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Poly 318 - 2 barrel to 4 barrel
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   Forward Look Technical Discussions -> The Exhaust Pipe - Modification & PerformanceMessage format
Posted 2004-03-11 3:45 PM (#2538)
Subject: Poly 318 - 2 barrel to 4 barrel


Posts: 24

Location: Warren, Michigan
I'm looking for advice on replacing the 2 barrel carburettor on my 318 ('58 Belvedere) with a 4 barrel. I'm thinking about going with the Weiand manifold with a new Edelbrock carb. Do I need to swap the camshaft also? If so, what are my choices? Is there anything else involved with this change? I'm not looking for a radical performance change, just a few more horses for my classic cruiser without compromising driveability. Thanks in advance!
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Posted 2004-03-14 1:31 AM (#2613 - in reply to #2538)
Subject: RE: Poly 318 - 2 barrel to 4 barrel


Posts: 130
Location: Warren, MI (4 miles north of Lynch Rd. plant)
I have had a cast 4 barrel intake on my 56 Plymouth 277 (aka 318 style) and removed my 2 barrel set up and it was nice, sucked a hell of a lot more gas, so I went to a 600CFM Edelbrock carb....sweeeeet! But I left the cam alone. I am now working on getting a custom grind camshaft for it (if you need help, email me) but that will give her the kick in the pants that I was looking for that the 4 barrel didn't quit meet my standards. The 4 barrel will help with performance, but just a little. Go for the cam too.
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Daven Anderson
Posted 2004-03-15 11:04 PM (#2690 - in reply to #2538)
Subject: Dual Exhaust too!

Extreme Veteran

Posts: 362
Location: Colorado, USA
The 4 barrel will definitely give you a few more horses without compromising your drivability.
However, I would suggest a dual exhaust also. The 4-barrel can take in more air, so it's only
logical that you upgrade the exhaust system so that the air can get out more efficiently. A
properly tuned 4-barrel dual-exhaust V8 will get BETTER gas mileage than a 2-barrel single
exhaust V8 in regular driving conditions. The stock exhaust systems on 55-61 cars (ALL 55-61
cars, not just F.L. cars!) leave much to be desired compared with a good custom exhaust setup!

I'd go for a modern dual exhaust for a poly 318 before I'd change the cam, BUT a custom-grind
cam for a poly is certainly worthwhile. The 318 2-bbl cams are around 238-244º duration, a bit
lower than what would be best for a 4-bbl dual-exhaust 318 (250-260º duration). Years ago I
had a '61 Belv. with 318-2 bbl., with new dual exhausts and the "power pack" 1961 4-bbl 318
cam (about 252º duration) and that setup worked really well. I just never got around to adding
the 4 barrel manifold and AFB carb before I sold the car! I'd say the stock dual-plane 4-bbl poly
manifold is superior to the Weiand shallow single-plane manifold for a regular street engine
application (especially for low-end torque), then again it does weigh about 40 lbs. more and
they are a bit hard to find nowadays...

Edited by Daven Anderson 2004-03-15 11:08 PM
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Posted 2005-02-07 9:21 AM (#23746 - in reply to #2690)
Subject: RE: Dual Exhaust too!


Posts: 1809
Location: Slidell La.
I have heard people complain that the Weiand intake does not have all the bolt holes for the original stock accessories,like coil bracket and throttle linkage.Don t know how big of a problem that really is. Charlie
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Posted 2005-02-07 2:21 PM (#23767 - in reply to #23746)
Subject: RE: Dual Exhaust too!


Posts: 12

I've got a 66 plymouth fury(poly 318), but like to come to this board now and then to see what the poly 318 crowd is upto here. The weiand intake does lose a significant amount under 3000 rpm, but also picks up quite a bit above 3000 rpm. I don't recomend it unless you loosen up the torque convertor, and get rid of your cruising gears. Im in the process of changing my torque convertor and gears now, but with 2.94:1 rear and a stock convertor stalling at 1750 rpm, the weiand intake, Chris Nielson 264m cam, dual exhaust(stock manifolds), and some of my amature grinding work to the intake ports dropped me from a stock 17.5 @77 mph to a 15.9 at 89.5 mph, ill update you guys when the gears and convertor are changed aswell.

Edited by moparkid1966 2005-02-07 2:23 PM
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Gary Pavlovich
Posted 2005-02-11 12:13 AM (#24109 - in reply to #2538)
Subject: RE: Poly 318 - 2 barrel to 4 barrel, Poly cams

New User

Posts: 1

Location: CA
I would suggest a complete package to enjoy the power and improved economy from a free-breathing system dual exhaust.
I can help you with new poly camshafts in stock or High Performance grinds as well as new Poly lifters and any Poly performance parts you might need.

Regarding the Weiand single four intake (#7503), they are better than a two barrel and make good midrange power as one has already posted; no real difficulty w/the coil & throttle cable/rod...

Let me know if I can help any Poly 318 fans.
Gary Pavlovich
402" Poly stroker motor
405HP/442 Torque (presently)
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