|
![]() |
#1 |
Member
Join Date: Sep 2008
Posts: 216
Likes: 0
Liked 6 Times in 3 Posts
|
![]()
I run a 350/ 330 IHRA crate motor with .435/ .465 valve lift. we just pulled the engaine apart for freshening and some of the push rods have slight rub marks on them from where they come up through the heads. i am definately going to add more clearance in these areas but i also have been reading lots on the trend to go towards larger diameter push rods. Mine are the 5/16 - .083 wall and was thinking of going to 3/8 dia. Any thoughts?
Thanks Ian |
![]() |
![]() |
![]() |
#2 |
Senior Member
Join Date: Feb 2009
Posts: 971
Likes: 424
Liked 205 Times in 93 Posts
|
![]()
push rods that rub slightly in the guide slots are norman. make sure there is enough/not too much clearence. i dont think that size a cam and springs warrent 3/8" units. be sure the ones you have are hardened. .083" should be fine & lighter.
|
![]() |
![]() |
![]() |
#3 |
Senior Member
Join Date: Sep 2006
Location: Bellevue Ohio
Posts: 984
Likes: 0
Liked 11 Times in 8 Posts
|
![]()
You cannot determine pushrod needs based on lobe lift only. You need to consider lobe profile as well as the spring pressure, I didn't see that you were running guide plates, however assuming you are it would be normal to see some rubbing. I found at bleast on my setup that going to larger pushrods actually made more power, of course every combo is different. Joe
__________________
Joe Buchanan SS/BX 3117 |
![]() |
![]() |
![]() |
#4 |
Senior Member
Join Date: Jul 2007
Posts: 578
Likes: 0
Liked 3 Times in 1 Post
|
![]()
Ian, the marks you're seeing are normal with that diameter pushrod. no need for 3/8, if you are uncomfortable, get some .116 wall 5/16 to reduce the flex. a small amount weight added on this side of the rocker is not as big a deal. do not enlarge the opening unless you're going to use guide plates.
Wade |
![]() |
![]() |
![]() |
#5 |
VIP Member
Join Date: Nov 2002
Location: Massapequa Park,NY
Posts: 1,281
Likes: 1,892
Liked 969 Times in 307 Posts
|
![]()
Go with the bigger diameter pushrods and thicker wall thickness. You can't get a stiff enough pushrod so it doesn't deflect.
|
![]() |
![]() |
![]() |
#6 |
VIP Member
Join Date: Jul 2008
Location: Liberty City [East Texas]
Posts: 1,760
Likes: 5
Liked 99 Times in 60 Posts
|
![]()
Ian,
do you have guide plates or self-aligning [rail type] rockers?
__________________
Larry Woodfin 471W |
![]() |
![]() |
![]() |
#7 |
VIP Member
Join Date: Jul 2007
Location: Anthem, Arizona
Posts: 2,766
Likes: 0
Liked 3 Times in 3 Posts
|
![]()
2x. And if you follow this advice I'll bet you won't need to clearance the push rod slots in the heads or have guide plates. The issue is flex, not lack of plates. Right? Fix the problem. Go faster.
__________________
Jeff Lee 7494 D/S '70 AMX |
![]() |
![]() |
![]() |
#8 |
Member
Join Date: Sep 2008
Posts: 216
Likes: 0
Liked 6 Times in 3 Posts
|
![]()
thanks for the replies and PM's. i do run guide plates and clearnaces look good by eye, the holes are tight but i wouldn't have assumed that much flex in the push rods or movement in the rockers. i will be opening the clearances in the head and will for certain purchase new push rods when the cam and lifters are ordered.
Ian |
![]() |
![]() |
![]() |
|
|