351W will not run right

Reply Subscribe

Thread Tools

Search this Thread

Jul 17, 2012 | 05:57 AM

79CrewcabCummins

Thread Starter

New User

Joined: Jul 2012

Posts: 3

Likes: 0

From: Craig, CO

351W will not run right

Hi, I really need some help with this one. I have a 351W in a 79 F150 4wd with the NP435 and NP205 that I completely rebuilt with new pistons, cam, lifters, bearings, timing set, etc, etc. I can not get the hesitation out of the mid range. It is so bad that it will not rev beyond 2000rpm driving in any gear or even in neutral. I have tuned the carb(Carter AFB) repeatedly, changed the ignition components out(brain box, pickup, distributor, ign wire from switch, plugs, cap and rotor). I changed the carb to a Holly that works just fine on another 351W. I re-torqued the aluminum intake twice after running it several times in-between. I checked compression and all are 120-121 across the board. Its getting plenty of fuel(new filters and I hooked a hose to fuel pump from a 5 gallon gas can just to be sure) Its the same with or without air filter in place. I have adjusted the timing from 2* to 18* with no change in the problem. I'm at my wits end here

, the next step to me seems to be to pull the intake and heads and look for something not right. Any advice or ideas would be greatly appreciated!!!

Jul 17, 2012 | 08:18 AM

Conanski

FTE Legend

Joined: Jun 2006

Posts: 31,930

Likes: 1,499

From: Ottawa, Ontario

Sounds like an ignition problem, have you tried another ignition box or distributor?

Jul 17, 2012 | 04:37 PM

79CrewcabCummins

Thread Starter

New User

Joined: Jul 2012

Posts: 3

Likes: 0

From: Craig, CO

Conanski, I have tried 2 different DSII boxes and after that I tried an MSD 6AL box. I also tried 2 different distributors one was new withe the rebuild the other from another 351W that runs just fine.

Aug 2, 2012 | 05:58 PM

79CrewcabCummins

Thread Starter

New User

Joined: Jul 2012

Posts: 3

Likes: 0

From: Craig, CO

Well I found the problem, PO had some issues with the wiring it seems and the harness to the distributor had the wires cut and spliced. Only problem was 2 wires were backwards. I swapped them back orange to orange and purple to purple and all is well. The splice was covered up by loom and I didn't see it until today. I'm not sure why it made a difference or why he cut and spliced them backwards in the first place? Any ideas?

Aug 3, 2012 | 07:36 PM

BaronVonAutomatc

Postmaster

Joined: Mar 2005

Posts: 2,949

Likes: 6

From: Earth

People are morons. I mean, geez, those wires are color coded. A toddler can match orange to orange.

On the plus side it kept the revs down until she was broke in real good.