push rod thickness

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smokie
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push rod thickness

Post by smokie »

i'm building a 383 sbc with dart heads & a hydraulic roller cam. the cam is Camshaft Part # 12-443-8 Grind # XR294HR-10
Duration @ 0.006": 294° / 300° Duration @ 0.050": 242° / 248°
Max Lift w/ 1.5RR: .540" / .562" Lobe Separation: 110°
Lobe ID#'s: 3317 / 3318 Intake Centerline: 106°

i know how long my push rods need to be, but i'm unsure how thick to get them. will howards .065" be thick enough or so i need to step up to a .080" wall thickness? the .065" are advertised as being used with spring pressure up to 500 pounds.

any help is appreciated.
statsystems
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Re: push rod thickness

Post by statsystems »

I run the biggest diameter, thickest wall pushrods I can fit. I wouldn't use an .065 wall pushrod in anything.
Keith Morganstein
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Re: push rod thickness

Post by Keith Morganstein »

5/16” dia pushrods? Even if 3/8” I’d go with .080”
The Trend style one piece pushrods are readily available.
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Re: push rod thickness

Post by Newold1 »

Thickness of push rods alone is not always a measure of push rod strengths. However a quality manufactured push rod with proper ends and fitment (alignment and guides) is also a prerequisite of a strong push rod. Buy a good length checker push rod and set your geometry up carefully and correctly to get your push rods the exact correct length.

Well made thicker push rods tend to be stronger depending on diameters and overall shapes and the added weight of these push rods do not within reason add to the sprung weights in the valve train and do not tend to create problems for the valve train with stability and control.

If there is a big cost differential in your case staying with a .060"-.065" thickness in your push rod selection should not have a problem with the valve train weights and spring pressures you will be using as long as normal hydraulic roller rpm maximums of say 6000-6500 rpms. if the costs are similar or fairly similar then buy the added insurance of a .080" wall push rod. Just buy good push rods from companies like Trend, Comp, Elgin, EngPro, etc. Just stay away from used push rods and cheap offshore brands being peddled out there!
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grant6395
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Re: push rod thickness

Post by grant6395 »

Call smith brothers. They have a lot in stock, and will make you what you NEED in a day or two. Awesome knowledgable guys.
Greenville68
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Re: push rod thickness

Post by Greenville68 »

Ditto on a quality push rod...i went with Manton, but Smith Brothers are very good too and were on my candidate list at the time. I personally chose to go thicker than stock on my BBC, just out of paranoia.
1968 Camaro
Dart Big M 10.2" 572 stroker (4.5 bore x 4.5 stroke)
CR 10.5:1 to 10.75:1
Comp Roller Cam .561/.581, 300/306 (248/254 @ .050), 112 LSA
Dart Pro 1 (Rev 2) as-cast, 345cc, 2.30/1.90
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Kbails
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Re: push rod thickness

Post by Kbails »

i know you can get the comp "high-tech" in .080 or .105 which should be plenty strong and last, or if you wanna spend a little more and have peace of mind manley sells .120 wall 5/16 that i believe are called there "pro series" and should be a shelf item. in not sure if the weight will affect the hyd. but somone else may have more info on that
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smokie
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Re: push rod thickness

Post by smokie »

thanks for the replies everyone. how much trouble is it to step up to a 3/8's pushrod in a sbc?
pdq67
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Re: push rod thickness

Post by pdq67 »

smokie wrote: Sat Feb 24, 2018 8:46 pm thanks for the replies everyone. how much trouble is it to step up to a 3/8's pushrod in a sbc?
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The easy way to do it is to have big round pushrod holes in your heads and install, "guided", rockers.

Otherwise, you will have to drill the pushrod slots out if your heads are slotted and then install 3/8" wide guide plates.

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tenxal
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Re: push rod thickness

Post by tenxal »

smokie wrote: Sat Feb 24, 2018 8:46 pm thanks for the replies everyone. how much trouble is it to step up to a 3/8's pushrod in a sbc?
You need to have the push rod holes in the heads opened up to accommodate the 3/8" push rods and use adjustable guide plates....my assumption is the heads have already been fitted for screw in studs. I've used the Isky and Jomar with the Jomar being my choice.

I've used the Trend/Comp .105 wall 5/16" over 7,000 with no issues. An .080 wall 3/8" is a good choice.
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340king

Post by 340king »

There are three ways that I know to strengthen push rods. You can increase thickness, increase diameter or shorten the push rod. Since shortening is out of the question, then the options are to thicken or increase diameter or both. There are some reasons to go one direction or the other. I like going to larger diameter before going thicker. You can keep the push rod lighter that way. There might be some harmonic benefits to running lighter push rods.
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Re: push rod thickness

Post by Ken_Parkman »

Actually the hyd roller should shorten the pushrods noticeably, which makes them a lot stiffer. For a street type deal to 6500 rpm good quality 5/16" should be fine. I went through the same debate and decided on a good quality 5/16" .080" wall.
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Re: push rod thickness

Post by 77cruiser »

I run 5/16 .080 with about 420 lbs. open with no problems yet. A 3/8 would be better but it would need some more room.
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Re: push rod thickness

Post by Krooser »

I think Smith Bros rates their .049 5/16 units at up to 400#'s open pressure.
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sanfordandson
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Re: push rod thickness

Post by sanfordandson »

I always put pushrod thickness higher in importance than thickness. pushrod weight should also not be a concern fwiw.
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