ive got a 85 305(yah yah i made a misinformed purchase awhile ago so i decided to just build it so the money i already spent wouldnt be wasted trust me i wouldnt do it again) anyway i plan on going with a twin turbo ebay setup prob running like 8 psi boost. i already have hypereutectic pistons 30 over, going to use the stock crank and scat oem replacement rods(the ones with the wav loc bolts in em) i have the gmpp main cap bolts(looks like arp ones im betting they make em and gm just puts there name on them) ill prob use one of comp cams smaller turbo cams or one of the smaller lunati voodoo cams for some low end power they look like they wouldnt be too bad. my question is i have the 305 smog heads with the 60 or 70 something cc chambers(at work so dont have a casting number) would these be worth while to use on the turbo setup if im porting and polishing them myself? trying to keep this on somewhat of a budget and if i can just use the heads i have it will save me some money, and btw the fuel i will be running is e85 so i dont think detonation will be a prob its has what 105 octane or something like that?

 

Hope your good at tuning efi. I think you will need an FMU if you dont change the computer. Bigger injectors. Those heads are bad and probably wont put you over 400hp. You could put some stock used vortec heads on it, keep your cam below .470 lift, and it would also drop your compression a little. From 58cc heads to 64cc. I put 76cc heads on a 305 and it took me down to roughly 7.5:1. You might see 8.5. Perfect for boost. Too bad you already put money into that 305.....those heads wont fit with your intake. Vortec lower plenums are pricey. If i were you Id scrap that tpi, and put a carb on it. You could do it for the price you sell your tpi. Put those vortec heads on for 300 bucks and youd be looking at close to 300hp. Add 8 psi and youd have probably 450hp. If it were a 350 youd have around 600. I would still scrap that 305 and pick up a 350 with some decently low miles.
That isnt the most important part though. Your trans wont handle over 400 unmodified, maybe even less. Mine didnt like it, but the tv cable was messed up and I still had the stock tq converter. I think you will be happier if you get your trans worked, get a good stall converter, and build a mild 350.

Oh and your fuel pump probably wont be big enough for turbos and e85. I didnt seem to lean out at 15 psi but i wasnt running alcohol which takes more fuel. Could maybe put an inline pump in.

 

well its going through a complete build atm it was carbed with the computer controlled carb bull but i will prob convert a lt1 intake for it and run it on megasquirt i dont have a car for ti anymore(theres plenty of shells in my area i want to get the engine built first) i was just wondering if it would be worth while to port and polish them for the low compression will prob go with a tko trans(looks like i can get one on ebay for a reasonable price) btw i do work at a dealership so i can get gmpp parts at a discount if i dont go with the converted lt1 it will be firsts setup prob be around 11-12k invested which isnt bad since there will be 3 of us working on it(me,my step dad, and his dad)

 

Thats a massive intake for a 305. you wont have any low end torque.

 

Not really. GM ran it on the baby LT1 (265ci) from the factory.

 

What 305 heads have 76cc chambers?!?
Find out what you have first, only then can we throw guesses around. PS - I doubt they're worth using for your application either way.

 

Baby LT1? This is news to me....

 

I haven't seen any 305ci heads with 76cc chambers either.
----------
L99 Caprice......the LT1 years

 

There arent 76cc 305 heads. They were just small block chevy heads. I think the factory ones were 58cc. Kinda silly comment.....
I didnt know that about the LT1, that intake has super short runners and an rpm max of like 8000! It cant be good for an engine thats spends most of its time between 2500-5000.

 

well i read that the the ho engine had 58cc heads with a 9.5:1 compression and the non ho engine had 60 or 70 something cc heads with a 8.5:1 compression david vizards book even said some 305s had the super huge compression chamber and thats what mine looked like. they dint look anything like the 58cc ones he pictured but i looked them up and they are the 58cc ho heads but i have dished pistons and going to get custom head gaskets made by cometic(for durability under boost and so i can get a good quench) so ill prob end up with a 8.9 or 9:1 compression ratio should be fine running e85. im also lightening the internals(professionaly lol) and using behive springs so that i can have a higher power band it will be mostly a strip car with some street time.
14014416...80-86...305..........1.84"/1.5" valves, 58cc chambers
thats what i got from moretec on my heads, which these are what are considered the "good" 305 heads correct?

 

They're as good as any.

Both the LG4 and the L69 (HO) used those.

Stock, they SUCK; but there's potential in them when ported with larger valves installed.

Like any stock head, by the time you upgrade them to typical racing setups (screw-in studs & guide plates, enlarged spring pockets, renew the guides, etc. etc. etc.) You'll end up with very near as much money tied up in them as just buying new aftermarket ones. Machine work isn't getting any cheeper, but aftermarket CNC casting is.

 

If your only going to run 8 psi you could run higher compression than that. If you plan on sticking with E85, 10 would still be very safe.