...provided I changed the intake? Or drilled the heads to accept them? In other words, will the bigger L31 350 Vortec heads work on a 305 without causing problems? I have a friend of mine who is looking for some cheap mods to his 305 TBI, and we're currently planning a LT1 cam swap. At the minimum were gonna port the 305 heads and change springs. He'd rather have my ported Vortec heads if they'll fit, although I'll be using a thin head gasket to make up for the compression loss from going from 58cc to 64cc. I'm just worried about if the smaller bore will shroud the valves, or worse, make contact. Any other cheap TBI mods I should know about so I can do them while I'm down there? TES headers, Flowmaster catback, underdrive pulleys, ported (or maybe an Edelbrock) intake, and a new tranny with 2000 stall...oughta keep him happy with about 250 HP or so (over the peanut anything's better!) Any suggestions would be great, I'm used to being on the TPI board so forgive my TBI specific stupidity! =) I was thinking either the ported 305 heads, ported stock TBI intake and LT1 cam, or; Vortec heads, Performer Vortec intake w/factory TBI injection unit, LT1 cam. All mods will go onto a 350 in the future, so I'm kinda reluctant to put work into the 305 heads now, and I plan on using an early 350 TBI computer program when that happens. Suggestions? [This message has been edited by dhirocz (edited September 01, 2001).]

I think the vortec heads are a no brainer. I've watched an LG4 powered Z28 run 99mph at Maple Grove using the L31 heads. His compression is about 8.1:1 because of the lousy dish pistons.

You will drop to 8.6-8.9:1 CR depending on the head gasket you use. I'd use the ultra thin steel shim gasket. Its not optimum but it will work.

An Edelbrock performer vortec intake and tbi adapter would be my choice also. Throw out the stock intake.

Since you are upgrading the valve springs you might as well get a larger cam. The Compcams XR258HR-12 at 206/212, would really be a nice match IMHO.

You'll also need a spacer to go from the Head to the intake. The non-vortec style intakes aren't wide enough to get to the heads. Edelbrock makes an intake made for the Vortec heads you can look into that. YOu can also mill the L31 heads .030-.040" and retaing your compression but then again you will need the machine shop to make sure that your intake will fit onto the heads properly. I've done a ton of research about putting L31 heads on a 305 and It's not a Cheap mod if you want to keep compression and have everything done right.

-Lars

I think that you can't use the stock EGR ports on the 305 becaude the vortec heads don't have the crossover on them, so you'll have to consider that if you want to pass the sniffer test.

As for some more info on the vortech heads:
http://www.goingfaster.com/spo/carcraft325hp305.html

I'm still trying to figure out all the crap that has to be done to these heads for them to fit.....

Edit, sorry did not realize what an old old post I dug up.

The stock compression is 9.3:1 using 58cc heads.

If you go up to 64cc heads (Vortecs) then use Felpro embossed shim gaskets (.015" think) then you'll stay at 9.26:1 compression ratio. And from what I've read and seen, these gaskets hold up fine. You just have to make sure the deck on the block is true, as well as the heads (which are if they're new or been resurfaced).


Here's a link to the gaskets. They're the last one on that page.

I have used the .015" gaskets before on a nice smooth clean block and refinished heads and had no leaking problems with plenty of abuse.