The Stovebolt Site Forums The Shop Area Engine Shop Hi-Lift rocker arms for 235-261???

I saw an ad today on E-bay for high-lift rocker arms for the 235/261 and wondered what advantage, if any, they offered over stock?

http://cgi.ebay.com/ebaymotors/216-...Z004QQcategoryZ33624QQrdZ1QQcmdZViewItem

Didn't realize that there was something kike that available for the 6. Anyhoo, the idea is that a higher ratio rocker will open the valve a farther distamce from the seat, it's along the same line as having a high lift cam. The more lift, the more air/feul mix that can be drawn into the cylinder, also better exhaust flow out. That equalls more power.

Longbox- Can you use higher lift rockers instead of a cam to get the same effect?

Yes, that would work. An old trick they used to do on smallblocks was to install big block rockers. They have a 1.7 ratio over the 1.5/1.6 normally found in them. I should also note that small blocks had 2 different rockers-1.5 and 1.6, many times the only difference between a standard car engine and a 'Vette engine was the rocker ratio, the cams were the same.

It will have a similar effect, however, a high lift cam usually has longer duration, in other words, the valves stay open longer. That ensures that even more gases get in/out. High lift rockers would be a good place to start, just be wary of too much lift, as you can break valves that way, especially if the head's been shaved.
-Lurch

I just took a look at that ad, and I noticed it is for intake valves only... Anyone else think this is strange???
-Lurch

Good points, Lurch. I have seen valves break from contacting the piston when there was insufficient clearance, either from rocker ratio or cam lift/duration. I don't think that would be too much of a problem on the 235/261 due to how the valves are laid out.

That's true, you usually see it on high performance V-8s...
-Lurch

Lurch,

Unless I don't understand the whole deal, I think it's REAL weird.

It seems to me that without changing the pivot point, the only way the achieve any "hi-lift" out of this style rocker is to fudge short on the pushrod end, or fudge long on the valve stem end.

Either way, the geometry is going out the window. I am guessing that is why they recommend stock pushrods...the skinny ones, so you can crowd the pushrod over a bit to fit the shortened side of the rocker arm.

If you lift the intake a little more, and allow a little bigger charge into the cylinder, you better do the same on the exhaust side, or it seems like you are wasting your time...a full "inhale" but a partial "exhale"..weird. :confused:

Stuart

Intake is always harder to fill, as the exhaust is under pressure and has very little trouble getting out. This is why intake valves are usually larger than exhaust valves. Typical SBC 4-barrel intake valves are 1.94 or 2.02, while the exhausts will only be 1.50 or 1.60.

When, how high, how fast, and for how long the intake valve stays open is probably the most important feature of a cam. If the intake valve opens too soon, the exhaust gasses can affect the incoming intake charge. If the intake valve opens too late, the cylinder will never have time to fill with the maximum air/fuel mixture possible. Once the intake valve starts to open, you want to open it fast and high to completely fill the cylinder. The hi-lift rocker arms (usually Barker or B&B) try to accomplish this by opening the intake valves a little more with the stock cam. Giving the exhaust valves extra lift wouldn't have as much effect as hi-lift on the intakes.

And yes, the hi-lift rockers can mess up the pushrod geometry on an engine. On SBC race car engines, we always checked pushrod geometry when using new cam or rocker arm profiles. We would mock-up a cylinder using light weight valve springs and rotate the engine to watch the pushrod contact angle change in it's seat in the rocker arm. By using an adjustable length pushrod made for such testing, you could play around to find the optimum pushrod length, and then buy or order pushrods made to that length.

Increased ratio rockers are a pretty standard thing. However, I usually see them as a complete assembly with the mount to the head offset from the original location. This is the geometry change needed.

So I see the reasoning behind only supplying intakes rockers based upon cylinder pressure etc... I also see how you could "fudge" the push rod end and valve stem ends a little to gain a little increased lift, but I don't think that this little amount of fudging could give you a 24% increase in ratio.

I googled the company name and came up with no matches. Fishy. Does Langdon or Clifford have this same type of item for sale? I havn't seen it. I suspect they would, if it made sense to do so and it worked. Fishy. It would not be hard to design (and mass produce) a new set of rocker shaft mounts. Might even find some rockers currently in production that would work with OEM valves and lifters. This would be an easy bolt on performance modification, that Clifford or Langdon could sell. These guys know what they are doing, so why aren't they? Fishy.

watch the billfold on this one,,,,snake oil??????doc

As stated in the Ebay ad, these are NOS (new old stock) and have been repackaged. The B&B casting logo is clearly visible on the rockers in the pictures. B&B commonly made these hi-performance rockers in the '50's, so the rockers shown in the pictures are approx. 50 years old. You can claim "fishy" or "snake oil" all you want, these hi-lift rockers have been around for 50 years and have been somewhat hard to find until this ebay seller stumbled upon a stash of them. I have some B&B and Barker rockers here (maybe some Fentons too) in the boxes, but would never dream of selling them. I see one of our sharper Stovebolters is the high bidder as of now, I hope he gets a set. Hopefully, the ebay seller has found a large lot of the rockers and will flood the market, allowing a sharp buyer to pick up a set later for less than what they will sell for now.

I wrote to the seller to ask the questions that were raised here. Here's my message and his response:
___________________________________
How can these be high lift rockers?

The adjustable end, pushrod end, is closer to the fulcrum by appx. .120~in. providing greater intake lift as well as a faster rate of opening, increasing the lift by over 20%

Originally made by Stellings&Hellings for B&B automotive. Other companies also made high lift rockers (FENTON) Ect.
___________________________________

I guess Atomarc is right, with stock push rods these rockers are closer to the rocker shaft and that is where the geometry changes.

There is a interesting thread about these on the Inliners site. One of the gentlemen indicates the pushrod hole through the head needs to be elongated to allow the pushrod to align with the shorter rocker arm.

The Inliners blurb (informative and knowledgeable) says the directions with the rockers indicate it is a "Install and Adjust" situation. A increase of 5 hp is said to be gained on a 216 by using these item's.


Stuart

I posted in the ebay forum about these back in February .... link

Not exactly a perfect match for 235s. Especially later years with the offset groove inside the rockers allowing for higher oil pressure.
Some say the pushrods will hit the head after installing them.
Probably works fine on early 216s.
May give over-oiling problems with 235s especially with later rocker assembly.
Save experimentation will tell, as always.

Atomarc, you are definitely right... I prefer high lift long duration cams... they don't muck up geometry as bad and they provide that quick opening that barry was talking about. The added bonus is the duration. The longer you can safely keep the valves open, the more complete the intake charge or exhaust scavenging will be.
-Lurch