Cadillac Owners Forum banner
  • Hey everyone! Enter your ride HERE to be a part of JULY's Ride of the Month Challenge!
1 - 13 of 13 Posts

·
Registered
1975 Cadillac Sedan de Ville
Joined
·
49 Posts
Discussion Starter · #1 ·
Hey guys,

I'm replacing the carby on my 75 SDV and I'm looking at the direct-replacement Holley 650 CFM #80555C. Anyone used this carbie, any thoughts?

The car's going to remain stock, with the only possible exception being block-huggers and dual exhaust (although this is not a definite by any means).


Cheers,
KiwiCadi
 

·
Registered
Joined
·
49 Posts
My dad had one on a 430 Buick and it was okay, but it might be a little too small for a 500. I am not sure if they have places to hook up the electronic kick down or the cruise...
 

·
Registered
Unicycle
Joined
·
11,009 Posts
Why are you looking to replace the carb?

Really, the factory Q-jet is perhaps the best carb for the big blocks unless you really start to get wild. Very good performance and return decent fuel mileage. I would just reccomend getting a rebuild by someone that really knows the Q-jet well, then be done with it.

Not sure about the 500, but my '79 425 had an 800 (795) CFM Q-jet.... I am sure a 650 on a 500 will be a bit too small.
 

·
Registered
1975 Cadillac Sedan de Ville
Joined
·
49 Posts
Discussion Starter · #4 ·
It leaks and I figured I would replace it anyway as the cost difference between that and rebuilding it isn't all that, plus if there's a brand-new piece of hardware there I shouldn't have to worry about it again (theoretically). If I do end up replacing it, can I still use the stock air-cleaner?

FYI - a rebuild here would be in the vicinity of NZ$400, I can get a new carb in from the US for about NZ$450, to buy a new carb here costs NZ$750-$850.

I do want the car to remain as stock as possible.
 

·
Registered
70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
Joined
·
3,310 Posts
It's too bad there aren't a lot of Quadrajet specialists over there like over here because a rebuild kit is less than $50 US and can easily be done in less than 2 hours. I am not a Holly fan but a brand spankin new one out of the box should probably work fine for you. There are many articles on the web on rebuilding Quadrajets but they can still be intimidating the first time you take one apart. If you take your time, work on a nice table and take some pictures it really isn't that hard. If yours is leaking then the float is probably sticking a little or the inlet needle/seat is dirty or worn. If you don't want to mess with it at all, then that Holly will work fine. I would still be tempted to try a rebuilt Quadrajet off Ebay. I got a rebuilt Quadrajet for my 70 Impala last year for $25 and it ran perfectly with no adjustments needed. I don't know why it was so cheap but there are deals out there all the time.
 

·
Registered
90.5 Allante, 02 Deville, 13 ATS 2.0t
Joined
·
119 Posts
You will get alot of opinions on this, but I would stay with the quadrajet. The quadrajets are known to leak internally into the intake from a couple of brass plugs in the base that are easily sealed with epoxy. This problem is well documented and a google search will expose the exact location of the plugs. This is a very easy fix and low hanging fruit. Is this the leak you have or is it an external leak?

Could you please provide me with the casting number from you carb. this number is stamped vertically on the secondary bore on the outside just above the secondary throttle shaft, the number is eight digits and begins with a 170. When I know the number, I can be more helpful. I want to be sure that this is not a California carb.
I have one sitting in from of me. If you can't find the information on the epoxy fix, I will send you a picture.
 

·
Registered
1975 Cadillac Sedan de Ville
Joined
·
49 Posts
Discussion Starter · #7 ·
Thanks for the responses guys!:thumbsup:

I took the car to the shop this morning, I found a mechanic I am very comfortable with, they actually build hot rods, and the mechanic himself is from Massachusetts! Best of they're only across the road from where I work.

The Q-jet is being rebuilt as we speak, it is also getting the plug wires and dizzy cap replaced, tune up, filters etc, also regas the a/c and look into replacing the current single exhaust with a twin system from the manifolds back.

Blue eldo - the car was bought new and lived its whole single-owner life in Laguna Hills, CA. I believe it was leaking fuel from the welch (sp?) plugs, which I guess are at the base of the carb?? I could smell fuel from inside the car anyway.

Cheers,
KiwiCadi
 

·
Registered
90.5 Allante, 02 Deville, 13 ATS 2.0t
Joined
·
119 Posts
The reason I asked is that the 75 California spec had a unique carb and the remainder75's had an even wierder one with a aneroid barometer altitude corrector and two primary power pistons. They say the best one is a 76 that has a nicer APT feature.
this is the core that JET likes to use.
If you go to www.circletrack.com/techarticles/ctrp_0607_quadrajet_tech/index.hmtl there is an article on how Jet does their rebuilds with pictures on how to epoxy the fuel well brass plugs. If you were smelling gas the float level may be too high.
Let me know how you are doing. I am out of town for a couple of weeks and my manuals are at home.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
74,063 Posts
Noticed the Q-jet in the thread title.......I build Olds 455's for boats, both race and cruise. Been at it for over 30 years.

Stick with a Quadrajet. Go to swap meets and pick 'em up for $5, tear 'em down and build a stock of primary and secondary needles as well as secondary operating hangers.

I have a couple of Holley 750 cfm vacuum secondary spreadbore marine replacements for sale, and the workboat guys around here won't touch them with a 10 foot pole.

Unless you operate at over 5,000 rpm all the time a 650 is plenty for a 455 - 500, and it gives great low-to-midrange response, tuned correctly.

A dab of epoxy in the well plugs under the carb base stops the fuel drip......
 

·
Registered
1975 Cadillac Sedan de Ville
Joined
·
49 Posts
Discussion Starter · #10 ·
Hey guys,

Well the Q-Jet was rebuilt, lasted a day and blew its lid. He said that fuel was all over the top of the carb. Unimpressed would be an understatement. Luckily it happened while the car was still in the shop. Apparently the carb was "a pain in the ass" to rebuild as it was consumed with dry rot. (I have no qualm with the work my mechanic's doing as he sent the carb out to someone else to rebuild.)

He says a Holley won't fit due to the A/C compressor, and that an Edelbrock probably would fit, but being a CA-spec emissions car could pose problems in hooking everything else back up, and that modifications would be necessary.

He sending the carb back to the so-called "rebuilder" to see what happened, but I really don't need it to behave for 2 months then leave me stranded 100 miles away. I can live without the cruise control (apparently that's run off the carb too) but I want my A/C.

Without getting into an argument about who thinks which carb is best, who has fitted an aftermarket carb to their 70s-era 500? Surely someone has by now?????? It has the original intake as well. All I want is a carburettor that works.
 

·
Registered
Cadillac
Joined
·
29 Posts
Check autozone.com for a rebuilt q-jet. They run $270 for yours. They are rebuilt by Holley. They have been rebuilding them for a while so they should have it down. Hope that helps. Good luck.
 

·
Registered
70 Deville 77 Fleet 78 Seville 92 Deville 03 Deville
Joined
·
3,310 Posts
Fuel all over the place is just a float problem or inlet seat problem but if they can't get it working, you may have to resort to one of those Holly rebuilds John mentioned. Good luck
 

·
Registered
1975 Cadillac Sedan de Ville
Joined
·
49 Posts
Discussion Starter · #13 ·
I've been looking at the Holley-rebuilt Q-Jets from the get-go anyway. We'll see what the story is Monday or so. Fingers crossed that it's something fairly simple and we're good to go (yeah, right!)

I took a bit of a gamble last night and bought a Q-Jet rebuild kit myself - http://www.carburetor.ca/carbs/kits/CK145.htm - I say "gamble" as I'm aware of the casting number I needed to check but the car obviously isn't with me, so I went by make, model, year, and everything I've read leads me to believe that it's an M4ME I've got. It was CA car from new so if that has any bearing on whether the kit will work or not, I don't know.

Thanks again for all your input, people. Much appreciated!
 
1 - 13 of 13 Posts
Top