Pushrod for hydraulic cam and 273 rocker arms

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krazykuda

krazykuda

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Does anybody make a pushrod for putting stock 273 rocker arms on a hydraulic cam in a small block?

What are you guys that have put adjustable 273 rocker arms and using hydraulic cam using on your engines?
 
64-91, 273 thru 360
“LA”
with hydraulic lifters and adjustable rockers, heat treated, heavy wall
Stock
7.330
5/16
C-4
B-3
69621-16
Crane brand
 
I sure hope so since Mopar made a pile of um.
 
I always thought it was crazy that Mopar solids were deeper than hydraulics. It makes sense from a weight and cost production (one piece) standpoint but it would be nice if all the pushrods were the same like brand X.....
 
I did some calculating and laid it out on AutoCAD, but the problem seems to be that they don't specify where the measurements are supposed to be taken...

I compared the two lifters and found that the push rod is .257" taller in the hydraulic lifter than on the solid lifter from a 273.

I then backed that into the push rod length and figured out how long the push rod would need to be for the hydraulic lifter.

See the illustrations below:

Hyd vs Solid Lifter v2.jpg


Hyd vs Solid Lifter C2.jpg
 
they measure from the bottom on the cup. to the tip of the ball.
 
Mopar Tim said:
they measure from the bottom on the cup. to the tip of the ball.
Click to expand...

That's what you would think...

One tech guy at Summit said to measure to the bottom of the cup to the tip of the ball on the opposite end...

Tech guy #2 said to measure the push rod with a 5/16" ball in the cup and go from tip of ball to tip of opposite ball....

He came up with Speed Pro SLP-RP3219 R100

We'll see in a couple days when the parts get here....

***************************************

It is not SUM - G6420, they are too long and hit the bottom of the rocker arm
 
SUM - G6420, they are too long and hit the bottom of the rocker arm. I found this out the hard way as well.

Jake
 
I hear the Comp 7821-16 may work also. Plan D.... (we're already on plan C...)
 
Karl, this thread is about the pushrods we talked about on the phone.

Comp Cam 7821-16 pushrods (340 w/ 273 rockers)

They ARE the correct pushrods for the LA with adjustable rockers and hydraulic lifters. I don't know how everybody else measures them, but Comp measures them from the ball to the top of the edge of the cup. They are listed as 7.389" and that's what they measure from the ball to the top of the cup. I just measured them, in my hand while we were on the phone. They ARE the right ones. If you are having trouble with not enough adjuster through the rocker and the cup is close to the bottom of the rocker, then you may have milled heads, block OR the most likely culprit is you may need more lifter preload.

ALSO, keep in mind, not all lifters are the same length from the flat that rides on the lobe to the recess where the pushrod sits. This can make a significant difference. That's why it's BEST to get an adjustable pushrod and find out for sure.
 
.....The AAR cuda and the T/A challenger 340s had hyd lifters with adj rockers from the factory....The last few I've done are 7.250 +/- .060 thou.............kim......
 
oldkimmer said:
.....The AAR cuda and the T/A challenger 340s had hyd lifters with adj rockers from the factory....The last few I've done are 7.250 +/- .060 thou.............kim......
Click to expand...

What pushrods did you use? Brand? Part number???

It makes sense that the 6 pack engines had the right push rods.... But with only 5200 of them made, they are kind of hard to find in the application listings...
 
RustyRatRod said:
Karl, this thread is about the pushrods we talked about on the phone.

Comp Cam 7821-16 pushrods (340 w/ 273 rockers)

They ARE the correct pushrods for the LA with adjustable rockers and hydraulic lifters. I don't know how everybody else measures them, but Comp measures them from the ball to the top of the edge of the cup. They are listed as 7.389" and that's what they measure from the ball to the top of the cup. I just measured them, in my hand while we were on the phone. They ARE the right ones. If you are having trouble with not enough adjuster through the rocker and the cup is close to the bottom of the rocker, then you may have milled heads, block OR the most likely culprit is you may need more lifter preload.

ALSO, keep in mind, not all lifters are the same length from the flat that rides on the lobe to the recess where the pushrod sits. This can make a significant difference. That's why it's BEST to get an adjustable pushrod and find out for sure.
Click to expand...

Thanks Rob... I'm hoping the ones that we ordered yesterday will work, if not we have an option...
 
krazykuda said:
Thanks Rob... I'm hoping the ones that we ordered yesterday will work, if not we have an option...
Click to expand...

Even more variation to keep in mind is the Crane adjuster. I am not sure that the Comp number I posted takes those into consideration. I believe they are for use with the stock adjusters and there IS some length difference between them, I believe.
 
Karl & Rob,

Thank you for all the assistance on trying to figure out the Push Rod dilemma. I truly appreciate it.
 
xLURKxDOGx said:
SUM - G6420, they are too long and hit the bottom of the rocker arm. I found this out the hard way as well.

Jake
Click to expand...

I also found this out the hard way too, I needed push rods that were 7.250" from the ball to the top of the cup. So I ended up having a custom set made from a company called OE Push Rods, was around $65 shipped to my door.
 
Last edited:
Thanks! Im going to order some today!


Jake
 
r72demon - Good morning. Thank you

Do you know how long they took on the custom request?
 
Thank you R72Demon. Sent them an email with the specs. needed.
 
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