I'm having issuses with my 351m stumbling with pretty bad vibrations in drive after I replaced my spark plug wires and spark plugs. I didn't have any issues or anything before replacing them so I'm almost sure it has to be something with the distributor or the wires... I've checked the firing order and I'm almost ceartin it's right, but I could be wrong I guess

Could I have screwed up my timing somehow? I'm kinda stumped because I haven't touched the carb or anything. It does start pretty easily, but it will backfire. If anybody could help me out that would be great.

 

a sudden back fire after plug wire change is a definite wire in the wrong place. i did one from memory and put it in a chevy rotation it would start and run but like crap.

 

Yes, most likely the wires have been installed incorrectly.

351C, 351M, 351W, 400

Firing Order: 1-3-7-2-6-5-4-8

 

Agreed, check the firing order, preferably against what's stamped on the intake. I had a similar issue one time, turned out to be an error in my Chilton's manual (misprint).

Also, I thought 351M and 351W had different firing orders, but I could be wrong. However I thought that was the mistake my Chilton's made - it grouped all 351's into one firing order, when in fact it was showing a 351M, and I needed a 351W. If I'm right (not saying I am), then maybe you wired it up as a 351W and not a 351M.

 

X2 on the firing order. Thats what I would check if prob persists, check that the dist. is stabbed right. I had a 400 that the dist was stabbed 1 tooth off and I put the wires on starting with the "1" on the cab and barely ran. I pulled the cap and the rotor was past the "1" AT tdc. pulled the dizzy and moved it to the proper tooth, retimed it, ran good again.

 

Try putting the old plugs back in. I don't know what kind they are but I have had a cupple of brands over the years that a few were dead right out of the box. The wires you can test with a multi meter. Look at it this way, it ran fine before you changed the wires and plugs, so it's one or the other.

 

Well I can't believe I did it, but I had the #4 and #8 switched. Thanks for the replies guys, I appreciate the help! Live and learn I guess!