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Discussion Starter · #1 ·
hi first post here. I have a 02 dyna lowrider with a 124". its got thewoods cams forget the number but its 678 lift 268 duration i think, its a strong runner and usually bring it to 6500-6750 rpm. i dont think i have any valve float. Im running s&s steel pushrods with comp springs again forget the numbers. the intake valves are 2.250 and 1.750 for the ex. i guess my ? is can i benefit from aluminum pushrods since these valves are fairly heavy and it revs pretty good. just lookin for a little more insurance by saving some weight . or is aluminum not strong enough to handle the pretty high spring pressure and rpm. i know the ? is a little vague and if you guys need the specs on the springs and other things i will dig them up . thanks for any info you can provide about aluminum pushrod reliability.
 

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Discussion Starter · #3 ·
thanks for the reply. can i get you to comment a little more lol if its not two much trouble. thanks
 

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Every set of Aluminum pushrods I have ever dealt with have bent or were bent when removed. I'll never put in another set of aluminum pushrods. If you want light find some titanium pushrods, they are strong. JMO
 

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Discussion Starter · #5 ·
ya i thought jims used to have titanium pushrods for a twincam , but dont see them listed anymore thanks
 

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I would stay away from titanium push rods unless you are using valve springs that are close to stock seat pressure. They tend to bend like spaghetti under pressure and when you remove the load they straighten back up.
 

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Chrome Moly Steel, heavy wall at that, especially with that grind and no doubt high spring pressure. Don't be concerned about the weight this is a spot where it pays not to have pogo sticks. Rigidity rules.
www.pushrods.net
No titanium
 

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I would stay away from titanium push rods unless you are using valve springs that are close to stock seat pressure. They tend to bend like spaghetti under pressure and when you remove the load they straighten back up.
Yup,
Here is some titanium pushrods flexing very nicely on the rear cylinder...Sounds like you have some hefty spring pressure-
Stick with chrome moly steel alloy -


 

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Discussion Starter · #9 ·
ok thanks alot for the advice . that flex in the pic is pretty crazy pwmorris. yes i want to say the spring pressure is around 170 lbs on the seat but not sure. i think ill be fine why fix it if it aint broke.
 

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ok thanks alot for the advice . that flex in the pic is pretty crazy pwmorris. yes i want to say the spring pressure is around 170 lbs on the seat but not sure. i think ill be fine why fix it if it aint broke.
I guess you know something I don't but 170# with that cam and valves?? is a lot less than Bobby Woods would recomend.
 

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Discussion Starter · #12 ·
your probably right . i have had many dfferent combos with this bike and probably four different cam grinds. but i bought the cams right from woods. this is a 4 year old build and dont have all my notes with me now. this engine was a test mule for a shop in ct who were working on kits for twin cams.
 

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Not to hijack this thread here, but If i may ask.

I have a set of adjustable crane aluminum pushrods in my engine, but I am running a stock cam.
Do you think I will have a problem?
 

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I guess you know something I don't but 170# with that cam and valves?? is a lot less than Bobby Woods would recomend.
Gotta agree with Don.
170# on the seat is quite light with that cam, and those rpms you are spooling to.
Watch those Comp springs with that cam as well.
But yes, a good chrome-moly pushrod is your man. S&S is the prefered flavor here.:)
Scott
 

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Discussion Starter · #16 ·
well i was off by a few lbs. it is 185-188# on the seat which was thought to be a little on the light side still. but no valvetrain noise at all ever. what are your guys thoughts on still running factory lifters with these springs and rpm, imo when we built this engine i didnt think any1 made a decent hyd roller lifter that was much better than stock harley, but id like some advice on this also. what my plans are is to get this back on the dyno this winter. imo this engine has more rpm in it. i have the airflow and carb to support more than 6750 rpm. any thoughts on 7250 rpm for a 4.625 stroke with S%S race flywheels and supreme rods. maybe i need better lifters an a little more spring pressure before that. thanks for the replies .
 

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That's a lot of piston speed with that stroke. Gonna need a lot of airflow!What RPM is the HP nosing over now?

I'd be changing the lifters and springs as a regular maintanence item. It's probably a lifter which will kill a motor like this.

Also, as Hillside said, Comp changed the vendor for their springs several years ago, quality isn't what it once was.
 

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any thoughts on 7250 rpm for a 4.625 stroke with S%S race flywheels and supreme rods.
Get a piece of 1" thick lexan to keep between you and the engine while running at those RPM. :boom:

Not saying it will blow up but I would be VERY cautious.

Piston speed is over 5500 ft/min and piston acceleration over 144,000 ft/sec2.

Travel limiters for the lifters would be a good idea.
 

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Discussion Starter · #19 ·
yes it might be a little much. but it will probably not be ridden much at all at this rpm.it will probably be dynoed 4or 5 times like this and its not sustained rpm. when it was last dynoed we felt like we left some power on the table. its a kinda i wanna know what its got in it thing thats all. maybe 7250 is a bit much 7000 might be more realistic. it didnt nose over at all at 6500 rpm it was still climbing but it was new then and we were cautious.
 
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