Broken Gn1 rocker stand

[jpwalt1987]

On the drive home today I noticed the car started making a valve train noise. The vacuum/boost gauge started fluctuating also. Got home and pulled the valve cover and what do I find? Broke a rocker stand in half and bent the T&D rocker shaft!!!!! Motor will be coming out in two weeks. Talk about bad timing with the holidays and all. Think it's fixable?

 

[cruzn57]

were you using springs with alot of open pressure?
or do you feel it was a casting flaw?

 

[jpwalt1987]

PAC1203s at an install height of 1.77
.545 lift
And heads that are from 2000-2001

That's my guess.

 

[TurboBuRick]

Looks like the hold down bolts are too short. Must be the ones that came with the rockers.

It can be fixed.

 

[BEATAV8]

Damn, the new springs must've been too much.

Maybe the other style of head with the stud mounted rocker would hold up better. Each individual rocker is secured to the head in a stud mount setup, instead of sharing the loads from all the rockers with 3 bolts along the shaft like the stock configuration.

 

[TurboBuRick]

The bolts that come with the rockers are too short. Been there done that.

 

[BEATAV8]

Ya I can see how more thread engagement would definitely help a lot, putting the load deeper into the casting.
Just wonder if that would be enough.... He's running quite a lot of spring pressure, well over 450lbs and high RPM too.

 

[bison]

I wouldn't run that style rocker with those springs. I have those springs and they are about 500lbs open.

 

[jpwalt1987]

I wouldn't run that style rocker with those springs. I have those springs and they are about 500lbs open.

Can these heads be modified to use the other style rocker arm?

 

[bison]

Yes. You could mill the stands off and drill and tap the heads for the other style rockers.

 

[jpwalt1987]

Anyone have a picture and part # for the new style T&D rockers?

 

[ek02]

Cheapest and easiest way would be to pull the head and have it tig welded, and then use the longest bolts you can. The stud mounted Chevy type rockers on GN1 heads are made by Scorpion. The T&D rockers used on TA Street Eliminator heads ( TAV1308) are pedestal mount with 3 bolts and 2 rockers per shaft. $879.00. TA also has an adapter to run your existing T&D rockers if you machine the head for the adapter. Either option would require a lot of machine work on your existing heads.

 

[bison]

Cheapest and easiest way would be to pull the head and have it tig welded, and then use the longest bolts you can. The stud mounted Chevy type rockers on GN1 heads are made by Scorpion. The T&D rockers used on TA Street Eliminator heads ( TAV1308) are pedestal mount with 3 bolts and 2 rockers per shaft. $879.00. Either option would require a lot of machine work on your existing heads.

There are t&d rockers available for the GN1 heads also and they are similar to the setup used on TA heads

 

[jpwalt1987]

TA also has an adapter to run your existing T&D rockers if you machine the head for the adapter. Either option would require a lot of machine work on your existing heads.

This option sounds the most attractive and cost effective. I saw T/As rocker stands that bolt on after the cast towers are milled off. 6 bolts are better than 3 cast aluminum towers I believe. That would save me big money on new rocker assemblies. I would need to buy just one shaft.

One rocker shaft
Rocker stands from T/A
Intake gaskets
Exhaust gaskets
Mill cast stands off
Machine holes for new stands

What else am I missing?

 

[ek02]

Push rod length may be different after all the modifications. The head would have to be machined to the right dimension so that the rocker shafts mounted on the adapter end up being the same height as they are now. Then the geometry and push rod length would be the same. I can't say for sure if this will work. Maybe someone on here has done it before?

 

[jpwalt1987]

Push rod length may be different after all the modifications. The head would have to be machined to the right dimension so that the rocker shafts mounted on the adapter end up being the same height as they are now. Then the geometry and push rod length would be the same. I can't say for sure if this will work. Maybe someone on here has done it before?

Rocker geometry must stay the same so the pushrods should stay the same also. Just a different way of holding the rocker shaft to the head. I have a machinist local to me that can handle this job with ease on a Bridgeport. I'll have to measure and document the height of the saddle that the shaft sits in and ensure that the new setup is the same.
If anyone has done this before and has any pointers let hear them.

 

[coldair85GN]

Ive seen this...and previously have seen the STUDS pull themselves out on GN1's....This is why I don't want Champion aluminum heads.

 

[TurboBuRick]

You would be hard pressed to pull the thread or break the stand with the correct length bolts.

 

[bison]

Ive seen this...and previously have seen the STUDS pull themselves out on GN1's....This is why I don't want Champion aluminum heads.

Buy the correct champion heads and run the correct rockers and you won't have this happen. The 8 bolt style head is the same as the 14 but uses a different rocker strategy that will work with very strong springs. I would not run the stock style rocker on anything but a mild hyd roller.

 

[bison]

Rocker geometry must stay the same so the pushrods should stay the same also. Just a different way of holding the rocker shaft to the head. I have a machinist local to me that can handle this job with ease on a Bridgeport. I'll have to measure and document the height of the saddle that the shaft sits in and ensure that the new setup is the same.
If anyone has done this before and has any pointers let hear them.

Try making a call to Tom and get the correct height. I remember typically needing .090" of shim under the rocker mounts on the t&d jesel style setup on GN1 heads. If it was machined ideally you wouldnt need any shims. I also had to mill the pushrod holes out on the intake side to prevent interference. Once this setup is done you will have a very strong and stable rocker setup.