Surprised I can't find stock cam #'s in my FSM or parts list book.

I'm degreeing my cam and I need to know stock cam intake opening and closing marks, so I can figure out where my cam is now. Had it re-ground recently but just to stock specs, though my grinder told me he added a little nominal lift to help it breathe better.

Is it necessary for me to know duration, lift, etc? I would think not. All I'm trying to do is get in and get out: I need to degree the cam (based on recommendations to do so), see what it is, advance it if necessary for performance, and then move on to complete the rebuild.

Thanks all.

It's in the FSM in the back of section 9 -- Engine.

I have only early manuals with the early valve opening numbers.

The 67 manual I have says:
Intake opens 10° btc
IC 50° abc
Exhaust opens 50° BBC
EC 6° ATC

with 240° intake and 236° exhaust duration.

BUT, if you had it reground they probably went with the 1971-up 244° duration specs.

But really I think you are barking up the wrong tree. The cam is NOT a stock cam any more. You can't generally change lift without changing duration. So your cam will most likely not match up to stock specs. Trying to make it match the stock numbers is just going to mislead you at best, or make you frustrated at worst.

Since you don't have a cam card, you have to make one.

Install the cam 'straight up' on the timing marks. Go use your new degree wheel and dial indicator to find the intake and exhaust opening and closing points. THEN post up those specs here and we can help you figure out where to time it.

The 76 manual I have says the late cam should be:
Intake opens 16° btc
IC 48° abc
Exhaust opens 54° BBC
EC 10° ATC

with 244° intake and 244° exhaust duration. .406 lift intake .414 lit exhaust

I pressed my cam grinder for a card when I had him do it, and he told me it's a stock cam, that any mods he made were so minor that one would never notice a deviation from stock figures. So, I have to go with that for now.

I've pored over the engine section in the 63 FSM, but no dice, no mention of opening and closing specs anywhere. There's ONE short paragraph buried in the middle of the chapter that talks about Checking Valve Timing, where it details that with the head/valves installed, and checking #1 intake with a dial indicator installed to read on #1 intake valve spring retainer that at .019, I should get a reading of 12° BTDC.

I don't totally understand this since I thought I'm measuring at .050. What I'm guessing is that .019 above refers to an altered number that takes into account the rocker ratio since they're measuring there. Still doesn't get me what I need.

Factory numbers are not at .050 lift, they are "seat to seat". But unless you are working with a NOS cam it doesn't matter. Install it straight up and find the actual numbers, then you can see where it should be for best performance with your compression ratio, etc.

Took 15 minutes to find this.
would probably be handy to have it in the FAQ section somewhere.
http://users.hal-pc.org/~bwhitejr/Slant_Six_Cams.pdf

Brendan.

_________________
1963 AP5 Valiant 225 PB 904 Stock except extractors & 2 1/4 inch exhaust.


1962 S series valiant 225 PB auto. factory every thing. Full restoration job.
Currently on hold till AP5 is on the road.

Brendan, thanks. I did find that PDF. Not sure if I should be looking at the first "Chrysler Valiant Stock" line for my particular application ('63 Dart), or even if this has the right information for my car/year. There is one line item with one comment that specifically says "1968 Stock" but nothing else is identified by year, regarding the line items that say "Chrysler" on them. Only other cam grinders and their catalog #'s.

The first cam is the one used before 1967. The next is the 67-71 cam (the numbers I gave you). DI gave you the numbers for the 71-up cam.

Ok, here goes. Something is not right, but I did check my TDC readings twice to be sure I wasn't off.

Intake opens at 11° ATDC @ .050 lobe lift. Ok, definitely not on stock spec, but I'll go with it.
Intake closes at 152° BTDC @ .050 lobe lift. :!: Can't be right, but I checked three times.

This would give me 343.50 rate of duration (opening + closing x 180).

This varies dramatically from the 180 rate of duration for a stock cam intake shown in the table. What did I do wrong? I was watching a Comp Cams YouTube video tutorial showing how to degree a cam, though they were measuring opening and closing events at the valve spring retainer and taking into account the rocker ratio. I believe they did start at 0° at the cam lobe heel. I didn't have to do their method since I'm measuring at the cam.

Here's my process:

1. Zero'ed the degree wheel at TDC.
2. Set up #1 intake lifter, pushrod, magnetic base and dial indicator.
3. Rotated crank (clockwise), found lowest readout on dial indicator. Set to 0°.
4. Noted max lift on dial indicator for #1 intake at .265. Seems copacetic.
5. Recorded #1 intake opening event at .050 at 11°ATDC on the degree wheel (again, rotating clockwise only). Ok....
6. Recorded #1 intake closing event at .050 at 152° BTDC on the degree wheel. Again
No rotating counter-clockwise.

Stock cam values according to the table supplied are intake opening at 4°, closing at 48° (table column says "Valve", but I assume they mean @ the lifter, because they give no other opening/closing values). At face value, compared against these numbers, that means I'm off by 7° from stock opening, and 104° from stock closing. Difference of 55°. Wow.

There are some micro-variations due to the pushrod-dial indicator setup. I can't touch the dial indicator (as in, zeroing it out) without causing a jump and subsequent adjustment in the reading, but it usually comes back to zero with a few rotations. Also, I was cheap: I printed out a degree wheel and adhesive-backed it with stiff cardboard. Seems to work ok but if I were building engines frequently, obviously I'd spring for something better. Question here: is it possible that my readings are off because I printed out a degree wheel that is NOT the right size???

Trying to get this....

I'm going to have to see if someone can double check my math as I normally do all this hands on and not looking at the wheel and block in front of me is a little out of the norm....so I may get this backwards...
(disclaimer)

So, we know from the table that the intake centerline for a stock cam is 106-107 depending on the year of cam.

We know that currently you have .050 IO at 11 ATDC, and the .050 IC is at 152 BTDC (which I will assume is counted from TDC clockwise on the wheel)...IC is typically ABDC so the number is really TDC-BDC=180 degrees +32 ABDC...212 ABDC (we need to compare apples to apples so each event starts from the same point on the clock in relation to the rotation of the engine).

The centerline is the average of the two points 11IO and 212IC
212+11=223/2 =intake centerline is at 111.5

111.5-106=5.5 degrees retarded

Before we go drilling the gear and adding bushings or lead shot...we might be able to save some time and money if we can advance the cam gear one tooth...

Count the teeth on the cam gear (lets say my silent chain cam gear is 38 for this example), the greeks say that there are 360 degrees in a circle...
360/38 = 9.47 degrees per tooth (note that rollers and silent chains have different tooth counts so verify what you have, don't assume, matk the start tooth with a marking pen and count).

So back to the real issue:

If we advance the cam gear one tooth...(round up), so 111.5-9.5= 102

Stock cam intake centerline is 106 and if advanced one tooth (102)...that would put the cam 4 degrees advanced (good for low end torque and general street driveability).

When you check your cam events the same thing will occur (but may be a fraction off due to 'rounding'):

So if you advance it one tooth, your IO occur sooner and will be 11ATDC-9.5=1.5ATDC and the IC 212-9.5=202.5 -180 = 22.5 ABDC...

If you wanted less advance, and you bought the bushing set, you'd add the bushing and place it for retarding or advancing per the need required (say you only wanted a 104 centerline so at 102, the bushing would retard the gear 2 degrees for a 104...). If needing lots of advance/retard, the same calc can occur at the crank gear (if it's the type that does not have the extra key ways....)

Another item to note for lurkers, if you have an assymetrical lobe mystery cam (where the opening ramp is not sloped like the closing ramp), and you are trying the centerline method, the .050 measurement will need to occur at the top of the lobe or crown/on either side of the 'max' lift to determine the centerline vs. some cam companies that do the .050 at the base of the ramp/off the seat (comp used to do .015...).

Good luck,

-D.Idiot

OK everyone has their own way of doing it bu I'm getting different numbers than DI ...

Assuming you are turning the degree wheel/crank the correct direction, I see:

Intake Open = 11 deg ATDC (your measurement)
Intake Close = 28 deg ABDC (360-152 measured BTDC = ATDC - 180 = ABDC)
Intake duration at .050 = 197 deg (180-11+28)
Intake centerline 109.5 degree (197/2+11)

As we said above, you are comparing apples (stock cams measured at 'lash') to oranges (some random cam measured at .050)

Correct assumption: that's what I did.
How is IO typically an ABDC event? Why and from where are you obtaining 32°? I'm reading the degree wheel and trying to follow what you're doing, but you're losing me.
Once I understand how/why you got 32°, then this other math makes sense to me.
Dumb question, but advancing the cam gear one tooth, would be rotating the cam gear clockwise, yes? Just double-checking.
Got it. Thanks DI.

Dont add the 180 *
you only add 180 * if the valve opening event occurs "BEFORE" TDC.
Eg:
IO at .050" = 5 *BTDC + 180* (which gives degrees to BDC in this case 180* + 5* = 185*)
Then get valve closing event , which is generally referred to as * ABDC
Eg 30*ABDC
so 185* + 30* =215* duration.

Now your cam:
IO = 11* ATDC ( so we minus 11* from 180* to get to BDC)
11* ATDC to BDC = 169* (180* -11*)

IC = 152* BTDC (or 28* ABDC)

SO duration at .050" is 169* + 28* = 197*

OK so this is the duration at the cam lobe.
However this is not the duration at the valve head.
Remember the rockers have a ratio of about 1.5 :1.( this will also explain your low lift measurements)
So the best place to measure for duration is at the valve itself.

If you are looking for the cam lobe center line , the method you used( the direct lobe measurements) are fine ,as we are mainly concerned with finding the point mid way between two points ,not actual valve opening time .

So your intake lobe center line is:
IO at .050" =197*
197* /2 =98.5* will give the intake lobe center line.
Now your IO @ .050" at 11* ATDC
so add 98.5* to 11* =109.5*
Your intake lobe center line is 109.5 * ATDC.

DI I think you got some things incorrect there.ie Intake open ABDC? you also did not take the 11* from 180* as IO was ATDC.
I have a wheel printed out ,and keep it next to this computer for cam theory work.
Its a lot easier that way to visualise.
Remember to spin the wheel clockwise.(engine rotation)

Do your exhaust lobe the same way(remember the #1 exhaust lobe is at the end of bump stick)
after this we can work out exhaust lobe center line and then determine the cam grind center line, which can then be compared to valve overlap TDC.
this will then determine cam advance or retard.

If you had a cam card( thanks Mr Lazy cam Grinder) all you would need to do ,to determine cam advance,is compare your installed intake lobe centerline (as found above) to that on the card.

Hope you can get your head around that lot!

Brendan.
P.S last 2 posts happened while I was typing slowly

_________________
1963 AP5 Valiant 225 PB 904 Stock except extractors & 2 1/4 inch exhaust.


1962 S series valiant 225 PB auto. factory every thing. Full restoration job.
Currently on hold till AP5 is on the road.

Robertob

you posted I think that should be 180-11+28 not a cool smiley!!

which is 197* !!

_________________
1963 AP5 Valiant 225 PB 904 Stock except extractors & 2 1/4 inch exhaust.


1962 S series valiant 225 PB auto. factory every thing. Full restoration job.
Currently on hold till AP5 is on the road.