Not stock, 351W timing

Hey fellas! Been awhile. I rebuilt my 351 last year, put dart heads (185’s) back on with a 260h comp cam. I ended up putting petronix on it. I just can’t seem to make this thing run like I think it should be. Where are you guys setting your initial timing at? I’ve tried anywhere from 6 to 12 degrees. It just seems to always have a miss. I can get it to run decent for about 20 miles then it’s back to the same issue. New plugs, wires, coil, carb. Adjusted and rechecked the valves several times. Also runs HOT, I usually shut it off at 220 degrees. I’ve tried 2 new radiators (2 core, 4core). I’m at a loss with this, and frustration is staring to set in. Any help would be greatly appreciated. Thanks!!!

Looks like you covered most everything. Check your timing chain to make sure it is timed right and not a tooth off. I would put a degree wheel on it so you know for sure that everything is timed correct. On some comp cams they will grind in 4 degree of initial timing so when you think you are at zero actually your at 4 degrees. They don’t list that out on the cam cards very well. Double check the timing and make sure the cam is ground for the 351w timing order and not a 302. New heads? you could have a valve sticking causing a miss. Make sure you have a full 12volts going to the Petronix unit.

I am running a 351 Windsor with a comp cams 268h, I have found that 12 degrees initial with unported (manifold vacuum) at the vacuum advance works great, total advance is approx. 38-40 degrees at 3000 (ajust your idle speed accordingly when you reconnect the vacuum to the distributor as it is going to increase). Mine does run a little warm when compared to stock (about 195-200) during extended periods of idling ( I just put in a new 2 row Griffin exact fit it seems to help) .I think if you advance the initial timing and use full vacuum at the vacuum advance a lot of the issues you are experiencing will go away and the car will run like a different vehicle. If you are running a distributor without vacuum advance, get rid of it and get one with vacuum advance.

That Comp 260 should idle almost completely smooth. Timing sounds right around 10-12. I run as much initial timing as it with start smoothly with after a hot soak on a hot day. If it kicks back, there is too much initial. Some engines I’d run about 18 or so.

A constant misfire? Or running rough?
If you believe it is an ignition mis, with the engine idling you can pull a plug wire off the cap one at a time. If the engine runs worse, that means that cylinder is contributing. Put the wire back on and try the next one. If you pull a wire that doesn’t alter lower idle speed/quality then that is the cylinder with a problem.

How about your timing curve? Is it advancing properly? In this day and age everyone should have a dial-back style timing light. Don’t hope your distributor has the correct curve----verify it and adjust it yourself. Vacuum advance is also tunable. The timing on my 351w is 14 initial with 34ish total with about 8-10 in the vacuum.

New plugs, wires and such. Check the integrity of the wires in the dark, and I mean complete darkness, look under your hood really close at the plug wires to see if any sparks are jumping out. Give your eyes a minute to adjust. Don’t do this in a closed garage to avoid asphyxiation. since you’ll have to get your face down close to the engine while it’s running don’t wear a necktie or hoodie with strings.

Perhaps you are having a carb problem? If your engine is running hot, the fuel may be boiling in your carb causing erratic running quality. Take some pictures of your engine. Take a video of it running.

The picture in my avatar was taken after I learned how to properly adjust timing. Initial, curve, total and vacuum. Proper timing will bring out a lot of pep hidden in your engine.

Thanks for the replies everybody! I will definitely try everything suggested.

I determined my old but new plug wires were bad by pulling one at a time like you suggested. I believe the heat may have killed them. So I got the new wires, that are supposed to be more heat resistant. Installed them and it made no difference. I’ve yet to test them. It’s still winter here… Waiting on warm weather which is expected this weekend :smiley: I’m gonna pull the plugs again this weekend. Would the timing cause it to overheat that much?? To the point I have to shut it off?? Thanks again.

Insufficient airflow is probably the biggest problem with the Cougars. I haven’t experienced timing making a big difference. The exhaust temp would be most affected by off timing. Cooling system performance is where I’d look for overheating.

After rereading your post saying the 260 cam should idle smooth, which it does when thing is running like it should. But when it’s not it sounds like it’s got a full on race cam in it, I guess that’s where I get the feeling it’s got a miss.

Did you install the relay kit with the Pertronix? Had the same issues with my 289, ran great for a while then would start to chug, and wuld eventually die at idle. It would immediately start, but same thing once it was on the Run circuit. Had no idea that the wire feeding the + side of the coil was a resistance wire, and wouldn’t feed the 12 v that my billet Pertronix dizzy needed. Bought the relay kit, installed it, and, presto!, problem solved. Engine is as smooth as a baby’s behind now.

Although I recently reinstalled the XE 256, ran the DE 275 for a while. With your initial timing, If you are running anything beyond stock (cam, intake,exhaust,compression), even mild, that factory spec on your timing should be a distant memory. My combo, while relatively mild, likes 12 deg initial, and 38 deg total advance with the vac advance disconnected (I do run vacuum advance but you should curve your distributor with it disconnected). That 260H should be a VERY smooth running cam in your 351. I would suggest the relay kit for the Pertronix before trying to sort out your combo.

As far as what your combo really likes? mark TDC, if you have a dial back timing light or a digital timing light that tells advance, try this: Hook up a vacuum gauge to manifold vacuum (the port that sucks vacuum all the time). Start your car and set your timing at first to tdc. Slowly advance the timing and make a note of your vacuum reading. Keep advancing until the vacuum stops climbing or doesn’t climb as quickly, then use the dial back to see how much before top dead center you are running at. As a precautionary measure I will bring it back a couple of degrees. This should be what your base timing is. Mark the damper. If you are running a bit hotter cam, and have actually degreed it in, this will be even more crucial as this will also affect what your base timing should be based on when the valves are closed in relation to your piston coming up. The fire should light off just before. I have tried this with all of the cars that I have that you can actually adjust the timing on, all Fords (3.8 Tbird, 300 I6 f150, '68 Cougar 289), and for these cars that are either stock or in the case of my '68 relatively mild, they all seem to like 10-12 deg btdc base timing. Now if I had built the '68 more radical, probably way different than the other two, and a far different advance curve.

Do you have a 1969 or 1970 351W? Timing pointers and harmonic balancers are year specific.

Yes I do have the relay for the Pertronix.

Engine is a 69. I’m assuming the pointer is correct. The engine ran fine until the valve spring broke, hence the reason for the rebuild.

1969 pointer is mounted on the driver side of the engine, 1970 351W timing pointers are mounted on the passenger side.
1969 harmonic balancers have 3 bolts for attaching the crank shaft pulley, 1970 uses 4 bolts.

In regards to the running hot issue, did you install a new temperature sensor in the intake? Most auto parts store sensors have the wrong resistance and will read on the hot side. Have been down the road with this; water pumps, alum rads, etc. on several cars. You need an original Ford sensor or to check get a thermostat radiator cap to verify.

69 It is!

Also, I tried 2 different mechanical temp gauges, it’s running hot for sure.

It could be something as simple as a faulty coil. I had problems with my Pertronix ignition after installing it and it was suggested that I run the Pertronix “Flamethrower” coil instead of the MSD Blaster coil I was using. It solved my engine miss problems!

So I have the flame thrower coil.

I do have 12 volts going to the distributor.

So I played around last night for a minute. I did find 2 vacuum plugs that were cracked. Replaced those. Finally got it running to the point it would idle on it’s own. Took an infrared laser thermometer and checked each exhaust port. Cylinders 1 thru 5 were all within a few degrees of 620. 6 was 190ish. 7 and 8 were both around 400. Obviously 6 is dead in someway. Is 7 and 8 possibly valves out of adjustment? Why are they lower than 1-5? By this point the headers were to hot to do anything else with and it was getting late so I called it a night. I’ll check back in and post my findings today.

Thanks to all that have offered up suggestions, I do appreciate it.

I would start with a compression check. You may have a bent valve on #6, or the valves may not be adjusted properly.

7 and 8 sound like they are running about right. 1 thru 5 may be running lean. I would suspect intake manifold being cracked, or bad intake gaskets, or maybe it is all due to faulty valve adjustment technique. 400 - 500 degrees is the normal range for exhaust manifold temps.

Well if it wasn’t for bad luck… 463 miles on the new engine and 0 compression on #6 and #8. Gas soaked plug on #6 and oil soaked plug on #8. I just had to walk away… Thanks all who offered up suggestions, guess I’ll be digging a little deeper now.

That sucks… This is one of those times when you just have to roll up your sleeves and get after it and fix it! Let us know what you find. Check the cam timing before you take it all the way apart to see if it was off and a valve hit the piston.

Man that does really blow. I’d check the cam timing also, just to be sure. I’ve seen timing gears being off by as much as 4 deg when they are lined up. That’s what the importance of degreeing in a cam. You could also have a wiped lobe. Just armchair suggestions, but I’m w/ everyone else as far as checking the things that don’t require disassembly first. But, hearing about 0 compressions doesn’t sound good.