i've got a 289 out of a 67 cougar which misfires badly when i hook up the vacuum advance hose from the distributor. i even run it straight off of the intake manifold and it still bucks, misses and backfires if you mash on the gas at all off idle. however when you disconnect the vacuum advance hose it runs, idles, and revs quite nicely so i don't suspect the timing. originally the engine was a 2 barrel, but has been replaced by a edelbrock performer rpm intake and 600 cfm edelbrock 4 barrel carb. it also has an isky mega cam in replace of the stocker, with 214 degrees of duration at .050" and .480" lift. its supposed operating operating range is supposed to start at 1500 rpm. do i need to reset the vacuum advance on the distributor because of the engine's possible lower amount of vacuum because of the somewhat lopier cam? or perhaps the advance springs in the distributor need to be replaced. i also have the factory manual for this engine and from reading it it seems like perhaps that may be the problem, because when you hook up the vacuum advance hose to the intake manifold the timing sounds like it's really late. anybody got any ideas? any help would be greatly appreciated.

 

give me some specs on how its currently tuned. base timing, idle speed, idle speed in drive, ignition system (point gap or electronic ignition). i believe that engine should have been set at 10 deg btdc at 600 rpm with an .018 point gap but my memory fails me sometimes.

 

The vacuum to the distributor needs to have the same type of source as it had originally.

I just checked my '67 Cougar shop manual and the the 2 BBL was an Autolite 2100. This carburetor provides vacuum from a port right at the throttle plate. Manifold vacuum is not going to work.

The installation instructions for the Edelbrock Carb should show the connection point for the the distributor vacuum. It might be labeld "ported" vacuum; I don't have the installation instructions available to me to be sure.

After you done this and it doesn't work please post again.

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi

 

I agree that the vacuum advance really should be on the ported side of the Edelbrock which I believe is on the front passenger side of the carb. You should try running it under load without the vacuum advance and see how it runs. It doesn't sound like your cam should cause that much of a vacuum leak. I do not like the stock Motorcraft distributors and I would suggest getting an MSD drop in distributor. It comes with an advance stop and the different springs to change your advance curves.

Once you get your base timing set, you may want to develop an advance curve. Disconnect the vacuum (make sure the vacuum source is plugged); Start checking your timing at 600-750 rpm, move to 1500 rpm and check your timing, then continue checking every 500 rpm until you hit 3000 or whenever your timing stops advancing. You will probably be around 40 degrees BTDC at around 3000 rpm, with full advance hitting somewhere between 2500-3000 rpm. If you put in weaker springs, the advance will come in quicker.

The ported advance will typically be closed at idle and not open until around 900-1000 rpm. You cannot get accurate timing once the vacuum is applied since the vacuum advance is designed to advance the timing under load or driving conditions.

'82 F150 2WD w/351W (orig 300 I6)
Slik

 

Steve,

Are you in still in Durham? I'm just east of Apex.

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi