The Stovebolt Site Forums The Shop Area Engine Shop 848 -> 261: rockers, springs, pushrods

261 has higher lift than 235 so what rocker arms pushrods and springs should be used? Block is rebuilt stock with reground 261 cam and lifters. What other tips and suggestions do you guys with 848's on your 261 have to offer?

Thanks in advance for your inputs.

I got the pushrods, lifters, etc... from patricks. You should check ebay, try 'chev 261' and see what you find.

The springs will depend a little on how radical of a cam you've got- The cam manufacturer will tell you how much spring pressure you need- Too little and you can have trouble. A mild cam can use stock springs, but anything with lots of lift will need stiffer valve springs.

I milled the head 50 and decked the block as much to increase compression. Then I checked valve clearance with the pistons and it was okay.

I had the valve seats replaced with hardened seats to run unleaded.

I tapped the front bearing cap to be able to install the two bolts from outside the timing cover rather than having to pull the oilpan to remove the front motor mount to change the cam.

I set mine up for a remote spin on oil filter- If your 261 is not set up for full flow filtration, it can easily be converted while you still have it apart.
http://www.speedprint.com/Deves50/oilfilterinstall.php

HEI igntion/12 v conversion/dual exhaust/upgraded intake and carb, etc...

As far as the carbs go, I'm using the offenhauser dual intake with carter=webber progressive two barrel carbs. Next time I'll probably use Cliffords intake and a small progressive 4 barrel just to have one less carb, and the dual linkage, to deal with.

Thanks for the reply. Let me add more info then rephrase my questions.
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Here is a fact followed by some assumptions:
There is more lift with a 261 cam and therefore I am assuming the 261 push rods should be longer than 235 push rods. The rocker arms are probably different since there will be be more travel, and the 261 springs might need to be longer and/or stiffer than for a 235.
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My current situation is as follows:
I have 261 push rods and 235 push rods. I should have measured them, but they look identical.

I have the complete 235 rocker assy. I do not have any 261 rocker assy parts at all.

I bought my block already fully assembled. It is a stock block all the way through bored .03". everything is new "stock" parts except it has reground original 261 cam, crank, and lifters.

I'll be installing W-1 carbs on a 2x1 intake and running with fentons.

I have no plans to install a new cam.

I've already spent enough to pay cash for a new pickup!!!
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Now for the questions:
Should I use the 235 or the 261 push rods?
Can I use the 235 rocker arms and springs or is it mandatory to buy something?

The 261 rocker arms are abit stouter than the 235 ones, but I think you'll be okay with them.

I think the push rods are the same for the 235 and 261- The difference between the engines is the pretty much only the bore of the cylinders, everything else is the same. ie- the cranks are interchangable, the stroke is the same, you could swap the rods although the stock 261 rods are stouter than the 235 rods. The springs are the same. A 235 head will work on a 261 if you drill the steam holes in it. You can use the 261 stock cam in a 235 to beef the 235 up a bit (thats what they did in the 54 'vette).

If you had a cam with more lift and put shorter push rods in, you'd lose the lift.


Whichever set of rods looks better, use 'em! As far as the rocker assembly goes, if you've got a complete 235 assembly, use it.

My 261 has been on the road 15 years with a 235 (848) head with all the 235 rockers, stock pushrods etc. I'm running the Howard cam from Patricks with stock pushrods and no probs.

I will need an explanation as to how shorter pushrods would affect lift. Alave geometry maybe, but if the valve lash is the same, the lift will be the same unless you actually change the cam lift or the rocker front to rear distance ratios.

261 springs are longer and are also higher strength according to the 1954 shop manual.

235 and 261 rocker arms are also different and it seems there must have been a reason?

Push rod length won't affect lift but it will change the angle and travel path of the rocker arms.

:confused: :confused: :confused:

Greg-H-

If your engine calls for 6" push rods and you shorten them to say 5.95", when your cam pushes up the lifter and the lifter pushes up the push rod, and the push rod presses one half of the see-saw rocker arm, the 5.95" push rod will not open the valve as much as the 6" push rod. Of course with such a small difference you could compensate by adjusting the rockers, but if the difference were 1/2 an inch that would be a different story.

g0 GMC 253- The 235 and 261 rocker arms and rods are the same length but the 261's are beefier. They are interchangable but the 235 doesn't have the strength the 261 does. Of course you don't want to mix and match a few 235 rods with a few 261 rods, but if you use complete sets I think you'd be okay.

I still disagree with the idea that pusrod length affects valve lift. I fully agree that if installed spring height is taller, then longer pushrods are needed to keep the rocker geomtry correct. On roller tip rockers, an engine builder will custom cut pushrods to length to center the roller travel across the valvestem thru valve lift. I still say that the only way to incraese valve lift is to use a higher lift lobe on the cam, lengthen the distance from rocer shaft to valve tip of rocker arm or shorten the distance from rocker shaft to pushrod side of rocker arm. Or to remove clearance in the valve train. Pushrod length cannot affect valve lift.

Greg is correct as long as the pushrod is not way too long or way too short. In other words, 6" versus 5.95" versus 6.05" will not cause this but 6" versus 4" versus 8" definately would.

Although it may be totally insignificant, 6" versus 5.95" will defeinately have SOME affect on wear at the push rod top end and with the rocker end that it contacts.

Having no personal experience myself I am probing to see what others have done and what results they obtained before I blindly make uninformed assumptions and screw up something.

I agree with Greg.

On the 216/235/261 mechanical-lifter valve trains, the geometry is affected very little by any length of push rod that fits under the adjustment screw on the rocker arm (and allows appropriate adjustment, with the set-screw safely/securely inside the rocker arm and the set nut safely/securing on the top of the screw). The higher lift 261 camshaft simply causes the valves to open "wider" and maybe longer.

Description of the 1954 261 engine. Almost every part of the valve train (plus the connecting rods) were beefier than on the 235; however, I agree that the 235 rocker-arm assembly, push rods, valve springs, and lifters should work just fine, unless you are going to race your engine or do a lot of heavy hauling.

Areas to check during build is coil bind, (there is a clearance spec at max cam lift). Then ideally, pushrod length should have the rounded part of the rocker arm centered over the valve stem with the valve lash set and like one thread above the adjuster ball exposed on rocker arm. Then check that the valve spring retainer does not interfere with the "pocket area" of the rocker arm where the arm starts to round down to go around the rocker shaft. I am sure that a good engine builder could give you many other things to check such as seat pressure and max lift spring pressure but these are the basic checks that I am aware of. The neatest trick I have seen lately is the beehive shaped valve springs. Man that is a lightbulb moment. I wonder why they took so long to think of. with smaller top diameter, coil bind is almost impossible, lighter valvetrain weight due to smaller retainers. looks like a neat trick to me.