What factors determine what thickness and diameter pushrod is needed for an application. I'm thinking that RPM, camshaft aggressiveness, spring loads, etc play a role. But, I'm wondering how do you decide which is best and/or sufficient. For example, what would be good for this application:
SBC
.180" offset lifters
.450" offset intake rockers (1.55 ratio jessel shaft)
240lb seat pressure and 625lb open pressure springs
Rollercam:
Intake 312@.020, 279@.050, 193@.200 .690"net lift
Exhaust 325@.020, 286@.050, 196@.200, .660" net lift
7400rpm
2.15"/1.6" SS valves
Thx,
Scott
Pushrod selection
Moderator: Team
-
bill jones
- Guru
- Posts: 2650
- Joined: Sun Sep 05, 2004 6:38 pm
- Location: salt lake city, ut
- Contact:
-How big a diameter can you get in there?
-Seems like the trend is to use the largest diameter you can fit and .080" wall seems to be about the minimum wall thickness unless you special order tapered which are ground to have a tapered wall thickness.
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-I see NO reason whatsoever to be running any 5/16" pushrod although we have run 5/16" .080" wall straight pushrods---less than .002" total indicated runout dialed from the ends being centered----and never had any problem.
-Bad stuff really starts to happen at about 8000rpm so your 7400 should be easy.
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-You didn't say what you had for valves---steel or titanium---but even with steel exhaust valves and .650" measured raceready valve lift and 274x279 @ .050" and 5/16" pushrods we never had problems on my sprint car engine and we ran that thing from 4000 rpm to 8300 and quite often to 8700 and that is 50 times each main event.
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-But larger pushrods were next on my list then the engine got sold.
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-One problem you might encounter is the bottom of a larger pushrod may interfere with the offset button in the lifter---encroaching on the inner wall of the lifter----and possibly with the inside of the retaining rivet that locks the wrench to the lifter bodies.
-Seems like the trend is to use the largest diameter you can fit and .080" wall seems to be about the minimum wall thickness unless you special order tapered which are ground to have a tapered wall thickness.
--------------------------------------------
-I see NO reason whatsoever to be running any 5/16" pushrod although we have run 5/16" .080" wall straight pushrods---less than .002" total indicated runout dialed from the ends being centered----and never had any problem.
-Bad stuff really starts to happen at about 8000rpm so your 7400 should be easy.
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-You didn't say what you had for valves---steel or titanium---but even with steel exhaust valves and .650" measured raceready valve lift and 274x279 @ .050" and 5/16" pushrods we never had problems on my sprint car engine and we ran that thing from 4000 rpm to 8300 and quite often to 8700 and that is 50 times each main event.
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-But larger pushrods were next on my list then the engine got sold.
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-One problem you might encounter is the bottom of a larger pushrod may interfere with the offset button in the lifter---encroaching on the inner wall of the lifter----and possibly with the inside of the retaining rivet that locks the wrench to the lifter bodies.
Call Terry Manton (Manton Pushrods 951-245-6565). You'll get good advice and some of the best pushrods available. BTW, length is also a consideration, but not significant for most sbc applications.
Roger Copeland
R&R Racing
R&R Racing
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flyin ryan
- Pro
- Posts: 234
- Joined: Thu Oct 27, 2005 10:09 am
- Location: Find me racing NA 10.5
Bill,
Stainless Steel valves. (that is what SS stood for in my original post
)
3/8" would fit. I'm currently running 5/16" with .110 wall thickness from Smith Brothers. I'm not having any problems that I'm aware of. I've been reading a lot on other forums where people have went to bigger push rods and had performance gains. So, I'm just looking for some opinions on this subject.
I wonder what is stronger or better..... a 3/8x.080 or a 5/16x.110 pushrod.
383malibu and flyin ryan.... thanks for the recomendation. I may give them a ring to talk some theory.
Scott
Stainless Steel valves. (that is what SS stood for in my original post
)3/8" would fit. I'm currently running 5/16" with .110 wall thickness from Smith Brothers. I'm not having any problems that I'm aware of. I've been reading a lot on other forums where people have went to bigger push rods and had performance gains. So, I'm just looking for some opinions on this subject.
I wonder what is stronger or better..... a 3/8x.080 or a 5/16x.110 pushrod.
383malibu and flyin ryan.... thanks for the recomendation. I may give them a ring to talk some theory.
Scott
-
bill jones
- Guru
- Posts: 2650
- Joined: Sun Sep 05, 2004 6:38 pm
- Location: salt lake city, ut
- Contact:
-I have dealt with Terry when I need pushrods for the big chief engines.
-Those things are something like $17 to $26 each.
-But Terry is good at answering his e-mails and I'd buy from him in a heartbeat for any special high class pushrods.
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-But I would probably start with Manley 3/8" .080" wall if clearance is not an issue.
-I seldom ever see an engine today that wants the same pushrods for the intake as for the exhaust---especially when the intake rocker and the exhaust rocker share the same shaft---so you might want to get cozy with your rocker arm geometry and see what you really need.
-Those things are something like $17 to $26 each.
-But Terry is good at answering his e-mails and I'd buy from him in a heartbeat for any special high class pushrods.
---------------------------------------------------
-But I would probably start with Manley 3/8" .080" wall if clearance is not an issue.
-I seldom ever see an engine today that wants the same pushrods for the intake as for the exhaust---especially when the intake rocker and the exhaust rocker share the same shaft---so you might want to get cozy with your rocker arm geometry and see what you really need.
-
Chief
Scott,
Here is some interesting reading about this subject:
http://www.aa1car.com/library/2004/eb30431.htm
Dave
Here is some interesting reading about this subject:
http://www.aa1car.com/library/2004/eb30431.htm
Dave