Gen3 rockers on a Gen2 FYI

[CSXT802]

For those of you who are thinking of installing the 1.7 rocker from a gen3 on your gen2. They are not a direct bolt on. Gen 3 motors used a conical (bee hive) valve spring with a smaller dia. retainer. The rocker arm hits the larger retainer of the gen2. There are 2 ways around this. 1. Buy all new conical springs and retainers etc.....$$$ 2. shim up the rockers by install a shim between the head and rocker mount. How much do you need to shim them up you ask? I made my shims from a sheet of 16 gauge aluminum witch is .0625 thick. They raised up the rocker enough so there was a .004-.008 space between the rocker arm and the outside edge of the retainer. So a minimum would be a .060 shim. If you do this make sure you have feeler gauges to check for clearance with each cylinder @ tdc so both valves are closed. That's it . It was an easy mod and only took me a few hours to install.

 

[plumcrazy]

a guy just did this and got his car tuned recently. wonder if he did this. i think he goes by 2002_red_gts

 

[Allan]

uh....when you shim the fulcrum point, you are changing the valvetrain geometry in a bad way. It may seem to work OK (the motor runs), but there are negative long term effects to this. -excessive side loading of the valves and valve guides. Correct valvetrain geometry is that when the valve is at 50% total lift, the rocker arm and valve will be at a 90 degree angle. That way the angles are equal from fully closed to fully open. Then mechanically the stuff is evenly loaded and wears evenly. What you did as a quick solution obviously worked (for now), but is not optimum. .......just so you know.

 

[CSXT802]

uh....when you shim the fulcrum point, you are changing the valvetrain geometry in a bad way. It may seem to work OK (the motor runs), but there are negative long term effects to this. -excessive side loading of the valves and valve guides. Correct valvetrain geometry is that when the valve is at 50% total lift, the rocker arm and valve will be at a 90 degree angle. That way the angles are equal from fully closed to fully open. Then mechanically the stuff is evenly loaded and wears evenly. What you did as a quick solution obviously worked (for now), but is not optimum. .......just so you know.

I see your point. But shimming up rockers is nothing new. Go to summit and look up rocker shims they are made by comp cams for fords. The only problem I could see is if you shimmed them up over .100 with a huge lift cam maybe you could have the rocker over travel and come off the tip of the valve. A .060 shim @ full lift with a stock cam is not even close to that happening.

 

[Tiago]

if anyone is looking for a set of gen 3 rockers
http://www.viperalley.com/classifieds/showproduct.php?product=8370

 

[IEATVETS]

WOW, it sure is a good thing that I am not a mechanic because I don't know what the hell you guys just said!! This thread is like reading chinese brail. My brain now hurts, I am going to take a nap.

BTW Darren, I'll call you next week because I found something else for my "former" car that you may be interested in!

 

[CSXT802]

WOW, it sure is a good thing that I am not a mechanic because I don't know what the hell you guys just said!! This thread is like reading chinese brail. My brain now hurts, I am going to take a nap.

BTW Darren, I'll call you next week because I found something else for my "former" car that you may be interested in!

Why make me wait Duane?..........pick up the phone. Are you holding out on me? lol

 

[fearsuch]

do you have any pictures of the install? what pushrods did you use?
Did you take your car for a ride yet? can you fell a difference?

 

[Jack B]

The T&D instruction sheet supports what Allan has just stated.

uh....when you shim the fulcrum point, you are changing the valvetrain geometry in a bad way. It may seem to work OK (the motor runs), but there are negative long term effects to this. -excessive side loading of the valves and valve guides. Correct valvetrain geometry is that when the valve is at 50% total lift, the rocker arm and valve will be at a 90 degree angle. That way the angles are equal from fully closed to fully open. Then mechanically the stuff is evenly loaded and wears evenly. What you did as a quick solution obviously worked (for now), but is not optimum. .......just so you know.

 

[CSXT802]

Sorry I didn't take pics, I used my stock push rods. Can't take the car out yet mother nature thinks it's still winter around here. I did start the car and take vid of it.

http://api.viglink.com/api/click?fo...641148190534&jsonp=vglnk_jsonp_13642030534894

 

[CSXT802]

http://api.viglink.com/api/click?fo...637333975181&jsonp=vglnk_jsonp_13642031612205

 

[Blown408]

Dude like I had said on the Alley I dont think (correct me anyone else if you can) anyone can see your videos lol, post them on photobucket or youtube instead of facebook.

 

[troublemaker]

This is one of the few technical threads that happen on here anymore, so the more information we get out of it the better. What exactly is the issue with what the original poster did?

 

[coupe]

Rocker shims are usually used to bring the rocker up to obtain proper geometry, not to compensate for a larger spring from a different application.

To check proper geometry, mark the valve stem tip with a sharpie marker, then rotate the engine through a few turns so that the rocker tip passes over the marked valve stem a few times. It will indicate where the interaction occurs allowing you to observe whether or not it is working properly. Too far either way from center gives extra side loading and premature wear on the valve guides.

IMO, someone who's already done this modification should show the witness mark on the valve stem tip before anyone else tries the mod.

 

[CSXT802]

Dude like I had said on the Alley I dont think (correct me anyone else if you can) anyone can see your videos lol, post them on photobucket or youtube instead of facebook.

Sorry about the vid not working. Buddy of mine shot the vid and posted it to facebook.

 

[Ryan_DSA]

video/pics work if your settings are on public, and the person trying to view is logged in

 

[CSXT802]

I'm not the first to do this.
http://forums.viperclub.org/threads...d-1997-Viper-GTS-523-RWHP?highlight=jts+venom

 

[CSXT802]

http://youtu.be/LwyNy4GXoyU

 

[CSXT802]

Dead link sorry

 

[Allan]

This is one of the few technical threads that happen on here anymore, so the more information we get out of it the better. What exactly is the issue with what the original poster did?

Re-read my initial reply to the original post. That should sum it up pretty good.

 

[CSXT802]

Re-read my initial reply to the original post. That should sum it up pretty good.

http://forums.viperclub.org/threads...d-1997-Viper-GTS-523-RWHP?highlight=jts+venom

 

[Allan]

Not to dis-credit any aftermarket speed shop, but I stand by my original post. I am not here to argue -tech A says this / tech B say that , who's correct? I am only trying to provide solid advice based on engineering and design principles for cam in block pushrod motors. It's your car, do whatever floats your boat. There are exceptions to every rule, but this one makes me a little nervous. Modifications are great and sometimes improve things, but usually at a cost of economy or reliability. Reliability is my concern with this one. ..........but it's your car so ,..whatever.

 

[CSXT802]

Not to dis-credit any aftermarket speed shop, but I stand by my original post. I am not here to argue -tech A says this / tech B say that , who's correct? I am only trying to provide solid advice based on engineering and design principles for cam in block pushrod motors. It's your car, do whatever floats your boat. There are exceptions to every rule, but this one makes me a little nervous. Modifications are great and sometimes improve things, but usually at a cost of economy or reliability. Reliability is my concern with this one. ..........but it's your car so ,..whatever.

Allen, While I respect your opinion. Think about this way if you install a higher lift cam you change the scrub area on the valve stem because the rocker travels farther. What I have done is the same just at a different point. I don't see you posting about how a higher lift cam is going to wear out valve guides prematurely. If that were the case you would have to change valve train geometry every time you change cam lift. With your thinking, I guess A reground cam with a smaller base circle could not be used because it wear out valve guides due to the scrub area changing on the valve stem. I will dyno my car and post results. Just think now you can sell your gen 3 rockers when you up grade them.

 

[ViperTony]

When I installed my T&D rockers I had to check rocker geometry. The kit came with two sets of differently sizes shims to place under the rocker stand base if needed. I used the supplied stand height gauge and the "sharpie" method. I didn't need the shims. After checking the gauge/angle and rocker "sweep" across the top of the valve stem it indicated the geometry was accurate. Pic shows the middle valve stem with the marker line:

I think I recall reading elsewhere that the OP did check this and it was fine.

So my question is: All things being equal meaning that the OP did check geometry: Why is it OK to shim up, or down, the T&D's but not ok to do the same for GenIII rockers with correct geometry and sweep pattern?

 

[opnwide]

Shimming is done to achieve correct geometry. Correct geometry should be the goal with any rocker change. I would expect that 95% of applications would NOT require shimming. Switching to longer valves would be one good reason to shim your rockers (+.100 is a common viper size replacement valve). If you are shimming to gain clearance, that would be a different issue. Now it is entirely possible that CSXT needed to shim his gen3 rockers to achieve the correct geometry, but without checking how would you know?

 

[Allan]

Allen, While I respect your opinion. Think about this way if you install a higher lift cam you change the scrub area on the valve stem because the rocker travels farther. What I have done is the same just at a different point. I don't see you posting about how a higher lift cam is going to wear out valve guides prematurely. If that were the case you would have to change valve train geometry every time you change cam lift. With your thinking, I guess A reground cam with a smaller base circle could not be used because it wear out valve guides due to the scrub area changing on the valve stem. I will dyno my car and post results. Just think now you can sell your gen 3 rockers when you up grade them.

Well, I don't need to upgrade my rockers cuz they work fine.
I have considered the Roe 710 camshaft though. But again, for every gain there is a loss. Everything is a compromise. You are correct about the smaller base circle problem. I will probably not mod the motor though. It stands to reason that it will tolerate more abuse and thrashing if left stock. I am more obsessed with improving my driving skills before messing with the car anymore. I already have the common idiot bolt-on mods. My current issue is with the nut behind the wheel.

 

[Garron]

The picture below shows incorrect geometry, The guides lasted 5000km (about 3000 miles) and were worn out. As others have stated, the car will run fine for the short term. This check is often overlooked

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correct geometry

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[Allan]

Thanks for posting those pics.

 

[Mopar Boy]

Great educational pics Garron!