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1963 401 Carb size???


TerryH
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Hey Guys looking for opinions on what size carb to put my 1963 Buick lesabre 401. It has a 2 bbl in it currently. I have found a 4bbl manifold and have ordered gaskets for the manifold and the carburetor including the heat shield. I also got the adapter for the tranny kickdown. I am looking for options on what size of carb to put safely on the all stock motor. Right now I'm looking between the Edelbrock AVS 2 650cfm and the next size up the AVS 2 800cfm.

Any help would be much appreciated.

Edited by TerryH (see edit history)
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  If you are switching to a 4 bbl, are you also changing the cam to take advantage of the extra 2 bbls?  I thought that particular 401 was an 8.5-1 compression engine.  Which means it could run on regular grade gasoline.  If you bump to the 4 bbl with a hotter cam will you need to bump to premium fuel too?  but equally important will bumping to a 4 bbl really provide the extra performance anticipated?

 

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Hi JohnD  the standard 2bbl in 63 was the wildcat 410 not the low compression wildcat375. Now that being said I have not yet figured out if infact I have the 410 or 375 still researching how to figure that out lol. But assuming I have the standard 410 at 280HP my understanding is that the 4bbl option that as far as I can figure out was pretty much carb and intake was 330HP. And Speaking with a few guys who seem to know there way around the Nailheads there is no doubt that it loves to have the fuel thrown at it. My concern is can I do it safely. 

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Just as a suggestion:

 

If you are set on using one of the clones, rather than an original Buick 4-barrel, try having a friend time you with a stop watch on 3 0-60 runs on your current two-barrel and compute the average time. Then, once you have installed the clone of your choice, run the 0-60 times again and compare the average to your two-barrel runs. You may be surprised.

 

Jon.

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You are right Terry. The 375 is probably the stick shift set up and the 410 is probably the dynaflow equiped model.  But I would think the cam is still not as aggressive with a 2bb carb otherwise at WOT theres a possibility the engine would run lean. I don't think Buick engineers would set it up like that from the factory. But I could be incorrect as I do not have direct experience to rely on.  

Please let us know how it works out. 

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On 7/23/2019 at 11:08 PM, carbking said:

try having a friend time you with a stop watch on 3 0-60 runs on your current two-barrel and compute the average time.

 

Or pull up next to another car with a large engine at a stoplight where you have two lanes. When the light turns green floor it and compare how you leap ahead to your car with the four barrel installed. Also watch for the difference in the other driver's expression between the two.

 

I had my son lie next to the road with a stop watch and a camera to check mine.

Dust-4.jpg.8a2e548ca485b331ea8b6925273c0fdd.jpg

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I think what people are getting at is that the upgrade will not make a huge difference in the way the car drives and may introduce a different set of variables to your tuning. We like to think that with 50 years on the original engineers, we're smarter than they were. The more I play with cars, the less I find that to be true. Those guys knew their stuff and knew how to make their own equipment work properly, regardless of what Hot Rod magazine has written.


If you're looking for peak numbers on a dyno, yes, the 4-barrel will do that. If you're looking for a tangible improvement in performance around town that will be easy to discern, I think you'll be disappointed given the cost and effort involved. I find that a lot of guys look at having a 2-barrel carb as akin to being under-qualified in the pants, if you know what I mean. They figure they need a man's 4-barrel to really swagger. In real-world situations, the difference in performance is less significant than you'd think and as the others have said, a properly configured 2-barrel can be superior for driveability and ease of use around town. Think about how often you drive with your foot flat on the floor--that is the only time a 4-barrel will make a notable difference. If that's more than 1% of the time, I'd be shocked.

 

That said, if you're doing it, a smaller carburetor is usually better than a big one, even on a big engine. Too many cars are over-carbureted and owners wonder why they don't idle well and throttle response is lazy. The 650 is a better choice than the 800, although you should be comparing the sizes of the primaries--there are some 4-barrel carbs with huge secondaries and tiny primaries and vice-versa. All 4-barrels are not created equal.

 

Good luck with the project.

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Thank you Matt. I am not trying to out engineer the engineers of yesteryear. I am only trying to mimic them! in 1963 the 2Bbl option was 280 HP and the same engine with the 4Bbl was 325ish and a extra 35 torque I am looking to match what they were able to do.And if you think you won't feel 40HP I mean come on! I have decided to go with the AVS 2 650 CFM carb. They look extremely easy to tune. I can't find anyone saying anything but good things about these carbs!!! And although I am not yet a Carb "specialist" give me a few months and I will be! My plan of attack is as follows.

 

I have a factory 4bbl intake manifold. I have already ordered the gaskets for the manifold and carb including the heat shield.

I ordered the adapter for the tranny kick down from Russ at http://centervilleautorepair.com

I have ordered a AFR Gauge I will install. 

I will start the process by changing the spark plugs and checking to make sure the timing is all good.

At that point I will swap the carb and intake and start the tuning process.

 

LeSabre.jpg

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Terry - when Carter was still manufacturing AFB carbs, their recommendations:

 

Buick 401 stock 4-barrel engine - ORIGINAL AFB

Buick 401 modified with headers and larger cam - 625 CFM AFB

 

Carter never recommended an AVS for the Buick.

 

As for bad things about the AVS (opinion) very worst 4-barrel that Carter ever made (including the first production WCFB's)! Chevrolet tried it for 1 year, and then discontinued it. Chrysler used it from 1968 to 1971 in order to pass smog emissions, and discontinued it when the TQ came out. Carter (at least on paper) offered an aftermarket AVS (left-overs) for various Chrysler products in 1972, but as a carburetion specialist that really likes Carter, and an ex-Carter warehouse distributor, I have NEVER seen one!

 

As Matt stated a couple of posts above: all 4-barrels are not created equal.

 

Jon.

Edited by carbking (see edit history)
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Jon you may just be right the AVS 2 might be a bad decision. And I promise if it is I will come on here and say you told me so. However this carb was released in 2017. I like enough of the design concepts such as the annular boosters. And worst case is I take it off sell it and find a Carter/Rochester to put on it.   

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Terry,  I have a freshly-rebuilt, factory-correct Carter 4-barrel carb available. It has never been used since the quality rebuild was done. It is the correct Carter carb number for a 1963 Buick, with 401. The linkage has the kick-down "hole" for your Dynaflow transmission (missing on generic Carter 4-barrel carbs). This carb was rebuilt by Carmen Faso, who's work is well-known to BUICK people here on the forum. I think it's safe to say his work is highly regarded in the old BUICK world. You can send me a PM here on the forum, if you'd like to see photos and get a price. Thanks. John

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If not, here's where they're located.  You need the PRODUCTION CODE NUMBER to be able to identify the engine's displacement and horsepower.  The ENGINE SERIAL NUMBER should match the VIN on the car and the title for the car.  If not, the engine has been replaced.  The PRODUCTION CODE NUMBER will help here as well.

 

129438385_Nailheadproductioncodestamping.jpg.2921dc1d03a7ec21904e4f262bf04f73.jpg

 

Here are the Production Code Numbers for 1962

 

1962
V-6 198
6I
V-8 215
I
V-8 215
HI hi comp. engine
V-8 401*, 2 bbl
2I
V-8 401*, 4 bbl
4I

 

The numbers above do not show how to tell the "Wildcat 375" 9.0:1 low compression engine from the "Wildcat 410" 10.25:1 high compression engine that was offered in 1962; the "375" was a no cost options for using low octane fuel; both had the two barrel carb  If you're lucky, maybe your air cleaner has the original decal on it that would tell you which.  I don't know of any reference to cam grinds for different engines for 1962.  The code number for the "V-8, 2bbl" is 2I (that's an upper case I, not the number 1)  Same with the 4I for the four barrel engine.  Buick used progressive letters to designate years.  I for 62, J for 63, K for 64, L for 65, and M for 66.  "66 was the last year for the nailhead.

 

This link shows how the VIN is used to help identify the 62 model cars.  https://www.teambuick.com/reference/years/62/62_vin.php

 

Here's a link that shows the model numbers for 1962 Buicks.  Funny. It doesn't show a convertible for 1962 in the LeSabre series. There is one however in the Invicta series..https://www.teambuick.com/reference/years/62.php

That model number will be on the data plate on the firewall above the booster for the power brakes.

Here's an example from a 1962 Special Convertible "STYLE62 - 4167"  STYLE 62 = year, 4167 is the model number for the Special Convertible.  The other numbers identify paint, interior, and options.

62 buick body plate

 

Let us know what you find out.

 

 

Ed

 

Edited by RivNut (see edit history)
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Found it.  For you and all of the other Nailhead gurus out there.  

 

There are only four engines listed in the 63 chassis manual for series 4400, 4600, 4700, and 4800 series cars.  At the time of the printing of the chassis manual, the 425 had not been introduced yet so there is no JW code in the chassis manual, nor is there any reference to a 425 in any part of the manual.

 

Here's what is listed on page 0-3 of the manual

 

JR - Standard 2 barrel carburetor 401 engine

JS - Low compression 2 barrel carburetor 401 engine (reg. gas option)

JT - Standard 4 barrel carburetor 401 engine (also Hi-performance on 4400)

JU - Low compression 4 barrel carburetor 401 engine (Export)

 

FYI: High compression  10.25:1

       Low compression 9.0:1

       Export compression 8.75:1 

 

Terry, 

You have the JR high compression 2 barrel engine.  It will respond nicely to the carb that JJ has for sale.

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On 7/25/2019 at 5:22 PM, RivNut said:

Here's an example from a 1962 Special Convertible "STYLE62 - 4167"  STYLE 62 = year, 4167 is the model number for the Special Convertible.  The other numbers identify paint, interior, and options.

 

 

 

Small clarification that isn’t really relevant to the discussion.

 

4167 = Special Deluxe convertible

4067 = Special convertible

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Yes they did, but not someting you could order. Year to hear they might change at what degrees a valve may open or close or what the overlap might be or how many dgrees the cam may be off set.  But this never changed the advertised horsepower or torque fiqures.  If anything was done, it was usually to smooth out the way the engine idled or something similar.  The cam used on the Super Wildcat 2x4 engine is almost identical to the 63 stock 401 cam. I think the specs by for 401 and 425 cams might be on the Rivowners website. 

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... just an option but I would not hesitate to install a 1000 cfm Thermoquad with adapter plate.  You have the heads and cam already stock to handle the carb ...... 

Edit: Oh also install an HEI distributor and gap your plugs to around 40 and your good to go and if you did not keep your foot to the floor at least 75% (WOT) most of the time I would not only be surprised but shocked ! 😉 

Edited by buick man (see edit history)
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14 hours ago, RivNut said:

Yes they did, but not someting you could order. Year to hear they might change at what degrees a valve may open or close or what the overlap might be or how many dgrees the cam may be off set.  But this never changed the advertised horsepower or torque fiqures.  If anything was done, it was usually to smooth out the way the engine idled or something similar.  The cam used on the Super Wildcat 2x4 engine is almost identical to the 63 stock 401 cam. I think the specs by for 401 and 425 cams might be on the Rivowners website. 

So, some years would be different but within a given year's product line, they would be identical? In other words, in 1963, there was one cam for all engine configurations? 

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The information supplied by Dennis Manner that was printed in the Riview was for 401 and 425 four barrel engines.  I don't know if there was a different cam for two barrel engines or low compression engines. 

 

I'm sorry but for some reason my computer will not let me attach that document in a format that you can read.  I bought a new computer a couple of years ago and it did not come with Microsoft Office.  Makes some tasks really difficult.  I'll work on trying to get this to a point where I can post it.

 

Ed

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1 hour ago, buick man said:

... just an option but I would not hesitate to install a 1000 cfm Thermoquad with adapter plate.  You have the heads and cam already stock to handle the carb ...... 

Edit: Oh also install an HEI distributor and gap your plugs to around 40 and your good to go and if you did not keep your foot to the floor at least 75% (WOT) most of the time I would not only be surprised but shocked ! 😉 

 

Much as I like the Carter TQ, this is not an option I would recommend for street use.

 

When selecting a carburetor, it is a good idea to ALWAYS (and I don't use that word often) select a carburetor of the same style (spread-bore or square-bore) as the manifold.

 

As far as the 1000 CFM TQ is concerned, it was designed STRICTLY FOR RACING!!!!! As such, it has a lousy idle circuit, as the idle booster was removed from the venturii area in order to acquire the extra CFM. Above a certain RPM (maybe 2500 or so) it would run well (but no better than an 800 or 850 until the engine was screaming), but idle for a street vehicle is almost non-existant (most that have one are happy with a 1400~1500 RPM idle). And the 1000 CFM carbs are EXPENSIVE!

 

The 850 CFM (expensive) or the 800 CFM (much less expensive) would be a far better choice for anything other than a trailered professional racecar.

 

It has been years since I did much with these, but had several customers who believed the hype that Buick engines love CFM and bought (elsewhere) the 1000 carb, and called us for help to make them work. For the folks with street cars, we tried to convince them that the 800 or 850 would be better. The ones that listened that called us back, ALL had better 0-60 times with the 800 or the 850 than with the 1000, plus a much more tractable vehicle.

 

The 850 is 250 primary and a variable 600 secondary.

The original AFB that has been discussed in this thread is 250 primary and a variable 375 secondary.

 

Thus performance with the 850 on the primary side (once dialed to the Buick engine characteristics) should perform about 3 percent (because of the cooler fuel in the thermoplastic bowl) better than the original Carter. Above 6250 RPM, the 850 would run somewhat better than the original.

 

To see any appreciable improvement from the use of the 1000, the engine needs to be running at more than 8000 RPM.

 

However, should anyone wish to ignore the comments in this post, I still have some 1000 CFM carbs (Carter part number 4847) for sale ;)

 

EDIT: the above RPM figures are for a 401 running tube headers through mufflers. A racecar running open exhaust would have slightly lower RPM thresholds, a street engine with normal exhaust and mufflers would need higher RPM's.

 

Jon.

Edited by carbking (see edit history)
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Found it on the Team Buick website.  Someone has made it into a very readable table.  Dennis Manner's discussion is not available but in essence he's saying that there's very little difference in the cams used on the four barrel and dual four barrel 401 and 425 engines from year to year.  The same cam is used in the 1965 425 with one four barrel carb as is used in the dual four barrel car.  So basically there is no performance factory cam for the Nailhead.

 

And  please do not be mislead by the part number for the 1965 cam's part number.  Unlike an urban myth that started some time ago. the 091 on the end of the number does not mean it was designed by Duntov as was his popular cam grind for a small block Chevy.  At a recent ROA meet, I asked Denny Manner about this and he got a chuckle out of it.  

 

 

OE specifications for 401 and 425 camshafts. Remember, these are measured at .002", NOT .005" or .050"! 

 

CAM PART NO. 1185918 1351515 1359442 1358100 1362242 1368091 1368090
NO. ON SHANK 1174480 1174480 1374480 1674480 1362241 1362241 1362241
401 1959-61 1962-63 Late 1963-64        
425       1963 Late 1963-64 1965 1966
425 2X4         1964 1965-66  
MACHINED GROOVE IN SHANK .060" NONE NONE .060" .060" .120" NONE
TIMING ADVANCE OF #1 EXHAUST LOBE AHEAD OF SPROCKET KEYWAY 2°30' 0°30' 0°30' 0°30'
EXHAUST DURATION .002" 299° 302° 295° 299° 299° 299° 295°
EXHAUST LIFT .441 .439 .431 .441 .441 .441 .431
INTAKE DURATION .002" 290° 295° 295° 290° 290° 290° 295°
INTAKE LIFT .439 .439 .431 .439 .439 .439 .431
SPACING 109° 114° 114° 109° 109° 109° 114°
EXHAUST OPEN BBC 75° 76° 76° 71° 71° 71° 76°
EXHAUST CLOSE ATC 44° 46° 39° 48° 48° 48° 39°
INTAKE OPEN BTC 33° 28° 28° 29° 29° 29° 28°
INTAKE CLOSE ABC 77° 87° 87° 81° 81° 81° 87°
OVERLAP 77° 74° 67° 77° 77° 77° 67°
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If the 401 2 bbl was indeed lower compression, then just like Buick did for 1957/58 364, indeed it would stand to reason it would have a lower milder cam  With less air, less fuel and lower compression there is no need to lengthen the duration of the cam lobe for increased intake.  Change that formula with increased compression like a dual carb setup or a single four and then the longer cam can be used.  But just slapping on a four barrel on a low compression short lobe cam would show really no benefit that would be practical especially in passing and/or stomping to WOT.  

 

Jon - Thanks for the schooling on 1000 cfm TQ and I knew my brother had a hard time with his GX 455 back in the day to get the thing to be streetable and we did not realize about the idle circuit back then and no doubt if not working on the 455 with Stage-1 heads would not work for our OP and his Buick.

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3 hours ago, drhach said:

I think the OP's engine code showed it as a "Standard" rather than low compression. I would take that to mean that it had the same compression ratio as the 4 barrel. 

You are correct.  Terry's engine is the high compression two barrel 401, not the low compression 401 regular gas option. He posted his Production Code number and I posted (July 26) the code numbers for the four different 63 401 engines.

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I realised last night that I have a reproduction parts book at home. It goes 1940-1976. It dawned on me that all cam choices should be in there. There were a lot. One thing that baffles me was that some of the part numbers on the team buick website were not in the parts book.  Anyway, for 1963 they do list two different cams for a 2 or a 4 barrel. No mention is made of high or low compression. However, the book also lists a cam as being for 62-64, "all engines" and it's different from the other two part numbers. T huh is isnt confusing at all. :)

 

20190803_090055.jpg

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  • 1 month later...
On 8/3/2019 at 10:09 AM, drhach said:

I realised last night that I have a reproduction parts book at home. It goes 1940-1976. It dawned on me that all cam choices should be in there. There were a lot. One thing that baffles me was that some of the part numbers on the team buick website were not in the parts book.  Anyway, for 1963 they do list two different cams for a 2 or a 4 barrel. No mention is made of high or low compression. However, the book also lists a cam as being for 62-64, "all engines" and it's different from the other two part numbers. T huh is isnt confusing at all. :)

Actually, its not that confusing.....1368090 lists all car models with a 401......1362245 is for 4000, 4100,and 4300 models (presumably Special and Skylark with a 300 2bbl, or a 300 4 bbl (1362246)

On 8/3/2019 at 10:09 AM, drhach said:

20190803_090055.jpg

 

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On 7/25/2019 at 9:33 AM, 60FlatTop said:

 

Or pull up next to another car with a large engine at a stoplight where you have two lanes. When the light turns green floor it and compare how you leap ahead to your car with the four barrel installed. Also watch for the difference in the other driver's expression between the two.

 

I had my son lie next to the road with a stop watch and a camera to check mine.

Dust-4.jpg.8a2e548ca485b331ea8b6925273c0fdd.jpg

 

 Ha Ha Ha,

I cold easily lie down next to the road,

but at my age and general physical condition, it is the "Gittin' Up Part" which has become more the challenge-

maybe look into that at 0-60?

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  • 1 year later...

i realize this is an old thread... but... run an 800avs2 on it.  really thats the smallest you would want on a 57 and later nailhead. anything smaller and you're leaving power on the table.  you really wont notice worse gas mileage either...   difference between a 600cfm carb and an 800s, even on a stock engine is close to 50 horsepower! its the single biggest, most affordable, performance gain you can do to a nailhead.  at the time, buick was using the biggest carb they had available.  stock afbs were only around 580 cfm.  the 66 qjet was  715.  thats why buick came out with the dual quad, which was probably around 800 cfm.  

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14 minutes ago, nailhead matt said:

i realize this is an old thread... but... run an 800avs2 on it.  really thats the smallest you would want on a 57 and later nailhead. anything smaller and you're leaving power on the table.  you really wont notice worse gas mileage either...   difference between a 600cfm carb and an 800s, even on a stock engine is close to 50 horsepower! its the single biggest, most affordable, performance gain you can do to a nailhead.  at the time, buick was using the biggest carb they had available.  stock afbs were only around 580 cfm.  the 66 qjet was  715.  thats why buick came out with the dual quad, which was probably around 800 cfm.  

 

By 1963, Carter produced, and sold AFB carbs in CFM figures from 400 to 939! Buick had access to them all.

 

Biggest carb available???

 

Holley had a PRODUCTION two-barrel that flowed 600 CFM on the 4-barrel scale in 1929!

 

Large carburetors were readily available!

 

Jon.

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there was no afb larger than the what they used during those years the nailhead was made.  hence they jumped on the qjet, and the qjet performs significantly better.  not because of the carb or the intake, but simply because it was bigger than the afb.    not as good as the dual quad, however.  

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33 minutes ago, carbking said:

 

By 1963, Carter produced, and sold AFB carbs in CFM figures from 400 to 939! Buick had access to them all.

 

Biggest carb available???

 

Holley had a PRODUCTION two-barrel that flowed 600 CFM on the 4-barrel scale in 1929!

 

Large carburetors were readily available!

 

Jon.

you got anything to add to the dyno results i provided?

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