can 305 sbc heads be used on a 350 engine?whats the good bad and ugly of it?

I wish people would stop trying to hot rod 350's with 305 heads because they insist the compression goes up. There are two types of compression. Static and Dynamic. Static is the physical calculated compression ratio and yes...it will go up considerably with a 305 head on a 350 as it has a 58CC chamber. Open chamber heads for 350's are 76 CC and some of the later stuff such as Vortec heads are 64CC chambers. That head on a typical flat top piston 350 will give you approx 10:1 compression even with the piston .025 in the hole at TDC. Of course, you can tighten that up and bring the piston to zero deck at TDC and you'll not only gain compression, you'll speed up the burn, fortify against detonation more, reduce both spark advance and octane requirements and the Brake Specific Fuel Consumption(BSFC) of the engine will be reduced. These are all plusses!

The dynamic compression goes down with a 305 head because the engine will make less cylinder pressure. Why is this so? Simple. The 305 head flows less air and therefore there will be less air in the cylinder to compress. Hence cylinder pressure goes down.

If you want to make good power out of a daily drivable and streetable 350, you will not under any circumstance out power the factory 062 casting Vortec head. At least not for the money. Don't put a 305 head on a 350. You're going the wrong way.

305 Heads On 350

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RE:

can 305 sbc heads be used on a 350 engine?whats the good bad and ugly of it?

I once bought a Nova that had a 350 with 305 heads. It was a rebuilt motor purchased at Kragen. What the builder did was use dished pistons in order to keep the compression down. It was also bored .060 over. A real crappy setup for performance, but it runs just fine for a 'round town car. I would never pay money to build a motor like that. Its what came in the car when I bought it. The builder made money on it. Cheap 305 heads with a cheap 350 block.

Assuming the 350 is a Chevy engine then yes, they will bolt up. You need to keep the camshaft type the same so that the valve train will be compatible, particularly the valve springs and rocker arms. You will loose horsepower and fuel mileage and will probably get bad spark knock unless you switch to premium fuel. It sure would be a lot of work to save a few hundred bucks. I don't recommend it at all.

Depending on the 305 heads, yes you can. If you get the right ones they'll give you greater compression but you'll still be able to run on pump gas. Check the casting numbers first though because I am pretty sure the ones you want are the 14014416 casting. You will also get good bottom end and mid but in the highs it wont be as good.

Both small blocks should bolt up fine.

If you bolt them up you will probably get more compression.

But because of the bigger displacement of the 350 engine probably won't like the smaller ports and valves.

So you could do it. Probably not entirely good.

almost all small block chevy parts are interchangeable, however what you are trying to build will be a boat anchor. The heads will fit, but will make no power, poor fuel economy, and lots of pinging noise.