1993 Caprice with L05 350 TBI needs exhaust work.

Hey everyone.. its been a while since I've been here... I had kind of stored my Civilian Caprice LTZ for a few years while I was working out some bugs that I initially thought were under the hood. Turned out my fuel pump was bad... even though it was newer.. I didn't think it was the culprit. As it turned out. I was wrong. Once I replaced it.. the LTZ roared back to life.

Anyway... I have a driver's side exahst manifold that has a gasket leak at the block. Problem is that one of the bolts broke off in the head.

My mechanic thinks he can get it out but he wanted me to buy a new manifold because he thinks its warped. I guess after 217K miles.. it stands a good chance of being out of alignment. Anyway... I checked Rock auto and they don't have an exhaust manifold for my specific 1993 car. Several guys I chatted with on Third Gen website said the manifold from the Camaro/Firebird TBI cars should work fine.

So before I get it.. I thought I would log in here and chat some of you up about my options.

Should I get headers and go true dual exhaust? I have a trans. cross member with a driver's side cut out already. So I could do that.

Should I use the LT1 manifolds that are supposed to flow better?

Here's the thing... I want to do this as cheap as possible. As many of you TBI fans know... the Civie TBI L05 was pretty weak and I am not sure the investment in the true dual exhaust will be quite worth it.

Anyway.. I could really use some insight on my options if you guys have the time to bounce some ideas off me. Thanks a lot.

The headers and duals will give you a good boost in HP, but they may be a tradeoff for some low end torque. You could get about 20-30 HP. If the headers are made properly, they may even increase the low end torque, but shorties will more than likely reduce low end torque.

You can use any exhaust manifold from a TBI car that looks like the one you are removing. Any of the 91-93 B-body TBI cars have the same exhaust manifold, even the 305. I do not know if the other bodied cars have the same manifold. LT1 manifolds may not fit the LO5. Headers that fit a Chevelle will fit the B-body.

The manifold may not be warped. The TBI cars came without exhaust manifold gaskets from the factory. If the mechanic can get the bolt out, check the manifold with a straight edge to see if it is warped. I would just put a manifold gasket on it, and it should seal.

Ok thanks a lot Fred! I think I will have him do what you said... that would be the cheapest solution. That way I can still use my in. outlet SEO 9C1 Y Pipe and not need to change anything right now.

Fred Kiehl wrote:

The headers and duals will give you a good boost in HP, but they may be a tradeoff for some low end torque. You could get about 20-30 HP. If the headers are made properly, they may even increase the low end torque, but shorties will more than likely reduce low end torque.

You can use any exhaust manifold from a TBI car that looks like the one you are removing. Any of the 91-93 B-body TBI cars have the same exhaust manifold, even the 305. I do not know if the other bodied cars have the same manifold. LT1 manifolds may not fit the LO5. Headers that fit a Chevelle will fit the B-body.

The manifold may not be warped. The TBI cars came without exhaust manifold gaskets from the factory. If the mechanic can get the bolt out, check the manifold with a straight edge to see if it is warped. I would just put a manifold gasket on it, and it should seal.

JBLTZ wrote:

Ok thanks a lot Fred! I think I will have him do what you said... that would be the cheapest solution. That way I can still use my in. outlet SEO 9C1 Y Pipe and not need to change anything right now.  

You have one of the 9c1 y pipes? Cool, I’ve been wanting one of those, the restricted y pipe they use on the LO5 has always bugged me.

You can have a 9C1 Y pipe made at a muffler shop.

Fred Kiehl wrote:

You can have a 9C1 Y pipe made at a muffler shop.

True, true. I’d probably just re-do the entire restricted system at that point, figuring that a true dual (or completely different y-pipe with heated O2 sensor) would be far better anyway? I assume that swapping the trans mount would help enable that.

If there was someone more local that I trusted I’d have already done it, there’s not a whole lot of local help for something like that where I’m at, so I’m waiting for it to need some help first.

The O2 sensor is located in the DS manifold, not the Y pipe.

You must get/make a trans support that has a hump in the left side to install duals. Other than that, no mods are needed. BTW, you can get an exhaust/muffler hanger from the right side of any 91-93 donor, at the rear cross member, and it will bolt to the left side...the holes are already there. You also must put heat shields at the gas tank, or wrap the pipes to protect the tank.

Thanks Fred - I was thinking more generically about the O2 sensor needing some power supply so it heats well when the flow opens up, I assume that’s a consequence of removing the restriction, right?

Thanks for the info on making it a dual setup, I always appreciate the education. I’m putting together a list of what to do when it’s time to do it, this is on it. I’ve got re-seal the roof rack on that list too, as well as a few other things. Could make for a good winter project, if I can get out from underneath my real job which seems to have buried me recently.

I used a regular O2 sensor with my shorty headers and duals. I had no problems, except that I had to make a patch cable because it was too far away from the original connector. I also had to use some small plumbing pipe to turn the oil pressure sender back along side of the transmission. It was too close to the header for my liking.

You can put the O2 sensor anywhere on a header, even on the reducer after the collector, and it will work properly. Just make sure it is in the top half of the pipe, not the bottom half. Water tends to collect in the bottom of the pipe, and it will damage the element. The one place it will not fit easily, is near the frame rail at the suspension arm.

When you are installing the left pipe, make sure the transmission is in 1st gear, or you risk having interference with the shifting mechanism. 1st is the lowest point the linkage rotates to. You should also put wrap on the pipe anytime it gets within 8 inches of a wire. I wrapped my shorties completely. I am planning to put over the axle pipes on my wagon with the 454, and will wrap them from the highest point to where they exit in back of the rear wheel opening to protect the tank, and I will probably insulate the wires to the fuel sender as well.

FWIW, I can confirm that the OEM LT1 Exhaust Manifolds will not fit on a 92-93 TBI Car. I tried and found that the starter is directly in the way on one side and bolts do not line up and either side.

Fred... what do you think the result will be if I did true dual exhaust with the stock exhaust manifolds and no headers? I don't want there to be any loss of power. I have the March under-drive pulleys as well.

At this point... I think I will just try to use the manifold I already have. I am not sure I REALLY want to invest in a more elaborate exhaust system for the TBI engine because sometimes I think I might eventually LSx swap it in the future. If not an LSx... then maybe a 383 TBI stoker for it instead. I don't care about the higher horsepower so much as having more TQ to move this big car around better.

But for now... I just want to keep the car running and replace all the things to get it to run as good as possible. I already rebuilt the TB, refurb'd the entire brake system, replaced a large majority of the sensors under the hood and I'm about to change the firewall cooling hoses in the back behind the engine as well.

Whatever I end up deciding to do with the exhaust... it will get done in the spring. At that time... I intend on stripping off the entire front end of the engine to replace the water pump, steering pump and steering gear box. Since I am in there... at the same time I want to remove the AIR tube and add the AIR pump delete pulley as well. After that is all cleaned up... and everything is back in its rightful place... I want to add the RAISS Air Intake and install a carb bonnet on the TBI to connect an air tube to the filter in the RAISS box so my Suncoast Ram Air hood will actually be functional for the first time in 15 years.

93capriceltz wrote:

FWIW, I can confirm that the OEM LT1 Exhaust Manifolds will not fit on a 92-93 TBI Car.  I tried and found that the starter is directly in the way on one side and bolts do not line up and either side.

Thanks for verifying.

Since you also have an LTZ.. what exhaust set up did you end up using? Was there any change in power or performance? As is... my 93 LTZ is pretty snappy off the line and I like it like that. I certainly do not want to lose that snap. I can generally chirp 2nd gear and under WOT... the single out 9C1 Y pipe with the 3 inch exhaust into a MagnaFlow muffler sounds pretty awesome. Honestly.. most poeple who don't look close enough think I have true duals.

JBLTZ wrote:

93capriceltz wrote:

FWIW, I can confirm that the OEM LT1 Exhaust Manifolds will not fit on a 92-93 TBI Car.  I tried and found that the starter is directly in the way on one side and bolts do not line up and either side.

Thanks for verifying.

Since you also have an LTZ.. what exhaust set up did you end up using? Was there any change in power or performance? As is... my 93 LTZ is pretty snappy off the line and I like it like that. I certainly do not want to lose that snap. I can generally chirp 2nd gear and under WOT... the single out 9C1 Y pipe with the 3 inch exhaust into a MagnaFlow muffler sounds pretty awesome. Honestly.. most poeple who don't look close enough think I have true duals.

I notched the crossmember and installed dual exhaust that was removed from a 96SS. Used this from cats back. Installed 2 Magnaflow bullet style high flow cats an had an exhaust shop fab pipes from the manifold to the cats. Yes, there was a noticeable improvement in performance overall. I'm happy with it. Only downside is that since I'm lowered, those bullet cats do sometimes scrape speedbumps and driveways.

Anytime you change anything on the engine it changes the torque and HP curves. Less back pressure will raise the HP, and take a little from the low end torque. What you need to do is match your torque curve with the torque converter. Another cheap and easy thing to do is put the electric fans from a 93 FW on, and remove the engine driven fan. It gets you about 5 HP. You can get a thermostat switch from JEGS, and the relays from the FW.

You do not have to add the air pump delete pulley if you just reroute the belt. You need a different length belt as well. There is a thread on what to do on the forum.

You will have the expense of the left side pipe, and making the hump in the trans support, so the cost of a set of headers is not all that much more, and if you go to a 383, they will bolt up. I picked up some header bolts that have a ratcheting set of washers so they do not back off.

Going to a 383 will require a larger TBI, and you must bore out the intake manifold to match, so there is no lip for the air to trip over. There are 46mm TBIs available. Stock is 42mm. Some late 80s early 90s 454s have a 52mm TBI, although I have read that they are hard to tune with.

You can also get the cam out of a 93 9C1 LO5 along with the computer for a base increase of 25 HP, to 205 HP.

93capriceltz wrote:

I notched the crossmember and installed dual exhaust that was removed from a 96SS.  Used this from cats back.  Installed 2 Magnaflow bullet style high flow cats an had an exhaust shop fab pipes from the manifold to the cats.  Yes, there was a noticeable improvement in performance overall.  I'm happy with it.  Only downside is that since I'm lowered, those bullet cats do sometimes scrape speedbumps and driveways.  

Thanks.

Fred Kiehl wrote:

Anytime you change anything on the engine it changes the torque and HP curves. Less back pressure will raise the HP, and take a little from the low end torque. What you need to do is match your torque curve with the torque converter. Another cheap and easy thing to do is put the electric fans from a 93 FW on, and remove the engine driven fan. It gets you about 5 HP. You can get a thermostat switch from JEGS, and the relays from the FW.

You do not have to add the air pump delete pulley if you just reroute the belt. You need a different length belt as well. There is a thread on what to do on the forum.

You will have the expense of the left side pipe, and making the hump in the trans support, so the cost of a set of headers is not all that much more, and if you go to a 383, they will bolt up. I picked up some header bolts that have a ratcheting set of washers so they do not back off.

Going to a 383 will require a larger TBI, and you must bore out the intake manifold to match, so there is no lip for the air to trip over. There are 46mm TBIs available. Stock is 42mm. Some late 80s early 90s 454s have a 52mm TBI, although I have read that they are hard to tune with.

You can also get the cam out of a 93 9C1 LO5 along with the computer for a base increase of 25 HP, to 205 HP.

Fred... a few things you mentioned I already have or have done....

1. My transmission has already been rebuilt with a Vette Servo, Trans Go kit and a 2000rpm stall convertor. (I believe stock was 1600rpm?)

2. I have a Flex-A-Lite dual electric fan on a custom 3 core radiator.

3. I already have a notched and modified 91-93 trans cross-member... so I'd just have to install it.

I think I would rather use the AIR delete pulley but I worry that pulling the AIR pump and blocking the EGR will throw a CEL... I already have gotten rid of the Cat Converter.

I really think my Civie Peanut 305 cam leaves a lot to be desired in terms of power... but I really really don't want to tear into the engine... I don't have the funds for a rebuild. It's my opinion that if someone starts tearing into an engine... they better be ready for what they might find. Me personally... I don't want to attempt to refurb the 217K mile engine very much... I think its lived its life and I don't want to tempt fate by trying to modify an engine that has that many miles. For me.. its a whole engine at that point. I know the L05 short block is actually really cheap.... Some places have them for $650... I just would rather have the 383 stump puller. So.. my goal is to make this engine live for as long as possible right now instead.

The EGR and AIR pump will not throw a code.

In your first post it states that you have an LO5. The 305 is an LO3.

My suggestion for the torque converter was without knowledge of your modifications.

Changing the routing of the belt does not cost but for a new belt. I did this on my 91 OCC, and will do the same for my 92 OCC. At 217K it could use a new belt anyway.

Fred Kiehl wrote:

In your first post it states that you have an LO5. The 305 is an LO3.

The L05 350 in the civilian Caprice LTZ has what is known as the 305 peanut camshaft... that is why its so weak as opposed to the 9C1 camshaft which is based off the F-Body L98 TPI camshaft.

I have tried to delete the AIR pump before but my cat converter got clogged. So I put it back on with a new Cat... I still clogged up the cat again. So now that it is out of emissions in Wisconsin.. I cut the cat out and welded in a straight pipe.

Also... I have changed the belt previously... but because I want to use the RAISS intake.. I need to AIR pump delete pulley to make sure the idler pulley arm doesn't interfere with the air tubing I want to install next to it.

I am glad to hear that the EGR will not throw a code because I plan to delete it and block the EGR port.

The idler pulley stays in the same place with the new belt, and no air pump.

Fred Kiehl wrote:

The idler pulley stays in the same place with the new belt, and no air pump.

Good to know. Thanks. I was looking at it and thinking it might be fine.. I just didn't want to take the chance.. plus.. I think I would prefer the way the AIR delete pulley makes the front engine accessories look.

Part of me also wants to delete the Air Conditioning temporarily as well... because the system needs a recharge anyway... but who drives a loaded car with no AC?

There is an FEAD on an early 90s chevy S10 6 cylinder that is similar to the one on B-body cars. You may be able to modify it to work with the drive pulley. It is either shorter, or longer than the OEM parts, but I do not remember which. If it is shorter, you can add shims under the bolt pads, and if it is taller, you can shim the drive and waterpump pulleys.

It does not have the air pump, and has an idler pulley in that vicinity. I adapted one to my 454, it works great, and looks factory. It uses the same AC compressor, PS pump, and alternator. You may even be able to adapt just the passenger's side. It does have a different idler, but it is in the same place.

You can get a left mount for the larger alternator from a 91-93 9C1, or 93 Fleetwood. It is a bolt up.