1966-300 to 340

**67chevygary** · 09-04-2009, 02:14 PM

I have a 66 skylark with a 300 2bl engine. Also in the garage i have a 340 4bl. out of another 66 skylark. are any parts interchangable-exhaust-intake-heads-etc? thanks gary

**Aaron65** · 09-04-2009, 02:41 PM

I believe the heads are interchangeable...the intake is wider on the 340, so that won't work, and the exhaust manifolds should be the same, but I am not 100% on that.

**67chevygary** · 09-05-2009, 09:46 AM

if the heads interchange then will the intake have to be changed to 4bl?

**BigDonno** · 10-25-2009, 06:35 PM

300-340-350 Same flywheel 166 tooth. I've heard '64 300 aluminum head intakes are all by them selves, where 300 cast iron head manafolds fit 340.

**gag67sky** · 10-26-2009, 01:07 AM

Hi, whenever heads or else interchange, that won't give you much improvement of perfs.....
The best bet is to swap the whole engine if the 340 is OK, then you'll have a big difference...
maybe you should check the 66' manual to ensure that trans fitting will be OK too but I don't think it's an issue, maybe the throttle linkage 2/4 bl is different also ?
Good luck, the 340 is a very nice engine when it runs fine

!
JC

**Bob Gibbs** · 10-26-2009, 05:30 PM

Originally Posted by BigDonno

300-340-350 Same flywheel 166 tooth. I've heard '64 300 aluminum head intakes are all by them selves, where 300 cast iron head manafolds fit 340.

300 intake fits 300 and not anything else. same goes for 340. the heads, timing cover, oil pan, balancer, flexplate, valve covers, rocker assemblies, distributor all interchange between 300-340