Timing settings for '74 318

[The_Handier_Man1]

From: Supplysunshine1  (Original Message)
Sent: 3/17/2005 4:43 PM

Do es anyone know what the timming is suppose to be set at. The 1974 winnie Brave model  318 motor . When you are driving it ,it spits and back fires through the carbuator and tail pipe. We have put on all new plug wires,new plugs,dist. cap, rotory bitton, and all new slectronic modules, all new vacum hoses. Would appreciate any input on this.

                                                      Thanks
                                                      Don



From: denison
Sent: 3/17/2005 6:24 PM

From the Service Manual, the 318 idle ignition setting would be 2.5° Before Top Dead Center, plus or minus 2.5°. Yes, really. That would be measured with the vacuum advance line disconnected from the distributor and capped. But even if its correct at idle, you cant be sure it would be correct at highway speeds. There is a centrifugal advance mechanism inside the distributor which makes the spark fire earlier at higher speeds. It depends on 2 small springs, which can weaken or break, and it depends on the outer distributor shaft being able to turn a few degrees on the inner shaft, when the advance weights are being flung outward. You should be able to turn the rotor a few degrees clockwise, then it should spring back when you let go. This would only be about 8 or 7 degrees, at the rotor. This equals twice that many degrees at the timing marks at the front of the engine, since the distributor spins at half crankshaft speed. You should put a drop of oil on the felt wick that you find under the rotor, inside the distributor. If that mechanism is sticking at one extreme or the other, it can drive you batty.
The actual centrifugal advance specs are: 0°-- 2° @ 500 rpm. 6.5°-- 9.0° @ 859 rpm, 13.5°-- 15.5° @ 2150 rpm. The vacuum advance specs are: 1°-- 3.5° @ 9.5” 7° -- 10° @ 14”. That 9.5” is what you would see on a vacuum gauge connected to the vacuum advance hose. I wouldn’t worry about the vacuum advance however, it would not have any effect in causing backfiring and afterfiring. But if its not working your mpg will be slightly lower.
I would advise doing a compression check, to see if you have a valve that is not quite closing. It would show up as very low compression in that cylinder. The backfiring and afterfiring might be caused by a Bad misfiring, and that could be caused by something wrong in the carburetor â€" like a clogged air-percolation passage or venturi fuel outlet, or a main jet that had come unscrewed, that sort of thing. In such a case I would expect all of the plugs to be similar in color, being very dark, and none of them a nice light brown. If it was a leaky valve, or a sticking lifter, the spark plug for the affected cylinder would be very dark compared to the rest.
You can sort-of check whether the ignition is firing steadily by turning on an a.m. portable radio right on the dashboard. The ignition noise will be easy to hear when tuned to a weak station. Good luck.
Depending on mileage, if the distributor shaft is badly worn, it can interfere with the pickup coil inside the distributor and mis-firing can result. That would be unusual though.. Is the PCV valve working okay? I don’t think your engine has an EGR valve on it, or I could suspect it being stuck wide open. Could there be a large vacuum leak due to a bad brake booster diaphram? You would have to close off the vacuum line to the boosters to find out, but don’t try and drive it that way. Without the power brakes they are Super Hard to stop.



From: rshaw500
Sent: 3/17/2005 7:37 PM

Don,
I would check all of your fuel filters.   One thing that a seasoned classic owner knows is that people would let these things sit for long periods of time with gas in the tank.   The gas would then turn bad and leave objects floating and then they would be trapped in the fuel filters.   You should then replace them with the see through type because the only way to really get rid of floaties in the gas is to drop the tank and open it up and clean out the insides.   If you have replaced everything pertaining to a tune up then the obvious choice is to check out fuel filters. 
Rick



From: mightybooboo
Sent: 3/17/2005 10:08 PM

Check the firing order on plug wires.More than one member here has had that problem of wrong wires to wrong plugs.

BooBoo



From: nitedriver57
Sent: 3/19/2005 3:53 AM

just went through the same thing on 77 Brave with 440. turned out to be the carb base gasket.
I am ssuming you have the 2bbl carb, so here is timing info for 318ci, in California,
With distributor vacuum advance hose disconnected and plugged the timing should be set to TDC@700 RPM.
For federally certified units timing should be 2 degrees BTDC.
Hope this helps



From: nitedriver57
Sent: 3/19/2005 3:55 AM

Firing order should be 1-8-4-3-6-5-7-2