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Push rod length

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pmrphil
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Push rod length Empty Push rod length

Post  HorsinAround November 24th 2018, 5:18 pm

Need some help getting the pushrod length set on a 302. I have tried various lengths with my pushrod checker and can't seem to get the tip right in the middle. I am using scorpion pedestal rockers. The photo below show the witness mark using a 6.310 length rod. If i try a 6.300, there is play even after torquing to 20 ft lbs. What am I doing wrong?

Push rod length Stem10
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Post  pmrphil November 25th 2018, 10:22 am

Pushrod length won't change that with a bolt down rocker - you need a rocker shim kit, FMS, Crane, etc. sell them. Once you have the right height and pattern, then you can check pushrod length.

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Post  HorsinAround November 25th 2018, 3:35 pm

So raising the pedestal with shims will move the rocker tip closer to center? Then use the adjustable push rod to determine zero lash+ preload?
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Post  pmrphil November 25th 2018, 5:46 pm

From what I have seen, yes, it should, and yes.

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Post  dfree383 November 25th 2018, 8:40 pm

Or possibly you may need to machine the pedestals slightly too
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Post  HorsinAround November 25th 2018, 9:28 pm

dfree383 wrote:Or possibly you may need to machine the pedestals slightly too

Did more checking today and raising the pedestal did not move the tip closer to the center. I didn't have any lash caps on hand, so I used a feeler gauge to add .080 to the valve stem, with no shim under the pedestal, and that actually worked was able to set the correct preload. So, with that, I ordered a few .080 and .060 lash caps to test further. In the mean time, I've got plenty of other things to keep me busy lol.

Dave, I came to that conclusion as well. It will either be lash caps or machine the pedestal or a combination of both that gets the geometry right.
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Post  rmcomprandy November 25th 2018, 9:56 pm

dfree383 wrote:Or possibly you may need to machine the pedestals slightly too

From the looks of it,
they do need some taken off the pedestals or removed from the rocker  pads on the heads; somewhere around .030";
it is close enough to leave it that way.

All the different pushrod lengths will only alter "Lifter Preload" with using that bolt down rocker arm set-up.

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Post  jbozzelle November 26th 2018, 11:18 am

What sort of combo are you building?

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Post  HorsinAround November 26th 2018, 8:36 pm

jbozzelle wrote:What sort of combo are you building?

302, stock mustang bottom end, x302 heads, F303 cam, edelbrock dual plane, 650 DP.

I started out looking for a set of GT40 heads, and was going very mild on the cam, but was offered the heads, intake, cam, new roller lifters for a VERY good price, so I didn't say no.

The motor is going in a 94 Ext. cab 2wd Ranger with a 5 speed. Swapped in an 8.8 with a 4.10 posi, but now that I'm driving 60 miles a day, I may swap in 3.55 gears if the motor proves solid and make a daily driver out of it. I have gone through the ranger from tip to tail, replacing almost everything. I'll post a couple pics when I get the motor finished up and installed.


Thanks to all for your replies. I will know more tomorrow evening when I get back in the shop.
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Post  Mark Miller November 27th 2018, 1:27 am

HorsinAround wrote:
jbozzelle wrote:What sort of combo are you building?

302, stock mustang bottom end, x302 heads, F303 cam, edelbrock dual plane, 650 DP.

I started out looking for a set of GT40 heads, and was going very mild on the cam, but was offered the heads, intake, cam, new roller lifters for a VERY good price, so I didn't say no.

The motor is going in a 94 Ext. cab 2wd Ranger with a 5 speed. Swapped in an 8.8 with a 4.10 posi, but now that I'm driving 60 miles a day, I may swap in 3.55 gears if the motor proves solid and make a daily driver out of it. I have gone through the ranger from tip to tail, replacing almost everything. I'll post a couple pics when I get the motor finished up and installed.


Thanks to all for your replies. I will know more tomorrow evening when I get back in the shop.


Sounds like a cool little Ranger you're working on,for sure post the pictures of the Ranger when you can!! Smile Smile

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Post  HorsinAround November 27th 2018, 10:29 am

Mark Miller wrote:
HorsinAround wrote:
jbozzelle wrote:What sort of combo are you building?

302, stock mustang bottom end, x302 heads, F303 cam, edelbrock dual plane, 650 DP.

I started out looking for a set of GT40 heads, and was going very mild on the cam, but was offered the heads, intake, cam, new roller lifters for a VERY good price, so I didn't say no.

The motor is going in a 94 Ext. cab 2wd Ranger with a 5 speed. Swapped in an 8.8 with a 4.10 posi, but now that I'm driving 60 miles a day, I may swap in 3.55 gears if the motor proves solid and make a daily driver out of it. I have gone through the ranger from tip to tail, replacing almost everything. I'll post a couple pics when I get the motor finished up and installed.


Thanks to all for your replies. I will know more tomorrow evening when I get back in the shop.


Sounds like a cool little Ranger you're working on,for sure post the pictures of the Ranger when you can!! Smile Smile

Will do. You can visit my youtube channel to check out some videos I did during the build. Sadly, I had the project all done except for the cut and buff when I fired it up and discovered the pushrod issue (lesson learned about taking someone's advice without checking myself) and the brand new autozone truck pan was leaking oil. So out came the motor to fix the issues.
https://www.youtube.com/channel/UCWVSa5kgbGqcpaZUgesS4JQ

At one point I was thinking about picking up a later model extended cab and building another drag truck with a BBF in it, but Im not too sure about it now.
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Post  rmcomprandy November 27th 2018, 10:29 am

HorsinAround wrote:So raising the pedestal with shims will move the rocker tip closer to center? Then use the adjustable push rod to determine zero lash+ preload?

NO ... a higher fulcrum point will move the pattern toward the outside.

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Post  HorsinAround November 27th 2018, 10:39 am

rmcomprandy wrote:
HorsinAround wrote:So raising the pedestal with shims will move the rocker tip closer to center? Then use the adjustable push rod to determine zero lash+ preload?

NO ... a higher fulcrum point will move the pattern toward the outside.

Thank you for the reply. I discovered that Sunday as I was trying to figure it out. The one good thing about this ordeal is I am learning new things.
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Post  pmrphil November 27th 2018, 2:02 pm

Yeah, me too. Embarassed

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