Carburetor thoughts - rebuild or replace

This area is for posting questions/information concerning 1964-66 year Thunderbirds NO FOR SALE POSTINGS

Moderator: redstangbob

Post Reply
dmtinker
Posts: 8
Joined: Sun Jun 03, 2018 5:22 pm

Carburetor thoughts - rebuild or replace

Post by dmtinker » Thu Jul 11, 2019 11:06 am

I have a 65 Landau 'Special Edition' with an FE390. I bought it not running and am starting the 'getting it running' process as it were.
I was told when I bought it that the carb leaks at the base plate. I'm wondering if it's better to rebuild the existing carb or get a new one?
I'm assuming I have an Autolite 4100 but haven't had time to look closely. I've heard arguments either way. I'm considering this one.

https://www.amazon.com/dp/B004DRNHIS/?c ... _lig_dp_it

Peddller
Posts: 225
Joined: Fri Jul 19, 2013 10:26 pm
Location: Bel Air, MD

Re: Carburetor thoughts - rebuild or replace

Post by Peddller » Thu Jul 11, 2019 3:40 pm

I have never had any problems with the Autolite 4100 if it is rebuilt and adjusted properly.
Bill Clark
Bel Air, Maryland
1957 F code
2005 50th anniversary
1963 Avanti R2
1956 GMC Suburban Carrier pickup
1966 Corvair Corsa Turbo
Prior Birds
1963 M code SR
1964 Convertable
1965 convertible

User avatar
Richard
Posts: 447
Joined: Mon Dec 05, 2011 8:51 am
Location: Long Island New York

Re: Carburetor thoughts - rebuild or replace

Post by Richard » Fri Jul 12, 2019 4:34 am

I had my carb replaced last year with the same Holley although got it from Summit on sale for $290..I am into originality but my Autolite was from a 62 Tbird and I have a 65..The car never ran and performed so well with the new carb..That said many on this forum will tell you to have it rebuilt which I can understand but it was going to cost me about the same money for a rebuild or buying a new one so decided on a new one.I used the original air cleaner housing so it looks stock..Good luck
1965 Hardtop Charcoal Gray Metallic
VTCI#12157

dmtinker
Posts: 8
Joined: Sun Jun 03, 2018 5:22 pm

Re: Carburetor thoughts - rebuild or replace

Post by dmtinker » Fri Jul 12, 2019 10:40 am

I'm inclined to replace it. I'm sure the Autolite is fine but I would think a newer carb would be less hassle. I'm curious what after market carbs are being chosen...

User avatar
Richard
Posts: 447
Joined: Mon Dec 05, 2011 8:51 am
Location: Long Island New York

Re: Carburetor thoughts - rebuild or replace

Post by Richard » Fri Jul 12, 2019 11:08 am

I think mostly Holley or Edelbrock brands..
1965 Hardtop Charcoal Gray Metallic
VTCI#12157

User avatar
RedBird64
Posts: 1963
Joined: Wed Oct 31, 2012 11:42 pm
Location: Bothell Wa.

Re: Carburetor thoughts - rebuild or replace

Post by RedBird64 » Fri Jul 12, 2019 11:14 am

My thoughts on this matter have changed over the years. Now, I feel that if you're going to stay with a carb, I would get the original professionally rebuilt (not just a kit).

Scott
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 42 years. It was my folks car before that (second owners). VTCI # 12013.

dmtinker
Posts: 8
Joined: Sun Jun 03, 2018 5:22 pm

Re: Carburetor thoughts - rebuild or replace

Post by dmtinker » Fri Jul 12, 2019 11:27 am

What do you believe is the difference

User avatar
RedBird64
Posts: 1963
Joined: Wed Oct 31, 2012 11:42 pm
Location: Bothell Wa.

Re: Carburetor thoughts - rebuild or replace

Post by RedBird64 » Fri Jul 12, 2019 11:15 pm

One big difference for me is the choke setup. The oem actually uses the true temperature of the eng to continuously adjust the choke as it warms up. An aftermarket carb uses a little electric heater element to mimick what someone believes is the correct warm up curve (adjustable by the user). Problem is, the elect. heater setup opens the choke at the same rate no matter what the temperatures are. So if a person lives where there are changing ambient temperatures and hence, the eng warming up at differing rates, they'll end up making lots of adjustments or just living with lousy choke function.

Also, the stocker is jetted right. You may be able to just bolt on a new carb and it works great but more likely, to get that little extra performance, you'll need to rejet.
Worse, if the jetting is off far enough you end up with eng damage even though it may seem to run fine.

One of the worst mistakes folks make (like me) is getting a carb that's too big. A perfectly sized carb is hard to beat for driveability and overall performance.
If you get a new carb, I recommend a 600~625 CFM unless you have a built engine with a lot of performance enhancements (hot cam, more displacement, etc).

Come to think of it, if anyone near me wants a super low mile Edelbrock 750 with tuning kit, they're welcome to stop by and take it home.

One thing that confuses me, they told you the carb leaks at the "base plate". The stock carb doesn't have a seperate base plate. So maybe it already has an aftermarket on it? Or, maybe it's leaking at the gasket underneath the carb, which has nothing to do with the carb itself.

Scott
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 42 years. It was my folks car before that (second owners). VTCI # 12013.

User avatar
paulr
Posts: 1439
Joined: Mon Nov 05, 2012 12:03 pm
Location: Seattle

Re: Carburetor thoughts - rebuild or replace

Post by paulr » Sat Jul 13, 2019 1:14 am

RedBird64 wrote:
Fri Jul 12, 2019 11:15 pm

One thing that confuses me, they told you the carb leaks at the "base plate". The stock carb doesn't have a seperate base plate. So maybe it already has an aftermarket on it? Or, maybe it's leaking at the gasket underneath the carb, which has nothing to do with the carb itself.

Scott
If your carb is the original 4100 and has been worked on at all by anyone in half a century, my wager is that the base is warped. It's very common and easily corrected.
Paul
VTCI 12014
Registry 45122
'64 Landau HT
"Beer, now there's a temporary solution!" ~Homer Simpson

64ZCODE
Posts: 215
Joined: Wed Mar 20, 2019 9:41 pm

Re: Carburetor thoughts - rebuild or replace

Post by 64ZCODE » Sat Jul 13, 2019 9:00 am

Yes, agree with the comment about the base plate. Should resolve what the issue is with the base plate before replacing the carb. A spacer (base plate) is a good thing to have, it increases throttle response and helps insulate the carb from intake manifold heat.

On my '64 390 I'm running a 670 cfm Holley and it works great.
Life is short, my friends, so take my advice
Pull down your pants and slide on the ice

User avatar
RedBird64
Posts: 1963
Joined: Wed Oct 31, 2012 11:42 pm
Location: Bothell Wa.

Re: Carburetor thoughts - rebuild or replace

Post by RedBird64 » Sat Jul 13, 2019 10:06 am

I think we're getting our terms a little mixed up orcould be a regional thing ;-)
A base plate on a carburetor is the term used to describe the seperate flange plate at the bottom of Holley and some other carbs.
Example: https://www.google.com/search?q=holley+ ... e&ie=UTF-8

This is in addition to the spacer plate like our cars use.

The Autolite is kind of a hybrid of the Holley (ahem, cheaper to build) and doesn't have a seperate base plate. That's why I'm suspect of the guy that said the OP's was leaking.

The problem with an over sized carb is velocity. The venturies of a smaller carb keep the velocity up and that makes for better throttle response.

Cheers,
Scott
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 42 years. It was my folks car before that (second owners). VTCI # 12013.

dmtinker
Posts: 8
Joined: Sun Jun 03, 2018 5:22 pm

Re: Carburetor thoughts - rebuild or replace

Post by dmtinker » Sat Jul 13, 2019 12:24 pm

I haven't looked that closely yet but my suspicion is a bad carb gasket. When I get time, I'm going to do a compression and leak down test to see if I should just pull the motor and redo it. No point messing with the carb if it's seized or I have a bad cylinder.

User avatar
sseebart
Posts: 1501
Joined: Sun Jan 22, 2012 1:45 am
Location: Northern California
Contact:

Re: Carburetor thoughts - rebuild or replace

Post by sseebart » Sat Jul 13, 2019 1:03 pm

dmtinker wrote:
Sat Jul 13, 2019 12:24 pm
I haven't looked that closely yet but my suspicion is a bad carb gasket. When I get time, I'm going to do a compression and leak down test to see if I should just pull the motor and redo it. No point messing with the carb if it's seized or I have a bad cylinder.
I'm a little late to the party here, but I'm with those who say to rebuild the existing carb. Also, have it professionally done by someone reputable. It's possible to flatten the base of the carb in your shop, but difficult to re-sleeve the bushings for the throttle butterflies--a common source of vacuum leaks.

As Scott pointed out, you'll get good performance from the original with no hassles.

~Steve

Cliff Rankin
Posts: 177
Joined: Tue Jan 20, 2015 12:24 pm

Re: Carburetor thoughts - rebuild or replace

Post by Cliff Rankin » Sat Jul 13, 2019 5:10 pm

My 64 has an edelbrock carb it works great. My 63 I tried
To rebuild several times and it just was not quite there.
I have been working on cars for a living for a long time
Rebuilt many carbs. Finally gave up and put a holly on it.
Ran good but it was a gas pig. I drive mine all the time , worry free. In the Texas hill country. I finally caved and
Purchased a replacement on rock auto. Money well spent.
The holly will go on the wall of the man cave. I have to set toy limits on my budget. My car runs good and fast &
I average 16-17 mpg out here. Not bad. Cliff

dmtinker
Posts: 8
Joined: Sun Jun 03, 2018 5:22 pm

Re: Carburetor thoughts - rebuild or replace

Post by dmtinker » Sat Jul 13, 2019 6:42 pm

I'm in Dallas so I don't get that much temp variation

Post Reply