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75 Eldorado Performance Ideas

Started by pplaut, April 04, 2018, 07:00:57 PM

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pplaut

From what I have read, this 500 CI engine was significantly detuned after the oil crisis in 73.
I am considering EFI Sniper conversion.
Is there anything I can do with the ignition?
Assuming I do the above, could the engine itself handle a low boost turbo?
Car runs pretty well, but very sluggish and seems to miss under heavy acceleration (a different problem I know)
Any other thoughts?
~P.
Peer L. Plaut
Head Baldie
Baldmen.Com

STS05lg

Peer,

Here is a good article and there is source in Florida for performance parts.

http://www.hotrod.com/articles/hrdp-9809-500ci-cadillac-big-block-engine-build/

Also some marine engine builders sup up 500s for inboard use.

pplaut

Peer L. Plaut
Head Baldie
Baldmen.Com

TJ Hopland

I put an FiTech Go 600 on my 73 2 years ago.  Its pretty much the same thing as the Sniper.  Before that I had a Megasquirt system I built.   It works fine but don't expect it to solve any mechanical issues like a bad timing chain or other basic mechanical issues.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364

I would check with MTS.
https://cadillachighperformance.com/
Its been a while since Larry was active and  lot of things have changed (for the better)
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

pplaut

Thanks for the feedback. Before I spend any money, I need to do some basic diagnostics. Check timing, etc.
Thanks!
P.
Peer L. Plaut
Head Baldie
Baldmen.Com

bcroe

Quote from: pplaut
From what I have read, this 500 CI engine was significantly detuned after the oil crisis in 73.
I am considering EFI Sniper conversion.
Is there anything I can do with the ignition?
Assuming I do the above, could the engine itself handle a low boost turbo?
Car runs pretty well, but very sluggish and seems to miss under heavy acceleration (a different problem I know)   Any other thoughts?  ~P. 

Don't expect EFI to cure existing problems, or increase power much. 
Your engine most likely needs a timing chain set, and a free breathing
exhaust would really help.  Check out the ignition too, an HEI should
not miss.  When existing problems are cleaned up, the car should not
be at all sluggish.  My 77 Olds with similar compression and weight
to displacement ratio, will do a 91 mph quarter mile. 

A mild turbo will really increase performance, using higher octane
fuel, and now an EFI with electronic spark control might do some good. 
Bruce Roe

TJ Hopland

Besides the likely chain issue the early HEI had a different advance design that was very prone to getting good and stuck so your mechanical advance may not be working as well as the vacuum canister not working with age.   Fixed timing (other than your chain flopping around) really flattens performance. 

That was the first year for cat converters and they were very prone to plugging.  Also if you want to be amused look at the 'manifold' between the 2 down pipes into the cat.   You would not think its big enough to flow a air cooled VW engine.

Some of the 75's also had a wacky 6 jet carb that wasn't well understood.  When they are working like mine apparently was it ran great and got me almost 20 mpg around town.  They only used it on some models some years so there must have been way more that had issues than worked.   

Nothing wrong with EFI as long as you are doing it for the right reasons with the right expectations.  If you or anyone else gets to that point I will be happy to share my experience on the subject.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

pplaut

Thanks for all your advice. I was thinking the CAT could be clogged. I have also suspected the mechanical advance. I have also wondered if it was a vacuum problem. I have replaced every hose I could find so far. I have not replaced the canister. These are all things I need to check before doing any conversion to EFI. :) I would suck to spend all that money and still have a problem. :)

Peer L. Plaut
Head Baldie
Baldmen.Com

76eldo

I have a 76 Eldorado.  When it needed a new exhaust system I put one on from a 71-74 Eldorado, eliminating the CAT and the stupid cast iron box in front of the CAT.

The car looks completely stock with the proper muffler and tailpipe with resonator.  I noticed a big improvement in low and mid range torque.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

The Tassie Devil(le)

Thankfully, I live in a place where there is no requirement for Cats after a certain mileage.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Scot Minesinger

Me too, make sure mechanicals are all correct; timing chain, no vacuum leaks (re-time after fixing vacuum leaks), EGR valve working well, distributor is good, heat riser is not stuck in warm up mode, and etc.  That EGR valve failing really makes the Caddy seem sluggish.

Another issue I read about is the carburetor, if it is a true original then a rebuild by you could work well.  If it has been sent out, apparently their are some unique parts for that year and if some parts are switched performance is degraded.  Then a lot of people use 1976 carbs because of the electric choke, and that may be a solution to getting it mechanically 100%

The main difference between the hot 1970 Cadillac 500 cu. in. (400 hp and 550 lb-ft) is the compression ratio and exhaust.  The other issue is the rating, 1970 was a gross rating, 1975 is a net rating (with accessories).  According to 500cid, on the dyno, a 1970 and a 1975 have about a 10% difference in power all things being mechanically correct and equal.  The 1970 Caddys are heavier than the 1970, so this 10% less power and added weight coupled with higher gearing (2.93 vs. 2.76 for 1975), made the 1975 Caddys seem less capable than the 1970 Cadillacs.

1975 should have the unleaded gasoline hardened valve seats, but make sure you do not need a valve job on your Cadillac.

If you can go after the exhaust as Brian wrote, as that is a bolt in deal. 

Then there is what is sluggish?  I found the 975 Cadillacs in good mechanical repair powerful enough for me, and I drive a 1970 Cadillac in excellent repair.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

James Landi

Not sure what the arrange is for your model year, but on my 72 Eldo, I changed out my Vacuum advance (ruptured) and routed the new one  DIRECTLY to the intake manifold... a much "crisper" throttle response with the advance modulating constantly.    Happy day.   James

bcroe

The final drive ratio on all 68-78 Eldos (and Toronados) was
either 2.73:1 or 3.08:1.  I have never actually found a 3.08.
Bruce Roe

TJ Hopland

Quote from: The Tassie Devil(le) on April 09, 2018, 08:45:50 AM
Thankfully, I live in a place where there is no requirement for Cats after a certain mileage.

Bruce,  you mean where you live its actually legal to remove things like cats after a certain age?   

People say that all the time in the USA but they are incorrect.   What they really mean is most areas don't have any sort of inspection after a certain age.  That is a lot different than saying its legal to remove them.  I think more recently they have even tightened the rules for 'off road' use too.   You used to see that in all the catalogs but I see that wording is gone now.  They must have the lawyers carefully write the descriptions now.       

75 should have the electric choke.   

I don't remember if the 75 had the heat riser, if it does that is a place to loose a lot of power if its stuck shut.   For some reason that was something they went back and fourth on so not every year had one.

I think 75 had the thermal vacuum switch that changed the distributor advance between ported and manifold vacuum.

I think my 73's were still 3.08, not sure when they went to 2.73.   Wasn't there a 3.50ish early like 67 only and a 2.50ish late?   And the EFI cars got a different ratio than the carbs?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364



From what I have read, this 500 CI engine was significantly detuned after the oil crisis in 73.

Essentially the combustion chamber and the pistons were re-configured to allow more power at the lower compression ratios required to meet emissions regs.

I am considering EFI Sniper conversion.

I think you will be very disapointed with this motor if the only thing you do is to convert to FI.  When EVERYTHING is working correctly it is a low speed "torque" monster

Is there anything I can do with the ignition?

The original HEI's were prone to sticking. They can be readily disassembled and cleaned up (bearings, etc).  A high performance module, cap rotor and coil will give you an excellent and bullet proof system.  Be sure to replace the Vacuum advance.  This motor needs lots of vacuum advance to keep cool, run smooth and deliver (12-14MPG) decent fuel economy.

Assuming I do the above, could the engine itself handle a low boost turbo?

Unless you just have a lot of $ to play with, and you are out to try and do some street racing that might not be the best way to go.  Cast pistons might do for a while but longevity will definitely suffer.


Thanks for all your advice. I was thinking the CAT could be clogged.

This is very likely, and when cats were first installed the testing method was the installation of a "test pipe" which was a straight length of flanged exhaust pipe that was installed in place of the converter.  The original owner of my 75 apparently had this test done and they never removed the "test 'pipe".


Car runs pretty well, but very sluggish and seeconnecting rod bolts, installed a very mild (224ms to miss under heavy acceleration (a different problem I know)
Any other thoughts?


I would suggest a compression and a leak down test to determine the condition of the basic motor.  If the rings and the valves are within specs you should have a pretty decent motor if all the above are correct.


If you find the motor itself needs work you have quite a few options, from "mild" to "wild".  When I got my wife"s 76 CDV (same motor as your 75), the motor needed to be rebuilt.  What I did was to use higher compression, flat top pistons (9.2:1 final static ratio) added ARP connecting rod bolts, added a mild (225 degree @0.050 lift) camshaft and the requisite heavier valve springs.  The heads got a slight upsize with SS valves, and the carburetor was rebuilt by Jet Performance to match the specs of the engine. Still single exhaust and no cat.

The car is 15 second quarter mile material and we typically get 16-18  MPG at a steady (cruise control) 70 MPH on these flat Texas highways.

You have got a lot to consider.  First make sure everything is functioning correctly and the motor is okay.  Then decide how much of your children's inheritance you want to use
Greg surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Carl Fielding

#16
Peer , where do you live ? Are you a CLC member ? I HIGHLY recommend you attend the Grand National coming up out of San Antonio , Texas. You will have the time of your Cadillac Life meeting the great Cadillac Family. Do arrive early if possible , and hang out a while after the G.N. One benefit from sticking around , could possibly reward you with a bit of "face time" with The Incomparable "Cadillac Kid". I am sure he will be typically hyper occupied leading up to , and during the event. Afterwards, R&R time on The Kid's home turf might present that rare opportunity. Can't speak for him , but I had the pleasure at the 'Vegas GN. , plus I have happily purchased from him , and speak on the phone from time to time. Multiply the Kid times all the other great Cadillac people , ........................ Hmmmmmm...........???? Oh BOY would I like to go again ! I can't actually see pulling it off , though I absolutely MUST be in the Southwest sometime soon. Problem with THAT one is that I will be driving one of my 400 hp M-Brand Xs. I would have to park 'way 'round back in shame.

Go man , GO ! Go ahead on to thet Texas G.N. You know about Texas hospitality , right ?

I have two modified FWD Eldos. One highly modified for deep exploration into off-road Mexico , the other is probably the fastest road car in the world on that platform because of simple suspension mods. 

                              Oops ! Gotta run to dinner. Bye for now !   - Cadillac Carl

cadillacmike68

#17
Quote from: pplaut on April 04, 2018, 07:00:57 PM
From what I have read, this 500 CI engine was significantly detuned after the oil crisis in 73.
I am considering EFI Sniper conversion.
Is there anything I can do with the ignition?
Assuming I do the above, could the engine itself handle a low boost turbo?
Car runs pretty well, but very sluggish and seems to miss under heavy acceleration (a different problem I know)
Any other thoughts?
~P.

The engines were de-tuned all the way back in 71. Compression ratio dropped by 2 factors; more pollution controls than you could shake a stick at, most of which weren't all that effective except for the cats which negated leaded gas... 1974s were already being sold during the 1973 arab oil embargo, so those are just about the worst for overall fuel economy across the entire domestic lineup. Of course 1975 & 76 were worse performers due to increased strangulation for both emissions controls and attempting to improve fuel economy.

It wasn't until the installation of the on board computers that performance started to slowly improve which finally rebounded around 1993-94, and has improved more since. NorthStar, LT1, and various other maker's engines finally started getting back to early 70s performance levels and nowadays they actually exceed the 1967-70 cars.

But they don't look as good or last as long!

You want to boost the performance of a 71 & later El Dorado? Drop in a 1970 El Dorado engine.
Regards,
"Cadillac" Mike

The Tassie Devil(le)

Quote from: cadillacmike68 on April 09, 2018, 11:37:05 PM
......But they don't look as good or last as long! 
Or sound as good.

Want a good sound?   Then one needs Compression, and lots of it.

The best engine I had for exhaust sound going through a tunnel was the L88 in mt '37 Chev Coupe.   130 Decibels at full noise, with mufflers.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

"Cadillac Kid" Greg Surfas 15364

Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-