The 361-383-400 low deck engines have always been decent performing engines. but were a bit lost in the cubic inch battles. The 413, 426 wedge, and the 440 RB blocks have received the most attention over the years and became the performance leaders. In recent months there has been a lot written about the popularity of stroker engines how to get there. results of the effort, and the cost of various combinations.
When it came time to update the street toy I began to seriously look at a big-block conversion for my '77 Volare Road Runner. The F-body cars are overlooked in most circles and are not as popular as they should be. My particular car was located in Uvalde, TX, had the 360, absolutely no rust, and the A/C blew cold. After being offered the car twice and turning it down twice, I bought it for $900.00 and drove it home. This Mopar has seen street and strip duty, finally running 12.70's at 112 at the 1993 ET finals in Dallas: with the 360 and the A/C. I sold the engine, and old reliable sat in the shop for two years. Time for the big-block.
Two criteria were established. Had to be parts around the shop and it had to be easy and cheap. After reading, studying, measuring, pricing, and researching, there was only one choice: the venerable 440. I've got lots of those. Hey, wait a minute! The 400 is 65 pounds lighter and has the biggest bore of any Mopar. (4.340) The rod journals are the same, but the mains are smaller (2.625) vs. (2.750). This is good news. Turn the mains down to the 400 dimension, poke this thing in the 400 block, bore it .030 and an instant 451 cubic inches of Lightweight Mopar muscle. Now, I have to admit that I'm not the first person to do this. or think of this. The combination is outstanding; it is approximately 65 pounds, lighter than a 440, much more compact when it comes to all important clearances around the headers, exhaust manifolds. brake boosters, etc. but there are a few things to watch out for: Do not use the .030 bore size: a 4.370 bore is very difficult to find rings for. Use .040 pistons and use the +.060 440 rings. (4.380). Do not be afraid of cutting the mains on the forged 440 crank, you will not have any problems with a street-strip engine. Use the 400 rod (the rod ratio is still 1.70) and there is an inexpensive piston now available from Keith Black, the KB 215, for this combination. I have used the pistons with no problems. The cost of a set is approximately $285.00 from Summit. Howard Fischer of Uvalde [Texas](210-278-8777) does my machine work and is familiar with this combination. There are many good machine shops in the San Antonio [Texas]area who can cut this crank. The biggest advantage to this engine is the tremendous difference in rotating weight. Lighter rods, lighter pistons, and lighter crank as compared to the 440.
Anyone who is considering a big-block conversion for an A-body should definitely give this a look. The smaller physical size of the low deck block is a tremendous advantage. All of the parts were easy to find and the cost was within $100.00 of rebuilding a 440 block needing to be bored. There are some minor clearance problems with the crank and the block that were taken care of with a diegrinder. I use 906 or 452 heads with 2.14 and 1.81 valves, along with minor pocket porting. The 452's work great for street machines, as they have the hardened seats and flow just as well with the same valves. The 3.75 stroke will let you get away with more camshaft, but don't go crazy. Something in the 485 lift range and 280-284 duration (adv) will work well. Remember when you read this that it is something that I have personal experience with. I can tell you first hand about engineering a mistake. I have made many, and spent much money on combinations that did not work. This one does!!!
The F-body big block. conversion is very easy and straightforward. The 440 will work but the 451 is much easier.
The stroker engines are the secret to relatively inexpensive horsepower. There really is no substitute for cubic inches. 500 cubic inches from the 440 is becoming common. and let's see; a 383 with the 440 crank would be a 426; and look like a 383. Hmmmmm.
Bob Doty
