Mopar Action On-line – Tech Questions
Michael Hogge, Kendallville, IN, 1985 Dodge Diplomat 318 c.i
My gas milage and performance are almost non existant. I would like to put a 4 barrel intake and carb on to replace the stock 2-Bbl setup, what do I need to do to get past all that electronic spark junk? What else might I need to do other than a cam swap to get some results?
Thanks for your help! I read all of your issues that I can find to buywhile I’m on the road. Keep up the Great work, and please show a few more1969 Cudas.
Michael, unfortunately, this is probably one of the lowest-peformance V-8 engines ever built by Ma Mopar. Besides being choked by a catalyst, small carb, restrictive air cleaner, and contorted exhaust, the cylinder heads are poor — and that’s being kind. When the factory fitted a 4-bbl to the 318, they almost always installed 360 heads.
What you really need is a complete decent 360 mill. Barring that, almost any other smallblock Mopar heads would be an improvement, with the ones from a ’89-92 360 truck (casting number 308) being the best bang for the buck. At that point, the engine would respond nicely to all the usual hopups – cam, headers, manifold/carb., ignition upgrades, etc. It’s pretty easy to get 300-325 HP with those heads – approx. 75% more than you have now!
If a head swap isn’t possible now, a stock 318/360 manifold with a very small 4-bbl would help marginally. Or just bolt on a slightly larger 2-Bbl. A less retrictive air cleaner, better exhaust (lose the cat, if possible) would all show modest gains in both performance and mileage — the current issue of Mopar Action (the April, 2006 issue) walks you through just such a series of bolt-on, painless, hopups.
The ESA system isn’t really a major drawback as long as it’s working properly. Since the timing reference is still a mag pickup in the distributor, you can just advance the timing about 5 degrees from stock for a slight mileage and performance gain.