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I scored me a 1998 vortec 350 engine. I am going to build a 383 for my monte for some strip action. The buildup that I am going to do is the one that Tech inspector layed out on page 5 of this forum. I am going to use a comp cam 230/230 286 XE. Can i use the OE lifters? They look to be in good shape. The heads are casting 062. Are the 906's better? Thanks for any help.
well firsth thing i would be check is that if your heads valve spring pressures are not going to adequate. some cams depand certain valve spring pressure on the cam. you can do some damage. now if your putting a new cam in and you don't want to have a worry about your valve train, get new lifters. yes roller are expensive and i recently have figured out the benifts. being a roller motor to being with, no retro fit are necessary. on the head stuff i'm sorry but i don't know those castings right at this moment
I have heard the 062's are better and that the 906's are prone to cracking.
NEW LIFTERS. No doubt.
Congratulations on the engine, Flanker. This can be a great motor to build and following Tech’s advice for components is a sure bet for a winning combination of 400 plus horse power. Here are several things you may find interesting about the head(s) you are referencing.
Internally, casting numbers 10239906 and 12558062 are identical with the exception of hardened exhaust seat on the 906’s. The 906 castings were used for heavy-duty truck applications and have a single-angle “Inconel” exhaust valve seat. Inconel alloys retain strength over a wide temperature range and are typically used in high temperature applications such as aluminum heads.
The 062 is a standard induction-hardened three-angle valve seat, typical of GM performance heads.
10239906 casting has one large single hump and the 12558062 casting has 3 small humps. If you were to go to your local GM distributor (or a wrecking yard), and ask for GM Part Number 12558060, you would get a Vortec head – that is made from either casting number. The GM factory specifications are:
Part Number: 12558060
Description: L31 with valves
Material: Cast Iron
Head Bolt Torque: 65 ft. /lbs.
Valve spring Seat: 1.300” O.D., 0.850” I.D.
Valve-guide Seals: Viton rubber positive seals, total 0.450” retainer-to-seal clearance Combustion Chamber Volume: 64 cc
Spark Plugs: Straight
Heat Risers: No
Valve springs: Single wire with damper 1.235” O.D., 0.875” I.D. 75-pound seat pressure @ 1.700” installed height Coil-bind @ 1.150”
Intake Bolt Pattern: Four bolts per side
Rocker Arm Style: Self-Aligning Intake Runner Volume: 170 cc
Valve Diameter: I: 1.94”, E: 1.50”
Casting Numbers: 10239906 and 12558062
Max. Valve Lift: 0.420” which allows 0.030” retainer-to-seal
Rocker Stud: Press-in, 3/8” diameter
Spark-plug Style: 14 mm, ¾ reach, tapered seat
Notes: LT1 Design Port with valves and springs.
Casting number 10239906 has been installed on 1996 (and newer) 350 engines. They are referred to as, "Vortec 5700" or, "L31"heads. They have 64cc chambers, and in their stock configuration, came with 1.94" intake and 1.5" exhaust valves.
Casting number 12558062 was used on 1998, 350 engines installed in GM trucks. Also known as, “L31” and “Truck Vortecs”, it too has; 64cc chambers, 170cc intake ports, and 1.94”/1.5” valves.
Interestingly enough, the production Vortec heads introduced in 1996 were intended for the new Vortec 350ci engine in ½-, ¾-, and 1-ton Chevy pickups. The Vortec head is the iron version of the LT1 style head with same chamber, intake and exhaust port design in a standard-water-flow head. This head with 1.94/1.50-inch valves actually out performs the infamous “Bow Tie” high-performance head.
GM designed the valve guide to also serve as the inside diameter centering device for the valve springs. It functions like a sleeve that keeps the valve spring centered. The guide is also machined at the top to mount the valve-guide seal. In stock form, total valve lift is limited to between 0.420 and 0.430 inch. The cam that you’re considering needs to have .480 lift. As such, you will need to modify the valve spring seat and valve-guide areas of the head. Have your machinist increase the spring-seat diameter from the standard 1.25 inches to 1.440 inches. While you’re at it, consider screw in or pinned rocker arm studs.
By all means, buy the valve train as a kit, i.e., cam lifters, valve springs, retainers and timing gears/chain. 1.5:1 roller tip rockers are fine, in my opinion – Tech may have some input here – but I don’t often see the justification of hundreds of extra dollars unless you’re looking for prize bracket money. That said, reducing friction is almost always a plus and if you have a budget that allows first tier true roller rockers, go for it. Don’t go cheap here buy brand names – no “Uncle Billy’s Bong-in-a-Box” stuff that will cost you more than it ever saves when your valve train comes unglued at 5500 RPM. Use the supplied lube and follow the installation/break-in instructions to the letter or you’ll be out a lot of money and repeating the process.
I recommend reading other posts, re: what to do in the build as far as safety, cleanliness, proper light, etc.
Have fun and let us know how you’re doing.
Regards,
Glenn
Thanks for the replies guys. Until recently, I had only built fe fords and pontiacs. The smallblock chevy is new to me.