390FE Timing?!?!

[nickpohlaandp]

Ok, so I'm done pussyfooting around with this 390. The EFI is running great, I'm ready to go tear into it BUT.... before I did that I wanted to double check the timing and make sure it was at an acceptable level (if you've seen any of my other threads you'll know I advanced the timing a bit for initial startup and break in).

Well, if I set it at around 10* BTDC at idle and then have my wife hold it around 3750 rpm the timing is way too high, like around 50* BTDC. If I adjust the timing to around 38* with the engine revved up, when I bring it back to idle it wants to die because it's trying to fire ATDC. What gives?! It seems like between mechanical and vacuum advance there's just too much. This is the stock distributor from 1965, so it's a points setup. I don't know much more about it other than that. I'm not sure if someone has messed with the mechanical weights or the vacuum diaphragm (or if the diaphragm is even adjustable). Any thoughts? Anything you could tell me would be greatly appreciated.

I'm tired, I'm kinda tired of this car, but I don't want to give it back to the owner if there's potential for him to hurt it. He's not a car guy. He knows they need gas and oil. Beyond that he's S.O.L. if he gets stuck on the side of the road. I highly doubt that he'll EVER wind this thing past 4 grand... but he does have a teenage son.

Thanks again for the help everyone!

[Firedome8]

Are you setting timming with vacuum adv conneccted??if so disconnect the vac adv and set total to about 36* then see what the Idle timming is. With vac connected @2500 50 * is about correct report back.

[Firedome8]

Woops

[nickpohlaandp]

Woops

Whoops as in I'm a dumbass or whoops as in you misspoke?

[In-Tech]

I just went through this on a '65 390 tbird actually. Do you have a welder available? If so, take the distributor apart and weld a bead on the "dead" side of the advance mechanism, this basically advances the distributor internally. Man, it's hard to describe and the pic I have is friggin horrible and before the welding. The reason you don't weld on the opening side of the advance is it messes up the rotor phasing due to limiting the amount of advance.

Click on the bottom pic to expand it, I drew a red circle around the advance limiter, right there it is in its' rest position, you want to weld a small bead to advance it further at rest, sometimes you might have to put a lighter spring on the rest of the advance since now it is preloaded a bit, but probably not.

20170713_212334.jpg

390_Dist.JPG

[nickpohlaandp]

I just went through this on a '65 390 tbird actually. Do you have a welder available? If so, take the distributor apart and weld a bead on the "dead" side of the advance mechanism, this basically advances the distributor internally. Man, it's hard to describe and the pic I have is friggin horrible and before the welding. The reason you don't weld on the opening side of the advance is it messes up the rotor phasing due to limiting the amount of advance.

Click on the bottom pic to expand it, I drew a red circle around the advance limiter, right there it is in its' rest position, you want to weld a small bead to advance it further at rest, sometimes you might have to put a lighter spring on the rest of the advance since now it is preloaded a bit, but probably not.

20170713_212334.jpg
390_Dist.JPG

Thanks for the advice. I think I might've screwed up setting the timing though. It feels like eons since I've used a vacuum advance distributor.

So on your 390 where did you set your base (idle) timing (no vacuum on the distributor)? I'm curious where I should be at baseline and total.

I'm thinking this over in my head and I feel like I'm recalling a little. I set the timing with the vacuum advance hooked up to a ported source, which should be zero vacuum, but I did not verify. Under normal driving the vacuum advance helps fuel economy, but at WOT there should be no vacuum to the distributor so the only advance I'd see is mechanical, isn't that correct?

If that is correct then I'll just go verify initial timing with the vacuum advance disconnected and verify mechanical advance while revving to around 3500.

[Sparksalot]

Yes, that is correct. Disconnect the vacuum hose from the distributer and plug it during setting timing by rotating the distributor. A golf tee was always in my box for that job. And, I don't play golf.

At no or light load on that engine with vacuum advance working 50 degrees advanced is where is should be revved up, no problem there.

[mag2555]

X3, 50 with the vac advance working but under no load is as intended for that era's gas, but NOT to days !

Drive under highway part throttle conditions and do the listen for ping check as these days depending on the car's weight and rear gearing I find that 15 added degrees of vac advance is about it with a iron headed motor between 9 to 1 and 9.6 to one.

[Firedome8]

Woops

Whoops as in I'm a dumbass or whoops as in you misspoke?

Posted twice can not delete.

[Firedome8]

X3, 50 with the vac advance working but under no load is as intended for that era's gas, but NOT to days !

Drive under highway part throttle conditions and do the listen for ping check as these days depending on the car's weight and rear gearing I find that 15 added degrees of vac advance is about it with a iron headed motor between 9 to 1 and 9.6 to one.

Crane adjustable vac. adv. Is the best one to use.

[nickpohlaandp]

Well, here's the deal with putting any more $ into this car. I don't care if the owner is willing to or not... I'm not willing to spend any more time working on it fooling with more new parts. I feel like I'm being more than gracious to even care about making sure the timing is right after how I got bent over on this deal. If it stops raining today I'll put a timing light on it with no vacuum line hooked up to the diaphragm and set the total mechanical advance to 36-38. After that, I'm done. If the timing still doesn't want to be happy then when he comes to pick it up I'll tell him it needs a new ignition system. This is not my full time job, this is a hobby that I like to tinker with after work and on the weekends, but for the amount of time and effort I have put into this car, it doesn't deserve another minute of my time for the compensation I received.

Bitter much?.... Yes

[Firedome8]

Well, here's the deal with putting any more $ into this car. I don't care if the owner is willing to or not... I'm not willing to spend any more time working on it fooling with more new parts. I feel like I'm being more than gracious to even care about making sure the timing is right after how I got bent over on this deal. If it stops raining today I'll put a timing light on it with no vacuum line hooked up to the diaphragm and set the total mechanical advance to 36-38. After that, I'm done. If the timing still doesn't want to be happy then when he comes to pick it up I'll tell him it needs a new ignition system. This is not my full time job, this is a hobby that I like to tinker with after work and on the weekends, but for the amount of time and effort I have put into this car, it doesn't deserve another minute of my time for the compensation I received.

Bitter much?.... Yes

I know the feeling,,,I have put in much free time if only to satisfy myself !!! Nothing is easy just do your best,,,, Try manifold vac adv at idle and see if it likes it...

[nickpohlaandp]

Well, here's the deal with putting any more $ into this car. I don't care if the owner is willing to or not... I'm not willing to spend any more time working on it fooling with more new parts. I feel like I'm being more than gracious to even care about making sure the timing is right after how I got bent over on this deal. If it stops raining today I'll put a timing light on it with no vacuum line hooked up to the diaphragm and set the total mechanical advance to 36-38. After that, I'm done. If the timing still doesn't want to be happy then when he comes to pick it up I'll tell him it needs a new ignition system. This is not my full time job, this is a hobby that I like to tinker with after work and on the weekends, but for the amount of time and effort I have put into this car, it doesn't deserve another minute of my time for the compensation I received.

Bitter much?.... Yes

I know the feeling,,,I have put in much free time if only to satisfy myself !!! Nothing is easy just do your best,,,, Try manifold vac adv at idle and see if it likes it...

If it's ok with 50* at no load, 3500rpm then that's where it's going to stay. Kickin it outta my driveway. If I were to charge this guy $30/hr for what I've done he'd easily be over $4k with the bill. It's my fault just as much as his because I never specified a price. The job was NEVER intended to go as in depth as it did. As things progressively got worse as I got into it I told him how much parts would cost, but never mentioned labor. I guess I was wrong to assume that someone would think they actually have to pay for labor as well as parts.

Either way you spin it, the car is mechanically sound and the FITech EFI is doing a good job of fuel delivery. I'm sure it could get more "fine tuned" than the base settings that the ECU sets itself to if I were to datalog it and make changes, but I'm not going to. He can have his car back how it sits. If he wants me to do anything more to it I will be VERY clear up front about what my time will cost him.

[topradman]

Nick, I just breezed through this post so might have missed something but I agree with those who say 50 is ok. I had an FE come in my shop overheating and the guy wanted a new radiator. After observing his vacuum advance being hooked to ported, I changed it back to manifold vacuum, reset his timing and then checked and came up with the same 50-51 you have simulating light load cruise rpm. It fixed his overheating problem immediately and didn't have to sell him any parts at all. He was happy and so was I. I agree with this timing, again, as long as it doesn't rattle when you pull a slight hill while cruising, you should be fine.

PS, that was on 91 octane.

[nickpohlaandp]

Nick, I just breezed through this post so might have missed something but I agree with those who say 50 is ok....

Yeah, I'm happy with it after the replies everyone gave.

Asshole Poll: So at the owners request I installed a gauge set (Volts, Temp, Oil press.). The gauges are functional, and I did a whole heck of a lot of wiring fixes prior to installing the gauges and had already re-loomed everything with aviation grade shrink wrap. That said, I have not hooked up the gauge lights. Would I be an asshole for giving it back like that?