Me being a man of meager means and a limited income. I was wondering how much horse power could be generated from a stock stroke 390 block, naturally aspirated and limited to .060 over bore. At a compression ratio e85 could be used. Blair patrick's 406 motor made great power at the engine masters and this sparked my curiousity. Would it have been possible to run the honda 1.9 rod journals on the 391 crank, or is that cutting it to much? If i am saving $3500 on a block buy using a stock 390; where is the best place to spend it. Aluminum rods, lite weight pistons, block girdle, and do i need to use blue thunder heads or can the edelbrock i own flow enough air after CNCing them. What size valves to use with the 4.11 bore? Is the 2.19 valve going to interfere or cause turbulence? would the block have to be filled. this motor will be going into my 1983 mazda rx7 (don't laugh i have pictures)that when i started building was going to be for the standing mile and the occasional blast down the drag strip. But then I discovered that i live within driving range of Beaver run raceway(road course). So now i am building a multi- purpose hot rod/street car. It Took ten years to finish my 390 powered 1983 Ranger (pro streeted and not that enjoyable to drive on long trips). So patience is not a big problem money is.
Like a lot of things with race engines it depends on how much you want to spend. The weak point will be the block and you can use a girdle and be good to maybe 700HP or you could install steel middle cross bolt caps and get a littel more. Then the cylinders become your next problem and you can fill the block to help them. At what point do you just buy a good block and save money other places. Your Edelbrock heads would work fine and you would not want to run any bigger valve than the 2.09/1.66 valve because of shrouding.
We make close to 750 HP with the Super Stock 428 engines and they have factory ported heads, 11 to 1 compression and stock 735 carburetor all mandated by the rules. So with 14 to 1 compression and highly worked heads with a large roller camshaft, T&D rockers, aluminum rods, lightweight pistons, vacuum pump, roler cam bearings, good oil pan, nice intake and carburetor you could probably make 2HP per cubic inch but would it be worth the cost to do all of that. This just depends on how much you want to spend and the power you want to make. There may be a easier way to get there. Good luck, Keith Craft
Realistically - - getting big power from a stock stroke 390 is possible, but not financially rational unless you are in a rules limited environment. You'll spend a lot of money for a fairly small reward. There are easier ways to "get there".
If I am building a street/track 390 I would look at the Car Craft engine Jay built. He used one of my stroker kits, a set of lightly shined up Edelbrock heads, a Performer RPM, and a pretty snotty flat tappet cam. He got to 500+ horsepower for around $6000 including oil, plugs, and paint. Since the block is going to become marginal at +/-600 horsepower you are already approaching the limits with a bigger cam, more work on the heads, and more compression - none of which need to cost big money. Stick to stock stroke and you'll be a little lower - pretty much a power/torque per cubic inch deal. Again - more cam and more compression will get some of that "back" but at the sacrifice of lower RPM power and driveability. Much past 500 on a stock stroke 390 becomes a pretty "nasty" street engine.
Much beyond that and it simply makes more sense to go to the aftermarket block and the rest. You'll end up spending an awful lot of money reinforcing and upgrading that 390 block and still not have the durability or power potential. Most of my CNC head programs are tailored to the 427 block since the it won't set a limit on power potential. Its surprisingly easy to get over 600 - and even 700 on an FE these days...
