Push rod clearence

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mikedevore

mikedevore

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Has anybody had a problem with the pushrods rubbing the holes in Edelbrock heads ar max lift? I just ran into this while assem my engine. I used a Hughes solid lifter cam. I called Hughes, they said this wasn't uncommon for this to occur. They were rubbing towards the intake side. I had to pull the heads back off & have my machinist open them up. No problems now. I'm using the ductile iron rockers & 5/16 Crane pushrods. I just thought I would give everybody else a heads up. These heads are some of the earliest ones made, circa 1999.
 
mikedevore said:
Has anybody had a problem with the pushrods rubbing the holes in Edelbrock heads ar max lift? I just ran into this while assem my engine. I used a Hughes solid lifter cam. I called Hughes, they said this wasn't uncommon for this to occur. They were rubbing towards the intake side. I had to pull the heads back off & have my machinist open them up. No problems now. I'm using the ductile iron rockers & 5/16 Crane pushrods. I just thought I would give everybody else a heads up. These heads are some of the earliest ones made, circa 1999.
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yep since this many times on those heads, the iron heads have bigger holes and some can even support 3/8 on iron, but you should be fine and thanks for the post!
 
Mine were really close but no rubbing. Seems like Edelbrock would fix the problem with as many people that have had the issue.
 
It depends on rocker type, manufacturer, cam choice, and pushrod choice. I just have the shop enlarge the holes on all of them for me now. It happens on big blocks too under the right circumstances...
 
Pushrod to head clearance should always be checked. Changing to more rocker ratio can do this too. Be careful that you don't remove too much from the 'sides' of the pushrod hole (tube). That can limit what you can do with the pushrod hump, how wide the port can be made (porting) at that point. Really only need to relieve on the intake and or exhaust ends of the hole. Drilling removes material on all sides (all the way around). Best way is to use an endmill cutter and mill the hole wider, on the intake and exhaust ends of the hole only. Almost like a semi slot, you lengthen the hole slightly. If you don't have access to this equipment you can do it by hand with a die grinder and a sharp carbide cutter. More time consuming but safer than just drilling them out to larger size. If porting is not in the future plans or not a consideration...then drill them. Sometimes the best ways are not the easiest ways...that's why they call us 'Hotrodders' a dying breed we are. Good luck, Terry.
 
My machinist used an endmill to slot the hole. This was used because of the intake ports. Thanks everyone, I should have asked this question before the heads went on.
 
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