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'91 9c1

2K views 11 replies 5 participants last post by  71choptop 
#1 ·
Have a '91 9c1, 350 Tbi, original single exhaust, considering putting headers and duals on, someone commented about needing to swap or modify the tranny crossmember. Mentioned putting a single 3" exhaust w/good muffler and free flowing cat instead, your suggestions? Thanks in advance
 
#2 ·
Easiest... Just add a 92-93 L05 (350) 9c1 Y-pipe. Its larger diameter than yours.

If you really want duals there is several routes you can take

Have the muffler shop run both pipes through the hump on the passenger side of the crossmember. It looks like crap and probably doesnt perform well.

Use a 94-96 Crossmember, but its not a simple bolt on. From what Ive read you have to weld some extra metal on to the frame to be able to bolt it up.

Add a second hump in your existing (or an extra) 91-93 crossmember. If you have a welder and a bit of fabrication ability or know someone who does, it would probably be the cheapest route.

Buy a Clear Image Auto tubular crossmember for $222. http://www.clearimageautomotive.com/Tubular Cross member.htm
 
#3 ·
I went with the modified stock crossmember in my 93. If I were to do it again I'd probably either just run a larger single or run the drivers side around the passenger side hump in the crossmember. If you go with the newer crossmember, I believe you need the newer tailshaft housing to mate with the different crossmember. I can't remember 100% sure though. And you will need to add length at the frame since there is nowhere for the other side to bolt to on the new crossmember.
 
#4 ·
exhaust



Thanks for the info, sounds like a lot of work/money to put a clean dual system on my '91. I have to find out wether I will pick up any hp by using a newer/bigger Y pipe off my manifolds and dumping into a bigger pipe w/free flowing exhaust and would it be much better at least putting headers on and dumping into the same single pipe configuration. Anyone, anyone.
 
#5 ·
Probably just my luck, but when i had my 92 9C1, besides the crossmember, they also told me that they wouldnt even attempt to run duals out the back without the left side fuel tank heat shield. This was at all 4 exhaust shops local to me. I ended up just running a 2 1/2" single with a glasspack... i hate ALL glasspacks now.
 
#7 ·
exhaust



I really won't be moding the engine that much, maybe a diff manifold/Tbi unit , I am thinking maybe some headers, 3" exhaust would not be a bad way to go, I am a dual exhaust guy but their seems to be a fair amount of work and money to be spent putting a full dual exhaust on amy '91 and if the performance difference is not that great, why not the 3" single.
 
#8 ·
Okay here we fall back on modding the TBI...

If you do run a differant manifold, you are gonna run in distributor clearance problems. Go pop the hood on your 91, look where the windsheild cowl hangs out over the distributor. 91-93 B-bodies use a specific intake and distributor. The shaft on the distributor is shorter and the hole for it in the intake is wider. This allows one to remove the distributor without pulling the intake manifold... because the windshield cowl would otherwise block it.

You can run a typical "standard" SBC intake (assuming you get one that will bolt up to the 87 - 9? intake bolt pattern) but you will have to use a non-B body distributor and wont be able to pull it without pulling the intake. The stock intake is not that bad!

Spend the money you would on the intake on exhaust. Even if its just the later Y-pipe. Get 1.6:1 stamped metal rockers (about $100-120), use new LT1 style valve springs and lose the rotators on the exhaust valve (removes weight from the valve train), do all the maintanance things, rebuild the throttle body. Get a caddilac TBI airbox and build you a good air intake with PVC pipe, ditch the stock belt driven fan for an electric.

visit http://www.thirdgen.org/ for info on enhancing the performance of a TBI engine. Here is a hint... you cant go far without burning chips or spending money on special ECM mods.
 
#10 ·
Okay here we fall back on modding the TBI...

If you do run a differant manifold, you are gonna run in distributor clearance problems. Go pop the hood on your 91, look where the windsheild cowl hangs out over the distributor. 91-93 B-bodies use a specific intake and distributor. The shaft on the distributor is shorter and the hole for it in the intake is wider. This allows one to remove the distributor without pulling the intake manifold... because the windshield cowl would otherwise block it.

You can run a typical "standard" SBC intake (assuming you get one that will bolt up to the 87 - 9? intake bolt pattern) but you will have to use a non-B body distributor and wont be able to pull it without pulling the intake. The stock intake is not that bad!

Spend the money you would on the intake on exhaust. Even if its just the later Y-pipe. Get 1.6:1 stamped metal rockers (about $100-120), use new LT1 style valve springs and lose the rotators on the exhaust valve (removes weight from the valve train), do all the maintanance things, rebuild the throttle body. Get a caddilac TBI airbox and build you a good air intake with PVC pipe, ditch the stock belt driven fan for an electric.

visit http://www.thirdgen.org/ for info on enhancing the performance of a TBI engine. Here is a hint... you cant go far without burning chips or spending money on special ECM mods.
Thanks, all very good info, I appreciate it.
 
#11 ·
The Single 3" Manifold-back System would be perfect for your Engine, that would be the equivalent to running a 2.5" True Dual Setup.... Since there wasn't alot of Performance Systems Available for the LO3/LO5's, the Majority of the F-body Guy's had Custom 3" Singles built, and even carried the same systems over to their LT1 F-bodies...

Assuming you're not in Calif, and If you have Emissions Testing to worry about, I would also be sure to run a 3" In & Out CATCO/Similar Highflow CAT to bring the new 3" Y the Proper end before into your Muffler..
 
#12 ·
Single 3"

The Single 3" Manifold-back System would be perfect for your Engine, that would be the equivalent to running a 2.5" True Dual Setup.... Since there wasn't alot of Performance Systems Available for the LO3/LO5's, the Majority of the F-body Guy's had Custom 3" Singles built, and even carried the same systems over to their LT1 F-bodies...

Assuming you're not in Calif, and If you have Emissions Testing to worry about, I would also be sure to run a 3" In & Out CATCO/Similar Highflow CAT to bring the new 3" Y the Proper end before into your Muffler..
Thanks. Talked to Clear Image yesterday about thier ceramic coated Tri-Y headers, seem reasonably priced just agonizing as to wether I want to spend $700.+ on headers and then the exhaust. I live in da sticks of Wi, but who knows what the damn beaucrats and tree huggin Gore lovers will start up in da way of emmision testing.
 
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