I'm about to swap out my 305 for a 350. I've heard of some people taking the heads out of a 305 and putting them in their 350's. Is this actually worth the work?

 

Usually not. Most peopole do this because they don't have 350 heads or the heads they have will give compression too low for their goals. 305 heads have considerably smaller chambers (58cc) which will bump up compression quite a bit over 350 heads (64 or 76cc). But they also come with smaller valves (1.74 or 1.84 intake, 1.50 exhaust) and very small intake runners which can help prop up low end torque some at the expense of high end HP.

If you've already got a complete 350 with heads and the compression ratio is roughly where you want it, don't bother swapping.

 

In the late 80's I did a bowl cleanup on a set of L69 heads for my then brother in law. I was curious so I did some measuring. The intake ports were about the same size as the ports on some 041 heads I had laying around off a 70 SS 350 The exausts were a few cc's smaller. I don't remember the measurements, except for the chambers which were 59cc's. But I do remember telling him how close the ports were in size to the 350 heads.

Heads went on a flat top piston 350 in a Nova, then into my sister's 69 Camaro. Never run at the track, but I figured it was good for low 14's. My brother now owns the car and I've been harping on him to take care of the issues the car has (it was parked for years) to make it roadworthy so it can be driven to the track for some time slips. But he has his own business and works 12 hour days, so the 69 is still on the back burner.

 

If the replacement heads are in good shape, then I would say just go with them, for sure. If you want to add a little power, do an at-home port and polish job, and they will out perform those 305 heads, without a doubt. As mentioned above, you would gain compression, but lose valve size, probably netting you about the same result. If you were to increase the valve size on the 305 heads and have them cleaned up at the shop, it might be a different story.