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05-06-2013, 06:49 AM
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#1 |
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Registered User
Join Date: Mar 2013
Location: hutchinson ks.
Posts: 14
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bent push rod
my 72 sbc has low compression even after wet test. dry everything is between 160 an 170, no. 6 is 135. wet everything came up about 5 bls. or so, no. 6 about 138. I pulled the intake and found a bent pushrod on no.6 intake would this account for the low compression. it seems the valve would be closed more an wouldn't cause low compression do I have a burned or bent valve. thanks
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05-06-2013, 07:23 AM
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#2 |
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Registered User
Join Date: Aug 2010
Location: Edwards, CA
Posts: 7,503
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Re: bent push rod
Sounds like a valve problem. Did you do a cylinder leakdown test?
__________________
Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID ** Blazer SPID ** Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders ** Do you have a 1972 Plaid Pickup? ** Plaid Blazer ** Plaid Suburban |
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05-06-2013, 09:16 AM
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#3 |
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Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,147
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Re: bent push rod
Yup, it's time for a leak down test.
Posted via Mobile Device
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1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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05-06-2013, 01:58 PM
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#4 |
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Cluster King
 
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,262
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Re: bent push rod
I agree, it is time for a leak down.
The intake valve has to open all the way to make good compression. My question would be why did the intake push rod bend? Did the valve stick in the closed position? It only takes one revolution to cause damage. You need to figure out the cause or it might happen again. Push rods typically don't just bend. |
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05-06-2013, 02:34 PM
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#5 |
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Registered User
Join Date: Oct 2012
Location: Apison, TN
Posts: 18
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Re: bent push rod
Yes, the bent push rod would prevent either a full intake of air, or a complete exhaust of air in the cylinder preventing a full intake charge. Replace the push rod they are available for cheap ~4.00 at your local parts store. That will likely fix the issue. Good luck.
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05-06-2013, 08:59 PM
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#6 | |
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Registered User
Join Date: Feb 2009
Location: southeasternfoothillsofusa
Posts: 1,557
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Re: bent push rod
Quote:
Sam |
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05-06-2013, 09:53 PM
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#7 |
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Registered User
Join Date: Mar 2013
Location: hutchinson ks.
Posts: 14
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Re: bent push rod
thanks guys, replaced the push rod on no. 6 it brought the compression up about 5 lbs. to 140. I went and bought a new compression gauge to make sure, other cylinders are 180 to 190 dry no. 6 is 140 I'm pretty sure i'm gonna pull the heads. thanks for the input guys. I don't have equip. for leak down test never done one before, i'm still open to idea's. how can I test for stuck valve lifter looks ok its going up an down doesn't look collapsed.
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05-07-2013, 12:17 AM
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#8 |
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Grandpa in the rustmobile...
Join Date: Nov 2008
Location: Spokane WA/Viola TN
Posts: 11,422
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Re: bent push rod
Had our 235 do same thing rebuilt the head. Vavle stuck
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05-07-2013, 02:12 AM
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#9 |
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Registered User
Join Date: Apr 2013
Location: bakersfield,ca
Posts: 13
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Re: bent push rod
might want to check the valve guides,could have had a valve stick in the guide,had this happen on my 396
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