CAMSHAFT DEGREEING

Trev · Post by **Trev** » Mon Jun 20, 2005 3:29 am

Hi guys
Can someone help

Im degreeing my first cam.

I have set up a piston stop and then rotate the engine each way until it stops the divide the difference, rotate the engine 1/2 that difference then align my degree wheel up with TDC.
So anyways, i can easily find my TDC.

The figure i have been given is 0.146 thou at TDC on the inlet and the cam has 272 degrees on the inlet and 282 degrees on the exhaust at 50 thou.

So what i did was set up my dial indicator to read zero when the lifter is on the base circle and then rotate the engine untill the indicator reads 50 thou.

Then technically the degree wheel should be at 272 degrees correct?

If I am right can some explain what the 0.146 thou at TDC means
If the engine fires at TDC or 10 degreees advance then the inlet calve is open.

Trev

Trev · Post by **Trev** » Mon Jun 20, 2005 10:32 am

well its now 2;30 in the morning and i have had a gutfull of degreeing a cam

I have it now so that when i have the lifter on the base circle and rotate the engine until i have 50 thou of lift i have the degree wheel at 262 degrees.

When i change the crank sprocket 1 notch it jumps up to 292 degrees at 5o thou lift.
What am i doing wrong

Trev

k-star · Post by **k-star** » Mon Jun 20, 2005 11:36 am

I personally cannot understand your numbers.... I have no idea what the .146 number is???? Maybe someone else can explane????

I think you are ok with the way you found TDC.

Now you want to check the cam timing. I would set the indicator at zero when the lifter is on the base circle of the cam. Rotate the engine until you get to .050 lift and record that number. Continue untill you are at .050 lift on the closing side and then record that number. That is your duration @.050 numbers. (Add them both plus 180) You should be able to look at the cam card and get the correct numbers. Depending what cam you have because different grinders will put different info on there cards...............
The actuall numbers in degrees on you wheel will be where the valve events are located. This you will also have to get from the card.... Can you give us the numbers that are on the card so we can tell you what the valve events should be?????

You can also check by the center line method. Rotate the engine untill the lifter is at max lift. Set you indicator to zero. Rotate in the counterclockwise direction past .050 fall. The rotate in the clockwise direction untill the indicator is at -.050 then record the degree wheel number. Rotate clockwise past max lift untill you get -.050 on the other side. Get that number, add to the previous number and then divide by 2 and that will be the installed center line.....

Keith

bill jones · Post by **bill jones** » Mon Jun 20, 2005 12:08 pm

-Lets talk about the intake lobe only here.
--------------------------------------
-The duration is supposed to be 262 measured at .050" lift.
-If the lobe spread happens to be 108:
-262 divided by 2 equals 131.
-131 minus 108 equals 23.

(1/2 the duration minus the lobe centerline equals the intake open point)
-----------------------------------
-This means that at 23 degrees BTDC the lifter should be at .050" lift if the lobe centerline actually came in at 108 ATDC.
---------------------------------------------------------
-if you take 23BTDC and add 180 to get to BDC you get 203 degrees out of the 262 total degrees you are supposed to have.
-262 minus 203 is 59.
-So the intake closing point at .050" should be at 59degrees ABDC
-------------------------------------------------------
-the intake lobe cams specs then should be something like:
-intake opens at 23 BTDC
-Intake centerline is 108 ATDC
-intake closes at 59 ABDC
------------------------------------
-If the cam is advanced then all the numbers will shift the same amount say the lobe centerline is found to be at 102 which is 6 degrees advanced from the numbers I just listed:
-so----
-intake opens at 29 BTDC
-intake centerline is 102ATDC
-intake closes at 53 ABDC
--------------------------------------
-29 plus 180 plus 53 equals 262
--------------------------------------------
-Once you get this figured out then we can work on the exhaust numbers.

Oldhemidude · Post by **Oldhemidude** » Tue Jun 21, 2005 12:01 am

These methods work if the cam is perfectly symetrical, if not tighten up to measuring .020 before and .020 after. add reading togehter, divide by 2 and check the centerline readings, then determine if you need adjustments.

(I have run into this over and over in the last couple of years.)

Trev · Post by **Trev** » Tue Jun 21, 2005 6:50 am

Spoke to the guys that made my cam today

They told me the way that they want me to degree the cam is the cam lobe lift at top dead centre

They told me that at TDC i should have .146 thou of lift but anything between 145 and 155 would be good.

Have any of you guys ever heard of this method

It certainly sounds easier than the other methods

Trev

jdperform · Post by **jdperform** » Tue Jun 21, 2005 8:28 am

Yes I have and yes I do. It is actually the easist method of degreeing the cam. However when you are first putting in a new cam you should also run the event numbers as well to make sure everything backs up everything else. Once you know the cam is what it says it is just bring piston to tdc, and rotate the cam without the bushing if so equiped until you have whatever number you want. This method is also a good way of roughing in v to p. You can also log lift numbers at 10 deg btc on ex and 10 atc on in, times the rocker ratio. That will be pretty close to where you will have closest v to p clearance. Say .170 in x 1.6=.272 measure your valve from head surface say it's down .020, piston valve pocket depth .300 , ad deck height say .015, and head gasket .040. Add up all those mesured numbers and subtract your .272 and thats your theoretical v to p clearence. It just a rough idea but if your valve angles and piston pocket angles are close it will tell you if you need to take more in depth measurments

Trev · Post by **Trev** » Tue Jun 21, 2005 8:46 am

hEY I HAVE SOMETHING THAT WILL MAKE YOU YANKS SO JEALOUS OF

I have an auusie made holden V8

It runs 2.08 inlets, 720 thou lift, 55 cc chambers and flat top pistons no valve reliefs. I dont even need to check P to V clearance ( well i really do check but anyway)

It has 5 degree valve angle so the valves are miles away from the pistons hey

Pretty lucky arent i

Trev

jwojtasi · Post by **jwojtasi** » Wed Jun 22, 2005 7:55 am

HI TREV RAY HERE I SPOKE TO CROW CAMS AND THEY ADVISED DIALING THE CAM IN AT NUMBER 1 INLET LOBE @ TDC OVERLAP . AND WELCOME TO THE HOLDEN V8 CLUB . I STROKED A 308 TO 383 CUBES TOO FIT IN A 8METRE LONG ISUZU MOTOR HOME. RUNNING TWIN THROTTLE BODIED GAS RESERCH STRAIGH LPG DOES GREAT BURN OUTS . YOU CAN CALL ME AT QUANTUM PERFORMANCE CENTRE. OR EMAIL.

jwojtasi · Post by **jwojtasi** » Wed Jun 22, 2005 8:01 am

SORRY TREV FORGOT PHONE NUMBER (07) 32083082

Trev · Post by **Trev** » Wed Jun 22, 2005 9:52 pm

Thanks everyone for the info on degreeing the cam

I now have it idalled in at 148 thou at TDC as per Come Racing spec sheet. I had to mill out the crabk gear key way and make an offset key to get it but thats cool.

Ray, I know you, QRI is who i bought my custom CP oistons off..

Trev

Jay Allen · Post by **Jay Allen** » Thu Jun 23, 2005 3:21 pm

jdperform wrote:It is actually the easist method of degreeing the cam

As long as TDC is REALLY TDC and as long as the cam that is being installed has been Cam Dr'ed. If the numbers that are given out come from the master lobe, then accuracy is in question. I'd bet that in this case that cam was NOT measured. That is why he was given a range of lift at TDC when he called. If you are just going to use a range, hell stick it in dot to dot and let it fly. Lift at TDC works GREAT as long as the cam in question has been measured.

idunno · Post by **idunno** » Thu Jun 23, 2005 3:49 pm

Jay Allen wrote:
jdperform wrote:It is actually the easist method of degreeing the cam
As long as TDC is REALLY TDC and as long as the cam that is being installed has been Cam Dr'ed. If the numbers that are given out come from the master lobe, then accuracy is in question. I'd bet that in this case that cam was NOT measured. That is why he was given a range of lift at TDC when he called. If you are just going to use a range, hell stick it in dot to dot and let it fly. Lift at TDC works GREAT as long as the cam in question has been measured.

I agree, The intake centerline on the Card is actually a reference for a starting point. Engine builders will often vary the centerline where the cam is installed to better suit the drivers. The Engine Builder ultimatly has full responsibility to make the power. The Engine Builder knows alot more about the engine he is building and the conditions that it is subjected to than what a Cam company will with information gained in a 5 or 10 minute conversation. I had a customer so called engine builder that insisted I custom grind a cam that was advanced 1 degree more from the pin location so he would not have to use any buttons on the top gear. What was so ironic was he was not going to even check it with a degree wheel and had no idea where his timing set was going to put it in the first place. Hmmm. You people should really get to know your prospective engine builders before shucking money over, there's a big difference between an engine "builder" and a person who assembles engines.

OldSStroker · Post by **OldSStroker** » Thu Jun 23, 2005 8:22 pm

idunno wrote:
Jay Allen wrote:
jdperform wrote:It is actually the easist method of degreeing the cam
As long as TDC is REALLY TDC and as long as the cam that is being installed has been Cam Dr'ed. If the numbers that are given out come from the master lobe, then accuracy is in question. I'd bet that in this case that cam was NOT measured. That is why he was given a range of lift at TDC when he called. If you are just going to use a range, hell stick it in dot to dot and let it fly. Lift at TDC works GREAT as long as the cam in question has been measured.

I agree, The intake centerline on the Card is actually a reference for a starting point. Engine builders will often vary the centerline where the cam is installed to better suit the drivers. The Engine Builder ultimatly has full responsibility to make the power. The Engine Builder knows alot more about the engine he is building and the conditions that it is subjected to than what a Cam company will with information gained in a 5 or 10 minute conversation. I had a customer so called engine builder that insisted I custom grind a cam that was advanced 1 degree more from the pin location so he would not have to use any buttons on the top gear. What was so ironic was he was not going to even check it with a degree wheel and had no idea where his timing set was going to put it in the first place. Hmmm. You people should really get to know your prospective engine builders before shucking money over, there's a big difference between an engine "builder" and a person who assembles engines.

Boy, ain't THAT the truth!

Trev · Post by **Trev** » Fri Jun 24, 2005 4:20 am

Guys
The Cam guy you refer too is actually an innovative engine bulider in Australai who actaully builds race engines and stroker kits for our Holden engine
I trust him with his specs as Im sure if you say the cam should have been measured it would be.

Have a look at the site http://www.comeracing.com/

Go to products and then cams and then ultimate pro roller cams
Mine was the CSBR 272

Trev

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