2 bbl to 4 bbl pros/cons?
- Thread starter Larsen74Dart
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Do it and have fun. Don’t overthink it.
Larsen74Dart
Well-Known Member
Larsen74Dart
Well-Known Member
Well that was fun!! Thank you very much for all the input. Some funny. Some expensive. Since the intake and carb are free, I'll get them for a possible swap if I keep the car. I like to keep things simple and as OEM as possible. If the performance/power was going to be more noticeable, I'd do it. But I'll keep it as-is for the time. When I bought the car (online), the pics looked a bit better than it was in person. But it drove far worse than I had anticipated. Just very "loose" driving/steering. Not sure if a new steering gear box will fix it. I'm probably nit-picking it a bit, and comparing it to prior Dart's and Nova's that I've had. Going to see how the summer goes and might put it up for sale this fall.
Larsen74Dart
Well-Known Member
Is free cheap enough?
I've swapped an actual 360-2 stock intake onto a 318 before with stock 360 Holley 2 bbl and it ran surprisingly good ... Those Holley,2210/2245 carbs as used on the 360 and 400s were a feast or famine game. Some ran great and others were nothing but problems. No "in between".
Don't know why there's so many anti 4 bbl, basically no down sides other than the time and effort, and with recurving the distributor make a nice bump in performance.
I'd say it's the basics for performance you can do to the engine plus exhaust with no real side effects.
I'd say it's the basics for performance you can do to the engine plus exhaust with no real side effects.
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Is the manifold off of a pre 72 340? Just asking because the later 340's and 360's used a spreadbore style manifold for the thermoquad carb. The TQ had small primary bores and provided excellent low end performance and great response when getting into it due to the larger secondary size. I used to run a TQ on my 1970 318 Duster and it gave excellent fuel economy.
If you already installed the duals it's like a half done project at this point, go ahead an put the 4bbl on!
Dave999
Well-Known Member
any carb inlet swap things to consider
1) linkage throttle
2) linkage trans
3) throttle cable routeing and connection
4) return spring set up
5) jets rods springs
6) initial lack of torque until you get it sorted
7) air filter, size, base tin bore, height in engine bay, clearance
8) vacuum connections booster PCV advance, cold running flaps, aircon
9) choke set up
10) how much have your or their heads and deck been cut, has the inlet been faced up for a different motor...how wrong is it......can you cater for it with fat gaskets....
11) do you or will you block off the heat transfer
12) does the inlet have an impact on coolant routing, thermostat housing etc
13) do the ports match your heads or has someone been at it with their favorite rotary tool
14) fuel line routing/banjo/fittings, does it fit with the air cleaner base.
Dave
1) linkage throttle
2) linkage trans
3) throttle cable routeing and connection
4) return spring set up
5) jets rods springs
6) initial lack of torque until you get it sorted
7) air filter, size, base tin bore, height in engine bay, clearance
8) vacuum connections booster PCV advance, cold running flaps, aircon
9) choke set up
10) how much have your or their heads and deck been cut, has the inlet been faced up for a different motor...how wrong is it......can you cater for it with fat gaskets....
11) do you or will you block off the heat transfer
12) does the inlet have an impact on coolant routing, thermostat housing etc
13) do the ports match your heads or has someone been at it with their favorite rotary tool
14) fuel line routing/banjo/fittings, does it fit with the air cleaner base.
Dave
DartGTDan
'71 Dart GT Fan
I too had the dual exhaust (2 1/4" pipes, FlowMaster 40s with the factory exhaust manifolds) installed on the Jaundiced GT about 2 years before my mechanic/friend put the 4-bbl on it (Edelbrock LD4B intake with a Edelbrock 1406 600 cfm carb). My mechanic/friend used Lokar throttle & "kickdown" cables.
My first Dart was this triple green '75 Swinger I bought from the fire chief of my home town (apparently he was tired of red vehicles). Picture from around '79.
My first Dart was this triple green '75 Swinger I bought from the fire chief of my home town (apparently he was tired of red vehicles
). Picture from around '79.Michael Harrington
Well-Known Member
The old car hobby is not only about owning the car but tinkering with it as well. Its a hobby. Back in the 70s and 80s it was a rite of passage for every teenager and older to convert a 2bbl engine of ANY make to a 4bbl. Commonly, an Edelbrock (Not ELDERbrock) Performer manifold and a 600 vacuum secondary Holley were purchased new from Summit and installed on a Saturday. Even if the car is and will remain a 20 second quarter mile car the sound and feel of those secondaries opening up is what it was all about! I say do the swap. You know you have some fabricating to do to make the kickdown function correctly- That fabbing is part of the hobby too!!!!!!!!!!!!!!!!!! You have a clean beautiful car. I say do the swap. Enjoy the car and enjoy the addition of performance oriented and application appropriate parts.
Easy swap. Go for it. Don't like it? Easy swap back. I bet you don't if your free 4bbl is any good.
My two cents on the steering. A few years ago I had a 72 Duster 340 with power steering and the steering was awful.. I have owned many Chrysler muscle cars and nothing was like this. So I bought a Firm Feel stage 1 and it made a huge improvement. My 72 Demon 340 that I have now (also power steering) had a pretty loose steering also not near as bad as the Duster so bought a new steering box from like Napa locally and again a huge improvement. I don't think I can add any extra to what everyone has said about 2bbl to 4bbl conversion. Btw it looks like a really nice Swinger.
Larsen74Dart
Well-Known Member
Wow. Beautiful motor and car.I too had the dual exhaust (2 1/4" pipes, FlowMaster 40s with the factory exhaust manifolds) installed on the Jaundiced GT about 2 years before my mechanic/friend put the 4-bbl on it (Edelbrock LD4B intake with a Edelbrock 1406 600 cfm carb). My mechanic/friend used Lokar throttle & "kickdown" cables.
View attachment 1716378325
My first Dart was this triple green '75 Swinger I bought from the fire chief of my home town (apparently he was tired of red vehicles
View attachment 1716378324
Larsen74Dart
Well-Known Member
I'm wondering if a new steering box will help. I'll have to ask my mech. Seems like it would, and it can't hurt. They went through the front end and only had to replace idler arm. Everything else was good. Didn't notice much improvement.
You might try adjusting you existing box before you replace it...
Very clean lookin install!I too had the dual exhaust (2 1/4" pipes, FlowMaster 40s with the factory exhaust manifolds) installed on the Jaundiced GT about 2 years before my mechanic/friend put the 4-bbl on it (Edelbrock LD4B intake with a Edelbrock 1406 600 cfm carb). My mechanic/friend used Lokar throttle & "kickdown" cables.
View attachment 1716378325
My first Dart was this triple green '75 Swinger I bought from the fire chief of my home town (apparently he was tired of red vehicles
View attachment 1716378324
MopaR&D
Nerd Member
Has to be the problem since the front end has been gone through, I've had my Duster since 2007 (I was 16 then lol) and one of the first upgrades I ever did was a Firm Feel stage 2 box, made a WORLD of difference. If I was to do it again I'd probably go with a Borgeson box.
@str12-340 has a point, you could try adjusting the one you have it wouldn't hurt. In most cases though it won't do much and you still have the over boosted, drive-with-your-pinky feel. Although if your PS pump is the Saginaw type there is a way to reduce the pressure and give some road feel back.
As for 4-bbl swap, I've done it on a few engines (2 318s and a 360), it really only picks up power above about 2500-3000 rpm so if you have stock 2.xx gears you won't really feel it unless you're revving it out in 1st gear or passing on the highway. If you have 3.23+ gears then it's a different story. Plus if you go with a common aftermarket carb they're easier to get tuning parts for. Then again like others have said most factory 4-bbl intakes you'll come across are the spread-bore type, can make them work with an adapter to a square-bore carb but it's not exactly ideal.
Isn't that the main purpose for a 4bbl, passing.
two of my 4bbl, dual exhaust 318s (they never ran like this with the 2bbl...):
I read through your post and didn't see where you were having an issue with the steering. Somehow we got sidetracked?
Poke around in the steering/suspension forum. Mopar's were known for over zealous P/S and a loose feel. Some have shimmed the pressure valve in the pump or gear to reduce the assist. Aftermarket companied like Firm Feel or Steer and Gear have rebuilt gears that improve that loose feeling.
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