The Stovebolt Site Forums The Shop Area Engine Shop high lift rockers

if you use high lift rockers on the intake do you need to use them on the exhaust side and does anybody make them.

sorry its a 261

Why bother? Changing the geometry of the valve train creates far more problems than advantages, and few engine builders have the engineering ability to do it properly. It would be necessary to change the position of the rocker shaft to do it correctly on a stovebolt engine, and the machining costs would be horrendous.
Jerry

High Lift Rockers for inlines have been around a long time.The
past manufacturers name escapes me at the moment. They are used only on the intake side. There is minimal change, so damage to the valve train is not likely in a mildly performance enhanced motor. I agree with Jerry in that damage is possible in a highly modified motor.
Here's a more modern,but old style set on ebay.

http://cgi.ebay.com/ebaymotors/Chev...torsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

thanks for the info

I have a magazine from the 50s that describes "hopping up the Chevy six" which includes the high lift rockers. It also has articles for the F*rd V8 and Dodge forever flathead. If you want I can scan it.

I've never tried to use high-lift rockers on a stovebolt engine, but it's pretty common to use a 1.6:1 ratio rocker instead of a 1.5 on a Chevy V-8. To do it right, it's necessary to move the center of the rocker stud about 1/16" toward the intake manifold. This corrects the tendency of the longer rocker to put a side load onto the valve stem and wear out valve guides. It also reduces the friction loss of side pressure on the valve stem. If a customer insists on setting up a set of small block heads for 1.6 rockers, I charge an extra $300.00 labor on the head work for the machining involved in moving the rockers and increasing the clearance for the pushrods.
Jerry

The "B&B High Lift" rockers, which are the most common brand, are shorter on the push rod side. The push rod is no longer centered in the hole in the head but clears fine.

I have a friend that is running these on his 1941 1 1/2 ton splash 235 and loves them.

In the summer of 1957 I attempted to install a set of B&B high-lift rocker arms abd tubular pushrods on my 1953 235. The pushrods hit the inside of the holes in the head pretty hard. They needed at least about 0.10" of additional clearance. Afteter several hours of attacking the holes with a rat-tailed file, I finally got enough clearance for the pushrods tl clear. However, after a few minutes of running, it became obvious that I went too far, as water started to seep into the pan. Should I have stayed with the stock pushrod? I found a Corvette six head, bought an Isky E-2 cam, and went back to stock rocker arms.

Hoyt

I seem to recall the last time the B&B rockers were brought up it was mentioned that you had to use smaller diameter pushrods. I don't recall the exact application pushrods that were needed, though. Possibly early 216?

longbox, how early is early. would a set of 50 216 sedan pushrods work in a 60 261 w/ a 56 848 head????

I'm thunking that they meant possibly pre-'47. I seem to recall (and I might be wrong) that the earlier 216s used a smaler diameter pushrod, 3/8" dia instaed of 7/16" (again, I may be wrong. Jerry, help me out here! ).
As to the rods working, I think they will. But new repalacemnt rods are relatively inexpensive, about $8 apeice for a 235/261.

Also, check your push rod length before ordering. Later 261's had a longer push rod, 11"+ .

Jerry,
Can these be shimmed higher/lower and run longer/shorter pushrods like modern adjustable roller rockers to overcome the rocker tip/valve stem contact point to relieve stem side-loading?

..........Doc

Doc, I'm in unfamiliar territory discussing the valve geometrty of the I-6 engines, but when we're approaching the practical limits of lift and rocker ratio on the V-8's, we use a screw-in rocker stud and an Allen screw locking adjusting nut, then we use an adjustable-length "Checking" pushrod to determine the ideal geometry. Once that's established, custom-length pushrods are fabricated. The idea is to reach a compromise between gross valve lift, rocker arm angle, and side loading where the side thrust is mimimized through the majority of the rocker arm travel.

On an engine with a pedestal-mounted rocker shaft like a stovebolt, it would probably be necessary to shim under the rocker stands and fabricate custom-length pushrods to keep the rocker angle and side thrust at the ideal relationship. In extreme cases, it might even be necessary to actually change the distance from the rocker pivot to the center of the valve stems by relocating the pedestal mounting holes in the head. It's much simpler to stick with stock-geometry rockers and do the timing and lift changes with the cam profile. Just about any cam that can benefit from changes in rocker arm geometry is probably too hot for use on the street, anyway. Doing race-engine stuff on street-driven engines is a good way to end up with something that's not much good in either venue.
Jerry

Bill, I'm not certain what year the pushrod diameter got changed. Cam grinders like Comp Cams, Isky, and others sell semi-finished pushrods that can be trimmed to the proper length for a specific application, and they offer all sorts of end shapes, ball, cup, and other custom shapes. It would be possible to duplicate a stovebolt pushrod in about any length you desire if necessary for special applications.
Jerry

These were made back in the day for a guy to install in his driveway and get back to work the next morning. Not as great as a new cam but cheap and much less work, must have made an improvement over stock or they wouldn't have sold many. Must remember, those were tough times, minimum wage was under a buck an hour and most of these guys worked under a shade tree.

I have some NOS B&Bs, simple instructions,other than remove and replace it states "Important, make sure end of each valve is smooth and free from any roughness". Separate sets sold for 216 vs 235 PowerGlide and later motor.

Today these things are just museum pieces vs. entertainment for the kid that always had grease on his clothes. Geeze I miss those days.

Cheers

Spot on there Jerry.
That was exactly what I was asking could be done to the engine.
Screw in studs, set the rocker height and use pushrods made to suit.
I was'nt talking about a StoveBolt engine either, just applying the same principal from modern roller rocker technology and applying it to the old six engine.

That is why I'm with you Jerry, why go to all that trouble at the end of the day, for probably near zero return in performance.
As said previously, the amount of work required to fit them would far outweigh any performance gains.
Would be better off spending that money on a re-ground cam or a decent carby/exhaust.

Each to their own........................Doc.