GN1 Push rods rubbing

[hemi8]

Was all set to re-assemble the valvetrain (new T&D shaft roller rockers 1.55) after switching from Scorpion stud mounted rollers and the new TA roller lifters. Things quickly have gone downhill as I installed the first pair I can see that the push rods are slammed up against the heads. What is the best course of action from those that have gone through this little nightmare? I went through all the proper fitment procedures as far as setting the shafts to the proper height and properly measuring for the proper length push rods etc.
Mike

 

[whitehot1]

That's weird I have GN1 heads,T&D 1.65 shaft mounted roller rockers also and didn't have any clearance problems like that when i installed them.

In the T&D installation instructions it says that at least 1/16'' clearance in the pushrod hole and the pushrod is needed and if not then the pushrod holes in the heads will need machining to get the clearance.


John :smile:

 

[lazaris]

If indeed you set the proper height of the rockers with the tool from T&D, and re measured the push rod length from the previous rockers used, you'll have to clearance the heads.

 

[hemi8]

Yes, used the T & D tool, yes, followed proper procedures for measuring push rod length. 1/16" should do us just fine, time for the die grinder. I have heard that Tom at Champion recommends to Not open the holes larger because of the water jacket being very thin in that area. But I think he is talking about the opening of the entire hole. I plan to grind on the upper most portion closest to the intake. People should know what they are getting into if they do this swap and it would be much easier to do during the engine build on the engine stand. I would also recommend to lower the torque values for the shaft, T&D suggests 55-65 ft/lbs, I say that number is too high and should be lowered to 45ft/lbs with lubed threads. That might save someone from ripping out the threads in the heads. It might be different for later heads, I have one of the first run GN1's, I bought them new back in 98.
Mike

 

[whitehot1]

I would also recommend to lower the torque values for the shaft, T&D suggests 55-65 ft/lbs, I say that number is too high and should be lowered to 45ft/lbs with lubed threads. That might save someone from ripping out the threads in the heads. It might be different for later heads, I have one of the first run GN1's, I bought them new back in 98.
Mike

WOW!! 45-55-65 ft-lbs I would never attempt to go that high.

I bought my GN1's and the roller rockers new in 2001 and the torque value for the rocker shafts is listed as 25 - 30 ft-lbs in the instructions.

John :smile:

 

[steve hughes]

I don't know about GN1 heads but the rocker stands on TA heads are offset . If you put them on wrong the rockers are moved closer or farther away from the valves. Are the rollers on the rockers centered on the valve stems?

 

[hemi8]

Rocker shafts are torqued to 25ft/lbs but the instructions do say to torque the shaft stands with the 7/16" bolts to 55-65ft/lbs. Yes the rockers are properly offset for these heads and are perfectly centered on the valves. I believe that it is a matter of tolerences adding up ie: milled heads and block decked and also related to head gasket thickness. It is so damn close the push rods just "kiss" the heads so I can get by with minimal material removal. After further research it appears this has happened to many others and is more pronounced on the 1.55 ratio rollers. Others swithed to 1.65 and problem was solved.
Mike

 

[gnxtc2]

Where did you get the T&Ds from?

Post a pic of all the rockers.

Billy T.
gnxtc2@aol.com

 

[hemi8]

Jack Cotton.
Mike

 

[hemi8]

Driver's side, rockers just set into position, not bolted down or adjusted. Also the 1 piece shim by Champion. I could see right away the RJC valvecover extension would interfere so I removed them. As you can see these are the first run heads ie; crackers.
Mike

 

[gnxtc2]

From what I recall, the first gen GN1s had pedestals. When I ran GN1s, the rockers were a one piece shaft that bolted onto the pedestals. Did you machine down the pedestals?

Another thing, are rockers you have for "R" heads?

Billy T.
gnxtc2@aol.com

 

[278cikiller]

G/N-1 Heads

I had the same problem with mine it was number one cylinder not all of them had to do a bit of grinding to got luck.