Roller Block: Pushrods Rubbing Against Head

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Dodge72

Dodge72

Odd one out
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92 LA roller block with earlier 596 casting heads. Using stock replacement Melling rollers. When trying to find the correct pushrod length, I removed the rocker and and pushrods to find that they rub on the bottom to middle portion of the hole. Enough to leave a bit of a lip of metal. I know there are many threads out there that say that they can be drilled out. I know to get a carbide bit, but which ones do ya'll recommend or which ones worked best for this type of job? Lots of different types out there. Also have a Harbor Fraud electric die grinder that spins to 25k. Thank you!
 
Harbor Fraud......I ain't heard that one yet. lol Can you post some pictures? It almost sounds like you might need a rocker shaft relocating kit. That would come from B3 racing. He's a super good dude and a member here. We can better tell with pictures though.
 
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I tried the best I could with perspective. Basically when you look at the rocker shafts and pushrods head on and perpendicular of the head, the contact is at 6 o clock. This may or may not have relevance but I have zero play in these things. Then again, I'm at #1 TDC and this is exhaust on #2.

EDIT : if needed, here is a pic of the rocker making contact with the valve.
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Do what you were thinking and go to HF for there die grinder and grab some carbide bits and run it up and down untilit clears. Be careful not to go overboard. I had to do this to several heads when going to a roller cam because of the shorter pushrod length and the taller lifters that aggravate the angle of the pushrods into the head. I used tan colored masking tape and wrapped the pushrod to see if it would rub at all and ground away until the tape didn't get touched.

This sucks. You'll need to disasemble the head in the end to keep things clean and clear of all the bits and dust.
 
Stupid question I know.........do you have the rockers oriented the correct way? There's right and left offset regarding the pushrod dimples. Also too, don't forget the rocker shafts have orientations as well.
 
Just drill the holes in the head a bigger size and you shouldn't have to use a die grinder on them.
 
If you try that, know, absolutely know how much wall you have on the intake port side of the pushrod hole!


 
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Did you measure for pushrod length? If not, custom pushrods may resolve the problem. "I" would look for any solution that does not require grinding or drilling at this point since your engine is already assembled. Not only that, but "usually" when you see this problem, there's always another reason for it than "just" the pushrod holes needing enlarging. I would look for another "more correct" way out. This of course, is only one man's opinion.
 
Yes this is a common problem when you go to a roller cam as the roller lifter is a lot higher. I took my heads off and filled them where they needed the clearance. mine appears to work okay but I am replacing my alloy heads with a fully ported set soon so I will be contacting B3 and asking him for the recomended geometry correction kit.
 
It's (pretty much) common knowledge that when you shorten the pushrods they end up on a funny angle, therefore will almost always rub on heads that were not designed for use with the roller lifters and the short pushrods.
 
It was a surprise to me. LOL!
But solved easy enough. It just takes time.
 
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Ok, '92 small block leaves a critical question. Is it a 318 or 360? If it's a 318, it would be a magnum and that changes everything. If it's a 360, it would still be the LA style roller block.
 
Dodge72 said:
EDIT : if needed, here is a pic of the rocker making contact with the valve.
View attachment 1715382196
Click to expand...

Oh hey! Added pictures! Nice.
What is the spring diameter?
The rocker tip seems a little inboard? And close to the spring. IMO, why don’t you take a few moments and contact Mike @B3RE to help on several fronts at once with your dilemma.
 
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318willrun said:
Ok, '92 small block leaves a critical question. Is it a 318 or 360? If it's a 318, it would be a magnum and that changes everything. If it's a 360, it would still be the LA style roller block.
Click to expand...

This is a 360 LA roller engine.
 
Okay goodness, was not expecting all the replies lol.

Here's the deal. It's a 92 LA 360 (my bad, I missed that detail). Springs are Comp 901s. Outer diameter is 1.494. The ticket shafts were correct in direction, I did mess it up but a quick fix showed me the problem still exists. I know the pushrods are wrong. I was in the process of looking at my contract point of rocker arm and valve stem tip with an adjustable pushrod to get the proper length ordered. I have a re ground camshaft and I'm aware of needing longer pushrods. When I took the adjustable tool out, I noticed it rubbed horribly on the head. Hence this post.

As far as the heads go, yes they were not original. The boyfriend picked this engine out of the yard and only brought one original head and then had another 596 head with it. I couldn't find later 308 heads in the local yards so I picked these out for $40 bucks a pair and had them rebuilt.

So yeah. Mainly my question was which carbide bit did people use to grind it pushrod holes, aka which shape worked the easiest. I would love to NOT have to disassemble these heads, but if it's the only viable option then I'll just have to suck it up. Then when I stop rubbing I can hopefully worry about proper pushrods length (unless it may help?) Sorry if I didn't word this all right, last night I wrote this quick and had to go to sleep for work early this morning. Thank you for all the replies!
 
I would use a egg shape or a flame shape, you can also get them in 6" length

cat-bur-se egg shape.gif


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You can also use a 1/4" ball on a 6" long shaft
That might fit better
 
Make sure that they are all hitting in the same area before you start grinding. Could be some variation from intake to exhaust or cylinder to cylinder. No sense grinding where it isn't hitting and then having to pull it back off to fix it. I'd use one of the two bits shown or a simple cylinder. I would not use a long shaft on the cutter. Shorter is stiffer.
 
Pulling heads I hope? you don't want that metal trash in your engine!!! You might get away without disassembly if you are careful. Tape off the intake and all around the valve springs; cover all you can. Getting crap around the valve heads and guides would be my concern.

BUT, before you do any of that......some thoughts on what you have:

If your rocker to valve tip contact patch is more towards the inside than the outside through the lift cycle from closed to open (see note at end), then what may be going on is that the valves were sunk into the heads when the valve job was done. This will raise the valve tips higher and cause the rocker to contact valve tip closer to the intake side when closed. (Which is what you show in your pix.) It will also make the pushrods ride towards the valve side of the pushrod holes, particularly when the valves are closed. (Which you also show.) And it will raise the retainer and reduce clearance between the retainer and the rocker.

So the valve job done may have sunk the valves into the heads and the valve tips were not ground to compensate (called 'tipping' the valves). One way you might figure this out is the measure the installed height of all the valves springs and compare to what it should be for those heads.

If the installed heights are all tall, then tipping the valves will help the rocker to tip contact locations. But it will hurt the rocker to retainer clearance, and will not fix the spring installed height. The better way IMHO would be to:
  • Shim the valve springs to get the right installed height
  • Use rocker shaft shims to raise the rocker shafts and get the rocker to valve tip geometry better.
  • Adjust pushrod length to match all of this
None of this may completely fix the pushrod to hole clearance. IIRC, the taller roller lifter is going to naturally push the pushrod towards the exhaust side of the pushrod hole as you show. Look at your 308 head's pushrod holes size and that will tell you.

Note on contact patch: For the rocker contact on the valve tip, it is normal for the stamped rockers' contact to move towards the inner edge of the valve stem at 0 lift. The contact point will 'walk' across the tip towards the outside as the lift increases. The contact patch WILL be wide....that's in the design of the stamped rocker system, so you cannot think about the contact patch in the same way with stamped rockers as you do for roller rockers. You just don't want it to be waaaay off center.
 
I had to go through this putting Edelbrock LA heads on my Magnum block, I mocked up the valve train before installing the heads permanently and there was no way in heck the pushrods wouldn't hit the tubes in the heads unless I clearanced them. Same exact issue, taller roller lifters moved the bottoms of the pushrods out towards the cylinders. I did get custom- length pushrods but that was to achieve the right lifter preload.

Since my heads are aluminum I got away with using a dremel with a cutting bit, a legit die grinder with carbide bits would have been much better though.

FWIW it's got about 1500 miles on it so far with no issues, took off my valve covers last night and everything looked perfect.
 
so smaller base circle than stock and stock rockers and lifters
so stock pushrods are too short
get the right pushrods then you may not have to grind (or you might with the larger springs but still get the pushrods right)
come to think of it rocker and retainer are going to be in same place when closed no matter what pushrod- still get the pushrods right because
check your lifters
are they "topped out" no clearance
that's bad
check the pushrod seat against the wire or snap ring needs to be down say .040
you might want to pm Slantsix64 Or read his thread 318 budget build
he found a shelf pushrod that worked with his cam reground to MP RT specs
what's your grind
 
If the heads havent been opened up , deep gasket match, then just drill them 9/16 and run it. Simple as that. It 90 bucks at rhe shop. Did this near same combo before.
'88 roller 360, used 974 casting heads from '74 . Runs a lunati. 585 hyd roller with mopar replacement rollers and spider.
All early casting heads need modifications to the push rod holes to run a roller cam.
 
MOPAROFFICIAL said:
If the heads havent been opened up , deep gasket match, then just drill them 9/16 and run it. Simple as that. It 90 bucks at rhe shop. Did this near same combo before.
'88 roller 360, used 974 casting heads from '74 . Runs a lunati. 585 hyd roller with mopar replacement rollers and spider.
All early casting heads need modifications to the push rod holes to run a roller cam.
Click to expand...

Not a small block , but it took me 4 tries to get mine clearanced , and I have 9.400 long pushrods . Finally drilled them w/ 91/6" bit , after all the grinding--------
They were fully cnc`d too , but must have been pushrod clearanced for a flat tappet cam . ???
 
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