4.0 OHV Pushrod Troubles

[Maxsaaty]

Hello all, I am in the process of rebuilding my 4.0 OHV and I’m at the point where I need to figure out pushrod length. I put in the Delta Cams 410 cam regrind so I was assuming I’ll need bigger pushrods. I checked pushrod length with my old stock pushrods to see if I would actually need to change anything and got the results shown in the attached pictures. From the pictures it appears the rocker is sliding all the way down the valve. Would this mean I need smaller pushrods? It is also worth noting that I had my rocker tips cleaned up by Delta cams but they told me that wouldn’t change the geometry. Any input helps thank you.

 

[SenorNoob]

Is that some kind of marking compound or wear on the rockers and valve stems?

 

[Maxsaaty]

Is that some kind of marking compound or wear on the rockers and valve stems?

It is sharpie to check where the rockers were touching.

 

[SenorNoob]

It looks so much like the wear pattern my original parts had that it's hard to tell.

 

[Maxsaaty]

It looks so much like the wear pattern my original parts had that it's hard to tell.

Yeah I was thinking the same for the rockers. I’m just worried about the valves. When doing the sharpie test with roller rockers the wear mark should be in the middle of the valve. Since these are flat rockers I’m not sure if the wear mark going completely down the valve is bad or normal.

 

[gaz]

@Maxsaaty
I am not exactly certain what you are trying to convey but when the rocker arm bosses are properly torqued, the pushrod should actuate the hydraulic lifter plunger and it will be retracted between 0.025" and 0.100"; this is known as "LIFTER PRELOAD".

PUSHROD LENGTH:
• More than 0.100" into the lifter is too long
• Less than 0.001" into the lifter is too short

When I use the pushrod measuring tool, I want pushrods 0.025" longer than the gap between lifter and rocker cup when the rocker arms are installed and torqued, with the cam is on the base circle.

If you desire higher performance from your valvetrain, there are adjustable valvetrain options available.

 

[Maxsaaty]

@Maxsaaty
I am not exactly certain what you are trying to convey but when the rocker arm bosses are properly torqued, the pushrod should actuate the hydraulic lifter plunger and it will be retracted between 0.025" and 0.100"; this is known as "LIFTER PRELOAD".

PUSHROD LENGTH:
• More than 0.100" into the lifter is too long
• Less than 0.001" into the lifter is too short

When I use the pushrod measuring tool, I want pushrods 0.025" longer than the gap between lifter and rocker cup when the rocker arms are installed and torqued, with the cam is on the base circle.

If you desire higher performance from your valvetrain, there are adjustable valvetrain options available.

When checking pushrod sizes I was under the impression the wear mark on the valve should look like the one in this attached photo. I guess my question is, is it normal that my wear mark looks like it does?

 

[SenorNoob]

Assuming you have correct geometry already, what would you do to change that? A sharper curve on the end of the rocker arm?

 

[Maxsaaty]

Assuming you have correct geometry already, what would you do to change that? A sharper curve on the end of the rocker arm?

Well that’s why I’m a little worried about with having the rocker arm tips reground. I’m worried they may be too flat.

 

[gaz]

@Maxsaaty
I do not see an issue with the way your rockers are contacting your valve stems. Additionally, the crew at Delta have been a big force supporting Rangers, BroncoII's and Explorer's in the PNW for decades.

 

[Maxsaaty]

Ok that’s honestly what I needed to hear. Thank you.

@Maxsaaty
I do not see an issue with the way your rockers are contacting your valve stems. Additionally, the crew at Delta have been a big force supporting Rangers, BroncoII's and Explorer's in the PNW for decades.

 

[avid]

@Maxsaaty
I am not exactly certain what you are trying to convey but when the rocker arm bosses are properly torqued, the pushrod should actuate the hydraulic lifter plunger and it will be retracted between 0.025" and 0.100"; this is known as "LIFTER PRELOAD".

PUSHROD LENGTH:
• More than 0.100" into the lifter is too long
• Less than 0.001" into the lifter is too short

When I use the pushrod measuring tool, I want pushrods 0.025" longer than the gap between lifter and rocker cup when the rocker arms are installed and torqued, with the cam is on the base circle.

If you desire higher performance from your valvetrain, there are adjustable valvetrain options available.

Hey Gaz (or anyone else), what pushrod measuring tool are you using for the 4.0 OHV? All of them I've found so far are either for 6"+ pushrods or don't have the 9mm ball ends the 4.0 OHV has.