273 Rockers on a 360

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BSACafe

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Hi all...I'm new to the board and need a little advice. I've followed the site for a long time and always research before I post, but I can't find an answer on how to properly set up 273 rockers on a 360LA. The heads I have are J Heads that have been shaved and unfortunately I don't know how much, but this will prevent me from using stock pushrods. I do have a pushrod checker, and once I get the correct length figured out I will order the correct rods. I'm having two issues that I believe both can be corrected by shimming the rocker shaft posts, but want to run it by here to see if there is something I'm missing.

The first questions is about the sweep of a 273 rocker arm across the valve tip. Here are a couple of pictures at installed height and at full compression. My thought is that this geometry is off and the tip should be closer to center when at installed height.

The second issue is that my pushrod is rubbing the guide holes in the head.

My thought is that I should shim the rocker shaft pedestals and that would correct both issues. What are your suggestions?

I've enclosed photos of the sweep and the rubbing in the push rod guide holes. Thanks for your help!

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This should be an interesting thread. I had the same type of issue with my 273 build and I ended up shimming the rockers and using longer pushrods. There will be more knowledgeable members than I am that will respond I am sure. There is a fellow around that has kits to correct the issue. I can't place his name though.
 
take a sharpie and mark the top of the stem, then cycle your rocker over them with normal spring pressure. youll see the track. it should be more or less centered across the sweep. Yours look like they could be raised a smidge moving the rocker over the stem more. snug, then 1/2 turn on a hydro. May get away with stock 273 pushrods as the adjuster can handle a few hundredths. No help on the pushrod interference 'cept maybe a little grind or get good chro/mo 5/16 rods
10786d1260846272-check-my-valve-stem-wear-pattern-rocker-pattern-001.jpg
 
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If it's a stock to very mild camshaft and the adjusters are in good shape, just bolt them on and go. If you have a pretty healthy cam with increased strength valve springs, you'll want to modify the rocker accordingly.

Yup, it looks like you're going to need to clearance the rockers at the spring retainer area and you'll need to enlarge the pushrod holes in the heads as well. You should contact Mike at B3 racing.
 
"You should contact Mike at B3 racing."
^^^^^^^^^^^^^^^^^^^^^^^ THIS.
Although I never dealt with Mike at B3 Racing, he's a wealth of rocker geometry wisdom (what a word :realcrazy:).
 
We used 273 push rods on Eddie's 340 when we put it together and did not have any issues with the push rod hitting the hole in the head...

After many tries to get the proper length push rod, we went to OE Pushrods and they made up a set in a few days cheaper than most off the shelf push rods...

Home - OE Push Rods - Manufacturer & Distributor

The issue is you have to give ball to ball length, not overall length when specifying the length of the push rod... That can be a little more complicated when you have a ball at one end and cup at the other...
 
Yup, it looks like you're going to need to clearance the rockers at the spring retainer area and you'll need to enlarge the pushrod holes in the heads as well.

We had to grind a little clearance in the rocker for the spring to clear in Eddie's engine also...
 
So...here's a little more info.
I've ready Mike's site at B3 and it's great information.
Stock pushrods definitely won't work in my situation....I would have no threads showing on the adjuster. In fact, it wouldn't thread all the way through.
I've considered clearancing the pushrod guide hole with a carbide bit, but believe I need to make sure the geometry is correct on the rocker arm first. All of the sweep data I have seen with rockers has to do with roller rockers. Is it the same information for the 273s?

If the correct sweep for a 273 rocker is closer to the middle, rather than what I have now, then the solution would be to shim the rocker shaft to make them higher on the posts. I've seen the concerns about splitting the towers, but that can be avoided with trimming the shims or getting tapered shims. The only shims I've seen are the non-tapered. Has anyone ordered tapered shims somewhere?

I've got lots to learn....thanks again!

PS....I will take some more pictures tonight to explain how a standard length pushrod would fit.
 
Hi all...I'm new to the board and need a little advice. I've followed the site for a long time and always research before I post, but I can't find an answer on how to properly set up 273 rockers on a 360LA. The heads I have are J Heads that have been shaved and unfortunately I don't know how much, but this will prevent me from using stock pushrods. I do have a pushrod checker, and once I get the correct length figured out I will order the correct rods. I'm having two issues that I believe both can be corrected by shimming the rocker shaft posts, but want to run it by here to see if there is something I'm missing.

The first questions is about the sweep of a 273 rocker arm across the valve tip. Here are a couple of pictures at installed height and at full compression. My thought is that this geometry is off and the tip should be closer to center when at installed height.

The second issue is that my pushrod is rubbing the guide holes in the head.

My thought is that I should shim the rocker shaft pedestals and that would correct both issues. What are your suggestions?

I've enclosed photos of the sweep and the rubbing in the push rod guide holes. Thanks for your help!

View attachment 1715363758

View attachment 1715363759

View attachment 1715363760


Here's the thread from when we worked out Eddie's push rods... This should help you figure this out...

Pushrod for hydraulic cam and 273 rocker arms


There's some more good info in....

273 stock push rod length?

Correct pushrod length
 
If it's a stock to very mild camshaft and the adjusters are in good shape, just bolt them on and go. If you have a pretty healthy cam with increased strength valve springs, you'll want to modify the rocker accordingly.

Yup, it looks like you're going to need to clearance the rockers at the spring retainer area and you'll need to enlarge the pushrod holes in the heads as well. You should contact Mike at B3 racing.


In the second paragraph, Rusty NAILS it.

There is no way your springs are so big that the rocker should be that close to it.

Get on the phone to B3 and talk to him.

I'm saying the shafts need to go UP and AWAY from the valve. Then the pushrods won't hit the head, the rocker won't be rubbing the spring and the geometry will be correct.

BTW, how much lift are you running and what is the stem height of the valve? Or, IOW's are you running a longer than stock valve?
 
Hi all...yes, I will be clearancing the inner radius of the rockers so they don't touch the spring caps. They were clearanced before, but it doesn't look like they took enough off. As the rockers push to valve down, it actually gives much more clearance. So the tightest, or lowest clearance from the valve cap and the rocker is at installed height. This will be taken care of.

The issue I'm trying to fix the most is the sweep of the rocker across the valve. I believe this change can also fix the push rod rubbing on the pushrod guide holes. My question is, does anyone have instructions on how to correct the sweep, or is it done by trial and error with shims under the rocker arms on the pillars? I've see the sweep patters on roller rockers, is that what I should aim for on these rockers?

I will do a sweep pattern of what it has now and then will see if I can shim it a bit to see what I can get. Trial and error.. :)

BTW...Yellow Rose...I bought the heads assembled and I don't know the stem height, or if it's longer than stock. It could very well be...it has a 205 intake and 165 exhaust....
 
Heres the current swipe pattern on number 2 intake.
This tells me if the shaft height is raised, it will move the tip of the rocker towards the center of the valve stem.
I will give Mike a call tomorrow.

15632312933286929337644751739544.jpg
 
I made some shims from what I have around the garage...will need to get some presice ones. The shims are .03 thick, and they made the slight adjustment and changed the pattern. It looks much better now.

The pushrod checker looks like it just touches the push rod guide holes when it's the valves are at installed height. I put masking tape on it and it didn't tear. I think my plans are to order shims, custom pushrods and see how it goes on a finished install. I may still hog the holes out a hair.

Here are the pictures.

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just for giggles lock a valve at half lift with a clamp around an old stem seal
put the rocker on and see if the line between the valve tip/ rocker pad through the center of the shaft is perpendicular to the stem or parallel to a retainer, use a machinist rule and eyeball it from the end
you easily will see if your shaft is too high or too low
then measure pushrods after you get shaft located correctly
 
You could also have the valve tips cut .030, which makes me wonder about the valve job. IF you are using OEM type replacement valves, and IF the seats are not sunk below factory levels, the rocker contact patch should be really close. You could have the geometry problem you have now if the valves have been set too deep in the head. Not saying this is your problem, but I've seen it before.
 
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