: 75 coupe deville 500 cu in upgrades tips?



jcunn2d
06-27-12, 09:22 PM
Anyone out there in caddyland have any tips on upgrading a 75 500 motor? Any performance tips would be greatly appreciated.

BRUCE ROE
06-27-12, 10:29 PM
1st things are get a replacement timing chain, a good dual exhaust
(without that terrible cat converter), and convert the trans to switch
pitch. These will improve economy & performance, a lot. After that
are dozens of possibilities, which trade off economy, expense, and
driveability. What do you want? Bruce Roe

jcunn2d
06-28-12, 04:52 AM
I'm looking to get more horsepower without compromising the comforts of a Caddy. Your advice is much appreciated. Thank you!

cadillac_al
06-29-12, 10:43 PM
That Bruce must be a glutton for punishment lol. I wouldn't pull out a perfectly good engine to change the timing chain unless there was some other reason to pull the engine. It would be a bear to do it in the car imo. Those timing chains are wimpy but they will still run a long time with the plastic off them. I took one out of a Chevy 400 last year with 120k on the clock and all the plastic was still on the cam sprocket!!

I like the idea of converting to switch pitch. I didn't know you could do that. Can you do that to any th400? Is there a kit for it?

I would just give the old 500 a good tune up, make sure the secondaries open on the carb and replace the fuel filter, and give it a nice dual exhaust.........and the switch pitch if it is easy.

BRUCE ROE
07-01-12, 02:16 AM
If your car has a TH400 trans, it can be converted to switch pitch. My
first conversion reduced 0-60 by a whole second, no other changes.
And everything else was smoother & more responsive, with a slight
improvement in fuel economy. This requires an electronic switch pitch
controller to complete the picture. Trans parts are best obtained from
a 65-67 Buick, Olds, or Cad trans; upgraded torque converters are
available, as is the controller.

I saw a request to improve performance of a 75 500. The first step will
always be, get all periodic maintenance up to date. And that means
replacing the OEM timing chain. Everyone may do what they want with
their car. You can chose when to replace the chain, or THE CAR will chose
when to change it for you (at the side of the road). Drive you car around
the block, and tow it home when it breaks down. Do what is easy, or do
what needs to be done. Accept degraded performance, or have it run
better than new. If it is fuel injected, we are talking preventing a major fire.
Do your maintenance, and drive it coast to coast. My 77 drove to Canada,
Florida, California, and New Hampshire in recent times, trouble free.

I read, improve Cad performance while retaining Cad Comfort: exactly my
method. My suggestions are a good beginning, no Cad compromises.
Do these, do all maintenance, then consider more drastic measures.

I have changed a lot of timing chains without pulling the engine, but
it's about as easy either way. Pulling an engine isn't a big deal; doing
an engine overhaul is a big deal.
good luck, Bruce Roe

drmenard
07-03-12, 03:57 PM
I agree the Bruce 100%... the timing chain must be changed after all these years.. Its the years that make those chains loose there plastic not the miles..And dont buy a cheap chain, get a good cloyes chain and sprockets.. NOT the cheap $40 set get the $80+ set that you can advance your cam timing 4 degrees..
Now Bruce... Don't you remember in the late 70's they took out alot of metal out of those TH400 cases and they can't be turned to a switch pitch...Don't know for sure what year they did that , but if I was going to do a switch pitch look for a 75 or earlier case...Or take it apart and look..

BRUCE ROE
07-03-12, 09:42 PM
I agree the Bruce 100%... the timing chain must be changed after all these years.. Its the years that make those chains loose there plastic not the miles..And dont buy a cheap chain, get a good cloyes chain and sprockets.. NOT the cheap $40 set get the $80+ set that you can advance your cam timing 4 degrees..
Now Bruce... Don't you remember in the late 70's they took out alot of metal out of those TH400 cases and
they can't be turned to a switch pitch...Don't know for sure what year they did that , but if I was going to do
a switch pitch look for a 75 or earlier case...Or take it apart and look..

Are you saying, all those engines need the cam advanced 4 degrees? Better get that on my list.

I believe that I was able to convert a '77 TH400 to SWP. Perhaps about 1980 they took out the
metal for the stator oil passage. But a case swap will take care of that. I heard someone
figured out how to avoid the issue, by a modification to the pump assembly. But I never
got the details, or studied it myself. So much to do... Bruce

drmenard
07-04-12, 09:47 PM
From what I am told that all the stock cams are ground retarted so to have a smooth idle ...so if your running a stock cam best to go with the 4 degrees advanced..