A little engine-building advice

ne of the hardest parts of being a mechanic for other people is when they come and ask what sort of motor they should put in their car. The first two questions I ask are, “how much can you spend and where is the majority of your driving done.” The most frequent answers are as follows, “not much” and “in the city”. With these two things in mind, I counsel towards low-end torque and simplicity. These two factors, in turn, produce the next four results: reliable, inexpensive, fast, fun. The last thing I try to impart is to stay away from the latest trendy/trick trick build-ups and stay with tried and true pieces and combinations.

When you build for low-end torque, you immediately turn to the factory parts shelf and stay away from too many trick parts that send budgets skyward and tend to make reliability an issue. High horsepower means either huge cubic inches or high revs per minute; both cost lots of money compared to the torque-y city street motor. With a true, budget street motor you first turn to the stock combination and see where and how you can improve the formula with minimal changes.

Carefully consider how each change will affect the whole combo. When building a simple 383 big block for the street that doesn’t need to go over 5500 rpm you can toss out the whole idea of gaining a few HP with trick aluminum roller rockers, or titanium valves. There really isn’t any point to it when the stock parts work fine. A case in point is one of my favorite street motors. The particular motor I am talking about is at the far end of what I consider a true street motor––there is over .500” of lift on the cam. What I like so much about it is that it makes nearly 500 hp and over 550 ft. lbs. of torque and the parts list is incredibly simple and pretty much straight off the Mopar shelf. Heck, it even has stamped steel, non-adjustable rockers. No mysteries here; bulletproof and fully reliable.

Let’s go back to that 383 that will top out around 5500 rpm. A stock Road Runner 383 got the job done admirably well with a little 600 cfm carb, not much cam, iron heads and a low, dual plane iron intake. Here are the stock, at the flywheel, numbers for 1969: 335 HP at 5000 rpm, 425 foot lbs. of torque at 3400. A regular 383 four barrel motor made the same torque at 200 rpm less and 5 hp less at the same RPM. Going simple, we can immediately look at the intake manifold. Sure, a performer RPM is a first choice proven piece, but many of the swap meet oldies are only a few numbers off and will give more oomph than the old iron intake for cheap. We can go for a slightly bigger carb while remembering to use a vacuum secondary 750 Holley (or a 750 AVS style carb) and the most basic one at that. Maybe spend some coin on some good shorty headers (remember, we are thinking STREET car here). As far as the cam goes, we can go over the stocker but keep it tight. There are great profiles that will give .475 to nearly .500 lift with nearly stock overall duration and overlap numbers. If we shoot for the best lift with the absolute closest to stock duration and overlap we will gain the best performance, reliability, and drivability.

When it comes to heads the choice becomes more difficult. Remember, the stock 383 made its power with uncut iron heads and stock valves. If we stick to the stock head, we can get a decent set of stainless valves or ask our machinist to back cut our stockers and we are gaining. Ask for a bowl cut below the seats and gain for cheap. Buy a Mopar template set and go to town with a grinder, be careful and port ‘em out. Now we have some power in the heads. The next step is aluminum and how can you really bitch about those? They might not fit the “budget” definition but they sure do get the job done. If you can go there, go there. No losing here.

What about pistons? Silv-o-lite. Choose a ratio that will give 9.0:1 and live happily ever after. End of story.

Already we are seeing a motor that might not have to break much more than 5500 RPM to make 400 horsepower, possibly more and be an absolute kitty-cat while doing it. By keeping our RPM range down low we are keeping it cheap and reliable. We are also closing the door on many “trick” parts that are really only good at an RPM range beyond what we’ve specified, so why spend money on them?

The real “secret” ingredient is to pay close attention to the assembly process or to find the absolute best builder you can afford. This is not the place to cut a corner at all. You can do without aluminum heads but you cannot do without an absolutely tidy, accurate and obsessive engine man. Check out Gaffo’s column from last month and see what he has to say about Dan Dvorak building a class motor out of a ’66 383. Talk about a dog with no cam and crap heads. By using every bit of experience and care, (Tricks? Hmmmmm.) Dan expects the doggy ’66 motor to run with a well prepped bracket motor no problem. There is horsepower lurking everywhere. Good tuning, post build and break-in, is also essential.

The reason I am writing this is because I have seen, and made, too many mistakes. I’ve pulled more than one too big cam out of a motor for a mellower one and seen the owner go crazy with the newly found torque and fun. I’ve seen too much money spent on parts that either broke, didn’t fit right, or really didn’t make any difference. If a new engine is one of your new year’s resolutions then resolve to get it right the first time. Carefully consider your goals, keep the recipe simple and stay away from exotic tricks or trends. Most of all, ask around. Talk to your fellow gearheads, call the most respected builders, do the research, read the Mopar engine books and then build it­­––or if you must, buy it! Happy New Year!