Nominal vs Measured Pushrod Length
Thread Starter
Teching In
Joined: Apr 2018
Posts: 10
Likes: 3
From: NJ
Nominal vs Measured Pushrod Length This is sort of a weird question, but is the length marked on a pushrod, say a Manley .080" wall pushrod, the nominal length? For example if I ordered a 7.375" pushrod is that what will be etched on the part itself?
My situation is this: I built this engine and used a pushrod length checker to determine pushrod length. I purchased Manley pushrods from a great company with great support who helped answer all my questions and determined I need a 7.375" pushrod. I put the engine together and it started and ran great, or so I thought. I got it running with open headers and maybe drove the car 20 miles like that. Seemed fine. I was finally able to finish my exhaust recently and now I hear a ton of noise from the valves. My suspicion is that it was always there I just couldn't hear it over the open headers. I suspected a collapsed lifter so I checked the rockers where I thought I heard the noise and immediately found 2 rockers (valves that were closed) that had a ton of lash when the car had only been sitting for a few minutes. Today I finally started pulling out pushrods and found they are marked 7.200" (no idea how this didn't catch my attention before I assembled it). They also measure 7.200" with a caliper. My understanding is that the actual measured length of a pushrod is not the "length" because of the parts that extend into the rocker cups, the oil holes, etc. which is why the length is determined with turns of the tool and not a caliper.
So my question is, are my pushrods which are marked 7.200" and also measure 7.200" correct for the 7.375" measurement I determined to be what I require?
I just wanted to gain more knowledge about this before I approached the vendor or pulled off the heads.
My situation is this: I built this engine and used a pushrod length checker to determine pushrod length. I purchased Manley pushrods from a great company with great support who helped answer all my questions and determined I need a 7.375" pushrod. I put the engine together and it started and ran great, or so I thought. I got it running with open headers and maybe drove the car 20 miles like that. Seemed fine. I was finally able to finish my exhaust recently and now I hear a ton of noise from the valves. My suspicion is that it was always there I just couldn't hear it over the open headers. I suspected a collapsed lifter so I checked the rockers where I thought I heard the noise and immediately found 2 rockers (valves that were closed) that had a ton of lash when the car had only been sitting for a few minutes. Today I finally started pulling out pushrods and found they are marked 7.200" (no idea how this didn't catch my attention before I assembled it). They also measure 7.200" with a caliper. My understanding is that the actual measured length of a pushrod is not the "length" because of the parts that extend into the rocker cups, the oil holes, etc. which is why the length is determined with turns of the tool and not a caliper.
So my question is, are my pushrods which are marked 7.200" and also measure 7.200" correct for the 7.375" measurement I determined to be what I require?
I just wanted to gain more knowledge about this before I approached the vendor or pulled off the heads.
Last edited by Grant2k; Dec 18, 2022 at 06:19 PM.
Thread Starter
Teching In
Joined: Apr 2018
Posts: 10
Likes: 3
From: NJ
After further investigation I have found that not all of them are incorrect. I spoke to the vendor and he said he's seen this before with Manley pushrods and is taking care of me despite placing the order a year ago. So the lesson is check every part before you install it.
Whoever assembled the engine should have picked up on that.. How could you bolt town the rocker arms, and torque the bolt, and then not notice that there is excessive lash present? I... don't have the words..
I didn't see you mention anything about preload in your original post but if you determined with the pushrod checker your length was 7.375 you also have to add the required preload to that based on whatever lifter you're using..usually you won't get a measurement of 7.375 with just the pushrod checker, it will be less than that, then you add say .050" preload to whatever number you got with the checker tool and order pushrods based on that. But from the sounds of it they just shipped you the wrong length all together.
When ordering pushrods, always tell your vendor how you measured them, meaning turns of a bolt, or a caliper. That will tell them the difference. Also…NEVER start an engine on open headers. This is exactly why. Always finish the exhaust first unless it’s a race car, then you better be sure your right.
Last edited by Che70velle; Dec 16, 2022 at 08:28 PM.
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This is sort of a weird question, but is the length marked on a pushrod, say a Manley .080" wall pushrod, the nominal length? For example if I ordered a 7.375" pushrod is that what will be etched on the part itself?
My situation is this: I built this engine and used a pushrod length checker to determine pushrod length. I purchased Manley pushrods from a great company with great support who helped answer all my questions and determined I need a 7.375" pushrod. I put the engine together and it started and ran great, or so I thought. I got it running with open headers and maybe drove the car 20 miles like that. Seemed fine. I was finally able to finish my exhaust recently and now I hear a ton of noise from the valves. My suspicion is that it was always there I just couldn't hear it over the open headers. I suspected a collapsed lifter so I checked the rockers where I thought I heard the noise and immediately found 2 rockers (valves that were closed) that had a ton of lash when the car had only been sitting for a few minutes. Turns out they all have a ton of lash. Today I finally started pulling out pushrods and found they are marked 7.200" (no idea how this didn't catch my attention before I assembled it). They also measure 7.200" with a caliper. My understanding is that the actual measured length of a pushrod is not the "length" because of the parts that extend into the rocker cups, the oil holes, etc. which is why the length is determined with turns of the tool and not a caliper.
So my question is, are my pushrods which are marked 7.200" and also measure 7.200" correct for the 7.375" measurement I determined to be what I require?
I just wanted to gain more knowledge about this before I approached the vendor or pulled off the heads.
My situation is this: I built this engine and used a pushrod length checker to determine pushrod length. I purchased Manley pushrods from a great company with great support who helped answer all my questions and determined I need a 7.375" pushrod. I put the engine together and it started and ran great, or so I thought. I got it running with open headers and maybe drove the car 20 miles like that. Seemed fine. I was finally able to finish my exhaust recently and now I hear a ton of noise from the valves. My suspicion is that it was always there I just couldn't hear it over the open headers. I suspected a collapsed lifter so I checked the rockers where I thought I heard the noise and immediately found 2 rockers (valves that were closed) that had a ton of lash when the car had only been sitting for a few minutes. Turns out they all have a ton of lash. Today I finally started pulling out pushrods and found they are marked 7.200" (no idea how this didn't catch my attention before I assembled it). They also measure 7.200" with a caliper. My understanding is that the actual measured length of a pushrod is not the "length" because of the parts that extend into the rocker cups, the oil holes, etc. which is why the length is determined with turns of the tool and not a caliper.
So my question is, are my pushrods which are marked 7.200" and also measure 7.200" correct for the 7.375" measurement I determined to be what I require?
I just wanted to gain more knowledge about this before I approached the vendor or pulled off the heads.
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Teching In
Joined: Apr 2018
Posts: 10
Likes: 3
From: NJ
In the end my set of 16 was mispackaged with 4 of the 7.2s thrown in. I did not look at each one individually before I installed them. The ones I did see all had the correct length on them so I just started throwing them in. They are clearly marked with the size. The open exhaust is why I didn't hear it but yes, once I did hear it a typewriter was a good description. 7.375" is the correct length. I measured them properly using the tool, accounting for preload, etc etc. After I torqued each rocker I didn't check lash on each one. Once the first couple felt good I just kept going. So complacency was my downfall. At least it didn't do any damage (this time). And I never considered the open exhaust hiding a problem like this. Live and learn I guess. Good thing I'm not a heart surgeon.