Oh wow! I was not expecting that kind of MPG gain. Thanks for the input man!
Keep in mind that i have my Jimmy Dyno tuned for the mods done to the engine like replacing the 1.5 rocker ratio to the 1.6 ratio.
There are 4 variations of rocker setups on the
Chevrolet 4.3L V6. The difference is in the stud base and in the rocker adjustment and alignment. The first thing you must determine when starting this project is what variation you have.
The first starts in 1988 and lasted until 1992. This setup uses a press in stud with a 10mm diameter and a rocker that is fully adjustable and NON self aligning. The second used the same stud but was a self aligning rocker arm. The third appeared on Vortec motors in the early 90's and also on some non Vortec motors and lasted until 1999. This setup uses a screw in stud with a 10mm base thread and a shouldered stud on top. The shoulder on the stud served as a stop on the adjusting nut. This setup is NON adjustable and is know as a Net Lash Rocker system.
In 2000 and up model years GM introduced a roller rocker. This rocker sat on a guide plate and was bolted down with an 8mm bolt.
Key points in determining what rocker setup you have in your engine.
1988 to 1992 all used press in studs, were NON self aligning and fully adjustable
1992 to 1995 Vortecs ALL used a net lash system with screw in studs and self aligning rockers
1992 to 1995 Tonawanda* Engines used a net lash system with screw in studs and self aligning rockers
1992 to 1995 Romulus** Engines used press in studs and were full adjustable. The rockers were self aligning.
1996 to 1999 All engines used a net lash system with screw in studs and self aligning rockers
2000+ All engines used roller trunion rockers. They were a net last system and self aligning.
* If it's a Tonawanda engine, it will have a "T" stamped on the machined surface on the block just in front of the right cylinder head.
**If it's a Romulus engine, it will have an "R" stamped on the machined surface on the block just in front of the right cylinder head.
1993 to 1999 with screw in rocker studs
These engines used a 10mm rocker stud top and bottom. The one problem with this is the lack of any available conversion stud to work with a set of narrow body rocker arms. Do not use a 60* V6 conversion studs They have the right thread sizes top and bottom but they are too short. All narrow body rocker arms on the market come with a 3/8" stud hole. So your option is to tap the head with a 7/16"-14 tap and use a screw in stud similar to above. However the tap does not bite in very hard so it is advisable to coat the threads with JB weld prior to installing the studs. If you go this route use the stud options above and the rocker options below.
Anyone reading this article should do the community a favor. E-mail ARP
www.arp-bolts.com asking them to produce a 10mm X 3/8" conversion stud that is long enough for use on a Vortec motor. The 60* V6 conversion stud would be perfect if it was 3/8" longer on top.
When you have your valve covers off you should change your valve springs. When increasing lift beyond stock specifications it is and important to be sure they do not bind. Stock springs should be ok as far as coil bind goes but the fact that roller rockers will allow you to spin your engine faster means valve float will can occur. Valve springs are cheep insurance against a potentially catastrophic problem. I myself recommend beehive valve springs found on GM's LS series of engines. Valve cover clearance will also be an issue. Any late model Vortec owners will have to switch back to metal valve covers found on engines before 1996.
When changing rockers, hand rotate the engine by hand to ensure the pushrod does not touch any part of the head. This is especially important on early engines with NON self aligning rockers. Comp Cams P/N 4710 will allow you to elongate the pushrod slot if need be.
