Push Rod Rub
- Thread starter TTipe
- Start date
Did you purchase GN1 specific rockers or are you using T&Ds that were originally used on iron heads?
turbodave231
Moderator
- Joined
- May 24, 2001
Wayne,
In my experience, T&D's never fit right from the factory. Their spacing is off and must be corrected. I move shims around to position the rockers side to side and avoid rubbing the pushrod holes. This seems to hold true for the T&D shaft rocker sets for iron and aluminum GN1 heads.I have not had this problem with the T&D individual shaft mount rockers (Jessel style).
In my experience, T&D's never fit right from the factory. Their spacing is off and must be corrected. I move shims around to position the rockers side to side and avoid rubbing the pushrod holes. This seems to hold true for the T&D shaft rocker sets for iron and aluminum GN1 heads.I have not had this problem with the T&D individual shaft mount rockers (Jessel style).
You can do not both ways.
Removing material from the head would be ideal but if your heads are bolted on you can use spacers.
I just Went Thru This With Harland Sharp rockers. I had material removed from the big spacers and then used washers on the other side.
HS even said that if the rocker hangs a few thousandths off of the valve not to worry. Mine were pretty much on the edge.
There is a thread about this.
D
- Joined
- Aug 1, 2003
your situation is off subject of the op
its not preload that caused that but detonation, usually from over revving ,and the pressure that built cracked the rocker shaft on the exhaust that same pressure also affected the intake valve when it tried to open it couldnt and the rod being the weakest part gave up
ive pulled out pushrods and broken shafts just like that always seemed to happen around the 1000ft mark , swap them out in the pits and went on racing , i was able to keep going but the failure almost always resulted in a hurt gasket at that cylinder ,
if you put better shafts in and the rods will still fail
if you put better rods in and the rockers will fail
if you do rods rockers and shafts and something will fail , on an aluminum 8 bolt head the pedestil will tear out of the head.
bottom line dont over rev and avoid detonation
on the op subject ,
you need to check everywhere when assembling
you may be rubbing the valve cover gasket
check clearance of the rod to the holes in the head sometimes shifting rocker to side is enough , sometimesthey need to be drilled , not sure why champion doesn't go a little further on the hole
you may need to clearance the valvecover , at the least when you install cover after bolts are in I always push cover toward intake before tightening down
also check the rod clearance at the head gasket , i have had to notch the gasket on some high lift setups
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I purchased T & D's from Champion with the specific offset for the GN1 head.
My friend and I purchased a pair of new GN1's from Champion, used 0.032 Cometics, 8.225 Trend pushrods, (1) T & D 1.6 rockers, (1) T & D 1.55 rockers. On my friends engine (T & D 1.55) we saw obvious pushrod rub witness marks (on the pushrods & in the tops of the pushrod bores) adjacent to the push rod pedestals. We also noted rub grooves in the valve cover gaskets. Tom at the supplier had suggested letting the pushrods "feature" the pushrod holes?????? Does T & D sell the shims or do I make my own? It's stupid to pay a large chunk of change only to end up fixing issues which originated from a very common combination and purchased from the same supplier!
turbodave231
Moderator
- Joined
- May 24, 2001
Wayne,
Don't be mad at Tom@Champion unless he sold you the entire package of parts. He can't possibly know what combination of parts you have.
Pushrods, lifters, and the type of block (on-center/off-center) will be different for each build. Offset lifters (like the Isky's and Crowers) on a Stage block will move the pushrods from their original locations.
The "Engine Builder" needs to measure and inspect everything for proper clearance.
Don't be mad at Tom@Champion unless he sold you the entire package of parts. He can't possibly know what combination of parts you have.
Pushrods, lifters, and the type of block (on-center/off-center) will be different for each build. Offset lifters (like the Isky's and Crowers) on a Stage block will move the pushrods from their original locations.
The "Engine Builder" needs to measure and inspect everything for proper clearance.
Dave, Tom did sell both of us the heads and rockers. Trends are the Buick pushrod of Champions. I'm not angry at Tom. My valve train geometry looks very good at present with 3 pushrods as possible rubs at the top of the pushrod hole. I'm checking everything with wire gages first. I can't check and fit pushrod rub without assembly. Between stack ups and core shift I'm amazed anything runs (LOL).
T&D does sell spacers and shims. Assuming that you are using a Jesel style rocker, sounds like your geometry could be off. How are you checking rocker geometry? Did you shim the pedestals upon install? Explain your situation to Tom, this isn't his first time around the block. As Dave mentioned, there are many variables depending on which parts you are using.
When looking down at the engine from the drivers side fender,you are viewing the push rod from the top end when you remove the rocker arm.Viewing it from that angle,which direction would you move the push rod to make the rubbing worse? Up,Down,Left,or Right?
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The pushrods have an excentuated oval motion when looking from to back. The rub that I have seen was near the top of the pushrod on the side. This is meaningless because different blocks have different stack ups from one block to another not to mention possible core shift as well.
My rocker system is a shaft style and the shaft seats properly into a shaft saddle. I haven't req'd any shims between the shaft and the saddle..This is the system Tom sells and I did talk to him. I checked my geometry using the current rocker system torqued in properly, an adjustable push rod and even calling T & D and getting a baseline of the rocker oiler relationship to the rocker body.
No irons; GN1's, 0.032 Cometics, & T & D 1.6 rockers.
The only differences between the T&D rocker assemblies for irons and the T&D rocker assemblies for Champion GN1 heads are the shaft lengths,the tube lengths,and the washer thicknesses. Since the valve stems on the Champion GN1s are farther apart because of their larger than stock diameter valves,the roller tips of the rockers don't contact the valve stems in the center. The chosen fix for this problem is to move the rockers over with different length tubes and washers with different thickness. The problem with this method is that the push rods are moved over also. The fix chosen by TA,for their Street Intimidator heads is to have T&D manufacture a wider rocker arm body for them. This method allows the push rod to stay in the stock location and the roller tip to be moved over by widening the rocker arm bodies. The rocker arm assemblies that T&D makes for TA use the same shafts that are used in the Champion GN1 assemblies and the same washers used in the assemblies for stock heads . The two unique parts in the TA Intimidator assemblies are the rocker arm bodies and the spacer tubes. I don't know why the TA assemblies wouldn't work on the Champion GN1 heads,but I haven't had the opportunity to see for myself.
The GN1 specific rockers have an offset in the rocker body which means a different nominal center line of the pushrod in the "Z" axis. The valve center lines nominal end points in space have been moved ( x,y,z) an I'm sure if a perfect length from the lifter (what lifter design) and a nominal thickness head gasket might be a good start. There is also no mention made to the potential stack ups of all the rocker arm assembly components and possible head casting core shift. I have only seen a couple of slight potential rubs on my engine which has not been fired yet. My friend's motor has many more rubs as shown on the push rods. The push rod coatings displayed witness marks for 0.496" at the top of the push rod. The rub is occurring in the push rod tube adjacent to the rocker pedestals. This situation was nothing which was obvious by either noise or performance. A necessary intake manifold change prompted a lot of inspection which pushed more inquiry as well. I won't be happy if I need to pull the heads. You can't inspect for this condition without building the longblock.
