All my seaching has been confirmed here that 305 Vortecs will not flow as well as 350 Vortecs and most people suggest just to use a pair of 350 vortecs for a 350 block. My question is, is there anything that can be done to a pair of 305's that will equal if not better the 350's?

I have a 86 Camaro (primarily used for autocrossing, less than 5400 rpm) with a 350 +.020 4-valve relief stock replacement pistions, XR258HR Hyd Roller Comp cam (258/264 adv. dur and .480/.487 lift), shorty headers, Edelbrock Performer intake with a Road Demon Jr. 625 carb. CR unknown. The heads are currently 350 tbi truck heads and either 305 vortecs or 350 vortecs would be an improvement. I was given (free) a pair of 305 Vortec heads cast #12558059 1.84/1.5 valves (64cc?). Obviously I'ld have to get a new intake to use these and to swap out the springs for the ones set up for the comp cam. I am the counterman at a machine shop, and my head man can install 1.94 valves and smooth out the exhaust ports for better flow. Unfortunatly we don't have a flow bench as we don't do much performance work. What else should be done (if anything) to help the 305 heads breathe, or should I just buy 350 vortecs and start from there?

Thanks
Gary R.

 

I believe a 305 vortec head is the same as a 350 Vortec head. i dont know. can someone clearify this for me and GMan 3MT!

 

check mortec.com for the casting numbers

 

They are different but close relatives. They have different chamber and valve sizes. I think most of us 305 guys are waiting for someone to bite the bullit and try a set. There is to much bad info/disscussion out there that keeps us from buying them.

 

it has the smaller 305 size valves and chambers and a similar but smaller set of runners.

Considering the results on this board with the regular 350 vortecs on a 305, just milling a set of 350 vortecs would likely get you where you would like to be.

 

He's considering using the free pair of 305 Vortecs on a 350.

 

From what i understand they have Vortec style intake ports, and do require the Vortec intake.

But they have smaller valves(as stated above) and have a L98 style combustion chamber, unlike the "fast-burn" style chamber on the L31 heads.

 

the smart guy with the funny name that writes in the back of one of those magazines (car craft?) first brought it up then made a retraction in a later issue stating something about the exhaust port or something like that.

I ported a set of 85 305 iroc heads for 13 hours and put them on a 406 I promptly blew up due to an oil pump failure the car was the fastest I had ever owned to this date. then a friend put them on a used 350 shortblock from a 79 vette and won the season championship in the "chevy monte carlo" circle track class.

I figure they cant be too bad. Maybe a stock LT1 cam or other smallish cam, and carb on a 350 they might do well.