Hardened stock size pushrods will be fine. I have a '70 LT-1 under the bench that regularly hit 7500 RPM (even 7800 a couple times) with hardened pushrods and guideplates.
Push Rods
Thread Starter
Team Owner
Joined: Apr 2002
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From: All humans are vermin in the eyes of Guru VA
Cruise-In IV Veteran
Cruise-In V Veteran
Push Rods
Being temporarily broke gives me the opprotunity to over analyze things:
So my question is: With a 7000rpm small block what is the place where these 3 requirements meet for a 5/16th push rod:
Lowest possible weight
Lowest possible price
Appropriate strength
My general feeling is that at street spring pressures there isnt really a need for the 200 dollar set of push rods with all the bells and whistles, and parts companies are just finding ways to fleece us of a few more dollars. Is there a reason that stock push rods wont work?
So my question is: With a 7000rpm small block what is the place where these 3 requirements meet for a 5/16th push rod:
Lowest possible weight
Lowest possible price
Appropriate strength
My general feeling is that at street spring pressures there isnt really a need for the 200 dollar set of push rods with all the bells and whistles, and parts companies are just finding ways to fleece us of a few more dollars. Is there a reason that stock push rods wont work?
Last edited by Guru_4_hire; Oct 16, 2008 at 08:40 AM.
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
What are the spring pressure rates of your springs?
Are you using guide plates?
The hardened rods are important when using guide plates. They are also important if you have high pressure springs, which doesn't always coincide with high lift. Roller springs tend to have higher pressures.
Are you using guide plates?
The hardened rods are important when using guide plates. They are also important if you have high pressure springs, which doesn't always coincide with high lift. Roller springs tend to have higher pressures.
Thread Starter
Team Owner
Joined: Apr 2002
Posts: 62,198
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From: All humans are vermin in the eyes of Guru VA
Cruise-In IV Veteran
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probably around 125# at 1.8" and 325-350 at 1.2".
Looking at a set of beehive springs and am in the process of comparing.
Thinking about some PAC springs.
Looking at a set of beehive springs and am in the process of comparing.
Thinking about some PAC springs.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Then your decision is easy. If you have guide plates in your build then you must have hardened push rods. The reason is if there is contact between the push rods and the guide plates...the stock soft rods will shave away and drop metal into the oil pan and the rods will eventually fail in a bad way.
Melting Slicks
Joined: Jun 2002
Posts: 2,842
Likes: 99
From: Orrtanna Pa.
This is a set of Comp HE pushrods that couldn't cut it at 6500 rpms. The next set were 3/8" thickwall chromemoly. I also went with 7/16 studs, and have no fear of twisting 7000 rpms now. This is something you should not skimp on for sure.
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Le Mans Master
Joined: Jan 2006
Posts: 6,504
Likes: 139
From: Butler Pa
Are you sure that's not from valve float?
Melting Slicks
Joined: Jun 2002
Posts: 2,842
Likes: 99
From: Orrtanna Pa.
I can't say I didn't float a valve, as that cam was a Comp XE-284 (hydraulic) The current cam is an Isky Z-35 flat solid.
The AFR heads have spring rates around 350 lbs open, 135 on the seat, and I noticed blueing on the rocker pivot *****. The machine shop that equalized my spring heights suggested the rate was just a bit too much for stck type pushrods, and also suggested the roller rockers to reduce heat on the rocker fulcrum.
I believe he was right. This 406 rips to 7000 with ease!
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
5/16" will be OK ... just get some good ones with 0.065" thick chromemoly & all one piece w/formed ends & hardened ... should be able to find those under $100/16.
A few things that've been overlooked but then erroneously blamed on pushrod design/material when something goes wrong:
- Ensure NO coil bind + some more clearance.
- Correct PR length & RA geometry.
- Guideplates adjusted to center roller on valvetip.
FYI ... Not beehive ... but some very good drop-in (~1.25" od) springs that're close to your specs & much less$: Elgin or Pioneer p/n RV1943X ... also Howard's Cams p/n 98215
Here're some real endurance race springs "PSI"
http://www.psisprings.com/index.php?...ask=view&id=17
Other good ones are Isky http://www.iskycams.com/onlinecatalog.html and
K-Motion http://www.kmotion.biz/springsintro.htm
A few things that've been overlooked but then erroneously blamed on pushrod design/material when something goes wrong:
- Ensure NO coil bind + some more clearance.
- Correct PR length & RA geometry.
- Guideplates adjusted to center roller on valvetip.
FYI ... Not beehive ... but some very good drop-in (~1.25" od) springs that're close to your specs & much less$: Elgin or Pioneer p/n RV1943X ... also Howard's Cams p/n 98215
Here're some real endurance race springs "PSI"
http://www.psisprings.com/index.php?...ask=view&id=17
Other good ones are Isky http://www.iskycams.com/onlinecatalog.html and
K-Motion http://www.kmotion.biz/springsintro.htm
Last edited by jackson; Oct 17, 2008 at 02:20 AM. Reason: moinfo
