Exhaust options 3.2 rebuild. 993 headers?

[ejp]

I'm planning a fresh motor for my '88 street car and am considering options for exhaust. The current plan is to go from 3.2L to 3.4L with higher compression pistons. The following is what I'm going for:

• Keep the car appearing stock - single factory-sized outlet is preferred
• Exhaust noise kept to a minimum (stock-like)
• Run cat/cats
• Heat

My understanding is that there is quite a bit of power to be gained (or lost) from an exhaust. There are a lot of options available and I've read quite a bit about this...and the path forward is about as clear as mud to me.

One option is to leave the stock exhaust on the car. I could go with a different muffler, but I'm concerned that the 3.4 P's & C's may be a waste of money without a good exhaust.

I have a set of 993 headers & heat exchangers available to me (I'm not sure which ones they are at the moment). I know that the flanges are flipped and have a different bolt pattern...but it seems like this would be relatively easy to overcome with a fresh rebuild. Other than that, are these a viable option for this car? I know that a standard 993 exhaust won't work with this body, so I'd have to get creative to make it work with something like a Dansk sport 2-in 1-out. Cats will also be an issue. Thoughts?

I had one engine builder suggest that I go with the B&B headers/heat exchangers with a dual inlet, single out Dansk sport muffler. I'm still not clear what they had in mind to run a cat/cats on that. That is a fairly expensive solution, especially without a clear indication of whether or not it will do what I want.

These are just a few options, there are so many more choices though - any input would be greatly appreciated.

[Cairo94507]

I feel your pain. I have 1 5/8" SS heat exchangers and a stock Dansk 2-in 1-out on my '87 3.2 that has 964 cams and a custom Steve Wong chip. Prior to the stock Dansk, I had a SS sport muffler that was much less restrictive on my car, again 2-in and 1-out. The car really ran strong across the RPM range but it was rather loud.

Now I am pulling the 3.2 out and replacing it with a '95 993 3.6 I bought. I understand my 1 5/8" SS heat exchangers will bolt right up and are the same size as the stock 993 heat exchangers. My dilemma is I want a free-flow, as much as possible, muffler that is 2-in and 1-out so the engine will run great, the look will be stock and not very loud.

My buddy is just finishing up a fresh motor with SS heat exchangers and he has a new Dansk Sport 2-in 1-out muffler going on that car. I am eagerly awaiting the start-up so I can hear how loud that is. I had already narrowed my muffler choice down to the steel sport Dansk. I wonder if the SS muffler sounds different than the mild steel version? I believe the SS version is about $300 more, so not bad really. I wish I knew how much less restrictive the Sport Dansk is compared to the stock Dansk application.

I have also considered the Dansk GT style muffler with 2 2.5" tailpipes centered next to each other but of course that is obviously not a stock look which causes me some concern.

Yeah, I know, 1st World problems... Good luck in your hunt for the perfect muffler.

[dg567]

I went with the larger SSI and the 2 in 1 out dansk sport muffler. Motor is also a 3.4 and it sounds great, not overly loud at idle, but you know something is going on back there when you get on it.

[Bill Verburg]

Originally Posted by ejp

I'm planning a fresh motor for my '88 street car and am considering options for exhaust. The current plan is to go from 3.2L to 3.4L with higher compression pistons. The following is what I'm going for:

• Keep the car appearing stock - single factory-sized outlet is preferred
• Exhaust noise kept to a minimum (stock-like)
• Run cat/cats
• Heat

My understanding is that there is quite a bit of power to be gained (or lost) from an exhaust. There are a lot of options available and I've read quite a bit about this...and the path forward is about as clear as mud to me.

One option is to leave the stock exhaust on the car. I could go with a different muffler, but I'm concerned that the 3.4 P's & C's may be a waste of money without a good exhaust.

I have a set of 993 headers & heat exchangers available to me (I'm not sure which ones they are at the moment). I know that the flanges are flipped and have a different bolt pattern...but it seems like this would be relatively easy to overcome with a fresh rebuild. Other than that, are these a viable option for this car? I know that a standard 993 exhaust won't work with this body, so I'd have to get creative to make it work with something like a Dansk sport 2-in 1-out. Cats will also be an issue. Thoughts?

I had one engine builder suggest that I go with the B&B headers/heat exchangers with a dual inlet, single out Dansk sport muffler. I'm still not clear what they had in mind to run a cat/cats on that. That is a fairly expensive solution, especially without a clear indication of whether or not it will do what I want.

These are just a few options, there are so many more choices though - any input would be greatly appreciated.

What are you doing for cams?

The chief benefit of equal length headers and collector is seen when there is some overlap for the headers to bite into, otherwise it's about efficient flow.

stock exhaust should be adequate for 3.4 w/ stock cams, particularly if cats and state emissions regs are involved

but w/ better cams the headers and freer flowing muffler become more attractive.

the 993 would be fine too the issue is connecting them to a muffler because of the angles and limited space which is available.

old type 38mm SSI are too small for a 3.2 let alone a 3.4 but the new 42mm SSI are great hooked up to a free flowing muffler., The issue will be cats and finding a muffler that is suitable noise wise.

The B&B headers are fine in 1 5/8" or 1 3/4" I didn't like the b&B mufflers though because of cracking and the design which includes a tiny outlet hole on the one side. B&B did have a cat tip option at one point, they work too based on a sniffer test but probably won't pass a Ca. style examination.

Best sound in low volume w/ great tone(no high frequency stuff at all) I've heard are the Fabspeed RSR system w/ 1 3/4" header pipes, they also allow for stock heat, so a total bolt on.

[ejp]

Originally Posted by Bill Verburg

What are you doing for cams?

The chief benefit of equal length headers and collector is seen when there is some overlap for the headers to bite into, otherwise it's about efficient flow.

stock exhaust should be adequate for 3.4 w/ stock cams, particularly if cats and state emissions regs are involved

but w/ better cams the headers and freer flowing muffler become more attractive.

the 993 would be fine too the issue is connecting them to a muffler because of the angles and limited space which is available.

old type 38mm SSI are too small for a 3.2 let alone a 3.4 but the new 42mm SSI are great hooked up to a free flowing muffler., The issue will be cats and finding a muffler that is suitable noise wise.

The B&B headers are fine in 1 5/8" or 1 3/4" I didn't like the b&B mufflers though because of cracking and the design which includes a tiny outlet hole on the one side. B&B did have a cat tip option at one point, they work too based on a sniffer test but probably won't pass a Ca. style examination.

Best sound in low volume w/ great tone(no high frequency stuff at all) I've heard are the Fabspeed RSR system w/ 1 3/4" header pipes, they also allow for stock heat, so a total bolt on.

Thanks for the reply. One builder that I've talked to is suggesting 964 cams to go with the B&B headers. Another advised me to stick with the stock cams. I don't know much about cams yet (not only the performance implications, but exhaust requirements associated with each option). I think that I'm going to have to settle on a builder and then work with them to come up with a plan - but I'd like to know more about what I'm talking about before I do that. I feel like what I want out of this limits my options. I'm working on a plan to get around emissions testing, but I would still prefer to run a catalytic converter.

[sus911]

I have a stock '84 ROW 3.2 Carrera with a 911 Chips upgrade.
I replaced the heavy stock exhaust system with 993 Bischoff HE's & an M&K 2 into 1 muffler, no cats.
The weight saving alone is massive.
Performance is fantastic. I have dyno before & after but unfortunately on different dynos so comparison would be flawed.
All I can say is the performance is enhanced everywhere, low down torque and top end.
The noise is rowdy at start up and at heavy acceleration in lower gears. At highway speeds the exhaust is barely audible and definitely no droning.
I couldn't be happier.

[JackkTheMackk]

Originally Posted by ejp

The following is what I'm going for:

• Keep the car appearing stock - single factory-sized outlet is preferred
• Exhaust noise kept to a minimum (stock-like)
• Run cat/cats
• Heat

If you NEED all 4 of those, your stock exhaust is the only option. You’re going to have to lose 1 or 2 of those requirements if you want your 3.4 to breath. If you want to keep all 4, it’s going to be custom and $$$.

Your best bet ditching the cat and getting the new 41mm OD SSI and a 2 in 1 out sport muffler.

[ejp]

Originally Posted by JackkTheMackk

If you NEED all 4 of those, your stock exhaust is the only option. You’re going to have to lose 1 or 2 of those requirements if you want your 3.4 to breath. If you want to keep all 4, it’s going to be custom and $$$.

Your best bet ditching the cat and getting the new 41mm OD SSI and a 2 in 1 out sport muffler.

Thanks Jack - that makes sense. It's looking like I might have to do at least some custom work if I'm going to use cats. I've seen it done before with the old SSI's - I think that I saw that Steve Wong did this at one point. I just found this thread where someone had a custom system built by M&K that may do what I want (possibly even CARB-legal).

There are some options out there - I was hoping to avoid spending massive money, but I don't think that there is any bolt-on. I only just heard about the new SSI's, that could be an interesting option for this car.

[PeteKz]

Increasing displacement is almost always a good idea, "there's no replacement for displacement." Even if the current exhaust limits the high RPM power, increased displacement will give you more torque across the rev range.

Another approach: Go at it in steps. Since you want to keep cats, I assume you are keeping the Motronic FI and the stock cams. So, build the engine you want, and put the stock exhaust back on. Go get it inspected, then change the exhaust. Swapping exhausts is a fairly easy DIY job.

BTW, If you are rebuilding your motor, or starting with a known good engine with moderate miles, avoid splitting the case. The 3.2 cases and bottom ends are stout. Only unbolt two connecting rods to check the bearing shells. If they are okay then your mains are fine too. Put new rod bolts in those rods and leave the rest alone. Splitting the case automatically adds $5000 and adds zero performance.

[ejp]

Originally Posted by PeteKz

Increasing displacement is almost always a good idea, "there's no replacement for displacement." Even if the current exhaust limits the high RPM power, increased displacement will give you more torque across the rev range.

Another approach: Go at it in steps. Since you want to keep cats, I assume you are keeping the Motronic FI and the stock cams. So, build the engine you want, and put the stock exhaust back on. Go get it inspected, then change the exhaust. Swapping exhausts is a fairly easy DIY job.

BTW, If you are rebuilding your motor, or starting with a known good engine with moderate miles, avoid splitting the case. The 3.2 cases and bottom ends are stout. Only unbolt two connecting rods to check the bearing shells. If they are okay then your mains are fine too. Put new rod bolts in those rods and leave the rest alone. Splitting the case automatically adds $5000 and adds zero performance.

This all sounds very smart, and I could certainly use the $5k. This is a known good engine, but with 220k miles - I'll certainly talk to an engine builder about options here.

As far as the plan goes, I'd like to stick with DME, although I'm on the fence on cams. One builder suggested keeping the stock cams, another suggested going with 964 cams...and I don't know much about these different cam profiles in a 3.4L motor.

[gtc]

Craig_D has a good thread about adapting a pair of small cats to SSIs. He's also in Colorado.

[Bill Verburg]

Originally Posted by ejp

This all sounds very smart, and I could certainly use the $5k. This is a known good engine, but with 220k miles - I'll certainly talk to an engine builder about options here.

As far as the plan goes, I'd like to stick with DME, although I'm on the fence on cams. One builder suggested keeping the stock cams, another suggested going with 964 cams...and I don't know much about these different cam profiles in a 3.4L motor.

You will wan to contact Steve Wong for advice about a chip an accompanying tune

You will very likely want to change cams, there are several choices that are available and work, a search will be instructive.

I'll just say that SC/Carrera cams have ~8° of TDC overlap and 964/993 have ~15°, and 993SS ~20°

The more overlap the better response to tuned headers of the SSI. BBI, Fabspeed type
as for cats will the typical after tuned header cat is stuck out by the tips does work, they are unlikely to be acceptable to a stringent state inspections as seen in Ca, Colorado's are unknown to me.

The stock exhaust is actually not half bad for flow, it is awful for tuning but w/ milder cams it's not that much of an issue and 964 versions may flow even better especially w/ custom muffler and if cats are needed a high flow cat which is readily available and will be state nspoection legit.

[PeteKz]

With 220Kmi on the bottom end, every pro rebuilder will want to open the case. They want to do that to protect themselves against come-backs for oil leaks or anything else that might go wrong. And, at 220Kmi, and doing the work myself, I would open it up to reseal it with the currently preferred sealants that work better than the original stuff. I hate oil leaks.

HOWEVER, I would still check the bearings and if they are good, reuse them. There are good engineering reasons to keep using bearings that have already proven themselves in service that I won't go into now. There are also bad new bearing sets in circulation now, so beware what you use if you have them replaced. Journal bearing shells do not wear in regular use, unless they got starved for oil or got dirt in them from initial assembly or poor oil filtering. If they are good, leave them alone.