I was directly over top of the lifter and over top of the valve collar during downward travel thus eliminating any of those type of variances.

 

Actually the measurement in question would be the indicator on the lifter. It is at an angle. That could cause a cosine error. If that's the case tho, I'd be wrong about the measurement. If it were cosine error the number it provides should produce a rocker ratio that is less than the specified rocker ratio not more. Still the measurement could be in error. Not sure what the indicator is running up against but if it's inside the pushrod cup, with the angle being off, it could be causing the error. Pull the cam and measure the lift with a caliper.

From what I can tell the lift should be 0.503. 0.495 is close enough.

BTW, That cam is shot.

 

Yes, the cam is definitely shot and was only used as a reference to determine the rocker arm ratio.

I had a flat washer that covered the entire surface of the lifter so the tip of the indicator didn't sink into the cup as it traveled.

Im pretty confident on the accuracy of this set up..

I'll make another one once i get my S&S 561 cam.

Kenny Wise

 

While I've not done standard rockers, I've done SnS rollers and they were loser to the 1.625 ratio that is considered standard. Crane cams used to like 1.650..

In your case I'd still suspect some error in setup even if I'd done it myself. If the rocker geometry is off you can pick up lift. Say the rocker pushrod side is not angled correctly compared to the valve side. Another issue might be that you have 1.700 rockers. In which case the numbers would be closer. Not sure how you bottomed the lifter when doing the valve lift. I assume you disassembled it and removed the spring? The pushrod does not look adjustable. How did you take up slack? You still have some cosine error when doing the cam lift but as I said it would decrease the rocker ration calculation.

Personally I wouldn't run the 561 in an EVO. Way too much overlap. You'll probably want a cr of about 10.2 to 1. I'd prefer a Woods 6(H), Crane H290, even a Makey 590.

 

I have adjustable pushrods and there was zero lash on the washer when I placed it on top of the lifter.

There was also zero lash on the rocker arm to the valve. I double and triple checked my clearances and even completely disassembled the entire set up several times and the numbers repeated.

I have no idea why the math doesn't equate to 1.625:1

I am currently building an 89" (4-5/8" stroke) for this engine.

As you can see the cases are bare with no crank assembly.

Per S&S the recommended cam for this set up is their .561" cam.

I would tend to think they know what they're doing.

 

Nothing wrong with overlap with a good exhaust. It's all the crap exhaust systems that don't play well with it that makes overlap a problem. It's always the cams that get blamed for the reversion/dips in torque of course.
It really helps with scavenging/cylinder fill and why some cams with late IVCs still do well in the lower rpms.
Ran cams with 56° overlap in an evo myself. I'm an overlap junkie.

 

So you don't think you have 1.7 rockers?

Yeah, with the front rod missing, I would have guessed you were trying to build a 40 ci single.

The 561 is at least a 30 year old cam design. Don't think anyone can improve upon it? With 58 degrees of overlap, it's going to be exhaust sensitive. Even the 675 only has 50.

They do have newer cams based on development in the twincams.

 

Thanks for sharing your advice and thoughts, ill keep it in mind.

I run stock mufflers on everything i own and have built many strong bikes..

Kenny

 

Well that's a mistake. But good luck.
This builder is putting cams like that in knowing this?
Define strong. Based on what?
You do understand why Max said exhaust sensitive?

 

No, im not running or installing this cam. I am only using this as a means of checking the rocker arm ratio.

Obviously this was my failed attempt to find the best method to determine what the stock rocker arm ratio was.

Kenny Wise