My 2.8 has an adjustable vac advance unit

[RCK974X]

Just thought I would post here for reference....

I discovered my Wedge has an adjustable Vacuum advance unit, which apparently Ford fitted to quite a range of different engines/dizzys.

My engine has a Motorcraft dizzy, with the Blue top. Engine is not original to wedge as numbers don't match, so I don't know if this applies to all 2.8 wedges or not - I know some had the Bosch dizzy (with red top) .

I had a lot of trouble getting the engine to run nicely on the (so-called) 'Super' here in NZ after moving here. It's supposed to be 98 or 100 octane, but I would still get pinking.
[Edit - noticed that the 'Super' they sell now is only 95 Octane in many gas stations....]

In the end I disconnected the Vac Adv and set static timing at 10.5 BTDC and accepted slightly worse economy. It runs quite nice but a little flat sometimes, no surprises.

Now I've found out vac adv unit is adjustable (a 1/8 inch allen key inserted down rubber tube connector) I will try again, and let you know what I discover, in case it's useful to anyone.

Edited by RCK974X on Monday 24th November 04:32

[mrzigazaga]

Hi Andy...Mine had a blue top Motorcraft distributor, Not sure if it was original or even adjustable..Possibly but i ended up buying a Bosch red top which was fine..With the 97ron and upwards i had mine set to around 8.5-9 degrees..No pinking..I don't recall any flat points in the power although you could call it a bit flat from low-mid range..Unless you pump the loud pedal like a wagging dog!

[RCK974X]

UPDATE -

My vac adv unit adjuster turns a total of 18 turns, so I set it in the middle, 9 turns from one of the stops.

Running 98 Octane with 10% ethanol, (in New Zealand, Gull Force 10 - not sure what UK equivalent is...)
10.5 degrees BTDC static.

The engine runs fine at speed, doesn't pink/detonate with this stuff, but it runs rough at very light throttle, i.e. just touch throttle for 30mph in town.
Almost like a misfire, but not quite, it's a sort of 'kickback' you can feel.
Disconnecting vac adv stops this 'kickback' behaviour, but engine seems slightly flatter than when connected...

Will try a stiffer vac adv setting and try again.....

[Jack Valiant]

Mark the dizzy on the current setting then I would add or subtract 2 degrees timing and test in each setting for the best performance on idle, light throttle and power

[mrzigazaga]

Hi Andy..Sounds like its too much advance if its "Kicking back"...If you put a timing light on the marks and suck on the vacuum pipe then it should be about 8 degrees..Be careful with too much advance!....Ziga

[RCK974X]

Yep, to explain....

I already set the static timing at what appears to be best point, where it just stops pinking under load, with vac adv disonnected. This is the 10.5 degrees as above. (according to crank marks, assuming they are right)

I was retrying the vac adv for my interest, after seeing on the web that it is adjustable.
I can always disconnect it entirely again, which I know runs OK.

It may well be that the unleaded (and E10 ethanol fuels) don't like any extra advance - and I know that this advance only occurs at light throttle anyway.

Edited by RCK974X on Monday 24th November 19:05

[RCK974X]

Update for anyone interested.

ANY vac advance with the E10 gas, 98 Octane, makes the engine 'kick' at light throttle cruise in traffic, around 25-30mph.

Disconnecting vac adv restores smoothness, and engine then runs fine throughout the range.
I'm now not sure if the throttle response is actually any flatter, at least with this 98 gas.

I do reckon that unleaded gas burns faster than leaded, even for same octane, as the lead helps knocking because it retards the burn speed. Web articles seem to confirm this viewpoint.

I'll try 95 Octane next, and log what happens.

So best advice seems to be to disconnect vac adv completely for the V6 engine for unleaded gas.

[mrzigazaga]

Hi Andy...I wouldn't bother with it really...I had a blue top motor craft dizzy in mine but when i had to replace it i went for a red top Bosch..Delilah used to run pretty well on standard unleaded 95ron but with a lead additive every 4th tank..I adjusted the timing to 8.5 and always had a good even power across the range..Not sure of the "Kick" you are talking about?...Doesn't sound good mate....Cheers...Ziga

[RCK974X]

Yeah, well I'm doing it for me really, I want to find out the best combo.

I will try the 95 'cos that's what most of the NZ gas stations sell as their "premium", with just the odd one or two selling 98 (which is equiv to 4 star, but without the lead).

Engine is fine, honest, just it seems with what NZ sells here it really does not like any vac advance....

At the 10.5 BTDC, it runs perfectly throughout, with vac adv disconnected....

[and anyway, I've still got that Buick 3800 V6 and T5 box sat at the back of the shed.....which runs 91 unleaded. Only problem is NZ requires recertification for engine changes, and it's about 3000 NZ dollars !!]

[mrzigazaga]

RCK974X said:

I've still got that Buick 3800 V6 and T5 box sat at the back of the shed.....which runs 91 unleaded. Only problem is NZ requires recertification for engine changes, and it's about 3000 NZ dollars !!]

Thats about the cost over here for an engine and replacement and that would be a cheap unknown engine really...Then the price for the gearbox..Removal & fitting unless its D.I.Y so can soon escalate into double that...I wish i had gone the John Toovey route and paid 2K for him to re-build a Cologne to hi-spec..That would of pushed over 200bhp...But no i chose the blower route which cost me double that..And failed!...I would save up and plant the 3.8 in there mate...