I am installing my EM long tube headers and thinking of also adding 1.6 roller rockers or even 1.65. Here are a few questions.
1. I will need new springs right? Thinking of LT4 springs from GM
2. Will I need to check/change the push rod length?
3. Will I need to switch to hardened push rods to eliminate flex with the new stiffer springs?
4. If I rotate the motor to TDC and then remove the springs on that cylinder will that be enough to keep the valves from falling into the cylinder?
5. I am thinking about Scorpion rockers what do you think?
Thanks for any comments and comments on things I forgot or need to consider?
93 LT1 Vett. stock motor, 6 speed.

 

I'm not familiar with LT1 heads, per se, but

(1) yes, you should install new springs and LT4 springs at around $44 are a bargain; but will they fit in the stock LT1 head spring pockets ? and will the install height be right ? any coil bind issues ?
(2) yes you should
(3) hardened push rods are needed to eliminate wear on the push rod from rubbing against the push rod guides
(4) maybe, what it won't do is keep the valve stem fully extended and stable during valve spring and seal reinstall.
(5) Scorpions seem to have a good rep and are affordable

first step, do you need, or are you going to use, self aligning rocker arms ?

I'm sure there must be a write up from someone on the forum who has done the same exact swap ; time for some research ?

 

The current issue of Chevy High Performance has a tech article on this swap. Article is based on a 396 but the principle is the same.

 

I used LT4 springs with 1.6RR (stock cam) and the valves do not float - loved the results.

I dont think you will need to bother checking the pushrod length so long as you continue to use the stock cam. I did not check it and have had no ill effects. But, it certainly couldnt hurt to check.

If the rockers are self aligning and you are using the stock cam you shouldn't need hardened pushrods. I'd hold off on purchasing new pushrods until you decide to cam the motor, otherwise you may end up buying pushrods twice.

No direct experience with the Scorpion brand but I believe the Summit brand 1.6 RR are rumored to be made by Scorpion. That is what I have and I do not have any complaints.

If you are sticking with a stock cam a 1.65RR may be the better choice to get just a little more out of them, you may be forced to get non self aligning rockers in that ratio.

Other tips I learned along the way when upgrading to 1.6RR/LT4 springs on my 1994 LT1:

Change the valve stem seals while you are in there. It is cheap, easy and there really isnt a reason not to do it. I used compressed air in the cylinder to hold the valves from dropping. Others use nylon rope and turn the engine until the piston pushes the rope up enough to contact the valves and holds them in place. Having the cylinder at TDC for when you are working on the valves may work, but they still might drop a little and make it more difficult since you'd have to compress the springs even further to get the keepers back on. There are a bunch of different methods/opinions on setting lash. I couldn't get mine right until I tried the engine running method.

 

jmgtp, Thanks for the reply, just what I was looking for. Did you have to modify the stock valve covers, the drip rail inside? If so how did you do it? With 1.6 rr's the lift goes to .298x1.65= .476 intake, .306x1.6= .489 exhaust but with 1.65 it goes to .491 and .504 which is a little more lift and reaching the .5 inch mark, but then I need guide plates and hardened push rods, not sure which way to go yet.
Did you have to modify the heads in any way to fit the LT4 valve springs?
Did your Summitt rockers fit the 10mm studs ok, they are make for 3/8" which I think is a tiny bit larger?
Did you feel any seat of the pants difference in the bigger lift after the rocker install? I hear it is good for 10 - 15 rwhp on some cars?
Where did you get the attachment to pump comp. air into the cylinders, there are a couple of plug holes that are very difficult to get to on the LT1 Vett, any problems there?
Thanks again for the help.
By the way cam is stock and probably will be for a while.

 

I gave & Installed 1.6 rockers on My Buddies 95 LT1
You will need to clip the composite tabs inside the valve covers<>the rockers WILL hit them... 1.6 will add about .30 on your lift..
you will feel a slight power gain.. it was pretty cute.
PS: If I were you I would just get CC roller tips

 

10 mm = 0.394 3/8=0.375 so 10 mm is larger not smaller..
Dave

 

Yes you need to trim the drip tabs. I used an air body saw which made short work of them.

The RRs had the correct size for the stud. I believe they are available in both stud sizes. You need to use the correct size.

I made my own fitting for the compressed air:
Spark plug non fouler from the Help! aisle of autozone and a male 1/4" air hose fitting threaded into it. Then I just clamped an air hose on the end of the 1/4" air line fitting. The cylinder closest to the firewall was a bit difficult to get the line hooked up, especially on the passenger side. I had to thread the spark plug non fouler into the spark plug hole first then clamp the air hose on.

LT4 springs worked just fine with the LT1 seats, no mod necessary.

I can't say if it actually made MORE hp, in theory it should. 10-15 hp isnt really a measurable by seat of the pants on a 300+hp car. BUT the noticeable difference was that the existing horsepower didnt drop off in the high revs (say above ~5,300 rpm) - it now will pull right to the rev limiter and that is definetly noticeable. Might be more attributable to the new LT4 springs vs the weak/old LT1 springs that probably let the valves float.

 

Does an LT4 have hardened pushrods?

 

No.. Purchase.. Trick flow rods they are the best deal!!!!!
if you install aftermarket rockers. the factory push rods will chip.

 

This is just my opinion, I would go with the comp cams 26918 springs. They cost more but you get more.One reason is if you plan on going to a bigger cam down the road you wouldn't have to change the springs later. There have been posts that say not to use the LT4 springs with performance cams,that they are not that much better than stock springs. Also the 26918 comp springs have a smaller retainer so less chance of problems with retainer to rocker arm clearance issues if you changed cams later too. also with the slightly higher 26918 spring pressure you might be able to rev it just a little higher too. Good luck Tim

 

Well tonight I got the drivers side manifold off (old one). It's incredible how everything on these cars is SO tight and difficult to get to. I can see now that I have the old manifold off it's now or never with new valve springs and roller rockers, there is so much more room with the manifold off, the asr off, the AIR that routes to the exhaust headers etc. and trying to get a compressed air fitting into the spark plug hole to hold the valves closed will be much easier right now.
Thanks for the info on the 10mm rocker stud size, I presume a regular 3/8" rocker will not fit then?
I really want to go with the 1.65 but they are not available in self aligning so that would also mean guide plates and new hardened push rods.
Just a question about the EM header and the pipe that connects to the stock exhaust. The pipe from EM necks down from 3" at the collector to 2 1/2" but the stock exhaust on the Vett is 2 3/4". Maybe it's nothing to worry about but why would anyone make a 2 1/2" pipe when the stock one is 2 3/4", there was a reason why the factory went with 2 3/4 and NOT 2 1/2", does anyone know of a reducer that goes from 3" to 2 3/4", there just isn't much out there in 2 3/4".
Thanks for replys.

 

FYI: Stock LT1 rocker studs are 3/8".

 

I thought the rocker studs were 10mm but you say no they are 3/8" right, if so that is great because I can't find any 10mm rockers anywhere. Can I reuse the stock spring retainers? I should get new keepers too right?

 

The Rocker Studs Are >>3/8<<
your purchasing new Springs Correct???
Retainers are cheap.. upgrade 10Deg it's better to be safe then sorry..

 

Stock LT4 rocker studs are 10 mm, LT1's are 3/8".