My engine is a 1983 Windsor. I've owned this truck for 5 years now. I have never driven it much, as it is a gas pig and I like being able to pass gas stations.

A couple of years ago, the Duraspark III system started giving me alot of trouble. The bearing in the distributor itself (which has no electronic parts inside) decided to freeze up twisting the shear pin off the bottom of the shaft.

I replaced the distributor with one that was set-up for a 1978 351W using a duraspark II system. It has a vacuum advance, etc, that the other distrib did not.

This truck had a variable venturi carb set-up at one time, but by the time I got it, the PO had replaced the VV with a 500cfm Holley carb. When I got the truck, I had the Holley rebuilt, and had an automatic choke installed on it from a kit that my Holley supplier got for me. It ran alright, but didnt have any real pep.

This weekend, I replaced the 500 cfm Holley with a 600 cfm... both 2 bbl. jobs, to see what might happen. The truck that had the 600 on it got my 500 cfm Holley installed on it just to see how it would run. Surprisingly, the 500 cfm carb ran great on the other truck, also using a 351W. My truck with little power, and no noticable improvement with the larger carb.

My truck seems to have lots of low-end torque, but when I get on it, I can feel the torque growing weaker the harder I press the gas pedal... feeling like it wants to backfire, but doesent.

I tried advancing the timing just a hair. There's no way to time this engine precicely, as the DSIII system didnt need timing marks on the damper pulley. I tune it by ear. Too far advanced, and the starter bucks, too far retarded, and I lose all the power that I have, which is not much. There is no happy medium. At high speeds, I get spark knock under moderate loads at all adjustment settings of the distributor.

The fuel system has been checked from the tank to the carb. Original fuel pump is pumping at capacity and at the correct pressure. New fuel filter, too.

Here's something to think about. Any chance this truck with 188k on it has possibly jumped time? When I use a timing light and shine it on the damper pulley, the marks dont move around like an old Pontiac that I had did back in the 70's, and did jump time. The marks are rock steady at all speeds. These marks are applied with a piece of chalk by me just to get some kind of indications.

I can apply vacuum to the advance on the distributor and the marks move accordingly. I just cant get a happy medium, and there is less than a quarter of an inch leeway in the movement of the distributor between running almost OK, and getting weak.

Anybody got any ideas before I end up having to rip the front off the engine? I sure dont want to do this.

I am still using the 1983 firing order for a 351.

Thanks for any ideas. The truck has run just like this ever since day one, 5 years ago.

Bruce

PS: ALL of the smog systems are disabled, and were messed up long before I got the truck. All vacuum lines are plugged or removed. Its running a dual exhaust set-up with dual cats and flow-thru mufflers. It shows no sign of overheating at any time. THANKS! Bruce

 

So, you're saying the timing marks you drew on don't move (i.e. no mechanincal advance) as engine RPM increases? If so, I'd wager that's your problem. IIRC, static should be ~8-10* and total advance should be ~30-32* at 3,000 rpm.

At this point, I'd also recommend a balancer with timing marks so you can tune that engine properly.

 

I do know that the replacement distributor has the weights in place.

I mis-spoke previously. The timing marks do move as RPM increases, and do not bounce around. Thats what I ment by stating that the marks were rock steady.

As for the balancer, every 351 I've seen around here has a totally different pulley set-up from mine.

I've been told that a 302 balancer is different, but I did find one that had the same pulley arangement on it.

If I retard the timing enough to stop the kick back on the starter, and I have replaced the starter with a new one, not rebuilt, the engine loses all power. Advancing the timing always makes it pull better, but then it has all of the spark knock at 2500 RPM and higher.

I've had one other truck, a 300 six, that I could time by ear, and it would run like a top. Other V8's I've been around had alot more leeway in the distributor timing location than this one does, and a Mercedes Benz 2.3 engine was within 2 degrees of being right on the money when I checked it with a timing light after adjusting the distributor after I replaced it. I dont always adjust things by ear. I promise!

Thanks for the comment. I'm going with any leads before I pull the timing cover.

 

I can think of two things that you can do. 1) Change springs in dizzy to adjust how cent. advance works, heavier springs will extend rpm for full advance. Plus Your Duraspark may have a limiter stop. 2) Vacuum canister may have an adjustment accesed w/ allen wrench thru vac. tube hole. Read this. The Ultimate Duraspark Distributor Timing Guide. - Four Eyed Forums

 

Thanks. This is good reading.

Today, messing with the 351 that I have here to use as a reference, my friend and I noticed that there is almost a full inch of timing adjustment on the 1982 351 engine (that currently has my 500 cfm carb bolted to it.) This is why I am interested in knowing about the timing chain troubles. This truck went through some rough times before I got it. It was not running at all. The gas tank had dirt in it, and the fuel filters were all clogged. I worked on it for about 5 hours before it would start. Then, I discovered all the DS III issues that were starting to happen.

Thanks for the DS timing guide link. I printed off a copy.

My guys at the parts house are pretty sure that the springs in my DS-II distributor are OK for use on my engine. Also, this engine ran just as bad with the old DS-III system in place. Of course, it was dead by this time. No O2 sensor, lines disconnected, etc, etc...

The saga continues.

Bruce

 

I found a limiter stop last night on the vacuum advance. I removed it, but it doesent change the torque weakness. Good call, though. Never thought of that one before. Now, there is a larger swing of the timing than before.

I'm dreading having to pull the timing cover. I had colon surgery a few years back and I cant lay over the front of the truck to get at the motor anymore without alot of discomfort.

 

Reread your post and was wondering how you determined your timing marks? If you haven't already, bring #1 to TDC on compression stoke, rotor will be pointing to #1 plug wire, mark your HB for a good ref. point. Of course this assuming you even have a pointer.

 

No pointer either. I did find #1 by bumping the starter until I was on the compression stroke. Installed distributor.

Remember, it was acting this way before I changed over from the DS-III to the DS-II systems.

 

Maybe it's just worn out. 188K is a pretty good run. Have you done a compression test? What sort of vacuum are you pulling?

 

At 188K miles I wouldn't expect miracles. With that said, I have a identical setup to yours. '83 F-150 XLT with the raging 139hp 351w. Mine still has the DS-III on it. It also came from the factory with the VV card but someone had replaced it before I bought it with a 80179 325cfm holley 2bbl. Otherwise it was bone stock. It has strong off idle torque but runs out of breath FAST. I'm mostly a chevy guy so a lot of what I have found with this truck was new to me. A stock lo-po 2bbl mid '70's 350 chevy will absolutely run rings around this thing, and get better mileage doing it. Tiny carb, tiny valves, tiny ports, tiny cam on a tight 108* lsa, dinky head pipes (they appear to be approx 1 3/4" or maybe 1 7/8") into a single non cat 2 1/2", etc etc...everything is geared towards under 2500 rpm power. Just today I finished the installation of an edelbrock 2181 performer and a 80457 vac sec 600 holley. Low end is about the same but it definately perked up the 2000-4000 rpm power. I am still using the DS-III ignition (at least until this evening when I install my Mallory HEI setup).
My advice would be to do at least a compression test, and preferably a leakdown test. With that many miles you could have a lot of carbon buildup in the chambers that can cause pinging when you try to run as much timing as the engine likes. I would also check for vac leaks as they can make it ping too.

 

UPDATE FOR ALL OF YOU:

This weekend, I have done it all.

Compression is 145 psi average on all cylinders. No vacuum gauge available.


I pulled all of the engine acessories away from the timing cover and removed the cover, harmonic balancer, etc, etc.

Found a severely damaged fuel pump eccentric on the camshaft, along with an un-stretched, undamaged timing chain, and crankshaft gear INSTALLED ONE TOOTH OFF.

I'm replacing the whole she-bang next weekend, weather permitting. I have a cousin that works on industrial engines that noticed the condition of the chain and gears. He said that they looked brand new. I've put 32k on this motor in the 4 years I've had it.

I'm replacing the chain, gears, eccentric, and fuel pump. Its a wonder the pump even worked. The metal on the pump was worn really thin at the eccentric contact point.

I HATE the previous owner of this truck more every time I find more bone-headed problems.

The fellow I bought it from DID NOT do any of this to this truck. He bought it and drove it for about a year. He is totally impressed that I can take it apart the way that I do.

I will update you guys later.

 

I got the engine put back together yesterday with a few issues. I bought the replacement parts from AutoZone.

I had to replace the fuel pump eccentric cam, too. That came from my local dealer.

I got the right chain and gears, but got the wrong gasket set. The nice thing is that my AZ parts guy was getting off work, and ran the correct gasket set by my house on his way home!

I got it running yesterday morning. The new fuel pump seems to squirt alot more gas than the old one did.

There is nothing leaking, and no oil coming out anywhere. The previous owner that did the timing chain didnt use a gasket set. He, or she, just used blue gasket sealer instead. It dripped the whole time I've owned it, until yesterday. Hot new gasket sealer sure smells good.

Anyway, I have a full inch of adjustment play in the distributor now. The starter is turning MUCH faster than before. Acts like it has a new battery, but it doesent.

It will take a few days of tweeking, but I am already noticing that the engine torque is much better, along with no spark knock.

Thanks for the PM comments, guys. Its good to be back among the drivers again.

Bruce