Pushrod Upgrade

Discussion in 'General IH Tech' started by Tom Mandera, May 21, 2020 at 11:23 AM.


  1. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    I'm returning to a long stalled project and in particular, the SV needs to get finished and stuffed in.

    On my last 392, and now on this engine, I've found that some valve spring choices don't work so well with the welded rockers - the retainer rubs the bushing area of some of the rockers. The stamped boat-style rockers fit fine.

    In particular, the Comp 924 BBC springs fit fine with either, the 930 springs don't. I'm not certain what springs Maulis put on the heads I'm using, but they don't clear.

    So the cleaned up welded rockers and ball/cup pushrods got put back in storage and I assembled some 9-stand boats, and then found.. 8 pushrods.. and I appear to be short the other 8.

    (Anyone need some 304 pushrods? Those are everywhere.. most of the blocks were recycled..)

    So I know the stock pushrods are 9.750" long.

    The factory calls out a 3/8 ball end.

    The replacement Melling MPR-201 pushrods show a slightly different story on the tip ends
    Likely that means the flat-ish spot is 5/32.

    Most pushrods run a 5/16 ball end (these days with a 210 deg ball, so the head of the ball is undercut to allow for more movement - like a trailer ball)

    I could order some of the factory pushrods - Jeff lists them, but darn it if I didn't read the Melling product details..

    I exceed 300lbs. Probably by a fair margin on this one. My street motors usually exceed 350 open.

    So what's a good answer?

    The balls I measured were 3/8" last night (seems I have a couple of different manufactured pushrods in the 8 that I do have - some with an obvious ball end, some with just a tapered end)

    Thus far the only off-the-shelf 3/8 ball to 3/8 ball of 9.750" I've found is Comp 8692-1 (or 8692-16) which is a 7/16" pushrod tube - but it is Chromoly and .165" thick with 3/8 diameter tips.

    I know FE Fords used 3/8 ball ends on some, but they seem to be too short.

    Otherwise, lots of 5/16" stuff out there.

    Anyone have anything to add to this discussion? :D

    I need to drop the rockers on and check clearance in the lifter bores on whether I could go to a 7/16" diameter pushrod without scraping.
     
  2. Darrel

    Darrel Dreams of Cub Cadets

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    Good aftermarket pushrods are around $100. Custom is only like $50 more.
     
  3. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    Darrel's probably right.

    I'm thinking I need to measure for sure, then Order some custom pushrods with the right ends.

    I did take a fair bit off the deck.. some might call it excessive..
     
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  4. 2dafloor

    2dafloor Farmall Cub

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    Smith Brothers.. I never used them but thats the name I hear all the time.
     
  5. 1975IH200

    1975IH200 Y-Block King

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  6. 2dafloor

    2dafloor Farmall Cub

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    Yes I forgot the link and its not there name in it thank you!
     
  7. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    Thanks, but when I look at the Smith Brothers I don't see a 3/8" ball end listed. :(

    Manton does.

    I hope to get back to checking the length today.
     
  8. 2dafloor

    2dafloor Farmall Cub

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    My understanding they will make anything for you.
     
  9. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    Finally got around to measuring tonight.
    I degree'd the cam. It came in with the margin of the accuracy I wanted to apply.. @.050 INT opened at 7 BTDC, Closed at 43 ABDC.. Exh was at 50 & 6.
    I measured the lobe lift at the 0.3510 specified. So real close to 0.6" at the valve.

    My pushrod checker goes from 9.7 to 11.

    9.7 seemed to be just the slightest preload.

    With .050" pre-load, I'd be right back at 9.750 factory length.

    (This, despite taking .054 to .063 off the deck)

    So, I could go with another set of stock pushrods - until I read the "300 lbs" bit I would have never given it a second thought. :)

    Or I call up and order some high-zoot but otherwise stock replacement units tomorrow when the stores are open again.

    Even those Comp 8692-16 parts I found, I now find a few sources that say 5/16 ball ends (including Comp's Site (despite showing this part when you search by 3/8 ends)). I think I could manage the extra diameter though.

    But with custom pushrods, we can just go with a better material/thickness and call it a day. Tomorrow.
     
  10. jordandoc

    jordandoc Binder Driver

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    Tom, maybe I missed it but are you considering pushrod length? What is the base circle of your cam? I have a set of pushrods .060 shorter than stock.
    Dan
     
  11. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    Good morning, Dan.

    I had a few things I was thinking about.

    It started by discovering I only have 8 pushrods and I needed 16. :)

    Several places to get new stock pushrods, but reading the specs, I noticed the "300 lbs spring pressure" clause and I run a good bit more than 300.

    So that sent me down the aftermarket pushrod path, looking to see what beefed up stock options were available and... well, custom pushrods are available.

    If I'm going to go to custom pushrods, I'd better make sure I have the right length - getting it right won't cost any more than getting it close. :)

    Turns out, the stock pushrod length is about right.

    I set the lifter at the bottom of it's movement, put the adjustable pushrod in place, and went for zero lash.

    In this case, I couldn't adjust the pushrod to zero lash, since it was "there" after I tightened the rocker shaft down.

    9.700 was just a little bit of preload.

    I also compared with a stock pushrod, 9.750 - now with ~.050" preload.

    I checked the intake and exhaust.

    I don't have confirmation that the new cam has a smaller base circle, but it must in order to get to 0.310" of lobe lift.

    This grind is a Comp "Xtreme Mopar" pattern for a big Mopar (.904 lifters vs our 1"-ers) ground onto the IH blank. 275/287 duration.
     
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  12. 2dafloor

    2dafloor Farmall Cub

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    I just looked at performance push rods for 6.4l hemis and there listing wall thickness of .083 or .105" so they can mess with the wall thickness ,material etc. Of course this is all on modern roller cam setups. Something to think about.
     
  13. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    I anticipate going to a slightly thicker wall 4130, but we'll see what they say.

    I'm typically in the 350lbs of pressure range, so just a step or two up from factory replacement will do the job - most (if not all) of my pushrod failures thus far involved a broken rocker arm.
     
  14. Tom Mandera

    Tom Mandera Dreams of Cub Cadets

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    Even though they didn't list a 3/8 ball on their site/catalog..

    Smith Brothers
    $166.40 for 16 x 3/8 diameter .049 heat treated pushrods, 3/8" ball ends, 9.750" OAL.

    Good to 500lbs of spring pressure.

    (Comp 924s with an Isky 262 come in at about 350lbs open spring pressure. I didn't set up these heads - I'm not sure what the spring pressure is for sure, but they are different springs and definitely a lot more lift)
     

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