rocker arm swap on a 96 Vortec 5.7
02-17-2013, 12:21 PM
#1
rocker arm swap on a 96 Vortec 5.7
This week I am going to be swapping my faulty fuel injection spider assembly, while the top end is apart I was looking for things that could increase the power. I'm going to port and polish the throttle body and was considering swapping the stock rocker arms for a set of higher ratio roller rockers. I'm looking for something that will fit under the stock valve covers, something that will bolt on the heads as is, and something that will give the best bang for the buck. There are some on eBay for around $100 but I don't know if I need them or if I need the aluminum body roller bearing fulcrum rockers that cost almost 3 times that. Please let me know so I can decide if I even want to do this. Thanks
02-17-2013, 05:21 PM
#5
Make sure you get what are labelled self aligning rocker arms as well. Basically the roller wheel on the tip has guides on either side of it so it can't come off the valve tip.
1.6:1's will help a little as they increase the valve lift about .030" but do nothing for duration.
1.6:1's will help a little as they increase the valve lift about .030" but do nothing for duration.
02-17-2013, 07:01 PM
#6
I understand how they work. I was just curious as to which ones I should get and if the roller tip, or full roller rocker would be better. And I am more than likely going to get it apart and pull the lower manifold and replace the intake gaskets as well.
02-17-2013, 07:54 PM
#7
The cheapest ones possible being just the roller tip. The additional cost of the full roller on an engine handicapped to less than 5 grand and otherwise stock is a complete waste of money. Yes it will rev higher but after 4500-4800 or so it's just noise. You can thank that lovely intake design for that. You will not be able to tell the difference one way or the other whichever you choose.
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02-19-2013, 12:09 PM
#10
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About 10-13 hp, ro about 1 tenth in the 1/4 mile. I have heard guys say that they noticed big gains by the simple rocker swap.
In 1996 GM used full rocker roller rockers and was the only stock GM V8 to ever use full roller rockers. They were extruded aluminum in a 1.6:1 ratio. They add some valvetrain noise to which GM used a composite valve cover to dampen some noise. They also added a specific LT4 knock module in the PCM to desensitize the knock sensor some in order toprevent the PCM from detecting the rocker noise as knock thus retarding the timing advance.
You can install this same LT4 knock module in any of the Vortec truck "blackbox" PCMs.
The LT4 rockers used a 7/16" rocker stud, but they can be had from GM for the stock 3/8" rocker stud.
The reason why GM went with the rocller rocker on the LT4 was because the rocker arm was galling on the rocker nut above 5200rpm. Since the LT4 has a stock rev limit of 6412 rpm, GM went with the full roller rocker. There was 2 recalls regarding these LT4 rocker arms. New Vette owners were told to not drive their new cars until the rocker arms were swapped out with updated ones. This was 1 of the reasons why GM never again ran a full roller rocker arm again in any production vehicle.
GMPP rockers, they are narrow body, self aligning rocker which are the type you need to run.
The above post is correct, to swap the spider out, you only need to remove the upper composite plenum, the lower aluminum intake stays in place.
You may find this article interesting. Its about the Vortec CSFI(central sequential fuel injection) to MPFI(multi port fuel injection) conversion spider.
CSFI to MPFI - Vortec Engine Fueling Fix - Fuel Injection - Off-Road Magazine
Your stock cam specs at 191º/196º at 0.050" with lift of 0.412"/.428" on a 111ºLSA. The Vortec 350 cam was laso used in the L30 Vortec 350, and in the 1994-96 iron headed LT1 used in the Caprice/Fleetwood 350 and in the 94-96 L99 4.3 V8 caprice engine.
I might be tempted to spend the rocker arm money in other places. I personally would not by a set of $100 full rocker arms. I think that Scorpion has had some issues IIRC.
A PCM tune and getting rid of the TINY 1/2 ton Vortec 350 headpipes would yield greater gains. Look at those horrible crimp bends that squish down quite small. The pipes beside are from a 3/4 ton Vortec 350 truck, much better stock pipes.
peace
Hog
In 1996 GM used full rocker roller rockers and was the only stock GM V8 to ever use full roller rockers. They were extruded aluminum in a 1.6:1 ratio. They add some valvetrain noise to which GM used a composite valve cover to dampen some noise. They also added a specific LT4 knock module in the PCM to desensitize the knock sensor some in order toprevent the PCM from detecting the rocker noise as knock thus retarding the timing advance.
You can install this same LT4 knock module in any of the Vortec truck "blackbox" PCMs.
The LT4 rockers used a 7/16" rocker stud, but they can be had from GM for the stock 3/8" rocker stud.
The reason why GM went with the rocller rocker on the LT4 was because the rocker arm was galling on the rocker nut above 5200rpm. Since the LT4 has a stock rev limit of 6412 rpm, GM went with the full roller rocker. There was 2 recalls regarding these LT4 rocker arms. New Vette owners were told to not drive their new cars until the rocker arms were swapped out with updated ones. This was 1 of the reasons why GM never again ran a full roller rocker arm again in any production vehicle.
GMPP rockers, they are narrow body, self aligning rocker which are the type you need to run.
The above post is correct, to swap the spider out, you only need to remove the upper composite plenum, the lower aluminum intake stays in place.
You may find this article interesting. Its about the Vortec CSFI(central sequential fuel injection) to MPFI(multi port fuel injection) conversion spider.
CSFI to MPFI - Vortec Engine Fueling Fix - Fuel Injection - Off-Road Magazine
Your stock cam specs at 191º/196º at 0.050" with lift of 0.412"/.428" on a 111ºLSA. The Vortec 350 cam was laso used in the L30 Vortec 350, and in the 1994-96 iron headed LT1 used in the Caprice/Fleetwood 350 and in the 94-96 L99 4.3 V8 caprice engine.
I might be tempted to spend the rocker arm money in other places. I personally would not by a set of $100 full rocker arms. I think that Scorpion has had some issues IIRC.
A PCM tune and getting rid of the TINY 1/2 ton Vortec 350 headpipes would yield greater gains. Look at those horrible crimp bends that squish down quite small. The pipes beside are from a 3/4 ton Vortec 350 truck, much better stock pipes.
peace
Hog