#41  
Old 03-04-2023, 11:27 PM
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I would put some lash caps on, might solve your problem. Then 1.65 should work, just might need shorter push rod.

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  #42  
Old 03-05-2023, 11:47 AM
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I'm standing by my comments that a 0.150 longer body rocker arm- trunnion to roller tip-is going to be way off . Unless you use a lash cap and a really short pushrod for sure. Even my 1.8 BBC with a 0.090 offset trunnion is a lot shorter pushrod.

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  #43  
Old 03-07-2023, 04:39 AM
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Quote:
Originally Posted by Skip Fix View Post
I'm standing by my comments that a 0.150 longer body rocker arm- trunnion to roller tip-is going to be way off . Unless you use a lash cap and a really short pushrod for sure. Even my 1.8 BBC with a 0.090 offset trunnion is a lot shorter pushrod.
x2

I'm going to double down and repeat what I said before. The OP's problems (including the first engine failure) are the direct result of the rocker misapplication. With Pontiac rockers, the pushrod length should be 9.20" just like the RA IV heads that the Edelbrocks are patterned after. The rocker arm ratio (1.5 vs 1.65) doesn't change anything enough to warrant custom length pushrods. Yeah, you can split hairs but the 9.20" pushrods are adequate unless a reduced base circle camshaft comes into play for extremely high lifts.

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  #44  
Old 03-07-2023, 12:34 PM
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Quote:
Originally Posted by NeighborsComplaint View Post
x2

I'm going to double down and repeat what I said before. The OP's problems (including the first engine failure) are the direct result of the rocker misapplication.
Have to agree 500% on that Statement.

He has been the victim of a lots of parts purchases (that he never needed) for his very nice vehicle restoration, in my opinion.

Tom V.

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  #45  
Old 03-07-2023, 02:35 PM
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I'll add that it only stands to reason that Pontiac rockers are misaligned on the valve tips now because the pushrods were likely sized to accommodate the offset of the BBC rockers. Put the 9.20"L Pontiac pushrods on with Pontiac specific rockers and the motor will be happy and healthy.

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Last edited by NeighborsComplaint; 03-07-2023 at 02:41 PM.
  #46  
Old 03-07-2023, 03:46 PM
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Just to say, you can use the same parts on a 'like' built engine, and you still have to measure for pushrods. Each engine can be enough different to require different length pushrods.

The mid-lift method for measuring geometry is the most accurate, or 'correct' way to determine proper geometry (pushrod length is the variable).

Contact pattern IMO is a poor way of measuring for geometry (pushrods).

Do it right, do it once.

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  #47  
Old 03-07-2023, 04:49 PM
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The mid-lift method for measuring geometry is the most accurate, or 'correct' way to determine proper geometry (pushrod length is the variable).

Swapping between rocker brands is also a problem with this. Every brand has a different relationship between the pushrod cup depth, the center of the trunnion and the center of the roller tip AND the roller tip diameter.

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  #48  
Old 03-08-2023, 09:18 AM
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Quote:
Originally Posted by Skip Fix View Post
The mid-lift method for measuring geometry is the most accurate, or 'correct' way to determine proper geometry (pushrod length is the variable).

Swapping between rocker brands is also a problem with this. Every brand has a different relationship between the pushrod cup depth, the center of the trunnion and the center of the roller tip AND the roller tip diameter.
Very true.

Correction - (pushrod length and rocker arms are the variables)

.

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  #49  
Old 03-08-2023, 11:19 AM
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Quote:
Originally Posted by Skip Fix View Post
I'm standing by my comments that a 0.150 longer body rocker arm- trunnion to roller tip-is going to be way off . Unless you use a lash cap and a really short pushrod for sure. Even my 1.8 BBC with a 0.090 offset trunnion is a lot shorter pushrod.
Skip, is there any place that shows what the length of the BBC rocker is from trunionh to roller tip.Also a Pontiac rocker?

Does all the change in ratio come from changes on the pushrod side of the rocker?
One reason I ask is that I have a set of Crower supposedly Pontiac 1.7 rockers. People keep telling me they are probably BBC rockers. I’m kinda looking to find out how I could tell..

Thanks
Murf

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Old 03-08-2023, 11:54 AM
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As the ratio goes up the push rod cup gets moved closer to the rocker stud.

If you had let’s say a ideal geometry working with a 1.5 rocker and you switched to 1.65s which moved the cup .050” closer to the stud, then a .050” longer push rod should get you back to having hood geometry.

The bad thing once you get above a certain ratio is that the cup will be getting real close to the trunion and with enough spring pressure and cycles that’s where the rockers will break.

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  #51  
Old 03-08-2023, 11:56 AM
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Closer to the stud, or further?


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  #52  
Old 03-08-2023, 12:53 PM
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Quote:
Originally Posted by 25stevem View Post
As the ratio goes up the push rod cup gets moved closer to the rocker stud.

If you had let’s say a ideal geometry working with a 1.5 rocker and you switched to 1.65s which moved the cup .050” closer to the stud, then a .050” longer push rod should get you back to having hood geometry.

The bad thing once you get above a certain ratio is that the cup will be getting real close to the trunion and with enough spring pressure and cycles that’s where the rockers will break.
Thanks Steve, I understand that. I guess what I’m asking is, “is there a place to find what the distance from the reunion to the roller on a BBC vs Pontiac rocker arm.”
I spose they are all over the place & I wound have to mock everything up to know what I’ve got.

Thanks again!
Murf

  #53  
Old 03-08-2023, 01:25 PM
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If you had let’s say a ideal geometry working with a 1.5 rocker and you switched to 1.65s which moved the cup .050” closer to the stud, then a .050” longer push rod should get you back to having hood geometry.

With my HS they took the same pushrod. And I'm betting RAIVs were just longer because of the longer valve not the pushrod cup and the stamped rocker.

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  #54  
Old 03-09-2023, 10:19 AM
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Quote:
Originally Posted by Skip Fix View Post
If you had let’s say a ideal geometry working with a 1.5 rocker and you switched to 1.65s which moved the cup .050” closer to the stud, then a .050” longer push rod should get you back to having hood geometry.

With my HS they took the same pushrod. And I'm betting RAIVs were just longer because of the longer valve not the pushrod cup and the stamped rocker.
i have HS 1.5 rockers and OF cam on E-heads with no issues.

dave at SD told me the same thing regarding HS 1.65 rockers vs 1.5. i was/am considering going to 1.65 from the current 1.5 & asked what pushrod length i would need, he said for the 1.65 HS rockers, i can use the same length i have for my HS 1.5.

  #55  
Old 03-09-2023, 11:29 AM
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Every motor I have built HS 1.5 and 1.65 take the same length pushrod.

As far as rocker length-yes the BBC is longer from the stud to roller tip. Ratio changes are on the pushrod cup size distance as the trunnion/stud to valve distance never changes. f you want to see something crazy look at ahigh ratio SBC! pushrod way up there on a really short body

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1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
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  #56  
Old 03-09-2023, 02:11 PM
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Quote:
Originally Posted by HWYSTR455 View Post
Closer to the stud, or further?


.

Pushrod cup is about .060" closer to the trunnion on the 1.65 ratio rocker.

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  #57  
Old 03-09-2023, 03:43 PM
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You can see the different placing on the stamped as well as HS in this picture and post 26
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1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
  #58  
Old 03-10-2023, 07:11 AM
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Thanks guys, some reason I always get that backwards! It's kind of a set-it-and-forget-it thing for me!

Guess because of the sweep during action that's done to prevent pushrod contact with the pushrod hole in the head, or more center it during the sweep/action because of load?

.

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