Thoughts on Engine Selection
The hardest decision for me was deciding what engine to build for the Barracuda. Rebuilding the stock 273 was never really an option for me. I don't really care about keeping it bone stock, 273 pistons are hard to find, and performance would be limited compared to other options. I started out with the idea of building a mild 318, more or less following a recipe outlined in Hot Rod magazine. I figured a stock exhaust system would be too restrictive for a hot 360 and I'm not willing to cut the inner fenders to run headers (at the time, the only headers I could find for early a bodies exited out the fender wells). I had a hard time locating a 318 core, though, and my machinist said a 360 would run OK (not great) through the stock exhaust. I decided to go ahead with the 360, then all hell broke loose - I found a set of TTI headers that wouldn't require cutting the inner fenders. If I've got a decent exhaust system, I might as well build this thing HOTTTTT. You know, stroke it to 408 inches, ported Edelbrock heads, huge cam, etc... Every time I turned around it seemed like I found another thing that would make more power for just a little more money. The problem was, when I added up all the "little money" I was going to end up with a $13,000 drag racing engine. I also started wondering if I would be happy with that kind of engine in a daily driver. I re-read the Hot Rod 318 build. I found a similar build in Mopar Performance that ran 12.76 in a '68 Barracuda (which is heavier than my '66). I decided to save the 408 for my next car (hopefully a '73 Duster) and go with the 318.
Deciding on the Mopar 318 was a big relief. The only problem was finding a core. It couldn't be any 318, it needed to be a 1986 or newer core with the high swirl cylinder heads (302 casting number). It took awhile, but I was able to find a core with the heads I want. I've read that these heads are prone to cracking, so I was really happy when they passed Magnaflux inspection. I wasn't so lucky with the block, which is cracked between the inside middle head bolt hole and the water jacket on both sides od the block. My machinist says it's easy to fix and the fix is a good one ("After the repair it will be just as strong as an original block"), but it's an extra $100 I wasn't planning on spending. I can't exchange it because the junk yard I bought it from only had one 318 on hand and it took me a long time to track this one down. It seems like 318 cores (which used to be about as common as dirt) are getting rare. If I had more time and money, I'd look for an earlier block and save this one as a backup. As it is, I'll probably just cough up the $100 and have it repaired.
The 302 castings (like all 318 heads) come with 1.78" intake and 1.50" exhaust valves. Most people using these in a high performance build step these up to 2.02" intakes and 1.60" exhausts. I'm going with the 1.60" exhaust valves, but I'm going to run 1.88" intake valves. This might cost a little power on the top end, but low end throttle response should be better. Also, after finding the cracks in the block I'm a little nervous about removing too much metal from any of the engine parts. Because most people run 2.02" intakes, the 1.88" pieces are hard to find. I finally found a set from Indy Cylinder Heads. In case you want a set the part number is 360-V1-AER-12. At $73.00 for a set of 8 they're way cheaper than a set of custom Manley valves which are the other option.
For the rotating assembly I'll be using the stock crank shaft, Eagle I-beam rods, and Keith Black Hypereutectic pistons with moly rings. At the rpm and power level I'm looking for, these parts should be plenty strong. The I-beam rods are about $180 less for a set than H-beam rods and quite a bit lighter. The hypereutectic pistons run with a lot tighter piston to wall clearance than forged pistons which means better oil control and quieter operation (at least when the engine is cold). According to the nice tech support people at Keith Black, they are plenty strong enough for a street performance engine. I do wish they used 1/16" instead of 5/64" rings, but I guess you can't have everything.
Updated July 16, 2010
