Can we run hollow pushrods?

M

MrWolf

New member
Can we run hollow-point pushrods?

I have taken a fair bit off both deck and heads, so I better get a set of shorter pushrods in order to get the lifters to work as they should. Engine is a 392 ic.

Now, the selection of hollow, oiling, pushrods is much greater than the non-oiling ones we normally use. I looked at a couple of sets of used pushrods I had laying around, 304 and 392 ones. Seems like the center of the ball tip is not even in contact with the boat style rocker or the cup in the lifter. So that tells me it shouldn't matter if there was a hole there or not. Correct or not?
 
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Okay, thanks for the input and recommendation! I have sent them a request, so we'll see what they say. I expect price to be steep though, compared to some off the shelf pushrods?
 
You can buy off the shelf non oiler pushrods. Don't know about the correct length you need. Assume you have ball/ball rods ?
 
Yep, running the boat style rockers.
The current pushrods are pressed in tips, ball-ball. No-oiling ones. Tube is 0.377, tips are 0.356 and the overall length is 9.75.

I've attached some pictures of my point here:
lifter end tip
rps20170222_212055_219.jpg

Lifter end tip. Almost looks like it's a hole there, but is just the dulled surface of the tip. It has been riding on the shiny surface along the edge.
rps20170222_212026_729.jpg

Rocker tip
rps20170222_211949.jpg

Same here, rides only on the edge. A bit more rough this one.
rps20170222_211700_807.jpg
 
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Re: Can we run hollow-point pushrods?

Pics fixed ! There was some kind of error in the links as I tried to post up from dropbox, getting the public links and writing the post with phone while still at the workshop.
 
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Re: Can we run hollow-point pushrods?

With the 0.09 I have removed from deck and head, ideally I should run pushrods 9.66 (the ones I have in my 345 are 9.75)
I guess this could realistically(at least) be stretched to 9.65-9.7 to ease the search of a new pushrod. I just searched summit (not sure where else to look, to get a good range to choose from?)
 
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I took close to 0.035" off my ic-196 and the stock pushrods still gave me about 0.085" clearance between the lifter's snap ring and plunger (preloaded) with the cam on the base circle, but my cam had been reground. Just curious here how you are determining exactly what length you need? Have you posted that info somewhere?
 
Mark pietz said:
I took close to 0.035" off my ic-196 and the stock pushrods still gave me about 0.085" clearance between the lifter's snap ring and plunger (preloaded) with the cam on the base circle, but my cam had been reground. Just curious here how you are determining exactly what length you need? Have you posted that info somewhere?
Click to expand...

Cool, thanks for sharing your experience! I was thinking of testing it as well with the new cam degreed in, existing pushrods, rockers and valves. But then again I thought why not check the stock ones, and just order shorter ones to account for the decking and milling? Going from that I will have the lifters working in the area where they are designed for, and a big thing is that I don't need to wait for shipping from us when I'm at that stage and just want to slap in the new pushrods and be done with it. I opened and dismantled one of the old lifters here the other day and thought the travel seemed pretty limited. Too much back-pressure in there so I didn't get to measure the spring-travel properly though.

For calculations I just took my existing, stock, pushrod and subtracted the amount I have done in milling. Numbers in the post above. Doesn't that make sense?
 
I agree with Mark and setting the lifter preload between .050 and .100". With that in mind read on.

In response to your original question regarding is you should run off the shelf drilled ball oiler pushrods, I thing it depends on how your existing components have worn in to the oem surface of the rod end. Presuming that the existing oem rod did not wear the rocker at the center of the socket, you run the risk of having issues where the hole edge in the drilled rod end, can run against the high spot in the rocker socket. Not a good thing. A full ball rod end will mitigate the risk of damage.

I have personally seen poorly selected rods wear right through the rocker during cam break-in. (not my build).

You effectively have 3/8 diameter ball/ball end pushrods.
I recommend not running anything with the oil holes in the ends.
I have rods made for every engine I build to optimize geometry and they are not that expensive. Smith brothers or manton can take care of you at a reasonable cost.
 
Jeff campbell said:
very well stated ! There's a reason for everything.
Click to expand...

😊 thanks for the input everyone. I agree, my best bet is to cut and thread a pushrod to check what length will give me the correct preload with my modified components. I wasn't aware there was a recommended preload measurement, thanks for pointing that out. Takes out the guesswork!

Calculations like I tried above won't cut it. I don't know if the isky 262 cam has the same base circle as the stock one, that's only one of the parameters I can't tell for sure.
 
You can buy a set of adjustable p.rod's, for just measuring, I've had a set for many years. But maybe easier or quicker to just make 1.?
 
Jeff campbell said:
you can buy a set of adjustable p.rod's, for just measuring, I've had a set for many years. But maybe easier or quicker to just make 1.?
Click to expand...

Yepp, I know. But as they already are hollow, a tube, it's pretty fast to cut one, thread it an put a piece of threaded rod and a nut in there.
 
Finally got the test done with the mocked-up engine now this weekend. Running the new cam and the radius cut valves and seats I adjusted the rod to zero lash and got a length of 9.53" with the lifters resting at the clip (maximum pumped up).

Now when I sit down and compare that to my old rods, which I measured to 9.375 I think there is something fishy going on. I'm confused - need to run that test again.. I thought I was going to need shorter rods, not longer... :icon_eek:

I have two setups with 9 stand rocker shafts and boat-rockers. Could run a new test with the other set just to compare as well.

edit: I measured my old ones again and they are 9.75, not 9.375!!! :)
 
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You know that the 304 and 392 use different pushrods? This is due to the taller deck of the 392 and 345. You mention earlier that you have both 304 and 392 rods.
 
Thanks, yes I know they are different :) I got a little collection of rods from these engines, but some of them are rusty and not in complete sets of 16.

I took the measurement of 9.375" off the ones currently in my running 345. They are right in the middle of the tall-deck (345-392) specified length. Puzzled by the measurement from the project 392. There has been some different steps done to it so far, so that explains it I guess

http://www.binderplanet.com/forums/index.php?threads/392-402-build.130397/.

Might be that isky grinds a smaller base-circle to the 262-262 cam, and not a taller-than-stock lobe (as I thought)?



edit: I measured my old ones again and they are 9.75, not 9.375!!! :)
 
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mrwolf said:
Might be that isky grinds a smaller base-circle to the 262-262 cam, and not a taller-than-stock lobe (as I thought)?
Click to expand...

The deduction in base circle is the typical mo to increase lift. The lobe height is for the most part limited by cam bearing diameter.
However when factoring the rocker arm ratio, the base circle change is fairly small to achieve the lift increase you are installing with that cam.

For s&g's install the 9.375 rod and see what it says. I know you made the measurement but .155 (from your measurements) is a bunch.
 
Did you factor in going from a .016 head gasket to a .040? This is assuming you went from the oem steel shim to the composite ones.
 
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