Pushrods on a regrind cam???

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xLURKxDOGx

xLURKxDOGx

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Anyone have any idea what length pushrods they used for a regrind cam? I pulled the ones from mine and theyre a bit shorter than what stock pushrods are listed at (6.9). I know there are a bunch of people that have done this, just hoping they can chime in.

Thanks,
Jake
 
xLURKxDOGx said:
Anyone have any idea what length pushrods they used for a regrind cam? I pulled the ones from mine and theyre a bit shorter than what stock pushrods are listed at (6.9). I know there are a bunch of people that have done this, just hoping they can chime in.

Thanks,
Jake
Click to expand...

A regrind reduces the base circle of the cam, so in theory you should need a longer pushrod. The actual length is not a given that applies to every combination. You must properly measure for correct pushed length. There are too many variables to be able to say you need "x" length pushrods. If your pushrods are shorter there's either a good reason for it or they're incorrect.
 
Fast01 said:
A regrind reduces the base circle of the cam, so in theory you should need a longer pushrod. The actual length is not a given that applies to every combination. You must properly measure for correct pushed length. There are too many variables to be able to say you need "x" length pushrods. If your pushrods are shorter there's either a good reason for it or they're incorrect.
Click to expand...
I figure that was the case but wanted to be sure. I think the dude had the wrong ones because they had a wear spot like it was rubbing against something. What is the correct way to measure on a magnum with roller rockers? I know the correct way with 273 ductile rockers where you want 1 1/2 threads showing for correct geometry but is that same principle applied on magnums? Thanks for the response.

Jake
 
xLURKxDOGx said:
I figure that was the case but wanted to be sure. I think the dude had the wrong ones because they had a wear spot like it was rubbing against something. What is the correct way to measure on a magnum with roller rockers? I know the correct way with 273 ductile rockers where you want 1 1/2 threads showing for correct geometry but is that same principle applied on magnums? Thanks for the response.

Jake
Click to expand...

Honestly, I'm a Mopar newbie and only have experience with a big block. I don't want to give had info here, but here's a link to some general theory straight from the horse's mouth. www.compcams.com/Technical/Instructions/Files/Verifying%2520Pushrod%2520Length%2520And%2520Rocker%2520Arm%2520Geometry.pdf&ved=0ahUKEwid9NfWreHSAhUEtBQKHc9KAvEQFggyMAI&usg=AFQjCNFESLhgPI--0TSi4f8CAbdQgotOQA
 
Magnum are ped mount, just turn the rocker mounting stud screw...? Or am I missing something?
hrdp_0804_10_z-small_block_mopar_engine-edelbrock_performer_rpm_magnum_heads.jpg
 
Fast01 said:
Ooops! Sorry 'bout that! Yeah, it was on Comp's site.
Click to expand...

Looks to me it's just like a small block Chevy....those I'm familiar with. If you're running a solid cam it's pretty straight forward with a checking pushrod and caliper. If you're running a hydraulic cam, you'll either have to use a solid lifter to check or swap out the springs on a cylinder with checking springs as to not compress the hydraulic plunger.
 
xLURKxDOGx said:
OH YEAH! So how would you know what is the correct pushrod size?

Jake
Click to expand...
well, I have no experience with chevy/Ford/Magnum heads but here is what I found:
"...Finding Center There are several ways to find proper pushrod length, but when it comes to stud-mounted rocker systems, the simplest way is to use a Sharpie and a wrench to turn the crankshaft. Even the most sophisticated engine builders use this method. Keith Dorton of Automotive Specialists says it is the most reliable and simplest way to determine correct pushrod length..
...you can use an adjustable-length checking pushrod designed especially for this task....
Whether you are using a checking pushrod or a standard piece that you think might fit correctly, begin by coloring the valve tip with either a Sharpie or machinist’s dye. Then, install the pushrod and rocker arm while the lifter is on the base circle of the cam. If you are using a solid lifter, set the valvetrain to zero lash. If you are running a hydraulic lifter, tighten down the rocker adjuster to your normal preload. Using a wrench on the nose of the crank, turn the motor over several times, then remove the rocker and check the mark left on the valve tip. The roller tip on the rocker should have left a shiny spot where it wore away the ink you placed on the valve tip.

ctrp_0608_12_z-pushrod_length-different_rocker_arms.jpg


If the pushrod length is correct, this mark should be centered across the top of the valve stem. If it is too high (closer to the lifter valley), try a slightly longer pushrod or lengthen the checker. If it is too low (closer to the exhaust ports), try a slightly shorter pushrod. Now simply repeat the process, adjusting the pushrod length each time, until you have the wear mark centered on the valve tip. Sometimes the low-tech methods really are the best."

So I guess you still gotta spend some dough to run "correct"
 
pishta said:
well, I have no experience with chevy/Ford/Magnum heads but here is what I found:
"...Finding Center There are several ways to find proper pushrod length, but when it comes to stud-mounted rocker systems, the simplest way is to use a Sharpie and a wrench to turn the crankshaft. Even the most sophisticated engine builders use this method. Keith Dorton of Automotive Specialists says it is the most reliable and simplest way to determine correct pushrod length..
...you can use an adjustable-length checking pushrod designed especially for this task....
Whether you are using a checking pushrod or a standard piece that you think might fit correctly, begin by coloring the valve tip with either a Sharpie or machinist’s dye. Then, install the pushrod and rocker arm while the lifter is on the base circle of the cam. If you are using a solid lifter, set the valvetrain to zero lash. If you are running a hydraulic lifter, tighten down the rocker adjuster to your normal preload. Using a wrench on the nose of the crank, turn the motor over several times, then remove the rocker and check the mark left on the valve tip. The roller tip on the rocker should have left a shiny spot where it wore away the ink you placed on the valve tip.

View attachment 1715029597

If the pushrod length is correct, this mark should be centered across the top of the valve stem. If it is too high (closer to the lifter valley), try a slightly longer pushrod or lengthen the checker. If it is too low (closer to the exhaust ports), try a slightly shorter pushrod. Now simply repeat the process, adjusting the pushrod length each time, until you have the wear mark centered on the valve tip. Sometimes the low-tech methods really are the best."

So I guess you still gotta spend some dough to run "correct"
Click to expand...
Thanks alot! This is priceless info!

Jake
 
You have to measure for correct pushrod length, regardless of whether you have adjustable rockers or not.
 
pishta said:
well, I have no experience with chevy/Ford/Magnum heads but here is what I found:
"...Finding Center There are several ways to find proper pushrod length, but when it comes to stud-mounted rocker systems, the simplest way is to use a Sharpie and a wrench to turn the crankshaft. Even the most sophisticated engine builders use this method. Keith Dorton of Automotive Specialists says it is the most reliable and simplest way to determine correct pushrod length..
...you can use an adjustable-length checking pushrod designed especially for this task....
Whether you are using a checking pushrod or a standard piece that you think might fit correctly, begin by coloring the valve tip with either a Sharpie or machinist’s dye. Then, install the pushrod and rocker arm while the lifter is on the base circle of the cam. If you are using a solid lifter, set the valvetrain to zero lash. If you are running a hydraulic lifter, tighten down the rocker adjuster to your normal preload. Using a wrench on the nose of the crank, turn the motor over several times, then remove the rocker and check the mark left on the valve tip. The roller tip on the rocker should have left a shiny spot where it wore away the ink you placed on the valve tip.

View attachment 1715029597

If the pushrod length is correct, this mark should be centered across the top of the valve stem. If it is too high (closer to the lifter valley), try a slightly longer pushrod or lengthen the checker. If it is too low (closer to the exhaust ports), try a slightly shorter pushrod. Now simply repeat the process, adjusting the pushrod length each time, until you have the wear mark centered on the valve tip. Sometimes the low-tech methods really are the best."

So I guess you still gotta spend some dough to run "correct"
Click to expand...
right on the money,...while doing this keep check of clearances and geometry of it keeping both in spec!
 
I just got it on the base circle and ran a checking pushrod out until it got tight and I could just barely still turn it with my fingers.
Then I count the number of turns to pre load the lifter the correct amount (there should be a depth of pre load recommended based on lifter). This will depend on the thread pitch in the checking push rod used.
 
Shainesboostin said:
Aren't stock 6.936?
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They vary from about 6.915 to 6.936 from what I have seen for stock.
I was able to use my stock rods with a regrind cam and EQ heads and have .040 preload.
Kind of surprised me, but I was ok with it. :D

I would have liked another .010 but it wasn't worth getting different ones.
 
pishta said:
Magnum are ped mount, just turn the rocker mounting stud screw...? Or am I missing something?
View attachment 1715029550
Click to expand...
problem with this pic is the parts are not stock-this aftermarket stuff has adjustable rockers. stock magnum is bolt down non adjustable rockers-so correct length pushrods are important. if you have stock rockers you want pushrods that give proper lifter preload
 
TrailBeast said:
They vary from about 6.915 to 6.936 from what I have seen for stock.
I was able to use my stock rods with a regrind cam and EQ heads and have .040 preload.
Kind of surprised me, but I was ok with it. :D

I would have liked another .010 but it wasn't worth getting different ones.
Click to expand...


Wow, I have a Comp cam, .512 lift I used my stock pushrods with Harland Sharp NON adjustable and had like .090-.100 preload!!! Been running strong. I've heard so many opinions on preload. Stock according to hughes is .06-.09
 
Shainesboostin said:
Wow, I have a Comp cam, .512 lift I used my stock pushrods with Harland Sharp NON adjustable and had like .090-.100 preload!!! Been running strong. I've heard so many opinions on preload. Stock according to hughes is .06-.09
Click to expand...

The magnum is .040-.060 stock from what I have found.
 
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