The only parts that will not swap are the pistons,the crank, and the damper.
And the engine oil pan and Left motor mount. The oil pan is slightly different where it touches the rear main cap.
Also 340/360 Left motor mounts are different widths (about 1/2" difference) than 273/318 engine mounts are. I have heard of people using washers to make up the mount difference – which will work but is not preferred.
1 cubic inch = 16.38706 cubic centimeters. Combustion chambers are always measured in cc’s.
You can get 340/360 cylinder heads to bolt onto a 318 (which is what the police 318’s have) – but for some reason the factory made the 340/360 heads with larger combustion chambers (higher CC (Cubic Centimeter)) – which effects the compression ratios, and a more.
A person can install 340/360 cylinder heads and manifolds to a 318 – but you will also need to change pistons because compression ratio will be way low, otherwise.
It comes down to a well-used, but true phrase – there is no replacement for displacement.
The 318 is a great engine – except for performance usage.
All 340’s are high performance engines. Many 360’s are also high performance (but not all). The larger displacement is another plus.
Stroker crankshaft kits are the way to go, now.
273, 318 and 340’s all share the same crankshaft stroke of 3.31”. The three different engine sizes have different bore sizes (3.63”, 3.91” and 4.04” respectably). 360 engines have a 3.58” stroke and 4.00” bore.
What a stroker crankshaft kit does is increase the crankshaft stroke (according to size you request). The common size is 4.00” stroke (up from 3.31” on 318 / 3.58” on 360) – which would give a 318 a new displacement of 390 ci or 408 ci on 360. The down size is a stroker crankshaft kit (consists of crank, rods, pistons, rings and crank bearings) run about $1,500-2,000 (US).
They also get the compression ratio back up to a better place.
To make use of the displacement, 340 or 340 cylinder heads (or Magnum) are now needed (so engine can breath) – or the engine using 318 heads will run out of steam at about 3K RPM (again – think small straw size and trying to push more air through it).
All AJ is saying, is if you already start with a 360 – you will already be ahead of the game.
Also, the 360 engine is a lot easier to make faster far easier (and far cheaper) than a 318 is.
I have a pair of 360 engines in my garage that I’d be happy to sell, cheap – but freight from Oklahoma City to PA will not be cheap.
I also agree with AJ, if you are looking at more than stock performance, you can’t go wrong with a 360. Add a 4-bbl, and you might be happy to stay there.
That said, I wouldn’t spend that much $ into a 318 just because you have to fork over tons of $ to get what is almost free on a 360. Also, if you want more, you already have a strong base to build upon.
Go find a used engine on Craigslist or at a salvage yard, even better, go find a 360 Magnum engine, transfer the timing cover, get a car 360 oil pan and a decent 4-bbl intake and you will be almost set. At that point – the sky is the limit.
BudW