Rocker ratios

Has any one ever measured actual valve lift when using Manton 1.8 intake rockers and Reid 1.7 exhaust rockers?
If I understand correctly when using a .500" lift cam, valve lift using a 1.8 rocker should in theory and at 0 lash should be .900".With the 1.7 rocker in theory and at 0 lash should be .850" valve lift.

Please correct me if I am wrong because I am getting nowhere close to those numbers when checking my valve lift.

Are the numbers Manton uses just for fun to sound good or am I missing something?

 

Pivot man

no, your probably seeing correctly. a hemi rocker ratio can vary due to head gasket thickness,which ball and socket adjuster your using, pushrod lengh,cam base circle, and just plain difference in the stands and rockers. on my fontana you can have anywhere from a 1.6 to 1.9 ratio depending on these variables. the dead giveaway on if your close is where the tip of the valve runs during the cycle and how many threads are left on the adjuster with a checking light tension spring. try a couple different variations and you will see much difference in lift at the valve. and also just because it does have a 1 inch lift measured at the valve, the motor will never see that when running due to flex in pushrods, lash, etc. the best thing to do is find out which gaskets work best with the rest and make a plan when you say change head gaskets, you know what length pushrods and adjusters to put in it to compensate for the change, otherwise you might really make things grind on each other without knowing it. its just basic engine building, but at least your smart by catching what some would just slam together and wonder why it blew up! do a lot of experimenting and you will be surprised how much it changes. the gauge doesnt lie!

 

Thanks for the response! I had nearly answered my own question as i was typing I had it figured out... your input reinforces my thoughts exactly

Thanks again.

 

Manton rockers

I remember talking to a few A-Fuel guy's and they were saying when they changed from BAE to Manton's stuff Valve to Piston really closed up. They couldn't use the thinner gaskets. Don

 

also i think youll find that the ratio advertised is not always correct,
we have had this trouble recently,

 

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Thanks Mike for posting this. The rocker ratio is the distance from the centerline of the rocker shaft to the centerline of the pushrod cup, compared to the distance from the centerline of the rocker shaft to the centerline of the rocker tip[or pad]. Nothing else in the engine, cam, or valve train can change this ratio.

 

Here is something for you to try. Check the lift with a long pushrod and short screw adjustment, then try a shorter pushrod with the screw extended. You will have less net lift with the shorter pushrod. (On a hemi)

 

need to keep your push rod as close to the rocker as you can
or you will lose lift

 

Lift

Push rod angularity also will decrease lift. Measure lift at the push rod end and it will not be .500.
The ratios on our roller rocker arms are actual measured numbers at half lift. The reason we do not use full lift when determining a rocker arms ratio is because the shorter the fulcrum length and the higher the valve lift, the faster we loose rocker ratio after the half lift point. The only place we cam accurately measure ratio is at half lift. With that said, If you measure ratio at full lift on your engine and do the same thing on another engine that uses a camshaft with a .400 lobe, you will find a major difference in measured ratio.
Checking net lift with a light checking spring will give you an idea of where you should be. Checking the engine with full spring pressure will show just how bad the deflection is.

Using a 60 mm camshaft core will make a marked decrease in lift loss.

As the engine speed increases the loss of lift continues to increase. That number is hard to measure, but is considerable.

Noel Manton
www.mantonrockerarms.com
951 674-2212

 

On my dads pontiac wedge I get 1.85 ratio out of t&d 1.8 rockers (.888 lift at the valve with a .485 lift cam and .026 lash) by running the rockers low (less shims under the stands) and the rocker adjusters almost all the way out of the top (shorter out of the bottom).

On a hemi I think you get more ratio with short screw adjustment also. It might be opposite on the exhaust.

 

Screw placement

When we extend the screw further out of the rocker body we decrease the distance from the pivot center of the screw to the center if the rocker pivot. This increases the rocker ratio. On a rocker assembly that relays on oil pressure to cool and lubricate the ball / cup adjuster we stand the chance of shutting off the oil transfer passage alignment. We also must be very careful, to insure that the push rod cup does not contact the rocker body, at full lift. If this occurs to end will come off of the push rod.
This is why most rocker arm manufactures offer more than one ratio.

Noel Manton
www.mantonrockerarms.com
951 415-7348

 

I measured black stands and they were 1.7 intake 1.6 exaust with checker springs.800 lift. With #525 closed #1200 open titanium springs the 4778/509 cam was only 450 475(at the lifter) .750 lift

and I make sure they're in the oil grove.

 

Thank you Noel for the respose. You and your outfit are first class and you have some beautiful parts! Can't wait to step on this new bullet! Thanks for taking care of us the way you Terry and Al have it is a pleasure doing buisness with you... Thanks again

Dan