Cadillac Owners Forum banner

1 - 7 of 7 Posts

·
Registered
Cadillac
Joined
·
100 Posts
Discussion Starter #1
Hi there.

Recently installed MSD 6a onto stock points distributor with pertronix & flame thrower coil.

Car was running better than it ever had.
The car is a 1969 Cadillac deville with a 472 7.7 liter engine.
My timing light hasn't worked in ages so I have been timing by ear and test drives.

Hot starts were always laboured and the stock starter died.
I replaced it with a powermaster high torque starter.
Hot starts are still hard unless I turn the timing way back, and then the engine is really sluggish / mileage is crappy

I then changed the dist to the MSD unit designed for the 500 472 engines.
Also installed MSD wires & coil.

NOW - car idles better, but there is a really bad vibration, shudder, stumble coming off idle to cruise speed - maybe 800-1200 RPM. Engine sounds really laboured. This doesn't occur when revving the car in park -Vac advance?

Also the vacuum advance can bashes up against my AC compressor - is this normal?

I have experimented with spring combinations but am reluctant to do so now, as the engine sounds like it doesn't like anything I'm doing and It sounds like I could kill it by messing around too much.

And if I may ask a really dumb question please :thumbup: .....
What does pinging sound like? Is it a vibration or a loud knocking sound?
When I have the initial timing too advanced, under acceleration some slight fuzzy sounding (sorry best way I can describe) vibrations can be heard increasing with rpm. It is hard to hear cos the engine in this huge boat is so quiet and far away !

Apologies for the long post, it's a long story.

Cheers

Jon
 
K

·
Guest
Joined
·
0 Posts
You really should be working with numbers here and not sounds and feelings. Research timing curves on the net and get yourself an adjustable timing light. Start with the guaranteed to work setup and then adjust to achieve better performance. Also, you really have to monitor your fuel curve when playing with engines. Tinkering takes real tools to do correctly. A wideband 02 sensor, an adjustable timing light and a stopwatch and you will be all over it.
 

·
Registered
95 FWB 81SDV 96 FWB 94 Fleetwood
Joined
·
1,510 Posts
If the vac advance is hitting the compressor, I would say you are off a tooth on the distribtor...
 

·
Registered
1969 Coupe DeVille, 1972 Sedan DeVille
Joined
·
159 Posts
If the vac advance is hitting the compressor, I would say you are off a tooth on the distribtor...
I second drmenard's idea. I guess you just got to put those huge HEI distros in just right, or you run the risk of not being able to adjust your timing. I put in a DUI distro, and my vacuum advance was close to hitting against the AC compressor. This was after a very smart mechanic buddy had set my timing by ear/feel. Sometime later when he wasn't around, I discovered the timing was way out [with a timing light], and I couldn't get it where I wanted it because it was hitting the AC compressor. So I had to adjust it by one tooth, like drmenard said. Boy did it smooth out when I dialed the timing in at 10* to 12* BTDC...
 

·
Registered
Cadillac
Joined
·
100 Posts
Discussion Starter #5
Thanks for all your replies

Well I have been on to MSD and I reckon I have the initial timing too advanced, I have been retarding it slightly and the hesitation and compressor-hitting problem are going away.

Shame, hope I don't loose all that low end power. It moves the car from a standstill like it weighs nothing.
 
K

·
Guest
Joined
·
0 Posts
Thats because the engine likes the advance in lower rpms. Check this thread. The module is a AC DELCO # D1941.
 

·
Premium Member
2006 STS V8 AWD, '95 Ford Ranger
Joined
·
28,973 Posts
Model T Fords had msd ignition. I came across a Model T coil the other day while going through my junk. About all that's different about the Model T is that it didn't have a distributor but had a separate msd coil for each cylinder and a timer. Spark advance was a lever on the steering column.
 
1 - 7 of 7 Posts
Top