Shovelhead bent pushrods, blowing oil, what's up? - The Jockey Journal Board

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Old 10-12-2016, 12:00 PM   #1
Blackbetty
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Default Shovelhead bent pushrods, blowing oil, what's up?

I rebuilt my 74/74 front the cases up with all new parts - S&S rods, new bearings, wiseco pistons/pins, .10 overbore, new S&S heads, S&S valve train, oil pump, the whole shebang. Bike was rippin but after a ride last weekend a friend said he was catching white smoke between my 2-1 downshifts.

I initially thought the bike was loading up on decel producing the smoke between downshifts and attributed it to jetting, but there's a wet oily residue in the pipes, and the next day the bike died due to wet fouling and I had to push. My first thought is valve stem seals, but on new heads I was skeptical.

I decide to do a comp and leakdown test for shits and the numbers weren't good. Pulled the pipes and raw oil is leaking past the exhaust gaskets. Pulled the pushrod covers and discovered both of the front pushrods on the front cylinder are bent, and at least one on the rear. Comp test and leakdown test with pushrods removed produced much better numbers.

I ordered a new set of pushrods but I'm wondering if these two problems are related. If a pushrod adjustment is too tight, is it possible the valve is hanging open just enough to create some kind of vacuum that's pulling oil past the stem seals? I'm using an Andrews B2 cam which requires at least .505 spring travel - the S&S heads can handle up to .590 of spring travel, so my cam and springs are within safe operation limits. Perhaps too tight of an adjustment whacked the stem seals?

Bike was powerful and the motor/top end was very quiet. One kick bike w the super E and hunt mag. It was the wet pipes that had me digging...

Any thoughts from you guys?

Last edited by Blackbetty; 10-12-2016 at 01:57 PM.
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Old 10-12-2016, 04:10 PM   #2
750Devo
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Default Re: Shovelhead bent pushrods, blowing oil, what's up?

Any chance the pushrods were to tight and the valves kissed the pistons? That could explain the bent push rods.

Only other time i have seen bent pushrods is when the top end lost oil pressure and rockers seized on the shaft. Maybe you had a blockage to the top end causing soft seizures on the rocker shafts.

I had a shovel motor built once and they left a chunk of oil line seal inside the rocker box oil galleries. Every once in a while the piece would line up just right and block off oil flow to front exhaust rocker. Rocker would seize and bend pushrod and adjustment tower.

Oil flows from rear head to front head, so the fact that both fronts were bent makes me think oil pressure problem up to the heads. Im going to guess it was the intake pushrod that bent on the rear cylinder? The rear exhaust is the first rocker to get whatever oil is going to the top end and will be the last one to seize.

Maybe your getting excessive heat in heads due to lack of oil flow? could be wearing out guides?

What were the actual compression and leak down numbers you got with pushrods out?
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Old 10-12-2016, 04:37 PM   #3
magnum45pete
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Default Re: Shovelhead bent pushrods, blowing oil, what's up?

did you check that at full lift the valve keepers cleared the valve seals and valve guide??
you may have not enough clearance and if the keeper hit the guide you would
A)trash a seal so you could have oil down the guide and
B)if the valve keepers hit the valve it would bend ya push rods
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Old 10-13-2016, 10:17 AM   #4
Blackbetty
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Default Re: Shovelhead bent pushrods, blowing oil, what's up?

Thanks for the replies fellas. I got the heads pulled last night and here's what I found:

- The oil consumption is being caused by failed headgaskets - both cylinders were pulling in oil from the drain back holes. I have used MLS head gaskets a bunch in the past, but not on a shovel. I think I'm going to rebuild with James head gaskets with fire ring.



- I checked the cylinders to make sure there wasn't a piston seizure or anything else going on. They look perfect, nothing out of sorts for an engine with a few miles on it:



- I confirmed there is no piston to valve contact as piston crowns and valves are intact with no evidence of interference:





- I confirmed oil flow to heads (I'm using Old STF oil lines which provides a feed for each head). I pulled the rocker boxes and there are no broken valve springs or interference with the roller rockers inside the rocker boxes. Rocker arms are within end play specs (I set these rockers up between .008-.010" end play) and move freely. Roller tips aren't flattened or galled.

So, I suppose my next plan of action is to pull the valves and make sure the guides and seals are ok.
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