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ALANSD 05-04-2002 04:28 PM

7.4l tune-up
I started out the day out to tune up my 454. I have worked on many engines, but this is the craziest distributor cap-coil arrangement I can remember.
As I took it apart I was amazed at the way the whole thing was made....the coil mounted in the cap top, the wiring plugged through it, and the way it was set up. Took a short time to replace, but I was careful to set it up correctly, wiring , rotor,and all.Missed replacing the condensor, but I will next time.
Then to the plugs...after crawling behind the front wheel, the plugs are very accessible...unfortunately neither of the 4 spark plug sockets I own would work, as the recess in the block is too small- so I guess a visit to NAPA is in order, tommorow.
I noticed while under there that the shocks are held on by what is not actually a "nut" but some threaded ring at the top? Any suggestions on taking it off? Vise grips?
The feel of turning the key to start the engine after replacing the cap and all is a charge, especially when it runs so smoothly.
The lousy rain in Atlanta is really holding me back on all this..

davidz71 05-04-2002 10:20 PM

The is the GM HEI High Energy Ignition system. I had one on my '77 K-5 Blazer. It was a good system while I had the truck (154,000 miles). I would think on a motorhome it would pay to not only have a spare coil for the system but also another part (can't remember the name of it right now) that fits inside the distributor. It is black and has blade connectors on each side so that the whole thing looks like a U with the edges canted outwards. It is some kind of control module and it went out on me just as I was passing a car. Did I feel stupid. Since it was late on a Sat., they could not get me another part but did have a used one on the bench they let me have. That truck still had the part in it 30,000 miles later when I sold the truck. Craig

FrankR 05-05-2002 12:42 AM

GM Engine performance Ignition
Modern engines are good engineering but there are lots of improvements. A company named MSD makes some really great improvements for gas engines. They make a timing device that allows the driver to control the timing eith 15 degrees later or earlier. Big hill, hard pull, retard the timing . Long flat or down hill, advance the timing for free horsepower. The coil in the cap GM uses is great for an all in one unit but the seperate coil has some advantages, as the complete unit will operate cooler. Cooler means the ignition modual will last lots longer. An action that hastens modual failure is dialectric grease under modual. The grease is slowly lost over time and is a path for any heat to be absorbed by the distributor housing. Using a divorced coil means a really "hot" coil can be used. A big power thief is a bad timing chain. Most factory chains are streached at 60-75K miles. Oh yeah, the engine is smooth, but power is down. Frank

PeterH-Airstreamer 05-05-2002 07:50 AM

The little flat u-shape thing in the buttom of the distributor is called the ignition module, an electronic replacement for points. Its not a bad idea to have a spare module and capacitor on hand.
When opening the distributor, its a good idea to check the mechanical advance mechanism, since I have seen it frozen before. The Jacobs system completely removes the coil out of the distributor.

davidz71 05-05-2002 01:23 PM

I had problems with the mechanical advance freezing and pulled the distributor twice to clean it up so that it was free to advance. I don't remember what I did the last time but whatever I lubed it with seemed to work.

I had the Jacobs Ultra-team on my '92 Chevy Z71 SB 4x4 and it really helped the low end torque as well as startup during cold weather. When this truck was rolled by my then 17 yr. old trying to miss a deer, I pulled the unit out. It went onto a '92 Camaro RS that replaced the Z71 last August and now that he found a '90 Chevy 4x4 Sport with Z71 pkg. it left the Camaro and is on that truck. I'd say it is making the rounds. Since it has a hotter than stock coil and we mounted it each time on the fenderwell, we eliminated the heat factor which you mentioned. I work for a State of TN. gov't agency and we had an old Dodge sedan that refused to restart after driving for 20 minutes or so. The coil was mounted on the manifold and I kept telling them that they needed to move it to the firewall to prevent the problem. They never did and got rid of the vehicle later on. Craig

ALANSD 05-05-2002 02:26 PM

Man, I already wanted the Jacobs, now more than ever...
two more quetsions for you 454 fans-
-lubricating the mechanical advance? What did you use, I cleaned mine up, as it had some surface rust, but did not really lube it with anything.
-Do you have to take off the individual heat shields on each spark plug in order to pull them? My sockets won't go around the plug as it is..thanks again

FrankR 05-05-2002 11:28 PM

Chevy engines are easy and strong
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There is probably no other engine that has been so modified or raced as the Chevy big and small block. Both of these engines use the same distributor. There lots of options for longivity and power enhancement. A distributor is merely a very reliable switch. Every RPM requires a switch to operate. The modern switch is a few transistors. The weakest link of transistors is HEAT. Ya know that grease is necessary under the ignition modual. The distributor is driven by the end of the camshaft, and the distributor drives the oil pump. Distributors can be improved in many ways. The coil maybe changed for more voltage to fire the spark plugs, the timing curve maybe changed to produce more power under different conditions, and timing maybe changed to meet varing load conditions. Picture is look into HEI distributor... Frank

FrankR 05-05-2002 11:37 PM

Must carry ignition part for GM engines
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An ignition modual is required parts for any RV. Learn to change this important part. With a little training, you will never be on a hook. Get one for your engine. Frank

Jim Clark 05-06-2002 08:15 AM

Frank I recognized that part immediately. That is the part that failed in my 80 Firebird and left me stranded TWICE. I do remember that it would fail once and then I could get the car restarted and a week later it would completely fail.

My question is failing then restarting and then doing a complete failure a characteristic of impending doom.

ALANSD 05-06-2002 10:43 AM

I guess I need to carry an ignition module on my next big trip. What about the condensor?
Did I miss it- what lube to use on the advance mechanism?

davidz71 05-06-2002 10:46 AM

That definately looked familiar.

Strange, I have always heard that when the ignition module went bad it went all at once like mine did. Anyway, instructions in my service manual said to make sure that I used plenty of diaelectric grease when the module is put back in to insulate it from heat.

PeterH-Airstreamer 05-06-2002 09:31 PM

Alan, I just spray the mechanism with WD-40 when I open the distributor. If you get a spare ignition module, install the new one to be sure you have a working replacement.

FrankR 05-06-2002 09:46 PM

Distributor maintence
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Hey Peter ya give good advice. WD40 is good stuff for the advance shaft. The advance weights have plastic bushungs at the pivots that require NO lube, also the weights ride on plastic pads. One small correction is the dielectric grease allows a path for the distributor body to absorb any heat from modual as unity is very heat sensitive.
A little tip....After washing or power washing an engine..and it will not start...... open distributor cap and spray WD40 over everything inside cap and all Take the plug wires out of cap and spray sockets and ends........ Engine will start immediately. WD40 displaces water, every time. Factory weight in picture. Note plastic bushings, Frank

PeterH-Airstreamer 05-08-2002 06:52 PM

Yeah, Frank, so I decided to follow my own advice and installed a new ignition module.
Guess what, I barely made it around the block @ 7 mph. The new module was bad. Funny, huh?

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