roller rockers

Where can I get roller rockers for farmall h & will they give more hp. Ball park cost. thanks.

Murphy's Motor Service has roller rockers. Their website lists them at $305
Murphys

I would bet the HP gain on those at the RPM they run at would be negligible.

It is not the roller that gives you power, but rather the rocker arm ratio. A higher ratio rocker will provide increased valve opening for a given cam profile. In addition the valve will open earlier and close later effectively giving increased duration for the valve event.

Murphy's web site has a graph showing the increased area under the lift curve. I am sure they can give you a ball park for the HP increase.

Ken, Increased rocker arm ratio will only affect total lift, not the time the valve is open. The valve will open and close the same as stock rockers. Opening and closing
time (duration) is determined by the camshaft.

(quoted from post at 17:44:04 04/09/17) Ken, Increased rocker arm ratio will only affect total lift, not the time the valve is open. The valve will open and close the same as stock rockers. Opening and closing
time (duration) is determined by the camshaft.

Click to expand...

Duration is typically checked at .050" valve opening. This allows for better accuracy since it is beyond the accel/decel ramps built into the cam. If you check the plot at the two .050" open points, on Murphy's web site, you will find the high ratio rocker provides increased duration. Opening, the valve reaches .050" earlier and closing, the valve reaches .050" later.

Also, reducing the valve lash will increase both valve lift and duration. Finally, increasing the lifter diameter will increase the duration however, valve lift is not changed.

The plotted points on any camshaft rocker ratio comparison curve shows the higher ratio rocker directly above the lower ratio rocker at exactly the same deg rotation of the cam lobe. The difference in the two curves is the difference in valve lift, nothing associated with the event timing.

Will higher ratio rockers increase HP? In theory they should help. If the cam has a .353 lobe height, a 1.5:1 rocker is going to produce a .530 lift, 1.85:1 will give .653 lift. An engine in good shape should respond to an increase. Its not going to be a "kick in the pants" increase, maybe 3-4%. In order to take advantage of increased rocker ratios, everything else needs to tie in, cam timing, valve size, port shape/size, comp ratio, cu-in, all play a part in increased performance. What works well for one engine type or combination of parts will not necessarily work for another type of engine. I have seen both dyno results and on-track performance suffer when things were not planned or thought out thoroughly, just copied from one engine to another.

If all that is going to be done is add higher ratio rockers without a camshaft regrind, new rings, good valve job, there is a good chance for disappointment. I hate to see people spend money on parts where they end up saying, "well that didn't help". Higher ratio rockers are one factor in the equation, but just by themselves are not the entire answer.

A 2 to 1 ratio will open the valve faster than a 1.5 to 1

We are running Murphy's roller rockers in our Oliver 88. When I ordered the rockers I also sent Jeff a stock cam. I told him exactly what the engine had for other mods, and where I was at rpm wise which is between 3000-4000. He then ground the stock cam do it would work best with the rockers and with our application. Seemed to liven it up. Like what has been said most performance parts don't do much on their own without other modifications. I will tell you one thing we had to send our head out for some clearance issues with the new cam and rockers. Also had a problem floating valves and had to get much stiffer springs. But I don't think you will have that issue.

You didn't say what has already been done to your engine. My last H had 210 cid, 3.75x4.75 and was almost always the smallest engine on the track in my classes. I had stock 350 cam, mild head work with slightly larger valves and the ports cleaned up. I was running .027 quench with flat top pistons at around 10.5:1. Stock 350 lp manifold, reworked 350 carburetor with opened up jetting and a 706 double venturi and M&W governor. I got 65 hp at 540 pto rpm on an M&W dyno and 70 hp at 600 pto rpm. I pulled it a couple years like that and could easily do 2nd in 3500 and sometimes in 4000, but had to do low in 4500. I heard about sawing 1/2 way through the rocker arms on the bottom of the short side, squeezing the gap together and welding them back together. I didn't get a chance to dyno it again, but I feel like I picked up half a gear because I could get to 2nd in the 4500 sometimes. One of my welds let go and I decided to spend the money on Jeff's rockers. They gave me similar results to my homemade set(except they were better built).

I would recommend them if your H has been bored/stroked and you have already optimized your intake/exhaust/ignition/carb/governor. If your H is more stock than not, you would be better off finding free hp. Loosen all belts when pulling, go through your transmission bearings, look for drags in your drive line, use a moly additive in your trans, get your hitch at the limits and make sure there is absolutely no flex under a load.

Good luck!

Duration at .050 will be affected very little, and would be negligible. Lifter diameter (flat tappet) has absolutely no affect on duration, unless the cam lobe is running
off the edge of the lifter face! Roller lifters are a different story.

Of course it will, but only the lift is changed.