Well being that I've yet to get an aftermarket RPM gauge (tachometer), I'm not sure where the RPM's are at any given time, but being that my lowly 3-speed automatic transmission redlines rather quickly, would it sound reasonable to wonder how much more HP I can push in the 2500-3000RPM range (I think the redline is in the 4400-4500 range on '88 models)?

Also, by altering the intake tract, would it help to remove the arm from the left side of the intake manifold (almost connects to the grille, near the radiator and fan) and put a cold intake on it instead?

And elaborate on camshaft timing? How would I go about altering that? Surely it can't be as simple as a new camshaft? And finally, I'd say I'm probably not at risk at having to raise the octane rating of my gasoline yet.

 

My truck wasn't taken care of very well The guy I bought it off of was using Quaker state motor oil, and it ran like crap. It was getting 13 mpg or less. I feel pretty good about my gas mileage now lol. And 50 mpg is good, but not really eye popping for a honda, especially the older 1st, 2nd, 3rd gen & 5th gen VX's. This is my 3rd 50 mpg honda (I've had 8 of em). I'm well over 200k on the odometer too. No smoke and very little drink haha. The CRX's can pull 60 mpg, and I've had 2 civic wagons that pulled 40 or better. I know people with the toyota prius that don't get 50 mpg. Anyways....good times in anything I drive

 

2500-3000 range is pretty conservative. The factory cam accomplishes that pretty good. The intake is also matched to suit. I would suggest, if you wanted to, changing the lifter height to allow a taller valve opening, and modifying your heads to include: deshrouding the valve area in the chamber and cleaning up the valve guides, cleaning up the casting slag, gasket matching the intake and cylinder intake bores for about 2", and addressing your exhaust (headers, and a low resistance exhaust). If you did that you would see about 10-20 torque increase.

Note that the base has been built (ie the factory engine), and you removing obstacles from its peak performance. If you wanted to get crazy and had the tools available, you could work the heads pretty far and fill with putty to augment the intake charge.

The head work should be similar to this:

From this


to this


This is not a picture of the finished guides, but it gives you the idea. DO NOT make a knifed edge behind the valve guide as it will cause negative turbulence. You could also offset your work to make the tract biased to impart twirl on the charge. This affects peak horsepower. If you tumble port, it will affect your peak torque.

I am fairly sure you have open chamber heads so you "could" mill them down to offset the compression loss from deshrouding. Smaller gaskets will have a similar effect. All in all, the factory heads are pretty sucky unless you hog out the bumps, casting slag, and rework the chamber. The chamber work WILL see the best benefit under .400 of valve height.

You can impart a slight cam timing adjustment by using a cam key that will advance or retard the cam timing up to about 5 degree's. You can also buy a new cam that will affect the lift, duration, and timing to your particular needs, but since you being fairly conservative, I would just recommend the new lifters.

 

This one is about done except a 300 grit intake sanding.

 

And here I thought I was being in the slightest bit demanding with the RPM range. I mean, I've been told that this truck just won't cut it, so I gave conservative expectations I suppose.

So suppose I turned it down a notch and wanted some pretty nice gains in the 1500-2000 mark?

 

Let's take a step back and reevaluate what your wanting to accomplish. Standard specs on a 3.9l engine, gasoline type, factory equipment would put the power band in the 1k-4k range. This is the typical range for street driving. If your ONLY wanting to increase torque, then your ONLY options are to increase the stroke, or minimize the losses.

Really, what do you really want? Redline for the stroke is around 6500 rpm (which is almost 3900 ft per sec) and about the limit for a cast crank.

If your wanting the extreme then look for a V6 Magnum core, 4" crank, low duration high lift cam, bigger TB (or convert to carb), headers, melling coated bearings, moly rings, lighter pistons, and balance the crank to within .01 gram. Aftermarket ignition, new water and oi pump, and the best heads you can find.
Heads=power, shortblock= durability, extra parts=tuneability

 

What I'm picturing in my head is a semi-quick-off-the-line, and some of the things I can do to increase the 0-60 time. Admittedly, I wasn't sure whether torque or horsepower would help more, naturally both would help, so I compensated my miss-knowledge for saying I wanted to increase both.

Now that's not to say some top-end wouldn't be nice, but that's not necessary, and not really what I'm looking for. Think acceleration.

 

Just get some lower gears for your rear end. Most likely you got 3.55:1. If you go to 4.56:1 you will get a sick launch! But on freeway you will loose some MPG. I should of suggested this in the beginning. Cheep and you don't have to mess with the engine.

Check out ring and pinion sets at www.ringpinion.com
Check out this chart to see where you want your power band and your MPG.
http://www.omix-ada.com/gear-ratio-vs-tire-size.asp

 

x2. Mechanical advantage is definately the easiest way.





With that said, 0-60 almost has nothing to do with the output of an engine. You can confirm this by reviewing the drag slips of cars between 400 and 6000 torque. The 0-60 ft times are the chassis response to weight during acceleration in relation to the instant center. Some of the older cars (drag type) tend to "lift" at the start so as to "plant" the tires harder, while Detroit produces cars that squat on acceleration to trick you into thinking the wheels are coming up, although it actually is reducing the weight on the tires in the rear. It is important to understand that the relationship between power and acceleration is not linear when you add traction to the function. A higher gear, a four link triangulated rear (or slapper bars if your cheap), AA rated tires, and about 200 lbs over the rear axle should help you achieve a sub 2 second 60 ft time. The slapper bars will prevent your springs from "bending backward" by reducting the frequency that is imparted toward the front (where the acceleration power is transmitted).
You should go to your library and order some of the books that teach this in great detail, and use the university's tools to your advantage. Unless you have access to a machine shop and a lift, most people can only dream of applying these ideas to their chassis. There is maybe a handful of older dakota owners that have put four links in their trucks, and of them most put airbags to lower their rides. A four link will allow you to adjust your squat/ antisquat to conditions, tire type, and power with good results. Plus, there just frackin cool.

 

Cheap? So a standard mechanic shop can pull it off?