I've pulled the driver side rocker cover and taken some measurements to see where things
are based on the mid-lift information from this post> https://www.camaroz28.com/forums/sho...d.php?t=594453

All I can say is WOW, everything is so far off it's hard to imagine. To set up for ideal mid-lift
criteria you want your ROCKER HEIGHT to be 1/2 of your net valve lift, which should be .266"
for me in a perfect world. My measured ROCKER HEIGHT is .655", which is .389" off. I would need
to raise my rocker arm trunnion centerline .389" to set up for mid-lift. This is clearly not
possible as I only have .245" available clearance in the rocker cover from the top inside to the
polylock. Even if I had taller covers the roller tip would be too close to the edge of the valve
by the time mid-lift criteria was met.

Now that my head is completely spinning I'll need to think about this a while. I'm also going to
install the 7.20" pushrods and see what the measurements look like tomorrow. I have 7.05"
pushrods in there now.

 

On my car the stock pushrod length is 7.200". To get to mid-lift I would need to have a pushrod length of 7.500" inch. I was able to get to that point with longer studs and a raised valve cover.

However the rocker roller was at the edge of the valves. The sweep at that point was .031". By the way my cam lift was .570". I compromised to get the roller to 25% of the valve stem diameter from the edge. I would up with a pushrod of 7.365" with a sweep of around .042".

With a stud system most will not be able to get a true mid-lift. The geometry is just not there from the get go. You would need special rocker arms to do it for your combination.

 

All though I aplaud the effort here, it would appear to me that the HP gains are not worth the headaches and stress that are going to result if working with studs.

 

After thinking about this some more this evening I'm just going to put the 7.20" pushrods back
in the motor and call it a day. It's pretty clear that there is no way to achieve the mid-lift
with the LT1 geometry w/o stand mounted rockers, and it may not even be possible then.

I will check and see how many turns on the polylock and install longer studs if I'm less than
10 turns. I've got a feeling that with the longer valves and 7.20" pushrods I will not get
enough turns on the polylock with the 1.77" (ARP 134-7103) studs. I can get a 2.00" stud by using
an ARP 234-7206 and doubling the guideplates. This will also fit under the LT4 covers and provides
another 4 turns with the polylock.

Is there anyting wrong with running double stacked guideplates?

 

I would use a #8 grade flat washer to add additional stud height.

WD

 

I'm no valvetrain geometry master, but it would seem like the higher you go on
those studs, the more flex could become an issue.

All of a sudden, shafties make sense.

 

Will you have enough thread engagement in the head? As I remember the torque on the studs is 50 ft. lbs., and even with the helicoils will there be enough engagement not to pull the threads?

 

The max thread length for the studs into the heads is 1/2". You can use any combination of stud,
guideplate and washer as long as you maintain the .50" +- into the head. The limit seems to be .245"
for my setup with the LT4 covers. You probably want to maintain some safety margin on clearance
so maybe .200" - .225" is the most I can lengthen.

It looks like the most cost effective way to extend the stud length is to use ARP 100-7101 studs
(1.90" length), guideplates and a .100" washer. This will provide .500" into the head and will result
in 1.90 + .10 = 2.00" stud length which will raise it .23" more than the ARP 134-7103 studs. This is
putting the lock very close to the top of the cover, but without going to taller covers it's the limit.

Considering the geometry, to raise the roller trunnion .10" you need to increase the pushrod length
.16". If the max. I can raise the trunnion is .23" then the longest pushrod I can use w/o getting taller
covers is 7.05" + .368" = 7.418", and even this will only bring the ROCKER HEIGHT down to .425", when
it needs to be .266" to be "ideal". As stated previously, this is an exercise in futility. The one thing that
is crystal clear is that needing shorter pushrods when you install heads is complete BS.

The morale of the story is probably to just stick with 7.20" pushrods and save yourself all the trouble
of measuring, thinking, etc. In this sense it really simplifies H/C swaps.

I'm going to install a 7.20" pushrod today and take all the measurements again just to punish myself more.

 

Are you guys sure the rocker should go up? From what I'm understanding on those pages it should go down.

From what I'm reading, you have to find the height to the center of the valve stem roller. Then you make sure the center of the trunion is 1/2 the net valve lift *below* the the center of the roller at the stem. So, if you had a .600" lift cam, you'd want the center of the trunion to be .300" below the center of the valve stem roller. This would mean lowering the rocker to me, not raising it.

 

Here is the latest from todays measurements. I'm using #3 as my reference since it's a bit
easier to work with and measure than #1. Some of the prior measurements were off
so the ROCKER HEIGHT is .579" instead of .655", which is not good, but better than what I thought.
I also used some play-doh to check the clearance inside my rocker covers to the polylocks. It
looks like the most I can raise the polylocks is about .170".

All of this is probably a moot point as marshall93z found out since pushrods longer than 7.20"
will probably put the roller too close to the edge of the valve. A 7.20" pushrod will raise the rocker
.094" and will result in a ROCKER HEIGHT of .485". It would take 7.55" pushrods to achieve the
mid-lift criteria, which can't happen. This is almost the same length that 1989TransAm posted.
A 7.30" pushrod would probably work but I don't feel like buying another set.

As for turns on the polylocks, I have 9 turns with 7.05" pushrods and 7 turns with the 7.20" pushrods.
You want a minimum of one bolt diameter on the lock which is about 9 turns, so I'm going to need
longer studs to run the 7.20" pushrods. I'll just use a set of ARP 135-7101 studs that I have on hand
and add a .120 washer to raise them and get 2.4 more turns on the lock.

 

And it took me 10 pages to figure out to leave it alone!

 

I've now measured the ROCKER HEIGHT with 7.05", 7.20" and 7.30" pushrods. I stopped with 7.30" because
that is the max. I can raise the rocker stud and still clear the inside of my covers. Here is the
ROCKER HEIGHT measured for each pushrod:

7.05 > .579"
7.20 > .504"
7.30 > .432"

ROCKER HEIGHT should be about .266" to be at ideal mid-lift criteria. I also took several pictures to
show how the roller sits on the valve in the closed position. Based on eye ball accuracy it seems like the
7.30" pushrods will work without putting the roller too close to the edge. Looking at the photos makes the
funky alignment with the 7.05" pushrods really stand out. As you go longer and longer with the pushrods
the rocker starts to level off and sit very nicely.

I'm going to order a set of 7.30" TFS pushrods and see what kind of swipe mark I end up with. I have to
change out the rocker studs anyway so I might as well swap everything at the same time. I need the longer
studs for both 7.20" and 7.30" pushrods. Here is the number of turns on the polylock with the different
length pushrods:

7.05 > 9
7.20 > 7.25
7.30 > 6

The minimum number should equal one stud diameter which is 8.75 turns. I'm glad that I mistakenly purchased
a set of ARP 135-7101 studs a while back. I can use these with a .120 washer under the guideplate and it
moves the studs up just enough to get about 9.75 turns with 7.20" pushrods and 8.5 turns with 7.30" pushrods.
Either way I'll have all the parts ready to go for the swap out. I'll also switch to the ARP 12-point locks
to get some extra clearance inside the covers.

I'm really glad to have gone through this exercise because there is no other way I would have been able
to see the difference in the rocker geometry. I'll post up links to some pictures later tonight.

 

When you use washers with the guideplates be sure to use a good washer parallel ground if atall possible, maybe some spares from an old set of headbolts or the like. Or maybe someone has a set of worn GMPP plates they could donate and you could open up the slots so there is no contact?? Use them as a "washer".

 

I'm going to use ARP washers PN 200-8531 which are .120" thick, .438" ID and .75" OD. These are high
quality pieces like the head bolt washers.

Here are the pictures I took. It's a PDF file with some notes> Rocker Pictures

 

I figured you would have something figured out, mostly wanted it noted so sombody else didn't go and try and use a cheap washer that you can see the taper on.