kaptinkafeen

iTrader: (2)

I am already planing some winter projects and was wondering if anyone could chime in with their opinions regarding what I could do to a set of 305cid vortec's I have - casting #12552520.
I am not looking to spend much on them, but just want to fiddle with them. I am newbe to the porting scene and want to explore over the winter months.
Besides upgrading the intake valve to a larger 1.9" size, gasket matching the heads to the intake, what else can/ should I do to help these heads out - I guess I am getting at the issue of porting. I know that vortec's are a decent flowing head, but what type of work could I do. Is pocket porting worth the effort? Cost is an important factor, as I am aware that most will argue that these heads are not worth throwing $ at. I just want to learn.
TIA
-Andrew

ScottyRS

iTrader: (2)

You could buy a do-it-yourself porting video. And be careful with that valve size, the 305 cylinders aren't that big.

F-BIRD'88

305 vortec heads are not the same as or even close to the "vortec heads" (350 L-31) 062 and 906 castings.
The only thing they have in common with the 350 heads is the vortec specific intake manifold bolt pattern layout. But if you want to play, you can improve these heads with larger valves, complete porting and strategic chamber wall deshrouding to allow for the closer proximity of the larger valves edge to the chamber wall. Put the stock vales in the head and eyeball/ guage the clearancve to the combustion chamber wall as you open the valve. Now imagin a larger valve with its edge .050" closer to the chamber wall as it opens. All in all if you think you're going to end up with a set of "Vortec heads" equal or better than the real deal, think again. But you can learn and improve these heads.
You will need a vortec intake manifold thou. may be better and cheaper ( more bang for the buck) to get start with another 305 head casting like the 416's or 081's that use the conventional intake manifold. (lots of used performance intakes around) Sell or trade your heads for the more popular other 305 heads. They port up pretty good.

kaptinkafeen

iTrader: (2)

Thanks for the insight guys.
I already have a vortec bolt-pattern intake, so this aspect is not an issue.
So pocket porting, deshrouding the chamber wall and gasket matching will help these heads out.
I have a do-it-yourselfer headporting video (produced by bad-*** racing) - and the info presented is understandable for a newbe.
I am aware that these heads will not be anywhere near the 906 or 062 castings, I just want to get into the porting aspect of engine building and this is why I wrote the post.
-Andrew

five7kid

iTrader: (14)

Member "SSC" built a 305 Vortec than ran pretty well for him. Try searching for that with his username.

kaptinkafeen

iTrader: (2)

Thanks five7
-Andrew

five7kid

iTrader: (14)

I should have done the search myself before talking. He used the Vortec 305 shortblock, not the heads.

jr. gearhead

get the vortec heads from jeg's pn 12558060. complete ready to bolt on. 249 (last i looked)

Fast355

iTrader: (2)

1996-1997 chevrolet/ GMC fullsize vans have the 305 vortecs that you would want to use. They are the same as their bigger brothers. The difference is the chamber volume and intake valve size. The ports are the same, combustion chamber shape is the same, springs are the same, etc. They are simply scaled down versions (081 vs 083). GM only used the good heads for the first couple of years on the 305 vortecs, then went to the 520s, but even those heads will still flow over 220 CFM in stock form with the same exhaust flow as the 062/906 castings. I have a pair on a 305 vortec in my garage as we speak (059s). The ebay 305 (from a wrecked 1996 G1500 with 55,000 miles) had a LT1 cam put in it by me and was pulling a 6,000# 1997 chevy express, running on the stock 1997 350 PCM calibration and did its job well. I eventually pulled it for a GM goodwrench 350 when # 5s compression went to basically 0, oh well.

kaptinkafeen

iTrader: (2)

Fast355,
That's some good info. So my casting #'s are for post '97 vortec's which means they are not the 'scaled' down version of the larger L31 castings....
You mention that the #520's will flow as well - what other porting do you think I should research and attempt? I'm new to this stuff. The most difficult thing for me to comprehend is how to unshroud the valves without cutting into the combustion chamber shape too much... I have read and re-read Vizard's book, but interms of how much and how deep to cut I am still a bit unclear. Besides this, gasket matching and basic pocket porting seems straight foward.

My goal with these heads is to simply increase flow without having to open up my wallet too much. I can justify the larger intake valve, and I guess I can have the valves touched (back cut/three angle valve job) - but that's it. Heck even having the valves done is somewhat pricy (IMO) up here in Canada. In the end I won't be taking my heads to a flow bench because of the cost, but I would like to perform some head work that will produce a noticable (no matter how great) change in engine breathing capability.... (Currently I have these heads on a 355cid, and as some of you may recal the motor starts to run out of breath @ aprox 4500rpm; so I would like to do some experimenting )
Any help with the work required to de-shroud valve would be appreciated. Or can you guys lead me to a source that I can research that may have some pics?
-TIA
Andrew