Well, I guess my time has come. The new 390 in my truck is pinging. It happens at cruise, when the vacuum advance comes in. Going down the road, at 50mph on a straight, level surface with no wind, it gets about 20" vacuum. If it wasn't pinging, it'd be good. 91 octane makes the ping kind of sick, but it's still there. 87 or 89 octane is horrible. I did have the fuel injection set up to run a little lean at part throttle; I set it back to stoichiometric (sp?) and that helped a little, but it's still there. Other than that, it runs great, plenty of power and decent gas mileage. Somewhere between 12 and 15 mpg is the results so far.

When my brother had the distributor I'm using in the old 360, he put in the light flimsy advance springs, along with moving the total advance to the 15L position. I think if I put the regular springs back in it should get rid of the ping. Unfortunately, the junkyard wants to sell me the whole distributor. So I went to Napa and got a reman distributor. It'll be here tomorrow. I'll need the spare for the 352 ethanol engine anyway.

In case anyone forgot, here's my build details:
1. Ford 390, 4.080" bore, 3.784" stroke
2. C7AE-A heads, fully ported, polished chambers (that helped didn't it )
3. ~9.75:1 compression, depending on how you figure it
4. TRW L2291F30 pistons
5. Fel-pro .041" head gasket
6. Performer RPM intake
7. Crane 343941 cam
8. Holley 700cfm TBI electronic fuel injection - programmable
9. Hedman headers, dual exhaust

Any more ideas for getting rid of the pesky ping? What about spark plug heat ranges? I haven't messed with different spark plugs yet, the ones I have are stock 360 type plugs. I was thinking of grinding some off the electrode so it wouldn't get so hot, think that'll help? Other than that, what part number should I get for some cooler plugs?

Edit: Oh I forgot, I have timing set at 10 degrees BTDC initial with the vacuum advance pulled and plugged.

 

octane boost ?

 

Get one of the adjustable vacuum advance units and keep backing off on the advance until it doesn't ping anymore. Part of the problem is the compression is a little high for the regular gas.

 

Just plug the vacuum advance and don't use it Oh wait, this isn't a big block Mopar where you can actually do that.

 

i was reading this post yesterday learned some good info.

things to always check and try


https://www.ford-trucks.com/forums/s...d.php?t=360892

 

i was reading this post yesterday. i got some good info from it


things to try and things to do

https://www.ford-trucks.com/forums/s...d.php?t=360892

 

Well, actually you can; but just like on the Mopar the fuel economy will suffer, or any other engine for that matter.

 

[Editted - removed a paragraph of pure misinfo]

I'd start with retarding the timing until it goes away and see if you still have a decent amount of power at that "ping point" - if you do, recurve the dizzy until you get rid of it.

In my 360 dizzy, the two springs were one weak, one strong. The strong one did NOT fit tightly and would allow the weak one to take the initial timing way up and then the strong one would inhibit high-RPM advance. I would imagine that one weak spring and one strong would make the "cruise" timing even worse [ Editted again! ]

I'd see if you can retard until it goes away and check performance. Then, we can do other things to get the initial advance up - Read my posts from yesterday about what I did to my 390's timing... not exactly intuitive, but it worked.

With that big of a cam, and that "low" compression , there's something else timing-wise or fuel, it's not a motor design problem. Vacuum leak?

 

Everyone seems to brag up the Pertronix ignition system...something to consider?

 

Not I after three failures on installs on friends FE's. Used Crane's XR 700 for many years without any problem like over 600,000 miles. I stepped up to their XR 3,000 series with Cranes LX-91 coil, very happy! Before that went thru two MSD unit failures. Price is not an issue, reliability is.

Carl....=o&o>....

 

Try one "fix" before trying another. I suggest that you stick with the distributor idea first. Install the Napa reman and set the timing to 10 BTDC just like you have it now. Test and then evaluate the results. If the ping is gone, cool then you just fixed the problem. If you still have the ping, then retard the timing. Remember, between 6-12 BTDC is considered spec. It takes more time, but knowing exactly what caused the ping...now that's satisfaction.

IMHO Don't even waste your time on the plugs right now...

Idea's:
Can you fatten up the Holley commander 700 TBI even more?
Upgrade ignition (make it HOTTER) with a D.U.I. unit or similiar.

Please keep us posted. I have been contemplating the Holley commander setup for some time...and like the MPG you are getting now with the "ping". When the "ping" is eliminated...might result in better MPG's.

Good luck...

 

Just sounds like to me..If it pings when the Vacuum advance is coming in..the timing needs to be retarded.....a couple of Degree's

And Kurt..you have more time tuning that Commander..Hell you could have rebuilt a boat load of Holleys by now?? LOL!!

Good Luck Bud!!

Russ

 

Update:

I'm taking the Napa distributor back. I was informed from a good source that I paid WAAAAAY too much for it. To the junkyard I go, again. Last time I was there I tried to get at least 5 different distributors from 5 different trucks, but they were all stuck. I would unbolt the hold down, but they still wouldn't budge. Wouldn't turn or anything. Any tips on freeing a stuck distributor?

My brother tells me that the vacuum advance should be adjustable. How is this done? I was informed that the springs have nothing to do with it, and it's the vacuum advance that I should be concerned with.

On the pertronix idea, I'll stick with points, thank you. I can replace a LOT of points for what it costs for one of those. I've never had a set of points go bad, just replace 'em every fall with the quality blue streak set and they work fine.

No vacuum leak, sprayed starting fluid CAREFULLY around the base of the throttle body unit, and no change in idle speed.

Yes russ, I know I could have rebuild a boat load of holleys by now. If I had the decision to make again, I never would have even thought about fuel injection. But at the time it seemed like a good idea, so I'll stick with it. By the time the motor is worn out I might have it tuned.

Edit: I had the valve covers off the other day, and all the valves were opening all the way, and the adjustment was still right on where it's supposed to be. The cam broke in just fine. It's not that.

 

Don't listen to people saying 6-10BTDC at idle is enough - with your cam, you'll be lucky to be making ANY vacuum at idle

And guys, he already has the vacuum advance unplugged according to his original post.

The vacuum advance, if it's adjustable, can be adjusted with a hex key by sticking it in the vacuum port on the advance pot. Not sure what size, but it should be easy to find - that is, IF it's adjustable. Aftermarket ones are, originals, I don't think are...

Back to the drawing board. One thing at a time. If you retard the initial timing, does that cruise ping go away at all? Or is it always there no matter what timing?

OOH OOH - just realized you were using POINTS. If the upper bushing is wasted in the dizzy, the dwell (and timing!) will wander all over the place - junkyard dizzys will do it too, they wear out pretty easily. I had a bad dizzy like that (200K+ on a 360 dizzy!) and I would get misfires and pings at that mid-range cruise too! Something to look at. See, when the cam moves back and forth (end-play) it moves the dizzy shaft up and down, and it wobbles at different times. Check it out - grab the rotor and push back and forth in the direction of the points - if you see them open and close (or just move a good .005" or more) get a new dizzy (reman, but make sure the top bushing is replaced and honed correctly).

 

Yep Kurt....You might have just got a bad Dizzy too??? As mentioned above..I know the Older one's were adjustable in the Vacuum pot on the dizzy...I think I used an Eye glass scew driver and have adjusted it?? Shoot its been so long ago..

I'll shut up now!! Seems I have forgot more than I thought!!! LOL!! Old age..Thats when I call my son..and ask him what it was I taught Him!!! LOL!!

Russ