are we bumping?

86Shelby
04-26-2011, 10:58 PM
My totally amazing, hope you're sitting down before it knocks your socks off post of course! :lol:

Directconnection
04-27-2011, 10:17 AM
Are you guys degreeing these at the valve, or at the cam?

Re-grinds and cam grinders typically call for at the CAM from my conversation just minutes ago with my cam grinder.... (hence the cam card #s)


edit: I typed "at the valve" when I meant to say "cam...." doh...!

turbovanmanČ
04-27-2011, 02:25 PM
At the valve aka rocker arm.

Directconnection
04-27-2011, 03:04 PM
At the valve aka rocker arm.

Simon, I hope you're not doing it at the rocker....

PS: got my shat all boxed up yet? ;)

86Shelby
04-27-2011, 03:46 PM
Simon, I hope you're not doing it at the rocker....

How else would you degree the cam? If we shouldn't set the indicator on the end of the rocker I don't know of a good place to put it for an accurate reading.

turbovanmanČ
04-27-2011, 04:10 PM
Simon, I hope you're not doing it at the rocker....

PS: got my shat all boxed up yet?

Why wouldn't we? There is a direct mechanical link, no lifter to take up the action, hence why setting the cam timing on these engines is cake.

Yep, just need to get to the mail box and ship it out, :p

Turbo3Iroc
04-27-2011, 07:11 PM
I've done it off the rocker and off the retainer. As long as the lifters are pumped up any difference is negligable.

Directconnection
04-27-2011, 09:25 PM
Why wouldn't we? There is a direct mechanical link, no lifter to take up the action, hence why setting the cam timing on these engines is cake.

Yep, just need to get to the mail box and ship it out, :p

The geometry of the rocker isn't as direct as one would tend to think..... it's ratio varies as it sweeps across the valve, and also... advances and retards timing vs. what the cam is actually ground to. But.... you can still find your centerline I am sure... I was talking to the cam grinder tonight and his cam card is based off the cam (obviously) and I shouldn't go off the cam like on a sbc due to the way the rocker plays an important role in the ramping, but the final word off the valve... except w/out him having a complete head, he can't give me an exact # even though I sent him a rocker (they'll compute it later for me)

The specs I gave him from this thread on page one, he said those #s show that the cams have been retarded quite a bit.

turbovanmanČ
04-27-2011, 09:35 PM
The specs I gave him from this thread on page one, he said those #s show that the cams have been retarded quite a bit.

Can't remember which but IIRC, the exhaust cam is very retarded. I tried to advance it, didn't like it too much.

Your also forgetting Steve, we set these at max lift, so the rocker arm geometery changing has nothing to do with it.

Directconnection
04-27-2011, 09:38 PM
Can't remember which but IIRC, the exhaust cam is very retarded. I tried to advance it, didn't like it too much.

Your also forgetting Steve, we set these at max lift, so the rocker arm geometery changing has nothing to do with it.

Oh, I understand.... 10 degrees each way and find the middle.... the valve is just more accurate.

turbovanmanČ
04-27-2011, 09:40 PM
Oh, I understand.... 10 degrees each way and find the middle.... the valve is just more accurate.

I disagree, unless you install a solid lifter.

Directconnection
04-27-2011, 09:56 PM
I disagree, unless you install a solid lifter.

You guys aren't using a solid lifter?

turbovanmanČ
04-27-2011, 10:33 PM
You guys aren't using a solid lifter?

Why would we? The rocker arm works just as well.

iTurbo
04-27-2011, 10:56 PM
That would be a great KC article if somebody showed how to make a solid rocker assembly for doing cam timing on a TIII. I was pulling my hair out trying out different centerlines on my Spirit R/T because the dial indicator tip would walk around the tip of the rocker and it's really pretty difficult to get the indicator inline with the motion of the valve because the rocker moves on an arc (pivots on rocker shaft).

bakes
04-27-2011, 11:16 PM
http://www.allpar.com/mopar/t3-centerlining.html

iTurbo
04-27-2011, 11:21 PM
Ha that is pretty cool, I may have to try making one of those. So if you made one would you just adjust the screw for 0 lash at TDC and tighten the lock nut, and then you would be able to attach dial indicator to valve retainer for direct reading, correct?

Also, what thread size would you guys use for the screw? I don't have a whole lot of rockers to mess with, but I'm thinking 4 or 6mm fine thread?

turbovanmanČ
04-27-2011, 11:33 PM
Honestly Jeremy, I've never had an issue with the pointer moving around, maybe use another rocker or file one a bit flat at the tip.

iTurbo
04-27-2011, 11:46 PM
Yeah, I know what you mean as I was able to get repeatable results using the regular ol top-of-the-rocker method. But still, I found that the difference in motions (valve going up/down, and rocker pivoting) skewed the readings somewhat. Another thing that really bothered me is that the dial indicator shaft would get side loaded somewhat and change the axis of it as the rocker surface pivoting made it move around. You really couldn't put the dial indicator tip in the oiling hole (the obvious spot) and expect it to stay there during the whole revolution.

Turbo3Iroc
04-28-2011, 03:02 AM
You guys aren't using a solid lifter?

I repeated results from a pumped up lifter to reading off of the valve retainer.


Ha that is pretty cool, I may have to try making one of those. So if you made one would you just adjust the screw for 0 lash at TDC and tighten the lock nut, and then you would be able to attach dial indicator to valve retainer for direct reading, correct?

Also, what thread size would you guys use for the screw? I don't have a whole lot of rockers to mess with, but I'm thinking 4 or 6mm fine thread?

This tool really isn't necessary. If you want to take the oil variable out of the equation take the readings off the valve retainer.


Yeah, I know what you mean as I was able to get repeatable results using the regular ol top-of-the-rocker method. But still, I found that the difference in motions (valve going up/down, and rocker pivoting) skewed the readings somewhat. Another thing that really bothered me is that the dial indicator shaft would get side loaded somewhat and change the axis of it as the rocker surface pivoting made it move around. You really couldn't put the dial indicator tip in the oiling hole (the obvious spot) and expect it to stay there during the whole revolution.

If you position the tip of the dial indicator perpendicular to the rocker and as close to the tip as possible the side loading is very minimal. I might be able to dig a pic up.