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Bent push rod

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Bent push rod
#1
mseeley Avatar
mseeley Michael Seeley
Atlanta, GA, USA   USA
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1973 MG MGB GT "Barn Find"
1974 MG MGB "The Queen B"
No wonder my 1974 B had a serious "issue" running extremely rough on the #3 cylinder. I removed the rocker cover and discovered that the push rod on the #3 intake valve was mis-aligned under the rocker. I removed the rocker assembly and the push rod is slightly bent. All the other rods look OK.
I heated and straightened the rod, but I'm concerned about it breaking or some other catastrophe if I re-install the rod. Should I buy a new replacement rod, replace all of the rods, or do something else?

I appreciate all the advice!

Thanks,
Michael

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Re: Bent push rod
#2
stiffarm67 Avatar
stiffarm67 Joe Herz
Ridgefield, WA, USA   USA
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1969 MG MGB GT "The GT"
Michael,

Rods are pretty inexpensive so I would replace them but that's me. I'd be more concerned about what caused the bent rod in the first place. If I was qualified to comment on that, I would. Someone will be along shortly with useful advice, I'm sure.

Joe

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Re: Bent push rod
#3
mseeley Avatar
mseeley Michael Seeley
Atlanta, GA, USA   USA
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1973 MG MGB GT "Barn Find"
1974 MG MGB "The Queen B"
Thanks, Joe.
My guess is the PO didn't have the rod properly aligned when it was installed.
I bought the car partially restored, and the engine hasn't been run since the hardened value guides were installed by the PO.

Moss Motors has stock push rods for $3.65 each, so that's a no-brainer.
Moss also has high strength tubular upgrade rods for $16.95 each. I'm wondering if I should go with the upgrade?
Thoughts?

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Re: Bent push rod
#4
stiffarm67 Avatar
stiffarm67 Joe Herz
Ridgefield, WA, USA   USA
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1969 MG MGB GT "The GT"
Michael,

I'm in the middle of my rebuild on a 79B and will be using the stock equivalent rods from Moss. This on the advice of a respected member of this forum. This is assuming you have a typical street engine application.

I'd save the coin for something that would benefit you in either performance or bling or ??.

Cheers,

Joe

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Re: Bent push rod
#5
ca mgb Avatar
ca mgb darron small
ramona, CA, USA   USA
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1962 Triumph TR4 "Penelope"
1980 MG MGB
My car had the same issue.I bought it running very poorly and back firing through the carb.I pulled the valve cover off and the push rod has come off the rocker.The car was sitting for 17 years so I guess the po got it running and the valve stem hung up in the guide due to lack of lubricant causing the push rod to drop out.Loosened up the adjusting nut and bolt,spun the pushrod to make sure it wasn't bent, slid it back on and set gap.Has been running great ever since.

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Re: Bent push rod
#6
mac townsend
Fairfield, CA, USA   USA
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1973 MG MGB MkIII
I think that if it were me, I'd replace all the pushrods, for sure. And maybe tappets (hardened!) and the adjusting screws and jam nuts as well. Takes it out of the $10 range.

Inspecting the tappets is definitely called for, though.

Quickest way to check pushrods is on a large piece of glass...just roll them along the glass and watch what the middle of the rod does. If it rolls straight or is there's a slight wobble.


1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed

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Re: Bent push rod
#7
dickmoritz Avatar
dickmoritz Platinum Member Dick Moritz
Philly 'burbs, PA, USA   USA
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Michael,

Just replace the bent one with a new or used stock rod; no need to pay for the hi-po version...

If you're gonna get nailed for shipping just to buy one push rod, let me know and I'll mail you a good used one...

Dick


Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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Re: Bent push rod
#8
ca mgb Avatar
ca mgb darron small
ramona, CA, USA   USA
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1962 Triumph TR4 "Penelope"
1980 MG MGB
x2 with Dick.Stock valve train is good..Only $3.00 for a new pushrod.Dont mess around with a bent one.You might end up with a flat cam.

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Re: Bent push rod
#9
dipstick Avatar
dipstick Kenny Snyder (RIP)
La Center, WA, USA   USA
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1941 Ford N-Series
1958 MG MGA 1500 Coupe "Rosie"
1970 MG MGB GT "Pat's GT"
1971 MG MGB "Gifted To Me"    & more
Once bent the push rod is forever dead. Once altered the grain structure orientation of the push rod cannot be regained.

Like the others, I will give you a push rod free. No need for high performance push rods.

The serious question is how did the push rod get into a situation where it got bent? Valve stem sticking in the guide? Broken lifter? Failed rocker arm/adjustment ball threads? Generally push rods are bent in an over rev situation when the piston hits the valve. Something put the bent push rod into a serious bind.


Be safe out there.
Kenny

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Re: Bent push rod
#10
ErnieY Avatar
ErnieY Ernie Y
Albatera, Alicante, Spain   ESP
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1976 MG MGB GT
In reply to # 2663948 by dipstick Once bent the push rod is forever dead. Once altered the grain structure orientation of the push rod cannot be regained.

Cast your mind back to post's #17 & #18 here:Kenny winking smiley

http://www.mgexp.com/phorum/read.php?1,2335568,2336215#msg-2336215

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Re: Bent push rod - UPDATE engine rebuild! Thank you - may I have another?
#11
mseeley Avatar
mseeley Michael Seeley
Atlanta, GA, USA   USA
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1973 MG MGB GT "Barn Find"
1974 MG MGB "The Queen B"
I pulled the cylinder head to see if the valve had struck the piston, causing the push rod to bend. The valve was OK, but the #3 piston was seriously "pitted" from the pre-ignition/combustion/backfiring, looking as if someone had painted it with crinkle paint. The #4 piston looks like its had it's fair share of abuse as well, looking like someone left half of a spark plug inside the chamber! Picture 1 is #1 & #2 cylinders. Pic 2 is #3 & #4 cylinders.

I've decided to go "full-bore" and pull the engine for a complete top/bottom rebuild. This should be an interesting adventure....

Having The Queen B as a hobby is (supposedly) kinda like having a mistress - it costs ALOT of money and I'm getting screwed on a regular basis!

Dick, Thanks for sending me the free pushrod - very nice of you to do so. "Looks like were gonna need another boat." Dunt da dunt da dunt da...


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Re: Bent push rod - UPDATE engine rebuild! Thank you - may I have another?
#12
ErnieY Avatar
ErnieY Ernie Y
Albatera, Alicante, Spain   ESP
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1976 MG MGB GT
In reply to # 2665750 by mseeley I pulled the cylinder head to see if the valve had struck the piston, causing the push rod to bend

That would not have been the sequence of events because unless it breaks a valve cannot possibly make contact with a piston

There are only two things which can bend a push rod: a stuck valve, which is what happened to me, or a rocker seizing on the shaft but you would soon know all about that once you had the rocker cover off.

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