Degrreing My Cam Tonight, Questions And Critiques??

[Guest iskone]

I need to verify not only cam timing but my cam specs. I've got 4 differnet specs for this cam over the last year. Diferent Lift/ICL/LSA/Duration. Plan is to start with the lift then duration and narrow it down. As per advice from Braap I'm going to write down the lift at different duations. Sounds like the best plan so far.

 

Here are the specs.

 

1.

106 degree lobe center, 280 degree duration

ex. and in., .327 cam lift, .480 valve lift, 68 degree overlap,

intake timing - open 34 BTDC, close 66 ABDC, exhaust timing - 66/34

 

2.

Int. Lift .562

I.O. 22 btdc Duration 247 degrees

I.C. 45 abdc Int. lobe center 101.5

 

Exh. Lift .552

E.O. 46 bbdc Duration 246 degrees

E.C. 20 atdc Exh. lobe center 103

 

In this configuration, this cam would be 3/4 degree advanced.

 

3.

.580"/278° 108 centers

4.

530" Lift, 306 degree duration on 102 centers

 

 

Can you belive all these different specs I've got? After looking closer lift will tell me a whole lot. I thought some had the same lift. You can also see I don't have complete specs for everything I just listed.

 

Now to the questions. When degreeing a cam is there some trick to turning the motor the oppiste direction w/o loosing the bolt too much that the wheel slips? I've had my share of problems with that bolt coming loose and screwing up my timing (dizzy driven off the crank w/ belt).

Are there any other little tips?

 

Yes. I do plan to buy an adjustable Nissan Compition Sprocket

 

 

Thanks and wish me luck!!!

 

Isk

 

[BRAAP]

Isk,

First off, there is no need to rotate your engine backwards and for degreeing the cam, you should NOT rotate the engine backwards. Rotating the engine backwards while degreeing your cam will not only loosen the crank bolt if it isn’t tight enough, but will totally change the cam timing in relation to the crankshaft as the tension side of the timing chain then becomes slack which essentially advances the cam giving you totally erroneous values. Just rotate the crankshaft clock wise for EACH and EVERY time that you need to rotate the crank. As mentioned in the “how to degree your cam” sticky here in the L-6 forum, always rotate the engine in the direction it rotates while running which just happens to be clockwise as viewed from the front. This will keep that bolt from coming loose and help keep the cam timing where it would be as if the engine was running, which is what we are checking right? Cam timing as the engine is running?

As for which cam you might have? If you have a dial caliper or digital caliper handy, you can measure the cam lobe lift. This is how to do that. Measure the cam lobe across the nose, note that measurement, then measure the lobe across the base circle which will give the smallest measurement and make note of that. Now subtract the base circle measurement from the lobe measurement and that will be your “cam lobe lift”. Now take that “lobe lift” number and subtract your valve lash, (OE cams, it is .010” for intake and .012” for exhaust, aftermarket cams are different, but typically .008”-.010” is common). Now take this new number and multiply it by 1.5, which is what the rocker ratio is supposed to be for L-series engines, (it isn’t exactly 1.5, but 1.5 is close enough to give you an idea of what lift this cam will deliver). That will be your valve lift. If it is anywhere near the .477”-.483” range in your calculations, then you more than likely have the first cam you listed, or at least one with similar specs in regards to lift and duration.

 

Hope this helps… Good luck

[Guest iskone]

Insert the “piston stop†into the spark plug hole far enough that you know the piston will contact it on its way up the bore before hitting TDC, (see fourth pic “ABOVEâ€). Now slowly rotate the crank till the crank stops, that will be the piston contacting the “piston stopâ€. Do NOT force the piston any further up! Set the degree wheel to “0†degrees TDC at this point without rotating the crankshaft. (See the top pic BELOW). Now rotate the crank the other direction till it contacts the piston stop again which in this case ended up registering 57 degrees. (see second pic down.) Half way between this point and “0†on the degree wheel is ACTUAL TDC, which is 28.5 degrees in this example.

 

 

 

Taken from above this statment made think I need to turn it the other way.

 

Now rotate the crank the other direction till it contacts the piston stop again

 

What am I not understanding? I'm I suppose to remove the piston stop the first time it hits, roatate the crank past TDC, re-install the stop, then rotate till contact, then do the math too find TDC.

 

For lift it would be faser I suppose to use the method you mentioned. I'll use that first then plot things out too make sure what duration I have. Hopefully I can figure out the centerline too. If not that's partly why to have the adjustable sprocket.

 

 

Thanks

Isk

[olie05]

You can turn the engine backwards from the camshaft side of things to maintain proper tension on the chain.

[Guest iskone]

Ok, I jsut did the caliper measurments and based off that it is the #2 camshaft specs. I was off .0045" on the exhaust and spot on the intake.

I used the .010/.012 valve lash math verify the duration and IO/IC, EO/EC next then saee if she is the one.

 

More duration then the #2 cam would've been nicebut with that narrow center it wouldn't evn work, either way it's suppose to be a good cam and my butt tells me it is.

 

 

Isk

[Guest iskone]

ARRRRGHHHHHH

 

My dial indicator stand doesn't fit my dial indicator!!! I tried to rig it but it's not looking good. I hope the carry them at Sears.

 

Isk

[BRAAP]

Ah, yes, I stand corrected. I apologize for muddying the waters. When locating TDC using the piston stop, you will need to rotate the engine backwards. Sorry about that Isk.

The piston stop should have a hole through the middle of it to allow air to escape and enter the cylinder as the piston travels through its stroke with the valves closed. Also, remove the rest of the spark plugs and that will allow the engine to rotate easier as well, hopefully enough that it wont loosen your crank damper bolt. Also, you could remove all the rocker arms except for cylinder number one and that will take some of the resistance away while rotating the crank.

Sorry for confusion and good luck with getting your dial indicator set up…

[Guest iskone]

My stop doesn't have a hole in the center. It's the type that has an adjustable bolt. I'll just mark it location and remove the inner bolt.

 

I rigged my stand to work but I'm thinking I need a longer plunger. I can't get my dial right oin top of the retainer because the face hit's the cam tower. Went everywhere that's open I hope to find an extention tip tomorrow.

 

Isk

[Guest iskone]

More duration then the #2 cam would've been nice

 

I think I was way off base with that statement. I was thinking advertiesed duration not @.050", I saw a SBC cam that has 246* @ .050 and lists the advertiesd duration at 308

 

I need a calc for .050 to seat to seat. I' not sure if that 308 figure is right.

 

BTW: I've tried every single store I can think of to find an extension for my dial indicator. I'm gonna try to fab soemthing up, but I also tired a tap and die from all those stores too. No luck.

 

Isk

[Guest iskone]

How in the world to do stop the crank from moving!?!?!?!

 

Every time I have to loosen the bolt to move the wheel my crank moves about 10* on the wheel. So far the farhest I've made it was resetting to TRUE TDC but then it gets screwed up again. I'm turning the motor with the cam when I have to go backwards and even holdong the cam when I have to loosen or tighten the crank bolt. I think the slack in the chain is causing the problem.

 

I've tried to compensate for the crank moving but then it started moving less then ten or more. But that point it's already moved enought that I can't reset it at that step and have to start over.

 

Getting frustrating!!!!

 

Maybe a longer crank bolt that would allow me to have 2 nuts on it would be the trick. I could use the first nut to turn the motor and the second too secure the wheel.

 

isk

[Guest iskone]

Okay say Im done with this fore the most part and here's what I got, don't qoute these ceters as fact as I just used the peak lift values.

 

2.

Int. Lift .562 .552

I.O. 22 11 btdc Duration 247 degrees

I.C. 45 55 abdc Int. lobe center 101.5 115

Exh. Lift .552 .552

E.O. 46 35 bbdc Duration 246 degrees

E.C. 20 28.5 atdc Exh. lobe center 103 91.5

 

 

So the closet I can get this cam to be "the one" (lol) is if I have the cam retarded 12* or if it's on 112 centers. If I punch in either of those 2 it is VERY close. However I have not done the LSA yet so the 102.25 could be wrong.

 

 

 

Anyway I'm way tired so I'll mess around wit hti tomorrow.

 

Isk

[Guest iskone]

So I verified the cam timing is at 1. All links are where they should be, #1 dowel hole is lined up with the notch. There's no way it could be retarded that much with a stock sprokect anyway.

 

Looks like I dropped the crank key in the pan so I pulled the front cover and still can't find it. I always flipping lose that thing, never fails. I'm gonna try to poke a magent around in there before I have to pull the pan, all those bolts take forever.

 

I think I'm gonna check valve lash once it's back together. I know it's cold but I have .015 on my #2 or #3 exhaust and that seems like too much. I did notice the valve train was louder then usaual when I got her back.

 

Isk