What is the relationship between the crank keyway and the rod journals for pistons 1 & 6? Extra added bonus points for knowing where TDC is when the crank and the cam gear are dot-to-dot.
bwhitejr
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| Degreeing Cam - Dot to Dot! https://www.slantsix.org/forum/viewtopic.php?t=16918 |
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| Author: | bwhitejr [ Wed Apr 05, 2006 2:19 pm ] |
| Post subject: | Degreeing Cam - Dot to Dot! |
The cam is a CompCams 252S. It is a daily driver. The TDC stop I bought was allegedly for all Chryslers. Well.... it is not for my Chrysler SL6. The one I have is 14mm but won't screw into the head because the body hits the head. That's annoying!!!! I understand the Chebbie one will work. bwhitejr |
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| Author: | Dart270 [ Wed Apr 05, 2006 4:49 pm ] |
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OK, for that cam, 102-106 is a good range. I made my own TDC stop out of an old spark plug with a 2" piece of 3/8" bolt (rod) welded to it. Lou |
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| Author: | bwhitejr [ Thu Apr 06, 2006 4:47 am ] |
| Post subject: | Degreeing Cam - Dot to Dot! |
I have been using Desktop Dyno to study the difference it would make between installing at 106* or 110* and for my application it appears to be negligible. I am usually running below 3000 RPM. I figured it be more dramatic than that. What am I missing here? bwhitejr |
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| Author: | Dart270 [ Thu Apr 06, 2006 7:04 am ] |
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I wouldn't really trust DDyno for a Slant motor. Those things are usu optimized for short stroke, big bore motors. Also, 106 is likely too high, so 110 would be a step worse. The main reason to degree is that it could be really far off, like 120 or 85 deg. That will kill ya. With that cam, 102 or 106 or 110 will not be night and day, but it will make a noticeable difference. If you are consistently below 3000rpm, then 110 will hurt you in that range. Lou |
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| Author: | dusty7t4 [ Thu Apr 06, 2006 9:59 am ] |
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Quote: Quote: I have looked around for a degree wheel, but I can't find one that says it can do a slant. am I just not finding the right one or is there one out there that will do the job but isn't labeled right? (or one where I can get close enough)? I ask because everything is labeled a v-8 wheel
There is no such a thing as a V8 degree wheel, slant-6 degree wheel, etc. Degrees are degrees. There are 360 of them in a circle.-dave |
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| Author: | bwhitejr [ Fri Apr 07, 2006 6:05 am ] |
| Post subject: | Degreeing Cam - Dot to Dot! |
What is the relationship between the crank keyway and the rod journals for pistons 1 & 6? Extra added bonus points for knowing where TDC is when the crank and the cam gear are dot-to-dot. bwhitejr |
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| Author: | sandy in BC [ Fri Apr 07, 2006 7:02 am ] |
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You can beat this to death looking for the easy answer. The easy answer is....THERE ISNT ONE! When you degree a cam you are making sure everything lines up (piston position v/s valve opening). There are many variables from the crank gear key to cam lobe centre. Even if you knew the crank keyway/piston TDC relationship you still dont know if ALL the other variables are right. If you want the cheap and easy version you can locate an approximate TDC.....roll to intake centre and do a rough figure on how many degrees. That will check that the cam timing is at least not stupid. (thats what I did when I assembled my Hughes timing set with Comp cam in rebuilt short block)....this method is far harder with the head on....use a pushrod on the intake lifter. You paid to have your cam degreed.....get him to do it right. |
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| Author: | bwhitejr [ Fri Apr 07, 2006 7:23 am ] |
| Post subject: | Degreeing Cam - Dot to Dot! |
Sorry, I am beating this to death, but the quest for the true relationship just overwhelmed me.  I just gotta know..........  I know it is better done emipirically, but the Cloyes cam shaft gear is set up for 133* 49 secs from index pin for SOME reason. bwhitejr |
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| Author: | bwhitejr [ Mon Jun 19, 2006 11:44 am ] |
| Post subject: | Degreeing Cam - Dot to Dot! |
I got around to checking what dot-to-dot alignment does for the engine. It seems that the dot-to-dot alignment puts the piston at TDC. Anyone else get the same result? Anyone? bwhitejr |
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| Author: | Doctor Dodge [ Mon Jun 19, 2006 12:00 pm ] |
| Post subject: | Re: Degreeing Cam - Dot to Dot! |
Quote: I got around to checking what dot-to-dot alignment does for the engine. It seems that the dot-to-dot alignment puts the piston at TDC.
Yes, but which TDC? (exhaust or compression stroke)Anyone else get the same result? Anyone? bwhitejr Dot to dot should get you to the TDCE position where you can quickly check the lobe centerlines and overlap event. (I have seen some gears with the dots set-up at TDC compression stroke which is not real helpful.) DD |
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| Author: | bwhitejr [ Mon Jun 19, 2006 12:40 pm ] |
| Post subject: | Degreeing Cam - Dot to Dot! |
This particular set-up was the stock '72 Slant Six. The one with the nylon teeth on the gear. I guess I could put the head on and see whether it is compression stroke or not. bwhitejr |
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| Author: | DusterIdiot [ Tue Jun 20, 2006 9:29 am ] |
| Post subject: | Lou's right... |
Quote: I figured it be more dramatic than that. What am I missing here?
You aren't missing much, Lou has some of it, the program is meant for Chebby and Ferd V-8's in mind...also it isn't really set up for cams that are close to being "stock", in the Comp Cam 252 regardless of which way you go it has a very "flat" torque curve so anything you dial into it is only a couple HP or couple of ft/lbs change...if you are looking for a change, pull the bumpstick and put something in the 268 range in there.... -D.Idiot |
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| Author: | AndyZ [ Tue Jun 20, 2006 9:55 am ] |
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A friend of mine installed a Comp Cam that was so far off, his Slant ran backward! Just kidding of course, Always degree in your cam (cannot be mentioned too many times) and always be extra suspicious of a Comp Cam for a slant. Sometimes the slugs have mis-aligned oil holes mis-drilled pulley holes, etc and who knows how far the lobes vary from each other from spec. I lucked out with mine, only off by ~1.5*. (that was after blueprinting my bottom end) |
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| Author: | Tom Drake [ Tue Jun 20, 2006 12:54 pm ] |
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Quote: always be extra suspicious of a Comp Cam for a slant.
For what it is worth the last three cams we have run in the Simca have been Comp and we have had no problems with any of them. Tom |
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| Author: | bwhitejr [ Tue Jun 20, 2006 4:50 pm ] |
| Post subject: | Degreeing Cam - Dot to Dot! |
So a new cam out of the box will need the cam drive gear drilled for offset cam bushings in order to degree the cam and put exactly on the intake centerline. Right? How are the offset bushings held in? The cam bolt/washer assembly holds in the cam, tightening against what? bwhitejr |
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