Pushrod to Head Hole Clearance
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Pushrod to Head Hole Clearance I'm finally getting my Z06 back together. Installed PAC 1518 valve springs, Comp Cams trunion/bearing kit and some 11/32" OD Manton pushrods.
After installing the pushrods and rocker arms, noticed the clearance between the pushrod and the hole in the head on Cyl #1 intake is pretty tight ... more so than all the others. I'd say the tightest spot between the pushrod and hole is maybe only about 0.010 ~ 0.015", but doesn't look like it's rubbing from what I can see. Turned the engine over and can't see any pushrods rubbing anywhere.
I tried loosening are re-tightening Cyl #1 intake rocker arm, but of course it want's to seat back to it's natural spot based on the rocker trunnion and bolt hole location ... can't really change where these guys want to sit when tight. Maybe the hole in Comp Cam trunnion is off a bit, or maybe the hole in the head is off a bit .... don't know for sure. The clearance might have tight in the same spot with the stock setup too - but the stock pushrods are smaller in dia, so wouldn't matter.
Anyway ... is 0.010" enough pushrod clearance? These things are super stiff, so don't expect any bowing that would cause them to flex and rub.
After installing the pushrods and rocker arms, noticed the clearance between the pushrod and the hole in the head on Cyl #1 intake is pretty tight ... more so than all the others. I'd say the tightest spot between the pushrod and hole is maybe only about 0.010 ~ 0.015", but doesn't look like it's rubbing from what I can see. Turned the engine over and can't see any pushrods rubbing anywhere.
I tried loosening are re-tightening Cyl #1 intake rocker arm, but of course it want's to seat back to it's natural spot based on the rocker trunnion and bolt hole location ... can't really change where these guys want to sit when tight. Maybe the hole in Comp Cam trunnion is off a bit, or maybe the hole in the head is off a bit .... don't know for sure. The clearance might have tight in the same spot with the stock setup too - but the stock pushrods are smaller in dia, so wouldn't matter.
Anyway ... is 0.010" enough pushrod clearance? These things are super stiff, so don't expect any bowing that would cause them to flex and rub.
Last edited by ZeeOSix; Oct 2, 2011 at 10:41 PM.
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Forgot to add ... I checked the lifter pre-load by the zero lash & number of turns on the rocker bolt, and basically got 1-1/4 turns to 22 ft-lbs. Seems about perfect putting pre-load at around 0.060"
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I wanted to upgrade the pushrods while in the motor, so decided to go for the best I could get and not mess around. They are only 1/32" (0.031") larger in dia or 0.015" larger in radius. Stock pushrods are 5/16" dia. Price was about the same regardless.
Last edited by ZeeOSix; Oct 2, 2011 at 10:21 PM.
I will be ordering some Manton 11/32 pushrods when I get my engine back together also. I wish my new AFR 230v2 heads would accept 3/8.
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Anyone have a input on the original question? Is 0.010" ~ 0.015" clearance between the pushrod and head hole OK? I'm assuming so if there is no contact while turning over the engine. Vettnuts?, any one else have an input?
From Manton's website-
"Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more than needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient. The cylinder head and engine block can often be utilized like a big guide plate and dampening device, which stabilizes the pushrod. Just make sure that there is no interference problems when turning the engine over on the engine stand."
"Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more than needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient. The cylinder head and engine block can often be utilized like a big guide plate and dampening device, which stabilizes the pushrod. Just make sure that there is no interference problems when turning the engine over on the engine stand."
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From Manton's website-
"Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more than needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient. The cylinder head and engine block can often be utilized like a big guide plate and dampening device, which stabilizes the pushrod. Just make sure that there is no interference problems when turning the engine over on the engine stand."
"Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more than needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient. The cylinder head and engine block can often be utilized like a big guide plate and dampening device, which stabilizes the pushrod. Just make sure that there is no interference problems when turning the engine over on the engine stand."
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Does that explanation bother you as much as it does me? They are saying to use the head as a rubbing block??? Are their pushrods that bad? You sure don't see anyone else claiming that. If you use guideplates, they rub on the hardened part of the pushrod. This wouldn't be...unless the whole pushrod is hardened...which I seriously doubt. This just doesn't seem right to me.
http://www.mantonpushrods.com/Images/Manton_Catalog.pdf
Does that explanation bother you as much as it does me? They are saying to use the head as a rubbing block??? Are their pushrods that bad? You sure don't see anyone else claiming that. If you use guideplates, they rub on the hardened part of the pushrod. This wouldn't be...unless the whole pushrod is hardened...which I seriously doubt. This just doesn't seem right to me.
