Thanks in advance. I just bought a very nice, all stock '89 convertible with the L98 engine and it comes with the factory original restrictive exhaust and emission controls. I got the car for my wife and as much as she loves it, she also (thankfully) is just frugal enough to let me indulge in my passion for cars, but otherwise keeps a pretty tight rein on the accounts. Good for me as we'd be eating cat food when I retire if not for her. Then again, I may have a much bigger car collection if not. Anyway, I am hoping to see the best ideas for squeezing a bit more power from the stock configuration. Chip? Cold air box? I wouldn't want to spend any more than absolutely neccessary right off the bat as the car has a couple of immediate issues that I need to spend some $$ on. All ideas are appreciated!

 

1) Exhaust
2) chip
3) intake

 

If they don't smog check your car there are a lot of options.

 

"Speed costs money. How fast do you want to go?" I remember seeing posters like that in the old speed shops. So, you should start off with building a budget.

There are a lot of things that say they will increase HP/torque for not a lot of money and they are pretty much worthless. The Air Foil is one example. It really does nothing to help. Some of the so-called "performance chips" don't do much beyond turning the fans on a lower coolant temp and fools the ECM to go open-loop. Some say that cutting open the air filter lid and installing a K&N filter will give a slight boost of power.

Look into headers and true duals if you don't have to worry about emissions testing. You can get custom-made chips that will provide a power increase but you do need to work with a tuner to figure out what works. PCM For Less can help you. But you will have to go thru one or two chip swapping activities so be prepared to find and access the ECM.

You didn't say what transmission is in the car but there were a variety of rear end ratios available depending on it having an auto or 6-speed. Look at the SPI decal (also referred to as the RPO Sticker) and look for: GH0 (3.54), GM1 (2.59), GU2 (2.73), G44 (3.07), or GW4 (3.31). Convertibles had limited ratio selections. Changing the rear gears is another way to improve acceleration without touching the engine.

 

I also vote for headers and full exhaust, but you could consider some 1.6 roller rockers too. Search forums for 'free mods'.

 

I see that the plastic air box lid from Mid America is back in stock. Enlarging the air box louvers has been a measurable improvement, even with paper filters. I'm going to get this piece so I can keep my stock steel lid.

 

The car is still bone stock and thankfully, in MD, if the car is 20 years old, it is emissions exempt. Again, my goal is to spend as little as possible, so at this point a true straight dual system is out of the question. As are any hardware upgrades in the form of heads, exhaust, etc. Maybe I should research how to get rid of the emissions controls, but maybe they are not as restrictive as the old systems on carbureted cars given the '89 has TPI and an ecm. I am tempted to yank the cats and install straight pipe but I'm guessing there would be a host of additional sensors/remapping that would have to happen to keep all the systems happy?

 

Im not saying to sound like a smart a$$ but assuming your car is running good, there is a high probability that tires and new shocks would be your best performance upgrade.

i know thats not really what you meant when you asked but this really worth considering.

he compares doubling horsepower (probably more what u were thinking) to simply getting better tires. results were shocking to me.

anyway, here it is if u want to see it.

https://www.autoevolution.com/news/engineering-explained-talks-track-days-compares-better-tires-and-doubling-power-113005.html

 

When I bought mine, it had blown headgaskets, so I did a valve job, upgraded the springs, and did 1.6 rr. Big wake up! Wish I had money to do a cam too, but I was really impressed with what I got. h

 

Once you go cam, you'll never regret it.

 

If you want free take the catalytic convertor off and stick a bar in it and break the inside out to make it so you can see clearly through it. That will give you free 20-30 hp. Also cut the louvred out of your air cleaner box. Remove any extra weight on the car. If your AC doesn't work get rid of it, remove the air pump, then install shorter belt.

That's about it for free horsepower. You should give it a tune up with new plugs and wires and cap and rotor. Mine was running ruff then I pulled the plugs and most of the ends were rotted off and the wires were not sending the spark properly.

You could upgrade the wheels and tires to make them lighter. Stock wheels are heavy.

 

Unless the cats are completely clogged up (and the car would be telling you this if they were), the numbers above are highly inaccurate.

Best bang for the buck is a tune-up; new plugs, air filter, injector cleaning, fuel filter, etc.
Perform two tests: a compression check and a leak-down. If either of these test indicate a worn engine with problems, correct them before you start throwing speed parts at it.
You MUST start with a solid foundation.

 

I was going to say something as well, but those numbers aren't even close to right. I have gutted the cats on all of my cars and nowhere near 20 to 30 hp gains. my exhaust did smell more though that's for sure. And there was more drone. mine were falling apart and rattling inside. at the time i had no money. when i get around to my obx exhaust ill put a cat back into it.

 

LS swap. I have less than $3k into my LQ9 swap. Mostly done in my garage.

 

Way more drone and definitely not 20HP other than in your wildest imaginations unless you are severely clogged, in which case, you will have other symptoms.

 

I found a Dana 36 3.07 for $200. Undoubtedly the best bang for buck on my 2.59 car.

 

Exhaust

 

^ This is essentially what I was going to say. Also ohm test plug wires and replace if needed. Make sure there are no vacuum/intake or exhaust leaks. A good dyno tune will help too.

 

What does the ohm test do? I think that as long as there is a strand of wire intact, it will read good. I would think that if they are old enough, you can test it with a fine mist of water around the wires and see if there is any arcing. I'd do this in a dark garage for easier viewing.

For the easiest way, see if the ECM is compensating via the IAC. That requires a scanner to see if the ECM is compensating. IIRC, the O2 sensor is pretty far upstream so unless the leak is there, I am not sure if it will do much.

It could be but those are not cheap. IIRC they start at around $600 plus incidentals. There are fewer and fewer people that will tune the old stuff so he might have to drive further. For me, that is about 6 hours away so figure gas, hotel, food, etc and it might come up to $1000. For the stock system, I don't see that much gain to be worth that money. Now, if he were to do headers and intake, absolutely

 

Every wire that conducts electricity has some resistance. Spark plug wires are rated at a specific resistance value based on the design of the engine and the ignition system. Measuring the resistance (ohm test) indicates the internal condition of the wire and its ability to relay spark to the plug. A wire may be intact but its ability to conduct spark degrades over time. A wire may look good and the plug is firing the cylinder so the engine seems to run fine. But replacing an old wire and giving a better spark could improve performance.

Step 4 in this link:

http://www.doityourself.com/stry/how...ark-plug-wires

OR step 6 in this link:

http://www.wikihow.com/Test-Spark-Plug-Wires