Just curious, again. When I installed a real dual exhaust on a z28 recently I noticed a nice spot already installed to simply drill and turn the O2 sensor in. left side. Was thinking all this through recently and have to wonder what it is that some of are doing? The stock motor had a single cat and then a dual exhaust. Making the single O2 sensor seemingly just fine if I had the same thing.

But what if?? lets say I get a more modern system with a single exhaust, in a Blazer-Jimmy, s10, s15 style car as we discuss here. Do all TBI systems have just ONE O2 sensor, making it safe to just drill those headers and install it? How about the fancier fuel injection systems, how many are there and It seems to me there may be as many as three. If we were to run a simple set of dual cats, would that mess us up?

Seems there are number of cars produced with an O2 sensor AFTER the cat. What can be done to accomplish a true dual exhaust, anything?

 

Batch fired injection systems (any TBI & the CPI found in 4.3L 94+ s-series) use only one O2 sensor. This is simply because all of the injectors fire at the same time. Most sequential injection systems utilize 2 pre-cat sensors (B1S1 & B2S1) to monitor the AFR and adjust the IPW accordingly. The batch fire systems adjust the IPWs based on the AFR as read by the O2 sensors as well, but all injectors in a batch fired injection are fired at the same time unlike the individual firing in sequential systems.

Anything OBD2 (96+) will have an O2 sensor after the cat. If you were to install true duals with dual cats, I would recommend installing an O2 sensor simulator in the B1S2 location (post-cat). Do not use the existance of such a device as a way to remove the cats. Most all aftermarket cats flow well enough to not hinder the performance of the vehicle, while doing their job to clean the exhaust.

 

Do you know of any production reason for a third O2 sensor position to be already in place as if a sensor should be screwed in on the OBD 1 style systems? I have one that is just sitting there, right after the cat, as if it should have been drilled out, just like those headers I installed on the z28 sb v8 motor. It had me thinking there were actual production runs that used that very same exhaust yet also had the third, after cat O2 sensor. I havent run across it, but is it possible that in 95 there were other production vehicles using the 4.3 that needed the third O2 sensor? The way you explain it, there would have been NO third O2 position (at least on the s10-15 styles) untill 96. If that is the case then I hope this same exact exhaust is in use on other models, like full size pickups or the like?

The main reason for such odd question is to satisfy a curiosity I have about the ability of the consumer to actually make more than simple modifications to their rides without getting into problems. It seems that each and every model and year has one quirk or another to keep us confused, dont it? Anyone write the book yet?

If that same ehaust, at least through the cat, is in use in 95, and a third O2 sensor is there, how many folks have removed it in favor of the engine check lite being on?

 

The 3rd O2 sensor (post cat) is there on OBD2 vehicles and it's sole purpose is to monitor the operation of the catalytic converter.

The reason for the provision would be because those headers will fit a WIDE range of vehicles and years with that same engine. The 4.3L was available in full size pickups, s-series vehicles and mini-vans. The intake/exhaust sequencing hasn't changed on the 4.3L in a very long time and didn't change between the CPI and SCPI switch (same time OBD2 was implemented).

The shame of the whole thing is that the aftermarket companies have designed in the necessary provisions to allow their product to be utilized on all of these vehicles, but haven't marketed them to be able to do so.

 

I guess what I was saying is that since my own 95 jimmy has no 3rd O2 sensor, but does have provision for one FROM THE FACTORY, I might jump to some conclusion that during the 95 production year there were other models that DID use the third O2 sensor and thus those particular cars, wether they be vans or larger pickups or ANY model using that 3rd O2 sensor, it would be very wise for anyone working on a performance exhaust to be darn careful and use sensible substitution and replacement parts. Yes, I certainly agree that the marketing aspect of all the aftermarket parts is sorely lacking.

Been on the warpath about such simple things as serpentine pulleys; simply shiny. Millions of V belt pulleys out there and a simple chrome serp is inpossible to locate. Heck such a simple thing as a reverse waterpump pulley that IS NOT for the Vortec style, but for standard size reverse rotation pump (same as sbc) is next to impossible to find. Let me know if you see one? The serp and combo v CHROME pulleys are also step children.

To base the whole aftermarket in American cars on the SBC is not a good idea. Heck I have a 2.8 in an 86 Blazer that runs like a scalded cat. Up to about 80 anyway? Yet it has to stay stock cause aftermarket parts cost way too much.

I still think that somebody needs to get at least the chevy brand and starting with about 85 or so, show us how to make friends and influence people with good solid performing used auto's that look good also. I' like to see these cars hopped up with the computers and fuel injection systems still functioning and the emmissions standards still being met. It is possible and can be done. But there seems to be a mind set AGAINST this. No one is coordinated enough to get all the info in one place.

 

I feel your pain. Having owned a 1st gen Dodge Intrepid, the lack of an aftermarket is a HUGE stumbling block. But look at the arenas of performance parts. Things for even some of the older FORD and DODGE engines are still coming out, while the SBC has parts from 1000's of manufacturers that have been being produced for YEARS. The fact is, the aftermarket follows the OEMs sale numbers. The shear number of SBCs sold since their inception created the market. Now look at the number of vehicles produced with the 2.8L v6 or the 4.3L v6. Nothing but a pot shot at the quantities of the SBC. When you get into specialized parts, the price of those parts is going to be astronomical in comparison. Companies that thought about making these parts found a dwindling market and went under.

Now with most of the bolt on parts for the 4.3L, yes, many of the parts from the big brother v8 will work nicely on the v6, but the company that originally designed and marketed them didn't even think to try them out. That's up to the consumer. If it were me looking for parts, I'd run up to the local pick-n-pull and screw around with a vortec v8 and a vortec v6 and see what would fit and what wouldn't. I'm sure you'll find a TON of stuff that is cross platform. Heck, even the headers maintain the same spacing on the cylinders save 1 (EIIEEI or is it IEEIIE vs the v8 EIIEEIIE). So even the headers can be redesigned with ones that are already proven. Heck, taking a look at the lifters, push rods, rockers, valves, springs, etc. They are all pretty much identical to the 2nd gen 350s. Right down to the connecting rods and pistons, although manufacturing techniques I'm sure are different. GM was very smart when making the 4.3L, but many of the aftermarket companies have not picked up on that.

The problem with making friends and influencing people is that anyone in the know, knows that the market is very small. Another problem is that once the customers are satisfied, they're gone. So even if we could get say 100 people together for a custom set of cams or whatever... Those customers go home fat and happy, but they're gone. Then you've also got to look at the demographics for the products. If your average blazer owner is like me, and uses it to keep their other vehicles stowed away in the winter time, then you're looking at a fraction of the owners that will want to sink some serious money into their vehicles to enhance both performance or aesthetics of their vehicles. I hate to break it down like this, but being what I am and what I have experience with I know how the aftermarket companies weigh their new product ventures. I can have things made up for all of you guys that will work great. I can even have custom ground cams made. The problem is that the prices will have to reflect the limited run nature of the products produced.

When I had my Intrepid, I manufactured a limited run of throttle body spacers and sold them at cost. They were far more economical than the aftermarket equivalent, but I also made them for the smaller engine which had nothing available. The nice thing about that was the design took very little time to make. Many of the things for the 4.3L would take considerably more time to design and would be more complicated to manufacture, both of which would increase the price dramatically.

If I were to want to improve on the look of my engine, I would just have the parts powder coated. There are a lot of powders out there that can emulate the look of chrome and do a very good job at it. Powder coating is very durable, but I would have to specify not to coat the actual grooves on the pulleys to reduce the risk of squeaks as a result. Powder coating can be done to anything metal. You could even disassemble your Alternator housing and your AC housing and have them powder coated. Heck, a friend of mine just had his supercharger (completely assembled) powder coated for his Grand Prix engine he's