What might i expect in swapping from a 2bbl to a...
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1970FuryConv
Old Man with a Hat
I did it with a 360 on a 1973 Monaco. I used a new intake, so warpage was not a problem. With factory 4-bbl intake, a machine shop can sometimes correct warpage.
The biggest problem is the linkage. 4-bbl linkage is different that 2-bbl. For an aftermarket aluminum intake, you need a bracket to raise accelerator cable mount. Also, a part to extend the kick down rod. I think Edelbrock can help with both.
Also, Edelbrock 1481 Chrysler carb adapter is essential for most rebuilt carbs you buy online.
https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/1481.pdf
@Dana may have a recommendation and/or linkage. He'd be the man to ask on 2-bbl rebuild kit, as well
The biggest problem is the linkage. 4-bbl linkage is different that 2-bbl. For an aftermarket aluminum intake, you need a bracket to raise accelerator cable mount. Also, a part to extend the kick down rod. I think Edelbrock can help with both.
Also, Edelbrock 1481 Chrysler carb adapter is essential for most rebuilt carbs you buy online.
https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/1481.pdf
@Dana may have a recommendation and/or linkage. He'd be the man to ask on 2-bbl rebuild kit, as well
gyknot
Active Member
On the low compression 400, I just don't see it being worth the cost of a new manifold, carb, air cleaner, etc for what little power increase you might get.
I don't know what your end goal is, but if its a driver I'd keep what you have if it works well.
You could get the original 2bbl rebuilt professionally for much less than the cost to swap.
As for poor machining or warped surfaces, I'm not sure if you are suspecting issues with the original engine, or aftermarket parts? The original stuff should be just fine. It's all cast iron. Aftermarket stuff is usually good, but anything can happen.
On the other hand, if your heart is set on a 4bbl, then go ahead and make the switch.
I don't know what your end goal is, but if its a driver I'd keep what you have if it works well.
You could get the original 2bbl rebuilt professionally for much less than the cost to swap.
As for poor machining or warped surfaces, I'm not sure if you are suspecting issues with the original engine, or aftermarket parts? The original stuff should be just fine. It's all cast iron. Aftermarket stuff is usually good, but anything can happen.
On the other hand, if your heart is set on a 4bbl, then go ahead and make the switch.
As for power . . . more power above about 2800rpm, being that the primary side of a 600 cfm or so 4bbl is the same size as the 2bbl now on the car, fwiw. Which amounts to over 85mph in high gear, on the road.
Warpage shouild NOT be an issue. For the intake gasket, I use the stock valley pan gasket . . . BUT I also put some high heat black silicone sealer into the beads which touch the cyl head and intake manifold, filling in the bead and smoothing it flat. Basically making it a "print-o-seal: type of gasket. Then using the 440 6bbl application paper gaskets on each side of the valley pan gasket. One on the cyl head side and one on the intake manifold side. Let the sealer on the intake manifold cure for over a day or so, them put it all together. From my own experience using this set-up, it seals much better than the OEM gasket alone. Just my own experiences in making the OEM gasket set-up better.
Nothing special on the intake manifold. The OEM 4bbl was an emissions-calibrated Carter ThermoQuad. The modern re-incarnation of that is the Holley Street Demon, even with a phenolic fuel bowl. Other than the mounting flange also working on a non-spreadbore manifold and the shape of the secondary throttle valve, the innards and such are almost exactly as Carter built the TQ. Sit it on a Edelbrock DP4B-style dual plane intake and all should be fine.
It IS very possible that you will need some the Edelbrock adapters to attach the throttle and kickdown (and cruise control?) cables too. So check the Holley and Edelbrock catalogs for that stuff.
You will need to run a hot wire to the electric choke on the carb, IF it needs one. Or chase one of the OEM choke thermostats to work with whatever carb you choose.
Take care,
CBODY67
Warpage shouild NOT be an issue. For the intake gasket, I use the stock valley pan gasket . . . BUT I also put some high heat black silicone sealer into the beads which touch the cyl head and intake manifold, filling in the bead and smoothing it flat. Basically making it a "print-o-seal: type of gasket. Then using the 440 6bbl application paper gaskets on each side of the valley pan gasket. One on the cyl head side and one on the intake manifold side. Let the sealer on the intake manifold cure for over a day or so, them put it all together. From my own experience using this set-up, it seals much better than the OEM gasket alone. Just my own experiences in making the OEM gasket set-up better.
Nothing special on the intake manifold. The OEM 4bbl was an emissions-calibrated Carter ThermoQuad. The modern re-incarnation of that is the Holley Street Demon, even with a phenolic fuel bowl. Other than the mounting flange also working on a non-spreadbore manifold and the shape of the secondary throttle valve, the innards and such are almost exactly as Carter built the TQ. Sit it on a Edelbrock DP4B-style dual plane intake and all should be fine.
It IS very possible that you will need some the Edelbrock adapters to attach the throttle and kickdown (and cruise control?) cables too. So check the Holley and Edelbrock catalogs for that stuff.
You will need to run a hot wire to the electric choke on the carb, IF it needs one. Or chase one of the OEM choke thermostats to work with whatever carb you choose.
Take care,
CBODY67
mrfury68
Senior Member
Woodruff Carburetor Specialties. He is a sponsor here and should be able to get you what you need.
Justin Plant
Well-Known Member
I did it to my 75, you won't notice a great deal of power difference down low as stated above. Above 35-40 mph, it's quite noticeable. Then there's the sound of the secondaries too.
The biggest challenge is the factory brackets for the accelerator cable, cruise, and trans linkages. I purchased a Weiand intake from Summit and an Edlebrock AVS 2. I wanted the Edlebrock intake, but at the time they didn't exist. I had to purchase a 400, 4 barrel linkage assembly (ebay) after nearly a year of trying to get a 2bbl setup to work. The bell crank has to be hogged out to reach the bolt holes with the Weiand intake.
Just a heads up, EVERY damn piece is specific to the carb on the engine. So, change the carb and the linkage must be changed as well. Also, the rod assy. from the carb to the bell crank isn't long enough. Edlebrock makes an adaptor, and I had to drill a few more holes to get it correct. It's a process. Before you drive it, if you go this route, make damn sure the trans throttle valve linkage is adjusted correctly. If its not, you'll pulling your transmission and really kicking yourself in the butt for even bothering to begin with. Now Chrysler seemed to change everything possible part from one body style to the next, your setup is almost certainly different from mine. I would wager the above problems are the same, just different part numbers.
Carb, intake, gaskets, linkage, other little Edlebrock adaptors, and a Factory dual snorkle air cleaner. I blew past a grand in total. Financially responsible? No, but all that said, I'd do it again. Hands down.
The biggest challenge is the factory brackets for the accelerator cable, cruise, and trans linkages. I purchased a Weiand intake from Summit and an Edlebrock AVS 2. I wanted the Edlebrock intake, but at the time they didn't exist. I had to purchase a 400, 4 barrel linkage assembly (ebay) after nearly a year of trying to get a 2bbl setup to work. The bell crank has to be hogged out to reach the bolt holes with the Weiand intake.
Just a heads up, EVERY damn piece is specific to the carb on the engine. So, change the carb and the linkage must be changed as well. Also, the rod assy. from the carb to the bell crank isn't long enough. Edlebrock makes an adaptor, and I had to drill a few more holes to get it correct. It's a process. Before you drive it, if you go this route, make damn sure the trans throttle valve linkage is adjusted correctly. If its not, you'll pulling your transmission and really kicking yourself in the butt for even bothering to begin with. Now Chrysler seemed to change everything possible part from one body style to the next, your setup is almost certainly different from mine. I would wager the above problems are the same, just different part numbers.
Carb, intake, gaskets, linkage, other little Edlebrock adaptors, and a Factory dual snorkle air cleaner. I blew past a grand in total. Financially responsible? No, but all that said, I'd do it again. Hands down.
bronze turbine
Active Member
Back when I was 16 I inherited my dad's '68 New Yorker that some fly-by-night garage had swapped a 400 into. It had the 4-bbl thermoquad. No mechanic around here was able to get it running right until one of them put a 2-bbl on it. I thought it still had good pep off the line and ran a lot better. I imagine with a modern aftermarket 4-bbl reliability and driveability would not be a problem, but getting all the linkages and stuff swapped around and getting all working in harmony could be a headache.
'66 Fury I
Active Member
As many know, My Fury has an LA318. It had a BBD 2 barrel, which worked well. I put a 4-bbl manifold from a 340 and matching Thermoquad on it. I rebuilt the T-Q, modified the throttle cable bracket and made a throttle cable using a bicycle brake cable. Other than that the install was very simple with no problems.
In those days, (20 years ago), I was hauling my travel trailer and found that the smaller T-Q, with the smaller primary bores, caused the secondaries to be needed too soon. I switched to a T-Q from a 440 and that was much better. The T-Q's have been easy to work with, after reading up on them.
The 318 has a mild cam and I am pleased with the outcome. I do always remember that a 318 in a C-body is not a performance machine. Your 400 should see more benefit.
Just my experience and thoughts. FWIW Lindsay
In those days, (20 years ago), I was hauling my travel trailer and found that the smaller T-Q, with the smaller primary bores, caused the secondaries to be needed too soon. I switched to a T-Q from a 440 and that was much better. The T-Q's have been easy to work with, after reading up on them.
The 318 has a mild cam and I am pleased with the outcome. I do always remember that a 318 in a C-body is not a performance machine. Your 400 should see more benefit.
Just my experience and thoughts. FWIW Lindsay
If I could weigh on this, it's a one-in-a-million chance it'd happen BUT, so many of these parts have been passed around, I discovered twice in the last year that; heads were shaved requiring the intake to be shaved to correspond with the angles so they seat as a set, and either an intake doesn't fit right because it was machined to lower heads, or visa versa. Hey these parts have been around for 50+ years.
Back in my stone age days in the late 70s it was hard to find a used 340 that wasn't beat; the answer I got
"why else would a guy buy a 340?"
1970FuryConv
Old Man with a Hat
Sorry you have to sell. I hope you post pictures here in the for-sale forum. That will give you the best chance of attracting a buyer off of the our website. Best of luck!2bbl rebuild coming this week. Will check air horns via recommendation from member saforwardlook. Then the dual exhaust - then to marketplace for 8500.
More realistic offers from cbody site members will be honored
1970FuryConv
Old Man with a Hat
AWESOME!!!
Gerald Morris
Senior Member
FWIW, I got an Edelbrock 1405 freebeez and had it rebuilt by my fave octogenarian carb guru. Am running it on an old iron Mopar intake, and wound up using the original 2 bbl kickdown linkage with a very minimal investment in Edelbrock's adapters, and more on appropriate OEM Mopar springs meant for the VERY similar Carter 4 bbl for the late 1960s. I have a pair of Carter BBDs, one of which I had twiddled to decent running before the big top end upgrade including 915 heads, and the Brock carb. IFF I can get some decent weather here, I plan to put my dual pipes on after I swap in my other 742 rear end, so I can rebuild the 3:23 in now before it flies apart.
All told, I like the upgrade we put on that old motor, though now the bottom end concerns us. Still, having a carb which can be completely replaced with another NEW one of the same exact model counts for MUCH! I tired of the 1/2 dozen old Stromberg WWCs and Carter BBDs I have, which required much twiddling and diddling to keep in decent running. After a nasty carb fire last summer, from a leaky bowl, I decided it was time to step up to current COTS stuff.
All told, I like the upgrade we put on that old motor, though now the bottom end concerns us. Still, having a carb which can be completely replaced with another NEW one of the same exact model counts for MUCH! I tired of the 1/2 dozen old Stromberg WWCs and Carter BBDs I have, which required much twiddling and diddling to keep in decent running. After a nasty carb fire last summer, from a leaky bowl, I decided it was time to step up to current COTS stuff.
They're not too hard to rebuild, my first and subsequent mistake was tipping it upside down with the top off and the little check valve falling on the bench,+ where it came from? I can tell you it doesn't run well without it.
Hard to believe, a 4 barrel will get you a little better gas mileage, if you keep your foot out of it. You're running 2 smaller barrels most of the time, but why put a 4 barrel on except to hear it open up. Love that sound.
Gerald Morris
Senior Member
For better gas mileage. Holley made a 470 cfm carb in the mid 70s called an "Economizer" which did a good job of making many a 2 bbl more fuel efficient. A 500 cfm AVS2 might do the same, with a little adjustment, though, IDK. I like the roar of WOT also, and we pay for this indulgence, though mama and kiddoes like Daddy getting them through shitty traffic jams with the extra punch, combined w the 3:23 rear end ratio. That latter needs new bearings though, so we're going back to boring 2:76 for a little while this coming Spring Break......
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