400SBC Running Rough Help...

[Big Blzn]

I thought I fixed the problem with my engine running rough last week but when I pushed and tightened up all my plug wires it seemed to help initially. Now it seems to be a bit worse. It is idleing rough and when I give it some gas it acts like it is not running on all cylinders or missing and sputters a bit throughtout all gears and RPM ranges. No backfires to speak of. All the plug wires seem to be on tight. It doesn't die or stall too bad. Could it be the timing (HEI), which I know nothing about or how to adjust? New fuel filter installed about a month ago before last wheeling trip. It seems like it has to be something in the electrical system which makes me think it's the HEI. What should I check as I'm kind of at a loss? Being that I'm not the best mechanic in the world should I just take it to a local shop or could someone give me the quick version on adjusting/checking the timing etc. Thanks in advance fellas.
Hoby

 

[Disciples Performance]

could be your coil packing it in on the top of the cap on the HEI dizzy happens sometimes causing a miss

 

[k2mslskier]

Sounds like what I went through last month. Turned out to be a dead cylinder, no compression. My mechanic figured burnt or bent valves. So instead of spending money (that I didn't have)on a valve job I just swapped in the extra motor I had sitting around.

 

[troutbum_mt]

If it were me, I'd start by checking the plugs and work my way to the distributor. Could be a bad plug, plug wire, even moisture or crud in the distributor cap. If things look bad inside the cap, it could be time to replace the cap and rotor. As far as adjusting the timing goes, I just did a quick search and came up with this for you:

http://www.enginefactory.com/high_performance_hei_distributor.htm

Scroll down to step 10 or 11 and follow those directions on how to adjust the timing. According to my Chilton's, the timing for a 400 SBC is around 4 degrees before top dead center.

Hope that helps some.

 

[greg mgm]

My truck acted the same way which turned out to be a couple plug wires that were slightly burned which were resting on the smog injecter tubes. The wires were apparently arcing to the tubes....enough to cause the engine to run rough.

In any case, like troutbum said, start checking the plugs and wires first. Look over each one from top to bottom, then check the cap and rotor, and the connections to the cap. Simple stuff first.

Let us know what you find.

 

[Big Blzn]

My truck acted the same way which turned out to be a couple plug wires that were slightly burned which were resting on the smog injecter tubes. The wires were apparently arcing to the tubes....enough to cause the engine to run rough.

In any case, like troutbum said, start checking the plugs and wires first. Look over each one from top to bottom, then check the cap and rotor, and the connections to the cap. Simple stuff first.

Let us know what you find.

Fellas, I appreciate the help so far. This morning I dug into the wires head first and found that the MSD plug wires I repaced several years ago need to be replaced again. looks like some of the wires have been contacting the headers in several places (arching/burning) and some have started to crack a bit in the areas next to the manifolds because of the heat. Looks like I'm going to have to buy some of those spendy plug boot covers for each plug wire too.This is where I'll start but I can't really do anything til after Thanksgiving. Leaving in 3 days to go dear hunting for a week. Please keep the feedback coming as this may not fix the problems. Thanks again for the replies thus far.
Hoby