[Tiresmoke7]

I am having a problem with my ignition system in my sbc. It is a 355 with 10.7/1 compression,a 252/260 duration @ .050 camshaft and a Holley 750 double pumper with annular boosters.The ignition system is a HEI with an in cap MSD coil,an Accel control module and Accel super comp wires.

Whenever I put new plugs in it runs great for about the first 10 minutes ,then it begins to run rough.The engine seems to stumble and the tach needle jumps around between 1000-800 rpm with the car in gear.

I pulled the plugs and they still look new and they are a nice tan color so the carburator is tuned properly. The car also seems to run great except at idle.

I plan on uprading to a complete MSD ignition. A Pro Billet distributer,6AL ignition box, blaster 2 coil and a set of MSD plug wires.

Do you think this ignition system upgrade will take care of this problem? THANKS !! Mike

 

[DoubleVision]

Although I can`t promise this is your problem, but when I hear the word "Accel" I`d say you found the problem, a majority of there products are junk. I would just wait until the car starts to run rough, then I`d do a spark test, if the spark is yellow it`s weak. you may also see that it`s skipping on occasion.

 

[Tech @ BG]

The problem is most likely going to be either the carburetor being out of adjustment for the engines requirements, or not enough initial timing for a cam this large.

 

[Mighty Mouse S-10]

That sounds like a pretty big cam. What is this in and what do you do with it? What spark plugs are you running?

 

[RCastle]

The MSD setup you are getting is exact to what I run.I like it,the only problems I had wer my fault.I used a bad terminal eyelet for the coil once and it worked loose with the engine vibrations.The second my fault was when I mounted the coil to the firewall,I did not tighten it up enough.It worked it's way down and rubbed the bottom of the coil canister on the back of my valve cover.Eventually it rubbed a hole thru the cannister and let the oil drain from it.I noticed it at tune- up and replaced it,it never broke down but I may have caught it in plenty of time. I would get away from that Accel coil also.

 

[Tiresmoke7]

I am running 20 degrees of initial timing and the distributer is only giving me 16 degrees of mechanical advance for a total of 36 degrees. I am running AC Delco plugs # 41-629. Its in a 78 camaro with a th350 transmission with a 3500rpm stall and a 4.10 rearend gear.

 

[Tech @ BG]

Mike,

20 degrees initial timing should be enough. It doesn't sound like an ignition problem as quickly as you're saying it's happening. A stronger ignition should help with it, but it sounds like your carburetor is out of adjustment. Have you tried leaning out the carburetors idle circuit yet?

 

[bracketeer]

rough idle

Try a 650. 750 sounds too big.

 

[red65mustang]

rough only at idle?

can be a almost broken plug wire or lose/bad plug wire terminal.

while it's rough idling, pull each wire, one at a time while wearing a protective glove.

pull a wire, same rough idle (maybe a little rougher) = bad wire

It runs fine above an idle because it arcs across the fault.

(I don't buy that brand either).......