I saw on another thread about an L31 package from Vortec. I was wondering just what this was. I want to build up my LO3 a little. I have a friend with a 92 Z28 B4C (though I still say GM never made a Z28 B4C) And he thinks its the fastest thing ever with his TPI. Now this spiring I plan on putting in a new cam LT1? And a new rear(Do I need a whole rear or do I just need gears and a posi unit?) Well my origional intention was to find out what this L31 is? Heads I am assuming, anything else? Time to show people just what TBI can do

Yeah, L31 is the 350 vortec heads. Lt1 cam is good for the 305. Gears and posi will swap in but a complete rear is usually easier since everything "should" already be lined up. A bad gear install can make a $500 labor charge = 1 good 60' and you're pushing the car home! Sometimes you don't even get that far so a complete rear with the gears you want is usually the safe way. Keep in mind that a 4th gen rear will fit but the stock thirdgen wheels are offset such that it'll stick out a couple inches. Advantage of a 4th gen rear: can run 4th gen wheels with only spacers up front, low miles (usually), already have posi, already has disc brakes, easy bolt in!

GM made both the RS and Z28 B4C package police interceptors.

weve done this before. the b4c option was, by definition, a camaro RS with the Z28 drivetrain. i realize that other features(upgrades) came with the b4c but gm resource says camaro rs with Z28 drivetrain.

jptaylor

L31 is not a part number for the head it's a complete engine assembly or package. Like LT1 is a complete engine assembly. Now any part off those engines are refured to by the assembly number along with a discription of the part . LT1 heads, LT1 cam, L31 heads or Vortec heads. Whatever.

L31 was the RPO code for the Vortec 350. Saying you have L31 heads is synonomous with saying Vortec heads.

L03, L05, L31, LT1, LS1, LT4, LT5, L99 blah blah, L30 (305 vortec engine)
BTW, the head casting numbers for the 305 vortec motor are: 12552520, 12558059. The actual 305 vortec block motor casting number is 10243878.
and the L31 heads are 12558062, 10239906. The L31 block casting number is 10243880, that's my block .
Anyways, who wants to print all those numbers for the casting numbers when we can just say "L31" heads

edit: Astro, I like how you used the big word, "synonomous." You must be some libral arts school major
Also, I do believe there are NO 91-92 z28 B4C packages. There ARE however, the 1LE z28's but they didn't have power anything and lacked the a/c. If you're friend says he has a B4C z28 I dare him to take a picture of either the center console options tag or the drivers side door jam tag. Show me the B4C and I might believe it, providing nobody photoshops the image (trust me, I have ways of telling).

Yeah I get the idea. I saw L31, I should have known it was an engine code, just didn't register in my brain. Any idea how much the heads cost?

http://www.sdpc2000.com/cart.asp?act...tart&catid=277

"Requires special intake manifold to fit the Vortec bolt pattern."

Is this the manifold on the bottom of the page? If so I believe it is intended for a carb. Or will my TBI fit on it, rather work with it?

hehehe, nope. Mechanical engineer. Like libral arts majors even know what a cylindar head is! j/k

Yes carb manifolds work with TBI. You just need a plate adapter under the throttle body unit.

DM91RS, I like your alternator bracket . Also you stated in your sig that you have done ult tbi mods. Why does it look like the rear part of the bores still have a ridge on them? Just wondering.

Why use the L31 when you can get the L30 for the same price plus the L30's are for the 305 anyway. You won't have to mill the L30 heads like you will with the L31's. Just asking?

Can you drill your own holes on a different intake to fit the bolt holes for the L31 heads?

And DM91RS where did you get that adapter plate for the TBI?
Looked on Jegs couldnt find it.

This has to be the easiest question asked. But a good one!
The L30 heads have 1.84"/1.5" valves and a 64cc chamber.
The L31 heads have 1.94"/1.5" valves and a 64cc chamber.
See why the L31 heads are better?
The L30 heads have the same cc chamber so you'll need to mill them down also because the 305 vortec motor had dome pistons, Lo3 is flat top. Flat top is better for performance.
The L31 heads are more popular anyways and the 170cc intake port is VERY good. The vortec heads (L31) produce more power than the fastburns up till like 3000rpm I believe. That's why I'd take the vortec heads over fastburn for the street and daily driver. The vortec heads are iron and so they'll make more power with less compression (can use flat top pistons instead of dome).
Wow , I can't believe I know this stuff off the top of my head!

According to Jeff@SDPC:
"There are L30 vortec 305 heads. They are part number 12529180. They do not flow as well as the 350 heads, but they do have the 58 cc chambers. They cost $754.66 a pair. The 350 vortec heads flow better cost less and can be milled to get the compression needed."

http://www.mortec.com/castnum.htm

You can get everything you need for the L31s assembled with manifold and bolts and everything for 799. Dont know why you'd spend 750 just for the L30s.

There are no ridges. Just not a close enough photo to tell.

I would buy the intake made for the Vortec's as they have a different port height along with a different hole pattern.

As far as the adapter plate I made it out of .375 thick aluminum plate.