Thread: 305 heads on a 350? can you tell me why?

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im tryin not to be stupid but can someone tell me what the advantage is of running 305 heads on a built 355?

compression.

Like Scooter said, to increase the static compression ratio. Thing is, raising the SCR requires more cam, which requires more rpm's, which the heads are want to keep up with. Tough for the smaller runners to flow enough air to support the larger motor at elevated rpm's.

There's a fellow on another forum who swears by these heads, fully ported and with 1.94"/1.60" valves.....
14014416...80-86...305..........1.84"/1.5" valves, 58cc chambers

Key words, "fully ported". Are you handy with a rotary grinder and do you know where and where not to cut?

Personally, I wouldn't trade a truckload of 416's for a good pair of L31's. Cut 'em 0.030" and you have 60cc chambers if you want more SCR.

I'm running Vortec 305 heads on my 350 Vortec engine. Did it for the compression thing, plus I scored a brand new in the bag set and couldn't pass them up.

Don

the heads on the motor in ???? are ported and polished. im considering this motor for my car. seen this done many times just never really new why. thanx for the info guys. im gonna list out the parts in this motor and have you guys tell me what you think, and if its worth what he wants for it. thanx again and check my new thread and let me know!!!

if you deck the heads .030 do you have to cut down the intake too?

Originally Posted by jbuck72

the heads on the motor in ???? are ported and polished. im considering this motor for my car. seen this done many times just never really new why. thanx for the info guys. im gonna list out the parts in this motor and have you guys tell me what you think, and if its worth what he wants for it. thanx again and check my new thread and let me know!!!

Ported and polished, then equalized on a flow bench or just hogged out with a rotary grinder???? If the intake runners are polished, this is usually a dead giveaway that the guy is not a knowledgable porter, polished intake runners will allow the air fuel mixture to separate and form fuel droplets in the runners---not good.... Smoother is better on the exhaust side, though. Any porting work other then a bit of match porting of the runners and grinding out the casting flash when done without a flow bench is just a guess as to what happens to the flow charachteristics of the head..... Bigger is not always better...equalizing the flow to the cylinders should be the goal of porting, not just hogging things out till you hit a water jacket.....

he didnt mention anything about the machine shop doing the porting and polishing on the heads, but maybe they were done from befor? id have to ask. but even if i do, with out tearing things down i couldnt be sure of the truth.