Timing a modified 351w


#1

I have a 351 w that has the fireing pattern of a 302. How would I go about timing it? would I use the 302 timing? or just plug the light into the proper plug and time it like a 351w or?


#2

What does the underhood emission sticker suggest?

Tester


#3

If I remember correctly, this is a modified 351 in a '69 Falcon?

The timing may be one of those dink around with type of things since the engine has been cammed and whatnot.
Off the top of my head, it seems like it sets at about 6 degrees BTDC but that can vary quite a bit depending on the camshaft, distributor, whether it’s EGR equipped or not. Some of the small block Fords will run 12-15 degrees of advance with no problem.

Best to set it at 6 degrees, run it for 50 miles, and pull a few spark plugs for tip inspections.
Dial in more advance and keep repeating the tip inspections while making sure that you do not hear any pre-ignition rattling. Any rattling on acceleration means back it off a few degrees. Hope that helps.


#4

It is in the wrong car, and no stickers remain on the engine.


#5

Yes, you are correct. it is in the 69 falcon.

Ok, that sounds good. But, While the car can go on the road (it’s street legal) I don’t have it licensed or insured. Can I let it idle for an hour and check the plugs? or does it need more time than that?


#6

Forget checking the plugs, that will tell you little or nothing. Too many different things going on. There is a timing mark (a line) on the front crankshaft balancer and a scale of some sort on the timing cover. Connect a strobe light to #1, distributor vacuum (if it has any) disconnected. In addition to the static timing (6-10 degrees) the distributor will provide 20-25 degrees more of centrifugal advance and an equal amount of vacuum advance for a TOTAL possible advance of 45-55 degrees.


#7

When you get it running and warmed up let it idle and SLOWLY advance timing until it speeds up, then back up just a little bit.Do it 1 more time and listen real close so when you tighten dist bolt you can tell if it changes.
Mark dist or look at timing light mark to remember position.
This method has never let me down in getting real close.
After driving it some you can play with timing a bit.
If timing is retarded it will start instantly and if it is a little fast it will idle faster and seem to have more power but remember to fast and you will burn hole in piston.


#8

The 351W has the same firing order as the H.O. 302. The firing order of lesser 302’s is different.


#9

Ok. I just hooked the timing light up to the #1 plug and adjusted it by ear, watching how far it movied. the line moved (the top dead center line) moved about 1/2 inch towards the passinger’s side.
I did hear what you were talking about the idle coming up, then coming down more when I moved it back. It used to pause when you would step on it, now it jumps ahead when you step on it.
Did I advance or retard it more? I turned the cap clockwise. (advancing right?)


#10

Allowing the engine to idle for a long time won’t tell you much about the plugs at all; it will require a few highway miles. (about 50 or so)
Reading the plugs is the best method of knowing what is really going on inside those cylinders and NOT reading them is something I would never do.

I’m also not a fan of guessing about what is going on inside the cylinders. The idle will certainly speed up if you advance the timing (entirely normal) but the risk you run by eyeballing and guesstimating the timing is that if you have too much advance there is a strong possibility of burning some pistons and possibly the cylinder walls out during a highway run.
(And yes, going clockwise is advancing it.)

I mention this because I’ve personally been involved (as a mechanic) in several of these incidents in which someone dialed in too much advance and wound up on the side of the road with a blown engine. Matter of fact, a very slick, low miles Subaru I once owned was purchased by me on the dirt cheap because a fast-tune type of place did exactly that.
They tuned it, the next week the owner headed out of town, and the car was towed in from 80 miles out; where is where Number 1 piston disentegrated with Numbers 2 and 3 not far behind.

If the car were mine I’d wait until it was completed and streetable before playing with the timing. Reading plugs on a blown engine won’t accomplish much.


#11

Even if I timed it awful, idling it in the driveway would not damage it, correct?

Do I need to get the specs for the cam to properly time it? And when I timed it to within 6 deg, it ran awful. So I probably do need to dig up the specs. How much can a cam affect timing? it looks as though it is 20 deg advanced


#12

Is that 20 degrees with the vacuum advance hoses disconnected and plugged? For now I’d back it back down to about 10 and start playing with the timing when it’s streetable.

Some idling in the driveway should not hurt it and the cam does not change the timing in any way. It only alters the effects of the timing.

What kind of carburetor on it? Not overcarbureting it are you? Too much carb can turn an engine into a dog.


#13

Advance timing till it speeds up and when you retard it you will hear it start to stumbal, if you go half way in between I am confidant it will not be timed fast enough to hurt anything.
Only way that I know of to get correct reading of plugs is to have it warmed up.I like to use 2nd gear to keep tickets down.go half throttle for a bit then take foot off gas peddle then turn off motor and coast into a place where it can sit for a while, you do not want to take plugs out when hot, easy to pull threads with plug.
Read plugs and use anti-szeeze.
You can also do it full throttle and just putting along.


#14

Duh, yeah, I forgot to take off the vac lines.

I think the guy I bought if from said it was a 500 cubic foot per min 4 barrel. (he said it was a little under what an could be put on)


#15

All this “read the plugs” stuff is nonsense. You read plugs to determine fuel mixture and little else. What do you “read??” It’s a useless tool for setting the timing. The OP has found ONE timing mark, the one on the harmonic balancer. Now he needs to find the other one.

“Which way do I move the distributor to advance the timing” Remove the cap. Crank the engine and observe the direction the rotor moves. If it turns clockwise, you would move the distributor counter-clockwise to advance the spark timing, and visa-versa…


#16

When you just get a motor running its a quick way to see if its running to lean so you can keep it from seezing up.
If it is black and sooty you know you can try advancing timing before changing carb settings.
Just helps you get another piece of the puzzle of a good running motor.