Engine Problem Challenge
Senior User
Joined: May 2006
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From: Edmonton, AB
Out of curiosity, tell us about the spark plug wire set that you bought. Is it reasonable quality or is it a cheapie set? I've been burned twice by cheap wire sets, and I will not run anything but Motorcraft wire sets now. I'm not suggesting that you toss your new wires just yet, but if they are a "budget" set, they may not be working all that well . Just a thought.
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Junior User
Joined: Jan 2005
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I am going to try the wire swap idea. These were a premium set from O'Rileys when I put them on. I think I have a racing set that has never been used. It might help me spot a possible bad wire.
The brake idea has been checked and the truck will roll freely on a very slight incline. If memory serves, the fan turns ok but I will check that again.
I have thought of pulling the engine and having it rebuilt, but it tests out alright (compression, vacuum, leakdown, uses no oil, no odd noises). Obviously, this isn't a 460 or a big diesel but it should compare in pulling power to my stock '79 F150 with a 351M.
The brake idea has been checked and the truck will roll freely on a very slight incline. If memory serves, the fan turns ok but I will check that again.
I have thought of pulling the engine and having it rebuilt, but it tests out alright (compression, vacuum, leakdown, uses no oil, no odd noises). Obviously, this isn't a 460 or a big diesel but it should compare in pulling power to my stock '79 F150 with a 351M.
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Joined: Sep 2007
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The 351m was a different engine, made to have a carb on it with a camshaft that had a different lift and duration and timing (emisions were not as tight in'79 as they were in '88) and it was a big block (I think) so you are comparing apples to oranges, even though they are both 351. Plus you are pushing more weight with an f350, even when the truck is empty.
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Joined: Sep 2007
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Also, tell us about the carb. If it is too big there will not be fast enough air flow to "atamize" the fuel correctly. If you do the math (engine size x max rpm /3456), a 351 will only need 609cfm at 100% volumetric efficiency for 6,000 rpm (wich is past redline).
The Holley book tells you to figure a stock engine should run at about 85% VE. The Edelbrock book tells you to go to 120% of that figure. Either way you should not be much bigger than about 625cfm, and the smaller the better for a truck that is going to be running in the lower rpm range most of the time.
The Holley book tells you to figure a stock engine should run at about 85% VE. The Edelbrock book tells you to go to 120% of that figure. Either way you should not be much bigger than about 625cfm, and the smaller the better for a truck that is going to be running in the lower rpm range most of the time.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
True.. the '88 model of the 351w is no monster tire burner, but it should have no problem pushing a 1-ton crew around at better than legal speeds. It should better the '79 motor in power, that was the height of the fuel crunch era so that 351M would have really low compression and a pretty small cam even compared to the windsor. It sounds like from the discriptions that the motor runs fairly well and it trying to go, but something is holding it back. There's not much left besides the transmission, are you sure it was assembled with the right flexplate for the motor, and that it doesn't have issues.
More Turbo
Joined: May 2008
Posts: 585
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Ok how about this (I'm grabbing at straws here), the firing order is designed so that the engine has balanced "power" strokes, if the cylinder that is opposite of #1 is not firing, then you are only running on 7 cylinders, thus no power, when you have it idleing and you eliminate spark to #1 it smooths out the idle because now you are running on 6 "balanced power stroke" cylinders. Look at the cylinder that is opposite (in the firing order) from #1.
Start the engine and begin pulling wires from one plug at a time (don't get zapped), if idle changes when you pull a plug wire then that cylinder is not the problem, put the wire back on and move to the next.
Start the engine and begin pulling wires from one plug at a time (don't get zapped), if idle changes when you pull a plug wire then that cylinder is not the problem, put the wire back on and move to the next.
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Junior User
Joined: Jan 2005
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The carb should be ok, it is a 650cfm. The tranny hasn't been touched except for changing the fluid and filter. Driving it to the shop and the one trip to the hardware store seemed to open it up a little, but not significantly. When the rain stops, I will try pulling wires to check for something wrong again with the ignition, that seems to be the culprit.
I have a new DS2 distributor and module that I gave up on when I couldn't get any spark. I settled on the DUI as am familiar with the GM style and the ease of the one wire hook-up.
This flat bed truck was bought for less I was going to spend on a 16' trailer. I plan on occasionally picking up lumber and things that won't fit in the bed of my '79 shortbed. Not planning on pulling dozers or anything like that with it.
I get more logical help here from you guys than anywhere else. Thanks to all!!
I have a new DS2 distributor and module that I gave up on when I couldn't get any spark. I settled on the DUI as am familiar with the GM style and the ease of the one wire hook-up.
This flat bed truck was bought for less I was going to spend on a 16' trailer. I plan on occasionally picking up lumber and things that won't fit in the bed of my '79 shortbed. Not planning on pulling dozers or anything like that with it.
I get more logical help here from you guys than anywhere else. Thanks to all!!
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Junior User
Joined: Jan 2005
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On another note. Plugging up the air injection ports in the exhaust manifolds with a high temp epoxy putty like magnasteel doesn't work very well. Two of them popped out during my trip to the store. 
I welded up the holes instead.
I welded up the holes instead.
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Junior User
Joined: Jan 2005
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Got home early today and tried the plug wire isolation test. I did notice some results, but they were faint and then three wires had the connectors pull out from the wire. 
Using the 1-3-7-2-6-5-4-8 firing order, I noticed no change at all when pulling #6 and barely a spark, although there was an intermittent spark jumping to the plug. # 5 had a super spark, but not a significant engine idle change. Same with #7. The others had various spark sizes jumping from the wire and seemed to make the engine idle change some.
I had to stop when the connectors came out of the wires. That has not happened to me before with such a new set. Must be the wire set I'm thinking.
If I throw care to the wind and get a very-very good set, what brand / part number does anyone recommend? The factory wires seemed to fit funny anyway. Some were almost too short and the #7 & 8 seems to have alot of slack. Does the 302 and 351w use the same wires?
Using the 1-3-7-2-6-5-4-8 firing order, I noticed no change at all when pulling #6 and barely a spark, although there was an intermittent spark jumping to the plug. # 5 had a super spark, but not a significant engine idle change. Same with #7. The others had various spark sizes jumping from the wire and seemed to make the engine idle change some.
I had to stop when the connectors came out of the wires. That has not happened to me before with such a new set. Must be the wire set I'm thinking.
If I throw care to the wind and get a very-very good set, what brand / part number does anyone recommend? The factory wires seemed to fit funny anyway. Some were almost too short and the #7 & 8 seems to have alot of slack. Does the 302 and 351w use the same wires?
Junior User
Joined: Sep 2007
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I worked at a performance center in an autoparts store, and I began believe that msd wires are just about as good as they come. I'm sure you couldn't go wrong with some mallory's; and accells aren't tooooo baaad. I have never had a problem with stock autolites though (if you want to go budget). Most guys here will tell you to go with MOTORCRAFT and I could not disagree. Just stay away from the autozone generics.
More Turbo
Joined: May 2008
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Using the 1-3-7-2-6-5-4-8 firing order, I noticed no change at all when pulling #6
Senior User
Joined: Dec 2007
Posts: 199
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Something else you can do is point a infrared thermometer at the plugs while it is running. The dead cylinder will have a cooler plug compared to the others. It might be something stuck in an intake runner too, defueling that cylinder, or a chunk of something in the exhaust.
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Junior User
Joined: Jan 2005
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As always... thanks for all of the ideas! This past week, I bought the best set that O'Riley's sells...B&W. No change in performance when pulling the wires.
I will see if I can get my hands on a thermometer to check cylinder temps. Is there an easy way to check to see if the intake is blocked? It was used and may very well be restricted with something. If there is something else wrong with a cylinder, shy of compression and leakdown problems...what else could be wrong?
I am debating on finding another used engine or even having the existing one rebuilt, but I am dealing with money (like everyone else) and wanting to have this thing up and running quickly!
I will see if I can get my hands on a thermometer to check cylinder temps. Is there an easy way to check to see if the intake is blocked? It was used and may very well be restricted with something. If there is something else wrong with a cylinder, shy of compression and leakdown problems...what else could be wrong?
I am debating on finding another used engine or even having the existing one rebuilt, but I am dealing with money (like everyone else) and wanting to have this thing up and running quickly!