Looking for suggestions on pushrod length

What length pushrods should I get? I have a set of 8.550" and stockers that should be 8.500" I believe. Both look to be too long.




Would a 8.450" or 8.400" pushrod get me closer to where it need to be? Motor is a mild build for a truck. Zero deck, .030" over, 5000rpm and under type motor. Thanks.

Jess

If you want to determine the exact length, take 12 minutes and watch this video. This will get you the exact length you need for any build.

https://m.youtube.com/watch?v=o5is9BsH5OU

Mustang-junky wrote:What length pushrods should I get?  I have a set of 8.550" and stockers that should be 8.500" I believe.  Both look to be too long.




Would a 8.450" or 8.400" pushrod get me closer to where it need to be?  Motor is a mild build for a truck.  Zero deck, .030" over, 5000rpm and under type motor.  Thanks.

Jess

Either one would work OK on that valve stem side with a roller tip rocker arm ... the pushrod side is the side which needs to be closest to being right.

Okay. Thanks,

Jess

738drvr wrote:If you want to determine the exact length, take 12 minutes and watch this video. This will get you the exact length you need for any build.

https://m.youtube.com/watch?v=o5is9BsH5OU

While he is optimizing the valve end of the rocker arm he's not doing anything what so ever to optimize the pushrod end which is really more important and could very likely be out to lunch.

DaveMcLain wrote:

738drvr wrote:If you want to determine the exact length, take 12 minutes and watch this video. This will get you the exact length you need for any build.

https://m.youtube.com/watch?v=o5is9BsH5OU

While he is optimizing the valve end of the rocker arm he's not doing anything what so ever to optimize the pushrod end which is really more important and could very likely be out to lunch.

I 2nd that, I watched that video, can't spell it out any better.

I have 8 comp cam 3/8 8.45 push rods with no more than 8 passes on them I will sale I had 2 cracked rocker arms when I got my new rocker arms they would not work with them I had to go with 8.55 and 8.65 from 8.45 and 8.55

DaveMcLain wrote:

738drvr wrote:If you want to determine the exact length, take 12 minutes and watch this video. This will get you the exact length you need for any build.

https://m.youtube.com/watch?v=o5is9BsH5OU

While he is optimizing the valve end of the rocker arm he's not doing anything what so ever to optimize the pushrod end which is really more important and could very likely be out to lunch.

Dave - Can you elaborate more? I'm a bit lost on what you're referring to.

jbozzelle wrote:

DaveMcLain wrote:

738drvr wrote:If you want to determine the exact length, take 12 minutes and watch this video. This will get you the exact length you need for any build.

https://m.youtube.com/watch?v=o5is9BsH5OU

While he is optimizing the valve end of the rocker arm he's not doing anything what so ever to optimize the pushrod end which is really more important and could very likely be out to lunch.

Dave - Can you elaborate more?  I'm a bit lost on what you're referring to.

The pushrod side of the rocker arm also swings through an arc just like it does on the valve side. There is a place in the rocker arm's motion where the pushrod creates a 90 degree angle in relation to its cup/pivot point and the centerline of the rocker arm's trunion. What can happen is a sometimes radical change in the rocker ratio and when the pushrod seat is too low it tends to make the ratio higher at low lifts and lower at higher lifts and vice versa. This isn't being addressed at all in the video and by strictly concentrating on only the valve end of the rocker arm it most certainly could cause the pushrod side to be more compromised than it needs to be depending on the design of the rocker arm and the engine itself. In other words it might be best to split the difference and compromise both sides of the rocker.

Read some of what Jim Miller says about this with his "Mid Lift Geometry" rocker arm stuff it is very interesting. Does it all make a difference or is it all hot air? I think it might be some of both.

So you're saying that just shooting for the least amount of sweep across the valve tp is a better way to go? Or it's a crapshoot either way as long as the valve gets opened?

jbozzelle wrote:So you're saying that just shooting for the least amount of sweep across the valve tp is a better way to go?  Or it's a crapshoot either way as long as the valve gets opened?

NO ... as long as the pattern is withing the center 2/3 of the valve tip when using a roller rocker arm, the pushrod end to cup geometry will be the more important side to be near correct.
That pushrod tip friction being near correct is more important because it sees valve spring pressure TIMES the rocker ratio and is rubbing friction which really creates heat; not like a roller.

It is rare that both sides of the rocker geometry will ever be exactly right so, as Dave says ... some kind of compromise will probably need to be made to get both sides decent.

Is it a matter of trying to get the pushrod 90* to the rocker, similar to what you'd want to do on the other end?

jbozzelle wrote:Is it a matter of trying to get the pushrod 90* to the rocker, similar to what you'd want to do on the other end?

Very similar ...

Thanks. Always trying to learn from you guys...

.

For mock-up purposes I have 12 different stud type, Big Block Ford rocker arms to use.
1. old Crane gold
2. Isky
3. Comp Cams stainless H.P. (no longer made)
4. Angus.
5. Comp Cams red
6. Ford Racing
7. Lunati VooDoo
8. Crower steel
9. Harland Sharp S4073
10, Harland Sharp S4005
11. Scorpion
12. Comp Cams Gold

Only 3 of them share about the same geometry; 2 others are near the same as one another.
All the other 7 are all different geometry.
A lot of times I will split sets on the big block Ford using one on the intake side and a different one on the exhaust side.

And Randy didn't even mention the variation it "true'' rocker arm ratio in the 12 examples. Some more , some less . few "exact" . The irritating part is when the end customer thinks you are giving him "leftover" parts and doesn't appreciate the hours you spent getting the best geometry possible!

rmcomprandy wrote:For mock-up purposes I have 12 different stud type, Big Block Ford rocker arms to use.
1. old Crane gold
2. Isky
3. Comp Cams stainless H.P. (no longer made)
4. Angus.
5. Comp Cams red
6. Ford Racing
7. Lunati VooDoo
8. Crower steel
9. Harland Sharp S4073
10, Harland Sharp S4005
11. Scorpion
12. Comp Cams Gold

Only 3 of them share about the same geometry; 2 others are near the same as one another.
All the other 7 are all different geometry.
A lot of times I will split sets on the big block Ford using one on the intake side and a different one on the exhaust side.

Randy have you ever seen the Erson 1.73 429-460 Rocker Arms been using these for years?

Mark Miller wrote:

rmcomprandy wrote:For mock-up purposes I have 12 different stud type, Big Block Ford rocker arms to use.
1. old Crane gold
2. Isky
3. Comp Cams stainless H.P. (no longer made)
4. Angus.
5. Comp Cams red
6. Ford Racing
7. Lunati VooDoo
8. Crower steel
9. Harland Sharp S4073
10, Harland Sharp S4005
11. Scorpion
12. Comp Cams Gold

Only 3 of them share about the same geometry; 2 others are near the same as one another.
All the other 7 are all different geometry.
A lot of times I will split sets on the big block Ford using one on the intake side and a different one on the exhaust side.

Randy have you ever seen the Erson 1.73 429-460 Rocker Arms been using these for years?

I have seen them but, I don't own any.
There are lots of other brands out there beside just those 12.

rmcomprandy wrote:

Mark Miller wrote:

rmcomprandy wrote:For mock-up purposes I have 12 different stud type, Big Block Ford rocker arms to use.
1. old Crane gold
2. Isky
3. Comp Cams stainless H.P. (no longer made)
4. Angus.
5. Comp Cams red
6. Ford Racing
7. Lunati VooDoo
8. Crower steel
9. Harland Sharp S4073
10, Harland Sharp S4005
11. Scorpion
12. Comp Cams Gold

Only 3 of them share about the same geometry; 2 others are near the same as one another.
All the other 7 are all different geometry.
A lot of times I will split sets on the big block Ford using one on the intake side and a different one on the exhaust side.

Randy have you ever seen the Erson 1.73 429-460 Rocker Arms been using these for years?

I have seen them but, I don't own any.
There are lots of other brands out there beside just those 12.

Thanks I was just curious I've had pretty good luck with the Erson's knock on wood!!!