Hey everyone,

I am building a four bolt main L31 Vortec 357ci, with worked over iron vortec heads & fuel injection.

I just acquired a few ZZ4 take out parts; Forged crank, forged rods. In the pile of parts is a GM performance parts LT4 hotcam.

I am debating throwing 1.6 ratio rockers on that cam wich will make the specs.

Dur @ .050" Int 218 / Exh 228

Lift @ .050" .525 / .525

112 Lobe Sep

I know about elongating the pushrod holes for the 1.6 rockers, but what will I need to do to the heads?

Will I need to cut down the valve guides?

What kind of springs will I need to use, I hear vortec heads use a different spring than the old 350s.

Will I need different retainers? is there a spring & retainer combo made for the vortecs that will allow the lift I want?

I've opted to pin the studs, but if screw in is better I can go that route.

Cheers ~Mykk

Comp has a kit with springs retainers and locks that will allow .550 without any machining

http://www.chevyhiperformance.com/t...lift/index.html

http://www.chevyhiperformance.com/h...7458/index.html

http://www.chevymania.com/tech/vortec.htm

http://www.speedwaybids.com/tech/Vo...s_Max_Lift.html

http://www.carcraft.com/techarticle...rade/index.html

some different ways to skin the cat.

Thanks guys, I have the parts on order.

According to these carcraft articles, all I need to do to accommodate the LT4 & 1.6 rocker lift are beehive type springs. No machining necessary to vortec heads. (except to the pushrod holes)

http://www.carcraft.com/projectbuil...tall/index.html

http://www.carcraft.com/techarticle...rade/index.html

So I've ordered the Proform 1.6 ratio, full roller, narrow body, self aligning rocker arms; part # 66915



Beehive springs: Comp Cams 26918
matched retainers for springs: Comp Cams 774
and 7 degree locks for the retainers: Comp Cams 648



I also ordered the gear drive from Summit; quiet, for roller cams. part # G6705



And since getting the tall rocker arms nuts with the allen jam nuts to fit under stock stamped tin valve covers is unlikely, I ordered a set of tall, ball milled, polished aluminum covers.



A parts total around $600.00 getting closer to the engine build budget I've given myself.

Cheers ~Mykk

Mykk sounds like a plan. Good luck with the build. Not sure about the Gear Drive tho' if this is going to be a street engine. Most wish they would have got the old chain type. They do transmit more harmonic vibes.
Todd

The 774 retainer is for Gen-3 (LSx) valves, which are 8mm in diameter. You need the 787 for a Gen-1 motor, with valve stem diameter 11/32".

http://compcams.com/technical/Catalogs/106-07/308.pdf

I see what your talking about... Supposedly the 774 is what Carcraft used in their build of a vortec headed SBC with a LT4 hot cam. So I'll cross that hurdle when I get there.

have you heard of Fbird-88's 400hp combo ?

The springs, retainers & locks just arrived... everything looks great. The springs fit the heads, the retainers fit the springs, the locks fit the valve stem & retainers... I do not see an issue. I'm not sure why they had a different retainers for LS1's as long as you use 11/32" locks

This is a mock up, not attatched to the head.





nope, details?

I'm assuming they had a good reason for making a different retainer for the thicker valve stems. Could be the standard 11/32" (0.344") locks might not seat far enough down into the 8mm (0.315") retainer's hole. If not, it seems like it could limit your valve lift.

The hex nuts on those proform rockers are junk, Sometimes they don't even fit in the slot and bind the rocker and end up spraying aluminum dust all over your fresh motor.

I had some on my BBC and ended up purchasing a set of taller studs and arp rocker nuts.

So don't pin the studs just yet.

i've heard the same on those rocker arms and was recommended to a comp cams magnum rockers

I am curious as to the complaints of the rockers.

The polylocks seem to fit fine, and supposedly the polylocks don't fit the slots?

Right, on mine the hex style poly lock the corners of the hex would hit the sides of the slot. You would have to put these on and test them to see if you have the same problem.

Thanks for your help. I'll keep an eye on it when it's time for assembly