Pushrod Length confusion

-
70Hardtop

70Hardtop

Well-Known Member
Joined
Oct 14, 2009
Messages
333
Reaction score
68
Location
Australia
I know this has been discussed before, but the more i read, the more conflicting information i see and the more confused i get.

All i want to know is cup and ball p/rod lengths (for stock, unmachined engines) for 1. Correct p/rod length for
solid cam and adjustable rockers (eg Crane).

2. Correct p/rod length for hydraulic cam and adjustable rockers.

Also, where is the accepted way to measure cup/ball? from tip to bottom of cup, or total length, tip to top of cup?

All the following information is why i am confused.

70AAR Cuda says..."hydraulic and solid lifter plungers are located at different heights in the lifters...the solids are always lower and therefore take a longer pushrod.."

Mancini website says: A Engine, Hyd. Pushrod Set, Chromemoly, 5/16 in. Diameter, 7.330 in. Length, Ball/Cup Ends

A Engine, Mech. Pushrod Set, Chromemoly, 5/16 in. Diameter, 7.455 in. Length, Ball/Cup Ends

BUT...another Mopar forum guy says:

The Pushrod Length for all 'A' Engine is as follows,

A Engine Hydraulic - 7.514"

A Engine Mechanical - 7.340"

Then i go to Summit and see the Crower 3/8 cup and ball pushrods, 7.5" and the application is "Mopar 273-360 LA with with solid lifters and adjustable rockers."

So looks like the other forum fellow is wrong, assuming solid lifters are shorter than hydraulic.

Also, to add to the confusion, i measured a stock hyd ball/ball and it is 7.5". I then measured some 5/16 cup/ball rods i had, some stock 273 ones and some chr/moly Isky ones. Both were shorter, at about 7.34", measuring from tip to bottom of cup.

Locomotion says "Adjustable rockers with hydraulic lifters (cup/ball) tend to run around 7.21". (Like an OEM 340 Six Pack) Some companies advertise around a 7.31" or so length but I've never had a hydraulic combo that they would work with. Solid lifters with adjustable rockers tend to be around 7.50". (Like the early solid lifter 273.) But, as has been mentioned, get it measured. There is also 2 ways to measure. One is "effective" length, which is from the ball tip to the bottom of the cup. The other is overall length. Gosh darn it, now that said all that, I "think" that the numbers given are "effective" length. But I'm not 100% sure and don't have any pushrods handy to check. "

Thanks!!
 
confusing ...LOL

a off the shelf pushrod is always going to be a compromise due to any milling of the block and heads along with thickness of head gasket...

I have used crane 5/16 pushrods for solid lifter cams with adjustable rockers...although i have one set of erson 3/8 pushrods in use also with no problems...

all 4 engines have crane rockers also.....

dont know if that clears up the confusion for you...
 
Thanks for reply, but no, doesn't really clear it up as you didn't give any lengths. Off the shelf would still mean they make different standard lengths depending on the application. I really need hard numbers so i can compare different manufacturers' rods and make the right choice. I might actually make up an adjustable measuring pushrod myself to dummy it up correctly.
 
70Hardtop said:
I know this has been discussed before, but the more i read, the more conflicting information i see and the more confused i get.

All i want to know is cup and ball p/rod lengths (for stock, unmachined engines) for 1. Correct p/rod length for
solid cam and adjustable rockers (eg Crane).

2. Correct p/rod length for hydraulic cam and adjustable rockers.

Also, where is the accepted way to measure cup/ball? from tip to bottom of cup, or total length, tip to top of cup?

All the following information is why i am confused.

70AAR Cuda says..."hydraulic and solid lifter plungers are located at different heights in the lifters...the solids are always lower and therefore take a longer pushrod.."

Mancini website says: A Engine, Hyd. Pushrod Set, Chromemoly, 5/16 in. Diameter, 7.330 in. Length, Ball/Cup Ends

A Engine, Mech. Pushrod Set, Chromemoly, 5/16 in. Diameter, 7.455 in. Length, Ball/Cup Ends

BUT...another Mopar forum guy says:

The Pushrod Length for all 'A' Engine is as follows,

A Engine Hydraulic - 7.514"

A Engine Mechanical - 7.340"

Then i go to Summit and see the Crower 3/8 cup and ball pushrods, 7.5" and the application is "Mopar 273-360 LA with with solid lifters and adjustable rockers."

So looks like the other forum fellow is wrong, assuming solid lifters are shorter than hydraulic.

Also, to add to the confusion, i measured a stock hyd ball/ball and it is 7.5". I then measured some 5/16 cup/ball rods i had, some stock 273 ones and some chr/moly Isky ones. Both were shorter, at about 7.34", measuring from tip to bottom of cup.

Locomotion says "Adjustable rockers with hydraulic lifters (cup/ball) tend to run around 7.21". (Like an OEM 340 Six Pack) Some companies advertise around a 7.31" or so length but I've never had a hydraulic combo that they would work with. Solid lifters with adjustable rockers tend to be around 7.50". (Like the early solid lifter 273.) But, as has been mentioned, get it measured. There is also 2 ways to measure. One is "effective" length, which is from the ball tip to the bottom of the cup. The other is overall length. Gosh darn it, now that said all that, I "think" that the numbers given are "effective" length. But I'm not 100% sure and don't have any pushrods handy to check. "

Thanks!!
Click to expand...

First off Hardtop most "stock unmachined" engines use ball/ball pushrods since they also mostly use stamped steel rockers with the odd exception of a few that were supplied with ductile iron adjustable rockers and solid lifters.
The end all be all is if you're going to Crane roller rockers, or anyones roller rockers, you are going to have to make or have made a custom set of pushrods. This is so that the threads showing on the adjusters or within spec. and it covers any work that may have been done to the heads or block. Therefore yes you are going to have to get an adjustable pushrod and go through the procedure and if after doing that you do find rods off the shelf already to go then consider yourself lucky. Also if you end up ordering them from lets say Hughes or Smith, ask them what they prefer as the correct measurement, it's usually ball tip to bottom of cup. Have fun
 
I have a 273 with solid cam and adjustable rockers. I too find it frustrating finding the proper length after head milling and machining. I'm learning as I go. I bought a checker pushrod from Mancini but I didn't screw the adjusting nuts in far enough when I checked for length. I was excited to find Comp Cams had pushrods listed "off the shelf" that were the length I needed. When I got them they were too long and the cup hit the rocker arm body because I had to adjust the screw out too far to get the proper lash. The "two threads exposed" rule isn't enough I guess. I don't think there is a formula to come up with the proper length. toolmanmike
 
Thanks Demon Seed and Toolman, looks like you are right, will have to go the correct way and do a dummy-up. I plan to use Crane ductile iron adj , not the roller rockers with a high lift Hydraulic cam on my 340 and 273 adjustable rockers on a solid cam in a 360. So i will be ordering 2 sets of push rods. Double reason for getting the measurements right!
 
You must log in or register to reply here.
-

Back
Top