Thread: will 350 heads work on a 305 and will it give it any more power

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i have a 84 mazda rx7 with a 350 with an edelbrock performance intake but the motor is dieing, I have a 305 out back and i would like to know if i could put the 350 heads on the 305 and will it give it any more power or work at all.

Just give the 350 a rebuild cause when you get the 305 togther with the 350 heads, you'll think it's dying too.

what i mean bye work at all is will i have meny probs,how much power would i loose. is it worth putting 350 heads on a 305 and if i did would i have to use 350 head gaskets (most likely)

im going to use it to drive on weekends and race freinds (its road legal) and maybe go to the local race way. My freinds keeps bragging his s10 with 305 will blow the doors of any thing around here so i built a car, my little 2 seeter rx7 that had a rotory motor so i replaced it with a 350 but its dieing so what would be a good and cheap way to get as much power out of 305 as i can while i rebuild the 350?

whats a good web site that i can find a N20 kit

Usually 350 heads have larger chambers than 305 heads so when you put them on a 305 you lose some compression therefore you lose some power, but not that much, also the valve sizes are probably smaller therefor you lose more power. its like a lose lose situation.

There are a few options you arent exploring here. 1) shaved heads. Shave your 350 heads down, Bolt them on the 305 and you will re-gain your compression while having better flowing valves. 2) serious rebuild. Rebuild the 350 and apply a stroker kit during the process. 3) exhaust. From what ive read from your posts, you dont have a high flowing exhaust. A must for a High Performance Small block. Finally 4) a cam change. My guess would be your running a factory 400-something lift cam. Or maybe even high .300s A little lift can go a long way

In order to understand whether the heads will work properly you have to understand why the 350 is dying. Are the bearings going? Is it smoking? If its smoking, you have to figure out why its smoking. The heads could be going. If that's the case, then why bother sticking them on the 305. Tell us why you think the 350 is dying.

Think about it. If its the head gaskets, and you are removing the heads, you may as well replace the head gaskets instead of swapping engines. Think about what may be causing the problem. If its the lifters and/or cam, you can do that with a lot less work than an engine swap.

The 350 valves are bigger and on wider centers. You will need to do a couple of tria assemblies to ensure that the valves do not contact the lip of the 305's narrower cylinders. You can relieve (notch) the cylinders a bit but not very much. Think I would go through the 350 before I would try to build a 305 out of parts.