Author Topic: Need help identifing my 1972 Eldorado Convertible Engine  (Read 131 times)

Offline Flyer

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  • Name: H. Dean
Need help identifing my 1972 Eldorado Convertible Engine
« on: October 10, 2017, 09:03:24 PM »
I'm new to the club and this is my first post. I recently bought my first Cadillac, a 1972 Eldorado's convertible that has many unoriginal features. I bought because the price was right. Nice paint job, non- original color,  with good condition unoriginal pillow top seats. The fit of the car body is awful but can be corrected with time and work. The front end has been rebuilt, brakes are all new and there is only a little surface rust on the frame area which I can clean up to protect for the future. I believe the engine has been rebuilt as paint is very good and gaskets and seals are all new. Transmission shifts very good. I do have a few questions I hope some one can help me with. The engine appears to be a newer year motor. The Carburetor number is 17056230, 1099 which I think fits a 1976. I think the distributor is a Delco HEI as it has a coil in the cap and I don't think it came on a 1972. All in all it appears someone took a bunch of parts and threw them together on a 1972 body. How do I determine what year the engine might be? I need to fix a starting problem with the engine therefore need to know if this is an original carb to the engine. The car can turn into a beautiful weekend cruiser, as it rides good, cold air, and it looks real good from 5 feet. Any help on the engine ID issue would be greatly appreciated. H. Dean

Offline Mike Josephic CLC #3877

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Re: Need help identifing my 1972 Eldorado Convertible Engine
« Reply #1 on: October 10, 2017, 09:16:20 PM »
The HEI distributor didn't come into use until 1974 on that engine.
I have a 1973 (since new) and I can't remember where the engine
numbers are on the block.  Posting a few pics of the engine compartment
may help.  Someone knowledgeable about the 1972's may spot some
obvious clues as to what year you have in there.

Mike
1955 Cadillac Eldorado
1973 Cadillac Eldorado
1995 Cadillac Seville
2004 Escalade
CLCMRC Museum Benefactor #38
Past: VP International Affiliates, Museum Board Director, President / Director Pittsburgh Region

Offline TJ Hopland

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Re: Need help identifing my 1972 Eldorado Convertible Engine
« Reply #2 on: October 10, 2017, 09:25:08 PM »
Engine can be difficult to pin down especially if your pretty sure its been rebuilt.   70-76 both 472 and 500 used the same blocks which numbers ended in 5200.   Finding a head casting number could maybe give you some clues what the compression may be but even there you can fairly reasonably do custom pistons to get what ever compression you want with what ever heads you have.   You can more or less mix and match things from 68-81 so you could have just about anything going on there.   

What is your starting issue? 

head casting ending in 250 & 902 were the 76cc chamber heads with a smog rail.   120's were 493 smog and 552 non smog.  71 when GM mandated the compression drop Cadillac apparently figured it would be temporary and did it with some mega dished pistons rather than a new head.  74 they gave up and made a low compression head that used more typical pistons. 

FWD Eldo and the RWD engines were the same except for a few bolt on parts like oil pan and having to move the dipstick to a different hole so you could have a 472-500-425-368 in there since they were all almost identical externally.   

73 was first year for EGR.
75 was first year for electric choke.  Previous years had the choke well and coil in the intake with a rod.
73 was points  75 was HEI.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason

Offline The Tassie Devil(le)

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Re: Need help identifing my 1972 Eldorado Convertible Engine
« Reply #3 on: October 10, 2017, 09:47:02 PM »
Firstly, the engine number is stamped on the back of the block, directly behind the left cylinder head, on the casting piece that the transmission bolts to.

The '72 engine for the convertible will start with 6L67S2Q followed by the numbers

My '72 has been retrofitted with the later HEI, plus a lot of other modifications to increase performance, so a picture of it is useless.   But, I do have pictures of when I purchased it, when it was original.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
(Past President Modified Chapter)

Offline TJ Hopland

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Re: Need help identifing my 1972 Eldorado Convertible Engine
« Reply #4 on: October 10, 2017, 10:39:37 PM »
The VIN numbers in the block castings are often pretty hard to read on these engines.  I have seen them fresh out of a hot tank that were still hard to read.   Its like only Monday's engines got a good whack of the hammer,  the rest of the weeks run were barely a scratch.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason

Offline Flyer

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  • Name: H. Dean
Re: Need help identifing my 1972 Eldorado Convertible Engine
« Reply #5 on: October 11, 2017, 08:04:22 AM »
Thanks to all for the info. I'll start looking for casting numbers today and see what I can find. Starting the engine from a cold start requires much pumping of the gas pedal. When it fires it runs for a very short period then dies. After several cycles the engine will stay running as long as the RPM is maintained at about 1500rpm for a short period while the engine warms up. After warm up it runs fine. I'm in Louisiana so the temps here at this time of year have been running at 90+ degrees F. Most engines run fine this time of year with little or no choke. My Rochester repairman wants to know as much about the engine as possible before working on the carb. I'm concerned the evolving emission control issues at GM during the 1970-1978 could have an effect what needs to be done with the engine to get it running smoothly.

Offline Dan LeBlanc

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Re: Need help identifing my 1972 Eldorado Convertible Engine
« Reply #6 on: October 11, 2017, 09:26:47 AM »
Have you checked yourself to see if the choke is closing?  Not really sure why your carburetor guy wants to know so much detail about the engine first.  Sounds like a simple choke issue.
Dan LeBlanc - CLC # 27657
1970 DeVille Convertible
1953 Series 62 Sedan (Parts Car)
1953 Fleetwood (Project Car)
2004 Deville

Offline TJ Hopland

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Re: Need help identifing my 1972 Eldorado Convertible Engine
« Reply #7 on: October 11, 2017, 10:28:30 AM »
There should not be anything different enough other than the choke setup that would keep any Quadrajet from getting started.   I get what your guy is asking for.   If /when he works on it he wants to make sure he is looking at the correct specs for the engine.    If its got an EGR and no choke well in the intake it may be a reasonable guess that its a later motor.  On the head numbers I forgot to mention 950 is the 70 only small chamber non smog rail head.  To see the casting number you have to pull a valve cover.  its in the center on a rail that runs in line with the rocker pivots. 

Basic checks for starting:

On a cold engine when you expect to have the starting issue take the air cleaner off and lean over so you can see down the throat of the carb which is easier said than done on these ultra compact cars.   Stick a finger in to hold the choke open an while looking down stroke the throttle lever.   What you are looking for is squirting fuel from the accelerator pump.  You should see at least 3 good squirts.   What this is telling us is that the accelerator pump is working and there is fuel in the carb.   We will come back to this if there isn't fuel.

Next thing is pull your finger out of the choke.   It should snap fully shut and not easily want to open again if you poke gently at it.   If it doesn't do that its not right.   Next is start it.  Choke blade should open about 1/4" as the engine starts and over a period of 2-5 mins should fully open and not want to easily shut if you gently poke at it. 

If you were not getting the squirts you can try adding some fuel.  Where you want to put it in ideally with out spilling it is that 1/4" tube that sticks up near the choke.  That tube is the bowl vent so it leads directly to where the fuel is supposed to be.   If you add it there and it starts right that points in the direction of the issue being either a leak or the fuel is boiling out of the carb when its parked.   You can also do the check for the accelerator pump on a hot engine.  The choke should be open then and the bowl should be full of fuel.  Downside is its hot and there would be a slight risk of flooding it. 


Like I mentioned earlier 75 and up had electric chokes so they require extra wiring and controls to put on an older car.  In the 68-74 range there were some variants on the shape of the choke coil which mounted in the intake and then there is a rod up to the carb so there are a bunch of variables there including how thick the base gasket is. 


Look for fat vacuum lines running to the passenger side fender.  These would be for the vacuum powered air compressor for the rear air shocks.  The feed line tees into the PCV line.   Its possible to have the compressor fail in a way that turns into a big vacuum leak so its best to start off with that disconnected till some other bugs are worked out.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason