Y block Rocker arms

[Blackpearleb434]

I have a freshly built y block and was wondering if anyone has tried or know the performance effect of using stock 1.54 high ratio rocker arms on the the intake valve and stock 1.43 low ratio on the exhaust valve? The idea would be to increase intake flow and duration on the intake but limit the overall overlap for a smooth idle.... Addition info

Engine specs
-heads have 1.9 intake valves
-mild cam
-piston / bore are 312
-4bbl intake with 575 Holley (vac secondaries)
-after market exhaust manifold

Any feed back appreciated

Cheers Norm

[y'sguy]

I've read about and heard this discussed before and can't remember the actual outcome but the net effect wasn't worth the trouble as I recall. Much better to go with the higher lift rockers overall if you have them. jmho.
Ted Eaton may have results on this.
From what you have stated above your engine should still have a reasonable idle?

[Ole Don]

I agree with Y's Guys. If the car has a stick transmission, give it as much as it will take. If the motor will have an automatic, or is going in a work truck, then back off a bit. Try to look up pictures on how to pressurize the rocker shafts.

[Blackpearleb434]

I have both sets, later model engines ( not y blocks) have this set up as was curious to see if it was worth doing to the y block, my idle is ok and was just interested in a combination of torque and economy the low ratio rockers give and the power the high ratio give! Thought someone may have done it already...

Cheers

[Blackpearleb434]

It's has a ford o matic so starts in 2nd...and I run the partly pressurised rocker shaft set up, so you think the 1.43 rockers are the go for this set up??

Cheers guys

[scicala]

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Originally Posted by Blackpearleb434

I have a freshly built y block and was wondering if anyone has tried or know the performance effect of using stock 1.54 high ratio rocker arms on the the intake valve and stock 1.43 low ratio on the exhaust valve? The idea would be to increase intake flow and duration on the intake but limit the overall overlap for a smooth idle.... Addition info

Engine specs
-heads have 1.9 intake valves
-mild cam
-piston / bore are 312
-4bbl intake with 575 Holley (vac secondaries)
-after market exhaust manifold

Any feed back appreciated

Cheers Norm

Changing rocker ratios will not increase/decrease camshaft duration or overlap. It will just change the total valve lift and the speed that the valves open and close. Increasing valve lash would do it a little bit, but would not be a recommended way to go. If you don't like the lope, you need to change the camshaft.

[Blackpearleb434]

So I have just installed a set of high ratio rockers and set the valve lash to .18 and am getting a strange back fire through the carb when you stab the accelerator ...... Any ideas??

[Ole Don]

Causes; vacuum leak, one valve tight in the guide, it needs some miles to loosen up.

[Blackpearleb434]

Righto, makes sense given the valves are now opening a little further, I'll go for a burn.

Cheers

[PetesPonies]

Originally Posted by scicala

Changing rocker ratios will not increase/decrease camshaft duration or overlap. It will just change the total valve lift and the speed that the valves open and close. Increasing valve lash would do it a little bit, but would not be a recommended way to go. If you don't like the lope, you need to change the camshaft.

Well this is incorrect. The effective duration @.050 lift is increased when you go to a higher ration rocker. The advertised is not changed, but that is not the number that means the most anyway. YOu are increasing the amount of time the valve is lifted at least .050 . .fact.