Moparts
Figuring out pushrod length for roller cam
Posted By: bigblk66_coronet
Figuring out pushrod length for roller cam - 12/26/22 11:39 PM
Hey guys i need some guidence here. I'm building a 512 and was talked into switching to a roller cam not realizing what all was involved in doing that, I bought a Howards 565 lift hydraulic roller can and i ordered 1.5 Harland Sharp Roller rockers. I need to figure out pushrod length and i have no clue how to go about it. from what i understand you have to have an adjustable pushrod tool right? Well it looks like there is different lengths? How do i figure all this out. This roller can stuff is all new to me. I've been running a 292 purple shaft for 30 years. Im an old school guy and just sticks with what works. Any help would be greatly appreciated. The pushrods are the only thing left before i can finish the motor. Anyone? I'm an old school guy and don't like change and man have i paid for it...lol
Posted By: Stanton
Re: Figuring out pushrod length for roller cam - 12/27/22 12:07 AM
The adjustable pushrods have about a 1/2" of adjustment so "close" will work.
Snug down a bank of rockers. Pick a rocker and adjust it so there are two threads showing on the bottom. Get the corresponding lifter on the cam base circle. with the rocker firm against the valve, use a thin tape measure to measure from the pushrod cup in the lifter the the bottom of the adjuster. Whatever that measurement is you'll want an adjustable pushrod with that measurement at the midpoint. This will give you wiggle room either way to determine the exact length you're going to need.
Posted By: AndyF
Re: Figuring out pushrod length for roller cam - 12/27/22 01:13 AM
Take one of your old pushrods and try it. It will most likely be too long but it will give you an idea. If you have a buddy with some tools you can turn an old pushrod into an adjustable pushrod. You just cut it in half and then thread it and use a long set screw as the adjuster.
Posted By: Cab_Burge
Re: Figuring out pushrod length for roller cam - 12/27/22 02:03 AM
Contact Trend and see if they have some checking pushrods for your application
Posted By: INTMD8
Re: Figuring out pushrod length for roller cam - 12/27/22 03:33 AM
Not sure if you have old pushrods but when switching to solid roller I took a couple of the original flat tappet pushrods, removed the cup, slotted the end (so could easily install/remove cup) and ground them down until they were the right length.
I was going for 2 threads below rocker lashed.
I then used head shrink around the pushrod to determine max diameter that would fit.
Posted By: carnut68
Re: Figuring out pushrod length for roller cam - 12/27/22 06:39 AM
Comp Cams 7719 it adjusts from 8.8 -9.8. $ 37.95 from Summit. That's what I use 511 RB with Indy Ez and Harland Sharp rockers.
Posted By: fastmark
Re: Figuring out pushrod length for roller cam - 12/27/22 11:46 AM
The proper way is to buy an adjustable set of pushrods used for determining pushrod lenght. They come in a set. You pick out the correct lenght and it has a range of adjustments with two jam nuts. It’s made of aluminum so don’t turn the motor over with springs on the heads. It will bend them. Make sure you have the correct preload on the lifter with the proper amount of threads showing on top and bottom of the rocker. Then you remove this pushrods and measure it with a dial caliper. Manton or Smith Bros can build you the correct lenght pushrod.
Posted By: W.I.N. Racing
Re: Figuring out pushrod length for roller cam - 12/27/22 04:20 PM
Posted By: 451Mopar
Re: Figuring out pushrod length for roller cam - 12/28/22 09:52 AM
On my 512 RB stroker with a Comp hydraulic roller and HS 1.6:1 rockers on 440 Source stealth heads, the pushrods I bought were just a bit short of 8.5".
Looking at my notes, I think 8.4750"? I used the Comp cams adjustable pushrod, with light checking springs on the valves. I used Smith Brothers 5/16", and fairly sure the 0.083" wall pushrods.
I came up with a range of pushrod lengths for between 0.020 and 0.040" lifter preload, and the minimum number of adjuster threads (where the pushrod / adjuster starts getting oil from the rocker), to about three turns down (any more and the oil to the adjuster starts getting cut off.)
Your measurements might be different. My block was cut to zero deck the pistons, and used a 0.040" Cometic MLS head gasket.
Posted By: Hemi_Joel
Re: Figuring out pushrod length for roller cam - 12/28/22 06:42 PM
I made an adjustable push rod by taking an old one and cutting it in half at the proper spot, threading both ends with a die, then threading them into a coupler nut. After I have adjusted it to the proper length, I measure it with a dial caliper.
Posted By: BigDaddy440
Re: Figuring out pushrod length for roller cam - 12/28/22 11:18 PM
Once you have an adjustable push rod, you can determine the exact length you need to create proper load on the center of valve stem. If you're unsure how to do that, make sure you ask or you look into it. It's not hard, but you do want to keep the rocker tip centered on the stem at peak lift / open pressure.
Posted By: bigblk66_coronet
Re: Figuring out pushrod length for roller cam - 12/30/22 01:56 AM
So i ordered the pushord length checking tool. Ive been watching videos on youtube on how to do it. Some say you need to pull off a valave spring and put on a checking spring? but then ive been told its no necessary? I get the whole concept but its very confusing and i dont want to screw it up.
Posted By: 340SIX
Re: Figuring out pushrod length for roller cam - 12/30/22 04:07 AM
I ordered push rod checking ones from Smith Brothers.
They were cheap so got 2 even though you just need one. As someone borrowed mine (never gave it back) I allways say no more loan a tool but.
Package was at my door in 3 days.
Posted By: carnut68
Re: Figuring out pushrod length for roller cam - 12/30/22 01:08 PM
So i ordered the pushord length checking tool. Ive been watching videos on youtube on how to do it. Some say you need to pull off a valave spring and put on a checking spring? but then ive been told its no necessary? I get the whole concept but its very confusing and i dont want to screw it up.
It'll be much easier with a checking spring and probably more accurate.
Posted By: UCUDANT
Re: Figuring out pushrod length for roller cam - 12/30/22 01:30 PM
Contact Hughes engines, they will send you and adjustable pushrod checker. You set it to length, remove it and send it back and they will have some Smith bro's push rods made for you
Posted By: bigblk66_coronet
Re: Figuring out pushrod length for roller cam - 01/07/23 10:11 PM
Posted By: 440_Offroader
Re: Figuring out pushrod length for roller cam - 01/08/23 04:28 PM
Well, your rocker shaft isn't tightened down...
Posted By: RapidRobert
Re: Figuring out pushrod length for roller cam - 01/08/23 05:00 PM
the utube vid "engine tech valvetrain geometry" by "straub technologies" may help. EDIT & UTG had something on preload amount for hyd lifters, probably not valid here but I wanted to throw it out there. he was loosing alot of power till he corrected it.
Posted By: 451Mopar
Re: Figuring out pushrod length for roller cam - 01/10/23 01:48 AM
I mentioned, the pushrods should be about 8.5" so you could get the correct length checking pushrod.
Posted By: Stanton
Re: Figuring out pushrod length for roller cam - 01/10/23 03:04 AM
The OP shouldn't be playing with mechanical things !!!