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Carburetors. Keep stock? 4bbl? Pros & Cons. Newbie needs advice!

Joe Miller
Joe Miller

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Post by Joe Miller on Tue Jun 02, 2015 6:29 pm

Hello everybody.

Just a forewarning, I'm pretty green when it comes to mechanics, which is why I would love some second opinions and the 2 cents of you gurus out there.

First of all, the application is a 1970 Dodge A-108 with the 318 automatic.

I want this to be a safe, reliable campervan, capable of traveling long distances.

When I first got the van, I had a good mechanically minded friend take a look, and make suggestions on upgrades that would help it be a strong running vehicle. One of his recommendations was to replace the stock carb with a 4 barrel + intake manifold.

Well, I got myself a refurbished-by-manufacturer Edelbrock carb (500 cfm) and a used intake manifold (Edelbrock Performer for the 318/360).

The manifold is a little sketchy.. after giving it a clean-up, I found a small crack (under exhaust soot, doubt the seller knew of this) under the exhaust tunnel where exhaust goes to operate a manual choke. So I had it welded. Well, now there is another crack. And I don't even need that exhaust tunnel/channel, since my new carb has an electric choke. If I were to use this manifold, I'd have to get it welded again, and find a block-off plate (or have one fabricated) to block off that exhaust tunnel thing.

So, it's looking like a new manifold would be my best bet IF I want to pursue the 4 barrel carb.

After talking with my mechanic, I'm second guessing the whole 4 barrel carb conversion. Is it worth it? The van has been running for 45+ years with its current carb and setup. A 4 barrel may eat up a bit more gas as well. My mechanic (60+year old, good with old cars) said that I would want to get a camshaft kit and timing kit if I were to put a new manifold and 4bbl carb on. Is a 4bbl carb worth the time and $? I already HAVE the new carb, however it could be sold.

So, like I said, I'm unsure at this point. A 4 barrel would probably help climb hills and pass cars, but is it necessary? How important (or not) of an upgrade would it be? I would love your opinion and advice. I don't know if I should try to keep it stock, or go ahead and pursue the 4 barrel carb.

Any input is appreciated. My apologies for the long message.

Thanks so much,

Joe
gary h
gary h

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Post by gary h on Wed Jun 03, 2015 12:50 am

I Drive a '68 A-100 p/u with a 318 &  A/T and I am very happy with the performance of the stock Carter 2 BBl. Carb .The Engine has been rebuilt & The truck is mainly stock with points ignition.I have the best luck with Autoline rebuilt carbs. Hope that helps. cheers
Joe Miller
Joe Miller

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Location : Southeastern Indiana, United States of America
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Post by Joe Miller on Wed Jun 03, 2015 1:02 am

gary h wrote:I Drive a '68 A-100 p/u with a 318 &  A/T and I am very happy with the performance of the stock Carter 2 BBl. Carb .The Engine has been rebuilt & The truck is mainly stock with points ignition.I have the best luck with Autoline rebuilt carbs. Hope that helps. cheers

That does help (1 point towards Keep It Stock!) I appreciate the response. Would you advise against getting electronic ignition + new coil, or does it really matter much, besides less maintenance? My carb will most likely need a rebuilt, I think it needs a new diaphragm. If I can't find a good local place, I'll definitely look into Autoline. Any serious changes you've made to keep your '68 in good working order you'd recommend?

Twinpilot001
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Post by Twinpilot001 on Wed Jun 03, 2015 10:00 am

get the coil & the point-less conversion done!! happier with that too!
Joe Miller
Joe Miller

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Post by Joe Miller on Wed Jun 03, 2015 1:13 pm

Twinpilot001 wrote:get the coil & the  point-less conversion done!!  happier with that too!

I was planning on doing that, I have an electronic ignition and coil from Pertronix waiting to be installed. Smile
busman78
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Post by busman78 on Wed Jun 03, 2015 4:36 pm

A correctly tuned four barrel carb will deliver better gas mileage than a stock two barrel. The four barrel primaries are usually smaller than the primaries on a two barrel, since most driving will be with the primaries less fuel will be used, where all that theory falls apart is you have to keep your lead foot from constantly wanting to open the secondaries for those large diameter holes will swallow all your fuel savings quickly.
Joe Miller
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Post by Joe Miller on Wed Jun 03, 2015 5:55 pm

busman78 wrote:A correctly tuned four barrel carb will deliver better gas mileage than a stock two barrel. The four barrel primaries are usually smaller than the primaries on a two barrel, since most driving will be with the primaries less fuel will be used, where all that theory falls apart is you have to keep your lead foot from constantly wanting to open the secondaries for those large diameter holes will swallow all your fuel savings quickly.

Thanks for the info. I had read that a few times, but I've also been told otherwise as well. This makes sense though. Do you run a 4 barrel on your van?
busman78
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Post by busman78 on Wed Jun 03, 2015 6:05 pm

I will be, the slant six is out and the 360 magnum is in, just not wired up yet
winterwolf227
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Post by winterwolf227 on Thu Jun 04, 2015 4:26 am

busman78 wrote:A correctly tuned four barrel carb will deliver better gas mileage than a stock two barrel. The four barrel primaries are usually smaller than the primaries on a two barrel, since most driving will be with the primaries less fuel will be used, where all that theory falls apart is you have to keep your lead foot from constantly wanting to open the secondaries for those large diameter holes will swallow all your fuel savings quickly.

i lost 1.5 mpg with my conversion to 4bbl, but i do like to hot rod every once in a while..;-)
kookykrispy
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Post by kookykrispy on Thu Jun 04, 2015 10:09 am

If the other crack is also in the exhaust crossover, you could simply use JB weld on it.  

The edelbrock 500 cfm is a nice choice.  I think once you get it dialed in, you will be pleased with it.

You don't NEED to do a cam etc. to realize the benefits of a 500 cfm 4 barrel, but adding a mild cam, such as a performer #2177 grind (204/214 duration @ .050"), or similar "street torque/RV cam" type grind would really dial in your 318 with the 4 barrel.  Elgin, Melling, etc. make 'white box' copies of the edelbrock 2177 grind.  Make sure to always put new lifters with a new cam and break it in correctly. Another idea is to call Delta Cam in Tacoma, WA and have them grind you a custom profile, tailored to your engine and vehicle combo. I've started using Delta Cam exclusively for my engine builds. They are the experts, and getting a custom cam from them amazingily doesn't cost any more than a new 'off the shelf' cam.

The 4 barrel + cam, would be a nice little upgrade for your 318 engine.  Select a cam that shows it is optimized for low end torque, with a powerband that starts just off idle.  Also consider dual exhaust if you have just the factory single.

If you keep your foot out of it, the fuel economy should be about the same as the stock 2 barrel.  Once you put your foot down, it will be using more gas obviously.  But if you really care about fuel economy you should be driving a honda civic, not a vintage van lol.

Definitely upgrade the ignition.  Hotter spark will result in a more complete combustion event, will promote more power, and greater efficiency.
OutofSight
OutofSight

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Post by OutofSight on Wed May 15, 2019 12:42 pm

Has anyone switched to a 4bbl carb and retained the original throttle linkage? I have pulled my 318 and will be rebuilding it soon. I have purchased an Edelbrock 1406 carb and an LD4b intake. As for kick down linkage I’ve got the Lokar kit.
69
69

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Post by 69 on Wed May 15, 2019 1:59 pm

The orginal 318 is just not up to a 4bbl setup without proper tuning compression ratio / camshaft.

Honestly, keep the engine stock. Just exchaning the intake manifold + carb does not help you, but only the gas station.

I have a 318/AT PU with stock manifold and a 78 or so carb. I'd LOVE to replace the carb with an older one, which perfectly fits the manifold.

Same goes for my 69 Charger with 383/2bbl setup. Changing the manifold + carb would just increase my fuel bill, but nothing else.

Keep the money and do the Pertronix upgrade. That's IMHO the best investment you can do to improve reliability. Additionally, I would do a relay setup for ignition, head lights and perhaps a better alternator. Then, almost nothing can stop you onwards.
Other than that, a stock 318 is something to just run and not worry about. You still have plenty of power - I spin the wheels on every traffic light but loose every competition with almost any car. And I don't care. Very Happy

I'd change camshaft, manifold and even more stuff only if I'd be in drag runs or need to have MUCH more power.
Keith D
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Post by Keith D on Thu May 23, 2019 12:51 am

OutofSight wrote:Has anyone switched to a 4bbl carb and retained the original throttle linkage? I have pulled my 318 and will be rebuilding it soon. I have purchased an Edelbrock 1406 carb and an LD4b intake. As for kick down linkage I’ve got the Lokar kit.

OutofSight,

I have been looking at all of my van pictures but unfortunately I did not take any of my 318 before I started tearing it apart.

When I bought the van it had an Edelbrock 4 barrel on it and it was using the stock linkage with the stock kick-down linkage as well. I can't remember exactly what fittings were on the carburetor. I do know that the gas pedal was not the original but it was similar, probably out of another Chrysler product of the same era. Unfortunately the pedal hit the trash can a while ago.

So it is very likely that you can run the stock linkage with a Lokar kick-down. I wish that I had taken more pictures before I started ripping into it.

Keith
lws67
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Post by lws67 on Fri Jun 07, 2019 9:35 pm

If you do go with a 4-bbl I would advise using a composite body Street Demon 625, wont have to deal with heat soak or boiling while driving in traffic, work on getting it jetted for your engine. They are easy to work on, there is enough info on the web for how to methodically tune them, they work great, very responsive and the extra cfm will help in various scenarios. I would forget all the performance upgrades as it will just open you up to more headaches than (from what it sounds like) you'll want to deal with. Or just find a nice 2-bbl and leave it as is, just tune it again methodically,
sweetvan
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Post by sweetvan on Sat Dec 07, 2019 12:50 pm

Joe,
What did you wind up using? How well is that working?
rekbender
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Post by rekbender on Sun Feb 09, 2020 6:50 pm

sweetvan wrote:Joe,
What did you wind up using? How well is that working?

sweetvan, I just came across this post. I bought Joe Miller's A108 about two years ago. He had changed directions and found a Glasstron camper. The original Carter BBD two bbl carb was still there. I rebuilt the BBD, replaced the choke pull-off and choke thermostat. This '70 318 came with the Chrysler Cleaner Air System (exhaust manifold heated intake air to the air cleaner), and I replaced the thermostatic vacuum switch in the air cleaner base so the flap in the snout would send warm air at low ambient air temperatures. Everything works great. The BBD is entirely adequate, starts and warms up quickly, has plenty of power,  and runs with no hesitation. The engine runs cool (4 core aluminum radiator) and vapor lock has never been an issue. Mileage is in the 16 MPG range with the automatic and 3.23 rear.

Carburetors. Keep stock? 4bbl? Pros & Cons. Newbie needs advice! Dsc09710

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vanny
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Post by vanny on Sun Feb 09, 2020 7:19 pm

Nice work!!! cheers cheers


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