Adjustable rockers/push rod question

Hello all,
Just had a set of adjustable rockers from a 170 ci cleaned and rebuilt by my local machine shop. Plan to use in future on my 200 ci. I notice that they sell different size cup and ball pushrods to work with this assembly. My question is why are there multiple sizes instead of just one? Isn't the whole purpose of the adjustable feature so that you can set a given pushrod to the needed length? Thanks.

Well one reason is to get the geometry correct and another reasone is for use on the 250 inline 6.
I am using 1.6 adj rocker assembly and had to get my pushrods made for the added height of the 250.
Hope this answers your question.

It sort of does. It's just that, doesn't the adjustable nature of the rocker assembly allow you to adjust how far the pushrod is coming up for proper valve train geometry? I completely understand why they come in different sizes when you are working with a non adjustable rocker assembly. Isn't the "length" of the pushrod determined by how far in or out the adjustable screw is?

Howdy Back:

Q- "Isn't the whole purpose of the adjustable feature so that you can set a given pushrod to the needed length? Thanks."

A- Yes. The adjusters have a range of about .020" plus or minus. Any more and mis-alignment may occur. In cases of extreme wear, machining or mis-match of parts and a different length pushrod may be needed.

I hope that answers your question.

Adios, David

Ahh. Ok. I get it. The range is limited. So you need to find the best size push rod to begin with. I thought there would be more of a range with the adjustable rockers. Can anyone recommend a good adjustable push rod to buy that works good with the inlines? Also, when it comes to taking length measurements is there a certain cylinder order you should follow? Firing order? Thanks ahead in advance.

Howdy Back:

I'd suggest that you assemble with what you have, assuming that they are in good shape. Make a preliminary adjustment and then assess the contact of the rocker to the valve stem. If the rocker face makes good contact through the contact cycle you're done. If the rocker face contact slips off of the valve tip you will need to make a decision for longer or shorter pushrods to correct the contact.

I hope that helps.

Adios, David

Hi. Thanks as always with the replies David. I do have a copy of your manual and am learning a lot from it. The problem is that I currently have a non adjustable assembly on car. The push rods I've learned are a different style for the adjustable rocker assembly. I'm planning to do all of this after my cylinder head has been rebuilt. I plan to have it milled down and I suspect this is going to affect push rod length. Figured this would be a good time to switch over to adjustable and reconfigure geometry.

"...it milled down…"
Just Y I like adjustable - to take up the mill loss 'adjustable' to that amount.

"...and reconfigure geometry…"
'keep it' by:
'get back the correct geometry'.
U can get pretty close by ci of engine and current length, get one 'adjustable' & check er out. Order the set accordingly.

If U clean the 'assembly' make sure to clean the inside of that shinny rod & holes/grooves on the individual rockers themselves.

Howdy Back:

Yes, you will need a set of ball and cup pushrods to convert to adjustable rockers. I think Matt should have them.

FYI- I've machined to deck the block about 020", milled the head .030" and the stock adjustable rockers were still in a tolerable range. I did use a fatter composite type head gasket that gave back about .025". So set it up with a standard pushrod and assess from there.

Adios, David

For what it's worth, I had my head milled 0.070" and running an old OEM gasket with a 0.035" crush thickness. I am going to have to order shorter pushrods this winter as my adjusters are backed up practically to the positive stop. I'm running some RAU high lift rockers though and not stock adjustable. I don't know what the difference is in adjustment height between the 2.

I got an adjustable pushrod from ClassicInlines before Mike passed away. I don't know if Matt is selling those now too through VintageInlines or not. You can always ping him to find out.

Hi, yes as mentioned you will need the cup style push rods. If the stock size doe not fit, like if you run out of adjustment, and the geometry looks out of wack, like the ball is going to push the cup sideways, instead of down, than a shorter push rod may be in order. I would assemble the engine with the stock size push rod and check it out. Ask your supplier if they will exchange the new push rod set if you are not happy. I don't know if the same size push rod is used with solid and hydraulic lifters. I'm sure someone does. Good luck

Is there any other source for adjustable rods out there? My head will be back from the machine shop soon and I'm going to have some push rod changes needed, and I'd love to get an adjustable just to get me where I need to be.

Rockerarms.com ! These guys are great and know what they're talking about.

HOwdy Back Slinger:

IIWIYS I'd call Matt at Vintage Inline and tell him what you need. a set of stock length ball and cup pushrods. He'll get them to you quick. 99 chances out of 100 the stock length will be fine, but ask him about his exchange policy.

I doubt any of the local parts houses will have a set on the shelf. By the time they order and get them to you it's likely to be twice as long as Matt can do.

Adios, David

Why waste time, just get an adjustable pushrod from one of the cam companies & then adjust to the length that gives you the least sweep across the valve stem. At mid lift you should be close to the center of the valve stem. Then measure the length & order that demension from your pushrod vender.

That's what I had in mind, just need to find the adjustable rocker

Hi Guys, just looking for some advice here, i plan on putting a 69 250 head (non adjustable setup and milled to 0.095)
onto my 66 200 block,
I plan on purchasing the Chrome Moly Ball & Cup Push Rods for the 250ci, I just want to be sure im ordering the correct length.
Has anyone had issues with this setup before?

Thanks

Stephen
Ireland