Guys,
My engine is almost ready to assemble and I'm having problems understanding what Comp Cams wants me to do pertaining to the cam. They sent me a new timing chain and gears for the crank and Cam. The crank gear has three keyways cut in it, a -4, a "0", and a +4. They say to use the "0" mark when I install the cam. I was under the understanding that if you had the No. 1 piston top dead center and the cam and crank gears on "0", thats where the cam was suppose to be. Am I wrong or do I have to go through the Degreeing Camshaft routine. It's a 268H cam, suppose to be 106 degree centerline( or something like that). I thought I'd be able to use my original balancer to set timing with.
I had visions of not having to learn anything new, at 57 I'm entitled to start forgetting things, not having to learn more.
Thanks
Jim

 

well you can install the cam "straight up" or at the 0 mark with the engine at tdc, but it is always a good idea to degree the cam. But installing it without degreeing(?) it will not hurt anything. doing this will set the valve timing. your balancer is just used to set ignition timing.

 

set the 0 mark with the mark on the crankshaft gear with #1 piston at tdc.

 

using 0 or straight up is fine. The cam has 4 degrees of advance already. I think there is a wrong way to time an engine. Theres an intake, compression, power, and exhaust stroke. JUst bringing the piston up to tdc means you got 50% chance of ****ing it up. You will want to find the end of the compression stroke. You can use 2 lifters to see whats going on. Then the cam gear dot needs to be straight down and the crank dot straight up. Someone correct me if my thinking is wrong.

 

the cam is what basically makes the compression stroke and the exhaust stroke. it is what makes the valves open when they do. so as long as the engine is at tdc you are fine. it is ignition timing that can be out 180 degrees.

 

Valve timing is one subject that's made my vision blur and head hurt; there's a lot to read up on. And yes, it does affect performance characteristics.

Unless you are going to the races it's nothing to obsess over. Some people might degree to verify the valve events and circumvent QC issues. Just one more way to keep manufacturers honest.

Jim if you don't have a dial indicator to put #1 at the top of it's dwell, lining up the crank keyway should get you halfway home. The other half is lining up the cam index mark. It's cool that Comp sends an adjustable crank gear, even if it's more than you plan on using.

Like Durk said, use the balancer for ignition timing.

 

Unless you've got time, money and an interest in learning how to degree a cam, install it straight up. At the "268" level, gains would be minimal if any. Odds are, it's optimal at straight up.

otherwise, plan on $50-$100 in tools, plus an hour or two of learning and setup.

you need a dial gauge, a degree wheel and a piston stop.

here is a decent article:
http://www.cranecams.com/?show=article&id=3

 

Guys,
Thanks for the replies, I took a second look at the cam. Its an XE256H-10 comp cam. The guy at the machine shop ordered it. He ask me what I wanted to accomplish with this engine. I told him I wanted to be doing 30 mph, tromp on it and have it come out from under me. So this is what he ordered me.
I've decided to install the cam straight up, then check it with a degree wheel. How hard could it be. After all, I rebuilt my Lycoming 320 and haven't had any problems in 700 hrs.
I found in the instructions that degreeing the cam was an option, but recommended. So I guess I'll do it. Still doesn't make sense, I can see it if you use the original crank and cam gears but they sent me the valve springs, cam gear,crank gear, chain and lifters in one kit. Go figure.
Thanks everyone.
Jim Nolan
P.S. For the money you spend on these things, looks like they would have included a degree wheel if it were that damned important.

 

Jim Degreeing a cam is always best....that way there is No guess work and you can get your Valvetrain and cam and crank all in perfect Harmony with one another...

And as Rusty mention most Cams are allready ground with 4* advance in them from the Factory.... to provide more low end Tq... But with it Slightly retarded you will only lose a few Lbs of Tq..and pick up some Hp on the Big end....

I have the CompCams XE274 and it will be installed at a 114* centerline on the intake and well still make almost 400lbs of tq at 2500rpm... on my 428CJ build..

And plus running your Cam slightly Retarded helps with running pump gas!! JMO..

Russ

 

oh so I am Rusty now? I do have Rusty truck but thats because it was sitting by some chevys.

 

Who? What?

Anyway, it's probably best to degree your cam. If nothing else, it keeps the cam makers honest. But on a regular street engine with a good aftermarket timing set it's probably "close enough for government work".

 

" Sorry about that Matt" LOL...

Russ