The reason I ask, lately I have seen photos and video of the slack in worn timing chains. That slack retards the cam. Back when I had my GTO I had degreed the cam on it. It was between 1* & 2* retarded. Threw in a 2 degree cam key(in the advanced position) and it ran great. Few years later,changing the water pump I take the tining cover off to check the chain.
Edelbrock double roller. A lot of slack in the chain now. I changed the timing set from the straight up to 4 degrees advanced. To compensate for the stretch in the chain. The power was back. Almost to what it was when I built the motor. I think we are ignoring the basics of hot rodding an engine. Focusing too much on PCM programming. You need Both, if you want the most out of an engine.
Another thing to take into consideration is the rotation of the motor into relation to you actually degreeing the cam. When degreeing the cam you turn it both ways when in actuality the motor only spins one way. Now considering I'm about half asleep at the moment...I think that stretch should only effect the "slack" side of the chain which shouldn't effect TOO much on the degree of the cam.
Edit: I should have thought this through a bit further and mentally went through the degreeing proceess. I stand corrected that the reverse engine rotation is only done when setting top dead center, to which the timing chain has absolutely NO effect on.
And for a further retraction, it would effect the chain equally as far as stretch goes in a perfect world. (save for one link being stronger than another).
The chain stretches evenly over it whole length. Yes it show more on the slack side. The other side is still stretched. The only question is how many degrees the timing is off due to the stretching. This is a universal wear problem for every engine that has a timing chain. .
Just look at a double roller. Goes in tight when new. After 5 or 10 k on it there is slack. It is only a question of how many degrees. The Rollmaster is set up for advancing/retarding in 2 degree increments. It is there for a reason. One to degree when new. Two to advance to compensate for wear.
GM puts the chain tensioner in to keep it steady, and so it won't whip around and break. As to the comment that you turn the engine in both directions. Not while taking measurements. All the specs are in relation to the actual rotation of the engine. Intake closing event is measured in degrees after
top dead centre. It is a given that you have to measure this with in the direction the motor actually rotates.
On a further note....the multiple keyways on a timing set are NOT only for adjusting timing to compensate for timing chain wear. It is also to advance or retard the cam timing (one reason) for power band tweaking. This is provided you know your good on Piston to Valve (PtV) clearance.
Every engine you build should be degreed. I usually check or re-degree motors I build on teardown and they show anything from .5 to 2 Deg. of cam retard due to chain stretch, so in my opinion is degreeing your cam a good idea...Why wouldn't you? I usually install cams in at 1.5 to 2 deg advanced to compansate for stretch. The amount of stretch is also extremely dependent on the qaulity of the timing set. Being 1 deg. off of your recomended intake center line will affect were you powerband comes in more than you think, thats why they make multi keyway crank sprokets, for adjustability. Every one talks about having to much low end torque and the need for more top end power so maybe installing the cam back a few degrees could be a benefit. Just remember retarding the cam decreases Ex. valve to piston clearance and advancing the cam decreases In. valve to piston clearence, so clay your pistons on mock-up and make sure you have at least .080" clearance on the intake and .100" on the exhaust.
Not bashing anyone for not doing it, just my opinion and its peace of mind for me knowing that my customers engine is going to perform the way I built it to.
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