Pushrod length dilemma
Thread Starter
Pro
Joined: Oct 2004
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Pushrod length dilemma *updated w/ pics*
* See post #22 for pics *
LT-1 with LT-4 Heads; RR; double springs; 7/16 Rocker studs
So the ideal length pushrod for my setup (as far as roller against valve tip is concerned) causes the rockers to slightly rub against the base of the rocker studs. This may explain why the original pushrods seemed too long; the builder may have just been a little lazy?
Any guidance from the gurus out there; should I grind .150" from the base of each stud or take the same from the base of each rocker arm?
Any other bright ideas?
Oh - and I have measured it about 4 times using checking pushrods and valve check springs - and I have been careful not to preload the lifters for the measurements.
Thanks!
LT-1 with LT-4 Heads; RR; double springs; 7/16 Rocker studs
So the ideal length pushrod for my setup (as far as roller against valve tip is concerned) causes the rockers to slightly rub against the base of the rocker studs. This may explain why the original pushrods seemed too long; the builder may have just been a little lazy?
Any guidance from the gurus out there; should I grind .150" from the base of each stud or take the same from the base of each rocker arm?
Any other bright ideas?
Oh - and I have measured it about 4 times using checking pushrods and valve check springs - and I have been careful not to preload the lifters for the measurements.
Thanks!
Last edited by djxib; Dec 2, 2007 at 04:20 PM.
Burning Brakes
Joined: Dec 2006
Posts: 936
Likes: 2
From: Tyrone PA
LT-1 with LT-4 Heads; RR; double springs; 7/16 Rocker studs
So the ideal length pushrod for my setup (as far as roller against valve tip is concerned) causes the rockers to slightly rub against the base of the rocker studs. This may explain why the original pushrods seemed too long; the builder may have just been a little lazy?
Any guidance from the gurus out there; should I grind .150" from the base of each stud or take the same from the base of each rocker arm?
Any other bright ideas?
Oh - and I have measured it about 4 times using checking pushrods and valve check springs - and I have been careful not to preload the lifters for the measurements.
Thanks!
So the ideal length pushrod for my setup (as far as roller against valve tip is concerned) causes the rockers to slightly rub against the base of the rocker studs. This may explain why the original pushrods seemed too long; the builder may have just been a little lazy?
Any guidance from the gurus out there; should I grind .150" from the base of each stud or take the same from the base of each rocker arm?
Any other bright ideas?
Oh - and I have measured it about 4 times using checking pushrods and valve check springs - and I have been careful not to preload the lifters for the measurements.
Thanks!
Burning Brakes
Joined: Dec 2006
Posts: 936
Likes: 2
From: Tyrone PA
I really hope some others chime in here. There may be other rockers that will work, then you could sell your old ones. I would be scared to grind anything off the rockers as they might then be prone to breakage. There may be different studs available. I'm wondering if you could put a 3/8" stud and roller rocker on there and see if it still hits or not. Maybe more work needed done to run the 7/16". I feel sure there are more options, although I don't know them.
Last edited by dan0617; Nov 30, 2007 at 10:28 AM.
Burning Brakes
Joined: Dec 2006
Posts: 936
Likes: 2
From: Tyrone PA
join camaroz28.com and post it there. That forum is an almost exact layout to this one. It has tons of traffic and there seems to be quite a few motor guys there. There are a few guys here that can help too if they read this. JAKE where are you???? Curveit????
Racer
Joined: Jul 2004
Posts: 285
Likes: 0
From: San Diego CA
This is probvably no help at all in your unique situation - but stock pushrods on LT1 are exactly 7.200 inches in length. Im sure there is a method to compensate for the LT4 heads you have (taller deck height ?) and someone smarter than I am will have the answer - good luck sir ! 
Thread Starter
Pro
Joined: Oct 2004
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This is probvably no help at all in your unique situation - but stock pushrods on LT1 are exactly 7.200 inches in length. Im sure there is a method to compensate for the LT4 heads you have (taller deck height ?) and someone smarter than I am will have the answer - good luck sir !
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Pro
Joined: Nov 2005
Posts: 536
Likes: 0
From: Bardstown Kentucky
I am running the factory LT4 heads, Comp pro Mag rockers with ARP studs and guide plates. My rockers are close to the base of the stud but there is room. How does a 7.100 push rod look in your motor?
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
The actual problem could be the valve stem height is too low in comparison to your rockerarm stud boss in the head casting. It also could just be that you have the wrong rocker studs. There are a few other ways you could solve this problem.
A machine shop with a Bridge Port or a good seat and guide machine could mill the rocker stud boss's down the correct amount for you to fix the problem.
Also - Yes there are different studs availiable from APR, PEP, SPS and MSA that have varying hex heights.
Will
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Joined: Oct 2004
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Personally I wouldn't be afraid to grind anything off the slot (bottom inside edges around the trunion) of the rocker arms. It will NOT hurt anything to bevel the slot a LITTLE bit to gain clearance for the stud hex. I have done it in the past espc on very big bodied rockers like the Scorpion and early manfacture Erson's. Funny there was a thread on an engine builders web site the other day where Joe Sherman said he often has to grind rockers in this manner for clearance in order to get valve train geomerty "perfect".
The actual problem could be the valve stem height is too low in comparison to your rockerarm stud boss in the head casting. It also could just be that you have the wrong rocker studs. There are a few other ways you could solve this problem.
A machine shop with a Bridge Port or a good seat and guide machine could mill the rocker stud boss's down the correct amount for you to fix the problem.
Also - Yes there are different studs availiable from APR, PEP, SPS and MSA that have varying hex heights.
Will
The actual problem could be the valve stem height is too low in comparison to your rockerarm stud boss in the head casting. It also could just be that you have the wrong rocker studs. There are a few other ways you could solve this problem.
A machine shop with a Bridge Port or a good seat and guide machine could mill the rocker stud boss's down the correct amount for you to fix the problem.
Also - Yes there are different studs availiable from APR, PEP, SPS and MSA that have varying hex heights.
Will
I am going to check measure it all again; assuming I only need a slight bevel on the arm slots I will use this technique.
Thanks all!
Melting Slicks
Joined: Dec 2004
Posts: 2,137
Likes: 5
From: Howard PA
A little too little a little too late but the LT4 rockers are self aligning and need no guide plates. Then you can use any length push rod your heart desires. We ran into this same problem with a buddies 383 build, the rocker wound up extremely close to the stud bases, (thick guide plates) if we had known before hand it would be like that the rocker stud bosses would have been cut down a little to compensate. Or self aligning rockers would have been chosen.
Would it be too late for you to use some self aligning rockers?
Would it be too late for you to use some self aligning rockers?
Last edited by ALLT4; Dec 1, 2007 at 07:01 AM.
Pro
Joined: Sep 2007
Posts: 545
Likes: 2
From: st albert alberta
LT-1 with LT-4 Heads; RR; double springs; 7/16 Rocker studs
So the ideal length pushrod for my setup (as far as roller against valve tip is concerned) causes the rockers to slightly rub against the base of the rocker studs. This may explain why the original pushrods seemed too long; the builder may have just been a little lazy?
Any guidance from the gurus out there; should I grind .150" from the base of each stud or take the same from the base of each rocker arm?
Any other bright ideas?
Oh - and I have measured it about 4 times using checking pushrods and valve check springs - and I have been careful not to preload the lifters for the measurements.
Thanks!
So the ideal length pushrod for my setup (as far as roller against valve tip is concerned) causes the rockers to slightly rub against the base of the rocker studs. This may explain why the original pushrods seemed too long; the builder may have just been a little lazy?
Any guidance from the gurus out there; should I grind .150" from the base of each stud or take the same from the base of each rocker arm?
Any other bright ideas?
Oh - and I have measured it about 4 times using checking pushrods and valve check springs - and I have been careful not to preload the lifters for the measurements.
Thanks!
Last edited by makn u shiver; Dec 1, 2007 at 09:36 AM.
Burning Brakes
Joined: Dec 2006
Posts: 936
Likes: 2
From: Tyrone PA
I agree with you that if you already have new valves and springs I would not go with longer valve stems now. If the heads are still off or can be taken off easily I'd have them machined down for guideplates. If not, see if you can get thinner guideplates, I believe I heard of someone making them. Self aligning rockers is also a good suggestion. That is what I'm planning on in 2 weeks when I replace my heads, no guideplates, just self aligning rockers. I actually run them now, Summit narrow body self aligning narrow body rockers (narrow body ones to clear centerbolt valve covers). The last thing I'd do is grind material off the bottom of the rockers or off of the studs, but just because I wouldn't go that route doesn't mean it won't work or hasn't been done before. Sounds like it's possible.
Thread Starter
Pro
Joined: Oct 2004
Posts: 628
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Thanks for all replies and suggestions - lots of opinions here!
I have Crane rockers, not LT-4.. the Cranes are not self-aligning.
I spent a few hours this afternoon checking / measuring / turning the engine / checking and measuring again. I have an adjustable pushrod; and the correct valvetrain geometry has been measured.
I used all the usual techniques; coloring the valve tip; valve check springs; 2 x full rotation of the engine etc etc.
I considered getting thinner guideplates, and also getting different studs.
In the end I removed a very small amount of material from the edges of a rocker 'slot'. It measures up perfectly - so I am going to do this to the other 15.
I'll post pictures of the 'adjusted' rocker tomorrow for comment (and abuse, if necessary).
Just one question... per a previous post how on earth can use use 'any length pushrod you like' with self aligning rockers? Self aligning means side-to-side, not front to back... so the pushrod length is still a critical measurement. Someone correct me if I am wrong.
Thanks
I have Crane rockers, not LT-4.. the Cranes are not self-aligning.
I spent a few hours this afternoon checking / measuring / turning the engine / checking and measuring again. I have an adjustable pushrod; and the correct valvetrain geometry has been measured.
I used all the usual techniques; coloring the valve tip; valve check springs; 2 x full rotation of the engine etc etc.
I considered getting thinner guideplates, and also getting different studs.
In the end I removed a very small amount of material from the edges of a rocker 'slot'. It measures up perfectly - so I am going to do this to the other 15.
I'll post pictures of the 'adjusted' rocker tomorrow for comment (and abuse, if necessary).
Just one question... per a previous post how on earth can use use 'any length pushrod you like' with self aligning rockers? Self aligning means side-to-side, not front to back... so the pushrod length is still a critical measurement. Someone correct me if I am wrong.
Thanks
Last edited by djxib; Dec 1, 2007 at 05:34 PM. Reason: Added the fact I have Crane rockers and spelling
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
You can also use a lash cap that is .080 thick. This will raise the rocker arm up, and then you can remeasure the push rod for the ideal geometry. It is an easy thing to do and does nothing to the reliability of the valve train. The new LS7 Z06 engines uses them on all the intake valves and they run 7000 rpm without issues.
Instructor
Joined: Jul 2007
Posts: 181
Likes: 0
From: Boise ID
Funny I just had this problem last weekend on my L98 based mini ram 383. I adjusted the the rockers but on the last 1/2 turn of the full turn of pre load the rocker hit the stud base. I took a dial indicator on a magnetic base locked the base on the flat area that runs accross the front of the lifter valley ( the area you run the bead of silicone accross for the intake) set the dial indicator on the top of #1 exhaust rocker ( @tdc) on the push rod side lifted the rocker by hand until the roller on the tip was at the center of the valve stem my measurement was .137 so i got a set of .100 longer push rods and it's dead on the money perfect. Or you could wire your bench grinder backwards which makes it a REDNIRG ( grinder spelled backwards) and grind on .100 to your push tubes just kidding.
Melting Slicks
Joined: Dec 2004
Posts: 2,137
Likes: 5
From: Howard PA
Just one question... per a previous post how on earth can use use 'any length pushrod you like' with self aligning rockers? Self aligning means side-to-side, not front to back... so the pushrod length is still a critical measurement. Someone correct me if I am wrong.
Thanks
Thanks
Thread Starter
Pro
Joined: Oct 2004
Posts: 628
Likes: 6
You can also use a lash cap that is .080 thick. This will raise the rocker arm up, and then you can remeasure the push rod for the ideal geometry. It is an easy thing to do and does nothing to the reliability of the valve train. The new LS7 Z06 engines uses them on all the intake valves and they run 7000 rpm without issues.
Safety Car
Joined: Jul 1999
Posts: 3,946
Likes: 63
From: Marianna FL