Urgent Questions About My 3.8

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averagewhiteboy

Master Mechanic
Jun 7, 2006
370
1
0
Pittsburgh, PA
Hey guys.

Well, today me and my dad were talking about some gameplans for my GP. We basically decided to build the car up to be daily driven for now, then do the engine/transmission/rear swap later on. Afterall, some 3.73's would make my gas mileage go from 8 mpg to 2 mpg. haha! Regardless, we're gonna build the 3.8 / 3 speed up a little and get it ready for inspection. So I've got a couple questions here.

1. Quadrajet. For now, I'e got the stock 2 bbl Dual-Jet. It's pretty clean and all that, but would I benefit alot from the extra 2 bbl set-up? I'm new to carbs, so could I use a carb from a 305 for my 3.8? I have no idea how that works. But I can get a stock Monte SS 4 bbl carb pretty cheap. Or even a new one probably isn't too much. How'd that help me performance / gas mileage wise? Easy to install / tune?

2. Exhaust. I need a new one. lol. It had the stock 1 muffler set up. Well, I have no muffler on it right now. The exhaust ends under the back seat. It's got a clogged cat, etc. Bascially, I am getting a low-restriction cat, plus a new cat-back from Summit. I've seen a couple companies that make cat backs for the 3.8. I was really liking the Hooker one. Anyone use this? It's made for a Grand National. Or, does even Summit make one for this car so I could save more money?

3. Headers. Since I'm getting a cat back and a new cat, should I just get new headers to really optimize the exhaust? If so, who makes them for 3.8's? What kind of ball park price wise?

4. Anything else? Basically I have an un-inspected car right now. It ran well when I put it away for the winter, but I want to use it again for a daily (to keep mileage on my Cobalt down) and I need input on the 3.8. I know it's not a performance machine or anything (hell, the 305 wasn't either). But is there anything I can do to really maximise the performance and/or gas mileage for my lower mileage (86k) 231 motor?

Thanks a TON!!! Ireally need this info soon because I'm trying to get the car set-up to drive to the kickoff day of the Hot Rod Power Tour in nearby Ohio. So please, if you've got ANY info, please share it!!! Thanks!!!!

8)
 

jerrycad472

Master Mechanic
Nov 11, 2006
264
0
16
Detroit, MI
1. You would need a 4 barrel manifold in order to swap over the 4-barrel from the 305. I think the 4-barrel on the 305 is a spread bore, so you would need to make sure the manifold is set up the same. They make adapters, but you could run into hood clearance issues it you had to use one. Not sure who makes a 4 barrel manifold for the 3.8 but someone probably does. Try Edlebrock.

2. Honestly, I would put the minimum $dollars into 3.8 drive train. Do the minimum you need to get it running and to pass inspection. Unless you sink really big bucks into it, it still won't make very good power. Put money into the things that you will keep when you swap to a V8, like the interior, body and suspension, then save for the V8. Just my opinion

3. My last G-Body, I swapped from a 3.8 to a V8. I put a low mileage used 350 in it. Added an Edlebrock Performer Cam, Intake and a Holley 600. I used a cheap reabuilt turbo 350 Trans and the stock 2.56 rearend. It was relatively inexpensive and a blast to drive. With an automatic and if you keep it under 350 hp the stock rear end will hold up for a while.

4. If you are planning on driving it a lot, don't go with 3:73s unless you are going to change to an Overdrive Trans.
 

joe_padavano

Royal Smart Person
Sep 13, 2006
1,151
13
0
Northern VA
Is your Dualjet the electronic version with the computer-controlled mixture control solenoid? If so, the Qjet swap may not be as easy as you think.

First, if you are subject to emissions testing, I'm pretty sure the 4bbl won't pass the visual part of the test. You're only allowed to swap components that were factory available and certified for that year. Now, it's possible that the inspector you get won't look that closely, but it is a risk you need to be aware of.

Next, the electronic carbs (both the Djet and the Qjet) use a computer-controled mixture control solenoid. If you use a non-computer controlled carb you have to do something with the distributor since the advance curve is also controlled by the computer and uses inputs from the carb's throttle position sensor as well as other sensors. Removing the computer controlled carb requires you to also swap to a conventional HEI with vacuum advance. Removing the carb will also negate the torque converter lockup command from the computer, so if your trans has this you'll need to get the aftermarket kit to control lockup. If mileage is your concern, you want the TCC lockup to work.

Buick did sell V6 motors with Qjet carbs, so you should be able to find an intake in a wrecking yard.

The Qjet off the 305 will bolt up but will be jetted wrong. Also, is it a computer controlled Qjet or a fully mechanical one? If it's computer controlled, you may be able to make it work with the current computer in the car, since only the primary side is controlled. The secondaries are totally mechanical like all other Qjets. The primary side of the Qjet is the same as a Dualjet. The mixture control solenoid should automatically compensate for the jetting on the primary side, but you'll need to change the metering rods on the secondary side.
 

thebaron

Apprentice
Jul 11, 2006
89
0
0
How would you change the metering rods? I already picked up a 4.1 intake and have two quardajets available to have rebuilt. One is off a 81 Monte I believe and I think the other is off a 4.1 (not sure). The 4.1 carb is what we were planning to use.
 

averagewhiteboy

Master Mechanic
Jun 7, 2006
370
1
0
Pittsburgh, PA
Will a cat back for a GN work on my GP? Because I really need the full cat back, plus that'll give me dual exhaust as well. Hooker and Flowmaster are the two that are noticible. Does Summit package their own? I saw a Summit package for like 250 that includes everything header back, they wouldn't happen to make that for a GN would they? lol.
 

SBCregal

Master Mechanic
Jan 22, 2006
261
1
0
getting a local exhaust shop to bend and weld up some pipes might be cheaper than getting a kit thats made for the car. just something you can look into
 

Renthorin

Greasemonkey
Jan 5, 2006
107
0
0
Michigan
yes the dual cat-back from a GN, Monte SS, or 442 will work on your car. I put the Hooker dual muffler and Y pipe on my 84 cutlass with the 3.8. It was for a monte SS but wth, they are the same thing under there....

The hooker one they sell for the GN is that crazy marketing that makes people go..."wow...for the GN...must be extra nice...."

For the inspection you are talking about....is it emissions? If not, take off the cat....punch it...put it back on....and get a Y pipe into two muffs and two tailpipes and you are set.
 

averagewhiteboy

Master Mechanic
Jun 7, 2006
370
1
0
Pittsburgh, PA
So I could go buy a flowmaster catback for a Monte SS and it'll bolt right up to my factory locations? I only have single exhaust though...

But yeah, a shop might be the way to go. My friend is selling 2 Dynomax Super-Turbos for like 20 bucks, almost new. They're the same one's I got on my 04 Monte SS and I love them. So just get a good cat (because it is emissions, then weld on a Y pipe after the cat, weld the two mufflers on, then put straight tips to the rear basically? How much would that cost (ballpark) if I supply the mufflers??
 

Renthorin

Greasemonkey
Jan 5, 2006
107
0
0
Michigan
Yes it will bolt up. None of the G-bodies of the 80's had true dual exhaust. We all have the crossover and single downpipe into cat.

The cat is in the same place on the g-bodies so after the cat anything goes.

the 'dual' exhaust from a 442 is the same as the monte. The only exception is where the tail pipes exit. Either straight back or out the sides.

The Y pipe is about 150 bucks if memory serves. Then you have dual muffs and dual over the axle pipes...and tail pipes......

the Y pipe will bolt right up to the back of the cat. Same 4-bolt flange.

Price an entire system on Summit or Jegs or wherever and then go to a muffler shop and see what they would charge.

I do want to cover my a$$ by saying I have experience with the regal, cutlass, and monte....but have never been around a GP. I assume they are the same but don't hunt me down if they aren't :)
 

averagewhiteboy

Master Mechanic
Jun 7, 2006
370
1
0
Pittsburgh, PA
^^ haha! Alright man. haha

Now, having that said, Summit packages an full exhaust system. And it's far cheaperthan any other aftermarket brand. Could I got for that to save some cash? Because I'd really like "dual" exhaust, but I didn't know a y pipe was gonna be so much...The one style of Summit exhaust comes with headers all the way back, so obviously I just won't use those since they'll be for a 305, unless they make one for a 3.8 (GN). Anyone know this? Maybe I'll go take a look now...
 
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