About Jesse Moser Expertise I specialize in the Plymouth Duster from 1970 to 1973, allthough 1974 through 1976 Dusters are nearly identical. 340s, Twisters, Feather Dusters (the cars!), whatever "A" body Duster you have, I can probably give you some info.
Experience I own a 1973 Duster with the Twister options package. I've been searching for information on this specific car since 1995 and have acquired much general and specific knowledge in the process.
Organizations belong to: Mopar Mailing List
Question Hello
I asked this question before but never got a follow-up {was it you? I can't remember}
Anyway, I want my 225 slant-six rebuilt, but I would like to hot-rod it out a little bit.
What can I do to make it quick? It is my daily driver, so it wont be on the drag strip or anything. I just want it to be a little faster.Thanks, Jason
Answer Hello Jason,
it was me. I am terribly sorry it took so long to get back to you, but the fact of the matter is that I just plain forgot to make time.
Anyway, I did some research and found that you have an excellent base. According to the Mopar Performance engines manual; "the best production camshaft avaiabe for the slant six was used in the 1971-1977 engines". That in itself is a huge help and money saver. The book does say that the valve lash should be adjusted to .010" for the intake and .020" for the exhaust. These are performance, not original specs. Should you want a larger camshaft, the Plymouth Hyper-Pak 6 camshaft is a more radical factory spec shaft, though I suspect it would be difficult to obtain and the cost new would be as much as or more than an aftermarket unit.
The first thing that I would change on your car, if it is not already, whould be to remove the points style ignition system and replace it with an electronic ignition system. They are much lower maintainance, more reliable, and are more easily improved for performance; though even in stock forn they are an improvement over the points style.
Exhaust upgrades are a good step in the performance direction. Headers would give the best flow, and a 2 piece header (3 clyinders to each collector) would allow you to easily run dual exhaust. A crossover pipe is always reccommended for a street car with duals because it increases torque. If you happen to come across a 1976 Feather Duster exhaust manifold, it may be the next best thing for less money. While it still only has one outlet, it measures, if memory serves me correctly, 2 1/4", rather than the standard 2". It's a larger outlet than yours would be at any rate, regardless of numbers.
From there, induction will give you the most noticable performance gain. Lucky for you, the Chrysler corporation manufactured a factory 2 barrel aluminum intake manifold in the 1970s. Known as a "Super Six", this would be a good choice for a daily driver, in my opinion. If you wanted to go a bit faster, an aftermarket or Hyper-Pak 4 barrel would be good. The only consideration is that you will need only a 390 CFM carb, nothing bigger, according to Mopar Performance.
You might also raise the compression ratio of the engine. It seems to me that all 225 engines, according to my sources, have a compression ratio of 8.0:1, but check to be sure. This is quite low, not necessarilly for a stock engine, but in comparison to more performance oriented engines. A boost to 9.5:1 would be good for power, and should still be very streetable, as long as stock spec pistons are used. This ratio can be achieved by milling the deck surface of the head down by .090" if the originl ratio is truely 8.0:1.
Whatever you do, don't forget that the best performance will be attained when you build and tune taking the entire car into consideration. Vehicle weight, gear ratio, transmission type and where the most power is desired are a few of the external forces that also need to be figured into the engine equation.
Your dealership will have an engine building manual available for you to order through the performance catalog. Get it and work out an idea, then talk it over with a local engine building shop or other source that really knows the complexities of performance engine building.
Most of all, don't forget to have FUN!
Later.
