pushrod compatibility

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Lloyd Keigwin
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pushrod compatibility

#1 Post by Lloyd Keigwin » Sat Feb 05, 2022 12:42 pm

I am building a 546/2 engine with 1600cc cast iron Mahle cylinders, matching pistons, and 1956 1600N heads. I would like to use one of the three sets of pushrods I have: (1) the all steel variety with the wooden rattles inside. They are in good shape for their age, but only three rattle, suggesting it's a good idea to disassemble them, take out the dowels, clean up and reassemble. Problem is I don't want to risk screwing them up, not having done this before. (2) the all aluminum variety, in great shape, probably 912. (3) the hybrid super variety, also nice condition. I've searched the archives and there is a lot of info there, some of it contradictory. I seem to recall someone said the Al/Fe hybrid would work as a compromise with iron cylinders, and others have suggested OK to use all alloy ones but set the lash when hot.

Is there a consensus that the Al/Fe hybrid super ones would be OK with the iron cylinders? If not, is there someone who restores the iron ones?

Thanks, LLoyd

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Phil Planck
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Re: pushrod compatibility

#2 Post by Phil Planck » Sat Feb 05, 2022 3:51 pm

pushrod tool.jpg
pushrod tool.jpg (3.88 MiB) Viewed 614 times
I made a simple tool to remove the wood inserts.
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David Jones
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Re: pushrod compatibility

#3 Post by David Jones » Sat Feb 05, 2022 6:07 pm

Cool tool Phil, I like it. I shall make one for the engine currently being rebuilt and for the pushrods on the shelf.
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Vic Skirmants
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Re: pushrod compatibility

#4 Post by Vic Skirmants » Sun Feb 06, 2022 8:40 am

1) That tool should work, but you need two lifters to use when tapping the end back on. One lifter to hold the pushrod, the second one to put over the end being installed.
2) 912 pushrods are stainless steel in the center, therefore not magnetic. If they are 912, use those. If long center is aluminum, don't use those.
3) Not sure which hybrid Super pushrods you have. Photo?

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Martin Benade
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Re: pushrod compatibility

#5 Post by Martin Benade » Sun Feb 06, 2022 10:13 am

Did all 912 s use ss pushrods?
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Vic Skirmants
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Re: pushrod compatibility

#6 Post by Vic Skirmants » Sun Feb 06, 2022 10:37 am

Martin Benade wrote:
Sun Feb 06, 2022 10:13 am
Did all 912 s use ss pushrods?
To the best of my knowledge, yes.

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Re: pushrod compatibility

#7 Post by Lloyd Keigwin » Sun Feb 06, 2022 3:59 pm

Thank you Vic, attached photo shows the two types in question. On the left is what I think is later S and S-90 type and on right what I think is the earlier type for those engines. Each has the center part made of the same material: non-magnetic and soft enough to scratch with a knife blade, hence alloy. I checked in HCP's book and he quotes you as saying not to use to all aluminum ones, but others would be OK. That's gotta be 40 yrs ago now! Still the same advice?

Also thanks to Phil. Nice solution! All I need to do is go get a 3/8' NPT coupling. I like using the original pushrods, after surgery, for this engine but I will keep an eye on how long before oil pressure comes up. But that would be the same no matter what pushrods.

LLoyd
PushrodsJPG.JPG
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Vic Skirmants
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Re: pushrod compatibility

#8 Post by Vic Skirmants » Mon Feb 07, 2022 8:28 am

Left pushrod has about the same expansion as a steel one. Right one is aluminum, therefore I do not recommend it for iron cylinders.

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Re: pushrod compatibility

#9 Post by Mike Horton » Fri Feb 11, 2022 10:55 pm

Vic Skirmants wrote:
Sun Feb 06, 2022 10:37 am
Martin Benade wrote:
Sun Feb 06, 2022 10:13 am
Did all 912 s use ss pushrods?
To the best of my knowledge, yes.
+1

(it seems like I once read in an early "Up-fixin", that the ones as used in C engines, with the short AL centers, and long steel ends, would also work in any of the cast iron cylinders, as in the C P/C sets... )
Last edited by Mike Horton on Sat Feb 12, 2022 12:26 pm, edited 1 time in total.
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James Davies
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Re: pushrod compatibility

#10 Post by James Davies » Sat Feb 12, 2022 10:49 am

The left "hybrid" steel/aluminum pushrod was ostensibly designed for use with cast iron cylinders introduced in 1957 for T2 production (from P*67001* onward according to The Specs)? These hybrid pushrods would have similar expansion to aluminum heads, aluminum case and cast iron cylinders.

That said, these pushrods are pictured in the 1956 workshop manual (page E40, figure 133). But this was, presumably, published before the introduction of cast iron cylinders in mid-1957. Also, the 1956 workshop manual only discusses the aluminum cylinders that were used on the 616/1 and 616/2 ( and 506/2 and 589/2) engines in 1956.

The 1957 parts catalog actually pictures these hybrid pushrods (Illustration 4, page 24) and labels them for cast iron cylinders on 616/1 and 616/2.

So what's the story?

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Re: pushrod compatibility

#11 Post by Mike Horton » Sat Feb 12, 2022 11:31 am

Vic Skirmants wrote:
Mon Feb 07, 2022 8:28 am
Left pushrod has about the same expansion as a steel one. Right one is aluminum, therefore I do not recommend it for iron cylinders.
+1
... this AL type PR is what was in my '62 S90 when I bought it in '85, but it also had near new C cast iron cylinders, and shortened 30° head angle piston skirts, another mismatch.
I substituted the 912 SS PR, per Vic, and as it had the faded black anodized S90 heads, I bought the 22° AA cast iron cylinder/hypereutectic cast pistons, in 86mm, which correctly matched the 22° heads. I set the C/R at just under the 9:1 nominal S90 spec, in deference to the erratic fuels of today out on the byways, a stock -102 Cam with fresh spherically reconditioned tappets, from Jacques, corrected the prior "assembler's" sins, and the engine is otherwise a 1720 S90, a good cruiser engine,
Mike

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Re: pushrod compatibility

#12 Post by Mike Horton » Sat Feb 12, 2022 12:23 pm

the 2 C iron cylindered engines I had, the hybrid Al/steel PR were in both. Both the T5 iron cyl. Normals I had, and a spare N '59 A all had the steel PR, with the wood inside. My Friend Spike Jones, whose '58 A, originally a Normal, had been converted to a Super, in 1975, by Ray Litz, at CE, also paired the wood inserted steel PR with then new Mahle 82.5mm cast iron cyl., and cast S pistons, the early B "00" matched rods, and the old Performance Products type "Tri-com 105, RO 200.5 S spec cam. Paired with the original N BBBC 4th gear, it easily keeps up with other group cars.
Mike

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