i have been reading up on some of these guys that have ported thier stock 305 heads. they seem to get them to be able to flow fairly well but does anyone actually have any power numbers to support their flow #s?? does anyone have flow numbers for a stock untouched 305 head?? also it seems to me that putting 1.94 intake valves in the stock small chamber like that is shrouding them a bit. would there be any benefit to porting yet retaining the stock valve size? i have a 305 tpi wiht ported plenum and LPE 214/224 cam. the car runs good but i feel that i need to port my lower intake and get the heads to flow better to compliment my cam and headers and get to most out of my setup. what do you guys think?

 

Go for it! You will REALLY notice the difference a port and polish job will do for your 305

On a healthy 305 like yours, I would estimate a solid additional 25 to 30 hp from the head work and enlarged intake valve. Flow in cfm = hp. That is a scientific fact. And when you do these 305 heads properly, they will flow enough to suit a smallblock producing up to 450 hp, no sweat.

25 or 30 hp would put you in the 14.5x region

 

thanks for the reply. if you saw the car at teh track you guys would laugh because it is such a dog below about 1800rpm. and with my stock converter i cant get out of the hole for crap. i only cut a 2.19 60ft and teh tires were hooked, lol that is terrible! the car also went 93.5mph wiht only a 14.81 et, so with a 2000-2500rpm stall converter i am hopin to go mid 14s by simply swappng torque converters. but i want to go low 14s on the motor (nitrous in the future). so i am gonna have to do somethin with the stock heads and intake base. i think the runners will be ok, but the intake base especially needs help. keep the suggestions comin guys, i want to hear what you have to say!

 

Put the bigger valve in when you port your heads.
If the valve was "shrouded" the flow bench would show it.
It doesn't. It likes the bigger valve.
Besides you have to crave out the chamber wall a bit anyway to get the 1.94 valve to slide in onto the seat. No need to get carried away here, especially on a 305. If you're building for a 305 use a 305 head gasket to show where the cylinder wall is.
This is a low flow are anyways. The flow is concentrated
towards the sparkplug as it exits the port.
Don't be shy on your porting effort either. These heads
need key areas opened up. Especially betwwen the common wall and guide boss. Raise the roof about 1/8" at least all the way from the bowl area to the manifold opening. Use the manifold gasket as a guide. You can't make this head too big.

When u buy a converter for your 305, get one custom made for a 305 with a stall about 3000+ rpm. Most off the shelf converters are rated for a 350. A 305 with that size of cam will need this
stall as a minimum to launch the car properly.
A converter will show about 500rpm less stall behind a 305 compared to a 350. Don't be shy here either.

 

Can I put 350 heads on a 305 instead of porting the original 305?

 

Ya could but it would be a step backwards.
The larger combustion chamber size would cause the compression ratio to be much lower.

Stock 350 heads don't flow much better than stock 305 heads.
You'd be missing most of the gain. Kinda defeats the point.

 

anyone else got any opinions?

 

Yes...

Stick with your 305 heads and port them, it's the cheapest HP there is. It may in fact be possible to get more HP by replacing them, but that's many hundred $$$$ compared to $40 for a porting kit. get a good valve job on them, and replace the valve springs if you haven't already, before they start to break.