Hard miss in a 400

Posted By: dogdays

Hard miss in a 400 - 11/19/12 11:28 PM

I had the engine apart and it had a stock type timing set so I just to be "making it better" swapped in a double roller set and put it in the 4 degrees advanced slot. Keep in mind that it was a running engine and nothing else changed. Put the engine back together, stabbed in the distributor, turned it to around the right place and the engine fired up. But it has a hard miss in one cylinder. The plugs are new, the ignition wires are new, every other cylinder runs just fine, just not the "missing" one. It is not carburetion either.

My fear is by advancing the camshaft I messed up the rotor phasing. I'd hate to have to pull it down to change the timing set.

Any suggestions? I do have an extra distributor cap into which to drill a hole.

R.

Posted By: GTX MATT

Re: Hard miss in a 400 - 11/20/12 12:23 AM

Is the firing order correct? Did you check the timing? Assuming you installed the timing set properly its one of these. If you put the distributor back in the same location as before the timing is likely off.

If its not firing order or timing you goofed something with the timing chain install. 4 degrees shouldn't make the engine miss, but you could have read the marks on the adjustable crank sprocket wrong.

EDIT: I see you did not check the timing. I can almost guarantee with 99% certainty you need to adjust the timing.

Posted By: Cab_Burge

Re: Hard miss in a 400 - 11/20/12 02:15 AM

Quote:

I had the engine apart and it had a stock type timing set so I just to be "making it better" swapped in a double roller set and put it in the 4 degrees advanced slot. Keep in mind that it was a running engine and nothing else changed. Put the engine back together, stabbed in the distributor, turned it to around the right place and the engine fired up. But it has a hard miss in one cylinder. The plugs are new, the ignition wires are new, every other cylinder runs just fine, just not the "missing" one. It is not carburetion either.

My fear is by advancing the camshaft I messed up the rotor phasing. I'd hate to have to pull it down to change the timing set.

Any suggestions? I do have an extra distributor cap into which to drill a hole.

R.

On all the three way crank gears I've seen or used have two marks for each location, one directly above the keyway and the other one to the left of that one on the outside edge off the gear by the teeth, which one did you use

Posted By: Oyvind Mopar

Re: Hard miss in a 400 - 11/20/12 10:38 AM

Advancing gives less valve to piston clearance. Could be a bent valve? Check the compression.....
Normally a stock 400 should tolerate anything here.... But you did not tell about the internals in this engine. Hope it is nothing serious.

Posted By: Oyvind Mopar

Re: Hard miss in a 400 - 11/20/12 10:42 AM

Forgot one thing which is more likely: The cam has moved axially, and one of the lobes hit and lift on the wrong lifter. That could happen, and has happened, although not very often on Mopars. Easiest is to pull the intake, valley pan and look for it. My

Posted By: dogdays

Re: Hard miss in a 400 - 11/20/12 07:46 PM

Thanks for the responses. Here are some clarifications:

0. I live 600 miles away from the truck, am trying to get it to run so my wife can have something to haul dirt.

1. The engine starts and runs just fine, except for the consistent miss on the one cylinder. I am bringing a timing light with me on my next visit to make sure the timing is closer than in the ballpark, but i'm sure it's within 10 degrees of where it's supposed to be.

2. The engine is very low compression with a stock cam and there's no way a valve hit a piston.

3. The engine was disassembled in a hurry. I was trying to change head gaskets and clutch on a long weekend. I ended up taking the engine out due to some problems with the bellhousing. Also, the engine had to be turned over a few times to get bolts accessible. I know how to put a distributor into an engine that has been completely apart.

I will try to be honest and tell you what the problem really is when I find it. In the mean time, keep those ideas coming!

R

Posted By: BBR

Re: Hard miss in a 400 - 11/20/12 08:46 PM

Quote:

the ignition wires are new

Hey Rich!

Just because they are new does not make them good!

Clip the timing light's inductive lead over the dead cylinder plug wire and see if it is indeed firing. I'd swap plugs around too to rule out a new dead plug.

Posted By: rickstershemi

Re: Hard miss in a 400 - 11/20/12 09:15 PM

might want to pull the dizzy and see if any of the reluctor fins are broken off.....this happened to me on a brand new MSD unit...one cylinder was dead cold....????

Rickster

Posted By: dogdays

Re: Hard miss in a 400 - 12/03/12 07:10 PM

Keeping this thread alive...I was at the house for a week and didn't lay a hand on the engine. Too long a list of things to do before my daughter's wedding.
Thanks for the input. The distributor is the same one I took out.
R.

Posted By: B G Racing

Re: Hard miss in a 400 - 12/03/12 09:58 PM

Did you try a compression test on the one cylinder or check the plug or wire?