Copy and paste from another forum, hoping for added advice.

I emailed Barry this as the server seems to be on and off whenever I try to log in, looking for any and all advice here. Please share your insight as surely many will gain from it. Thanks in advance.

I have been attempting to get the 390 for the f100 off the stand and have had no luck getting the timing concern solved. The engine fires and runs, ran in ok and has shown no signs of serious issues due to timing being off. The build is rather simple.

I am at a cross road with the timing thing. Please help if you can.

Typical 390 build, with repop cast L2291 slugs. After some woes with a crank gear key, a Dorman unit was used. Worked fine.

The timing set is a factory style unit that came with the kit.

The cam is a 343941 Crane regrind. I got from the engine kit supplier. Lined it up the only way possible, straight up.

The distributor is a reman Cardone from Kragen and run via a used HEI unit based on a wiring schematic from a weblink supplied via the forum.

Checked TDC and it is good and true piston/marker.

It does start up fine, but the timing reads way advanced when a good vac reading is had at an idle speed. I haven't really looked to see if the balancer jumps way beyond when acceleration is had. At 10-16 the reading on a vac gauge is reading late valve timing and engine is real lumpy at idle.
With a good vac reading the timing is way up like 32 or so will confirm asap.

I have let it idle while trying to set the distributor at a reasonable degrees, and it just doesnt want it. However if the throttle is blipped at either the rough 10-16º or the good vac reading 22hg/idle 1100rpm unknown degrees status it will rev and not backfire or fall off. That make me think there is no more mech adv happening from the dist. So the late valve timing is due to missing spring or weight or something in the Cardone unit.

It's advanced period and will hardly find an idle at the expected timing state due to advance issue, but will not go beyond a said point due to mech limitations ??

**** MY HEAD HURTS!!

As a stop/think/do method: based on the setup, how would you proceed ?

 

You did make sure the dampener ring didn't slip, right?

Also, what was that about "Dorman" crank key? For the dampener?

 

I don't have a vacuum dist, but I noticed the best idle was up around 38degBTDC, but of course I can't run it there. If I had a vacuum advance, I'd be happy with an idle running in the 30 degree range and know that when I put the engine under load, the timing will drop back to a safe range and not cause damage.

 

Make sure the vacuum advance is disconnected when setting the timing and when connected it is hooked to ported vacuum and not manifold vacuum.
Ported is above the throttle plates and manifold is below.

 

Hi Folks!

I have about 18,000 miles on my 390 rebuild. Using an MSD drop and drive distributor and melling ML4 cam.

When initially installed and timing, I found that the advertised 6dbtdc timing was for FEs with the Thermactor installed. Mine doesn't have it. I finally bought an older Ford Shop Manual which told me that the timing without the thermactor should be 10dbtdc and could be advanced an additional 5 degrees for the cam and even five degrees beyond that for "performance."

So, the 6 degrees didn't work at all initially. After reading the old manual I set it out at 12- ran outstanding!

At about 10K miles had to retime and this time the vacuum gage setting took it out to 16dbtdc.

At 17K miles, the timing dropped back again (the engine would stall at idle, pop when the gas was stepped on and not run for sustained periods in stop and go conditions).

I reset the timing with the vacuum gage again and it runs great. But when I took a timing light to it it shows it's timed out to about 24 dbtdc!!!!

I guess if it works, don't fix it. But........What's up with that?

Thanks,

Joe

 

First off you don't know what your initial timing should be without knowing your total mechanical advance. Total mechanical advance (no vacuum connect if so equipped) should be no more than 38°. You set the total advance either with a degree wheel or an adjustable timing light. To do so you rev the engine until the timing stops advancing then adjust it to 38°. Then check the initial timing and then you now KNOW what the initial needs to be. Any other way is just guessing and besides usually for a stock motor. I can't believe so many people are still setting initial timing by the guess method.

 

Most people, including me, do it that way because that's how the shop manuals, distributor instructions, and rebuild books tell you to do it - you know, factory specs/manufacturers procedures, and all that! "If all else fails...follow the instructions??????" And I don't see how setting timing with a vacuum gage is guessing. It's a pretty true indicator and allows proper set of idle mixture at the same time.

I've never heard of your method, but I guess it's worth a try.

PS What do you do if it IS more than 38 degrees?

 

You are not doing a factory stock engine and that is why so many are disappointed with their engine builds. Following instructions is for the uneducated when it comes to hot rodding. Either learn what you need to know to do your build right or don't build it, let someone who know do it. Asking question will easily get you the answers you need.

Oh and the 38° comes right from Ford Racing and has been the Ford number since the early '60s. That is total mechanical advance. Vacuum advance can move that as high as 50°. I know this because I have been playing and racing with Ford FE engines since then.

If you are over 38° mechanical advance, back off the timing. You will end up with holed pistons if you don't. Especially with today's junk gas.

If your idle is poor, get the dist recurved. My last truly high performance FE had an initial of 18° because the dist. only had 10° of advance built into it. That's 20° at the crank. So 18 + 20 = 38°. I did a street 460 a couple of years ago and it had 12° of initial timing because the dist. had 13° built into it. Total once again 38°.

 

Wow, that' quite an opinion, thanks. I had an aunt once who thought herself a tremendous cook. She entered stuff at Fair. She cooked for her family for 30, 40, 50 years - prided herself on her special craft. Between you and me I wouldn't feed the crap she had cooked to my dog. Funny story if you were ever there and listened to her and her husband talk about her "great talent" and then saw the looks on people faces when the first bite hit the mouth - hilarious! Opinions and results.........

Anyway, here's the thing: I'm not "hot rodding." I am just working on a stock 390 with a few upgraded parts. If what you say works for you, great use it. But, I don't by any stetch of the imagination consider myself to be more knowledgeble than the people who design, build, and write the maintenance procedures for these engines. Nor would I ever be so arrogant as to claim such. If I'm ignorant because I follow qualified instructions then so be it.

I'll have to check out the Ford Racing stuff. If they offer the "frosting on the cake," then I'll pick that up.

When I have an opportunity to test out your method and see if it offers improvement/solution, then I'll assign it credibility and adopt it -with much appreciation. Until then I hope you don't mind if I continue to wallow in my ignorance - work on my truck and deal with my vehicle as I choose to.

Fact is, I'm not quite sure that my curiosity about the currently correct, yet dynamic, timing setting would be solved by assigning another fixed benchmark by using a different method. Fixed mechanical at 38 degrees; idle timing at 14 degrees; maximum vacuum minus one inch at 1100 - not looking for another reference point. The vacuum gage works fine for me.

Thus my original question btw was not about methodology, it was about why the timing setting is changing so much, and why it continues to move farther out in advance [12-15 degrees now at idle, beyond spec, when it wasn't out that far before - and was timed correctly] to properly run the engine. It's more of an oddity than a problem.

Fact is my engine runs very very well having been timed and tuned using the vacuum gage. I was just curious about why the setting moved as far as it has and why it continues to move as far as it has at each timing reset. Maybe it's possessed!

 

Couple of small thoughts:

The Thermactor thing in and of itself doesn't mean the timing has to change. Thermactor (air injection) was used for emissions. For whatever market, state, whatever (I suspect California or a different GVWR), both the timing is changed, AND the air-injection stuff is installed.

The air-injection doesn't require, nor necessitate a change in timing.

That almost sounds like the dampener ring is slippping. Turn the engine over by hand until #1 is at TDC and verify the timing marks on the dampener show 0 degrees.

Of course, that doesn't help with running like crap, you might have a vacuum leak getting worse, carb running lean, etc.

But, start with verifying the timing marks and we'll go from there.

 

Thanks for a great response!

Slipping ring....hmmm, there's a thought! Might explain alot.

Actually the truck is running great. But after retiming and adjusting idle mixture with the vacuum gauge I checked the timing marks with a light - to gain a point of reference. I was suprised to see it so far out - 24 to 26 degrees at idle!!!!!

I'll check out the rest of your ideas...

Thanks again,
Joe

 

I'll take a swing-

You don't say which MSD dizzy you're using, but you should know what the total mechanical is- its the initial, plus whatever you've got the MSD's centrifugal set at. I think the MSD models generally use a specific bushing to limit total advance- which one are you using?

Bear is right- you can't really use the shop manual here, because you're not using stock parts. You can (and should) stick to Ford's "38 degrees total timing", but using the shop manual's recommended initial setting of 6 or 10 degrees is meaningless, since the old Ford manual doesn't know how the mechanical advance is set up inside your new MSD dizzy.

as far as setting timing with the vac gauge...wouldn't increasing the rpm with no load on the engine increase vacuum...meaning that you'll see more & more vacuum as you continue to advance the initial timing? that doesn't seem like a good plan. use this method for tuning your carb, not your timing.

but...back to your original question of why the timing may be changing...are you sure your hold-down bracket is tight?