mdt424

Hi guys! Ran into a stag on my sons 68 Mustang. It has a C4 tranny that we believe is stock but don't know for sure. We replaced the stock 289 with a "built" 351W, so we were told. I know it's does not have a stock cam because we had to use the non Windsor timing of 15426378 instead of the normal Windsor timing order 13726548 but lifters, rockers ect all look basically stock. It doesn't have a big "Lope" a racing cam would have but seems to run very healthy. I have absolutely no info on the build other than it was built to race.

The issue is when we shift the car into any gear it stalls immediately. I have to turn the idle up to about 1500 to 1600 rpm's for it to be able to stay running then it's shifts very hard & motoring down the road at 35mph at idle. Not ideal for a 17 yr old. Checked for vacuum leaks, changed the vacuum modulator, changed to several different vacuum sources on the carb & manifold. We're using a Edlebrock Performer RPM manifold with a Edlebrock 600 cfm 1400 carb. The torque converter is stock as far as we know & the trans worked just find with the 289. I've been told I shouldn't need to increase the stall but that's all that's left for my skill level. We've been restoring her since he was 14 & it's his pride & joy. Any help would be great!!

Thanks! Mark 7 Aaron

jwog666

check your timing, and your idle mixture, either could cause stall when shifting into gear from park. if the trans shifts and will drive down the road, you can rule out the transmission as a cause

barnett468

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Check the timing at idle.

Unplug the distributor vacuum hose and check the timing.

Leave hose disconnected and plugged.

At idle, plug the pcv valve . . if the rpm drops more than around 50, it is too big.

Plug pcv valve irregardless

Disconnect the vacuum hose to the trans and suck on it . . it you can suck air, the hose is bad or fell off or the modulator.

If its good, reconnect it.

Lower the idle and spray FLAMMABLE brake cleaner with the long nozzle gently around the carb base and intake where it meets the head . . if the rpm goes up, it has an air leak.

Set timing to 12 degrees btdc.

Return idle to normal.

If there is no air leak, turn one fuel mix screw in 1 turn . . the rpm should drop, then turn it back out 1 turn.

Do the same with the other screw.

If one of the screws had no effect, you have a plugged idle circuit.

If all is good, put the trans in gear . . if the rpm drops much or it dies, your stall converter is too low.

Post all results.

boogerschnot

I agree with barnett. Go to harbor freight and get a vac gauge so you can tune that carb idle after adjusting timing. Tune the idle mixture for highest vac.

Another thought.. Do you have power brakes? You could have a leak in the booster. You hold the brake to shift out of park.. Just a thought.

mdt424

Thanks guys. After a weekend of tweeking...not twerking....we have it shifting fairly normal with the exception of going into third gear but I seem to recall that's just an adjustment but I digress.
All the vacuum stuff seems to check out. I ran through your list Barnett, with the exception of the PVC which this car doesn't have one. Should it?
Idle mixture screw affected the idle speed just as you said.
my issue is the is no way this car will run at 12 degrees, I can get it to about 20 degrees tdc. I've stabbed the distributor forward & backwards two teeth trying to correct this. I'm beginning to think the harmonic balancer is in the wrong place but I'm going to check it tomorrow with a piston stop to verify that it is. I don't believe that the motor is running at it's potential because of this timing issue but I've had more than one person tell me if I have it running this well that there's nothing major to do, I'm not so sure. I also agree & will pick up a vacuum gauge tomorrow. Any other suggestions?

Thanks again!!

Mark & Aaron

jwog666

good idea to verify the balancer, they can slip and mess up timing readings, i would ALWAYS recommend running a pcv valve in every engine, the reason is this draws in fresh air to remove blowby gasses and moisture from the crankcase, its for emissions yes, but it will keep the crankcase free of sludge producing moisture and corrosion causing gasous byproducts of combustion. and that is the real benefit

barnett468

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ok, you do not need to know where tdc is to do this test but it might help.


CHECKING TIMING CHAIN PLAY

Remove distributor cap

Facing the engine, rotate it counter clockwise until the tdc mark on the damper lines up with the pointer on the engine.

Now, slowly rotate the engine clockwise until the distributor rotor just barely starts to move then put a mark on the damper where the pointer on the engine is pointing . . you might need to do this a few times.

Measure the distance from tdc to the mark . . if it is more than around 3/4 inch, your chain should be replaced . . this play also affects where you need to set your timing relative to the marks on the damper.


MARKING THE DAMPER

use a cloth tape measure and measure from the tdc line on the damper to 10 degrees.

now take that measurement and measure from 10 degrees to where 10 degrees was on the tape and put two dots with liquid white out there, one in front of the other . . you now have marks at 20.

measure 10 more degrees from 20 and put 3 dots like above . . this is 30.

measure 10 more degrees from 30 and put 4 dots like above . . this is 40.

measure 10 more degrees from 40 and put 5 dots like above . . this is 50.


The following quick and easy test will give you an idea as to what the optimum timing is for any particular engine . . Doing this test and making the appropriate changes suggested by the results may save you some time on a dyno and therefore save you money.

After the test, if you have a vacuum advance, i would also set it for a max of around 6 - 8 degrees and connect it to ported vacuum not manifold vacuum . . if your ported vacuum port has vacuum at idle, you need to fix it before connecting the vacuum advance.


IGNITION TIMING TEST

Incorrect timing can easily cost 10 hp or more.

Too little initial timing can cause engine to idle hotter than it otherwise would.

Check for carburetor and intake air leak.

Plug the vacuum advance line.

With the engine warm/hot, loosen the distributor bolt 1/4 turn

Start engine and note the timing . . stock is around 6 degrees btdc, 8 – 10 is often better.

Let engine idle and advance the timing 3 degrees.

If the rpm increases and the engine still runs perfectly smoothly, reset idle and advance timing 3 more degrees.

If the rpm increases and the engine still runs perfectly smoothly, reset idle and advance timing 3 more degrees.

Next, reset the timing and idle speed to the pre-test level.

Turn up idle screw so engine is revving around 2500 rpm and note the timing.

Advance the timing 3 degrees.

If the rpm increases and the engine still runs perfectly smoothly, advance timing 3 more degrees.

If the rpm increases and the engine still runs perfectly smoothly, advance timing 3 more degrees.

Reset timing to previous setting and post results.

mdt424

Okay, left out a couple things. First, no power brakes. Second the old distributor had no vacuum advance but the Pertronix does. Barnett if I understand you correctly I want to hook the Vacuum advance to low/no vacuum port at idle? The port I have it hooked to now has a high vacuum which does increase the idle. Also I have marked the balancer up to forty degrees & as of now the further I advance the timing the better the car runs. I hit the water neck with the advance before it ever runs badly but when its advanced that far my marks on the balancer are out of sight.

Mark & Aaron

barnett468

ok, big, big mistake using manifold vac for the vac advance.

plug the vacuum advance and leave it plugged . . AFTER, your completely done tuning etc, then set it to advance 6 - 8 degrees and connected it to the port that has 0 vacuum at idle no matter what anyone else says.

remove your distributor and rotate the rotor counter clockwise 1 tooth . . your distributor will not go in all the way . . bump the starter over while gently pushing on the dist . . it will drop into place.

connect the timing lite and check timing while turning it over . . set it to 12 in your case.


follow these instructions to the letter

Plug the vacuum advance line.

With the engine warm/hot, loosen the distributor bolt 1/4 turn

Start engine and note the timing . . if it changed from 12 degrees make a note.

Let engine idle and advance the timing 3 degrees.

If the rpm increases and the engine still runs perfectly smoothly, reset idle and advance timing 3 more degrees.

If the rpm increases and the engine still runs perfectly smoothly, reset idle and advance timing 3 more degrees.

Next, reset the timing and idle speed to the pre-test level.

Turn up idle screw so engine is revving around 2500 rpm and note the timing.

Advance the timing 3 degrees.

If the rpm increases and the engine still runs perfectly smoothly, advance timing 3 more degrees.

If the rpm increases and the engine still runs perfectly smoothly, advance timing 3 more degrees.

Reset timing to previous setting and post results.


SUMMARY

Basically, you want to turn the distributor at idle and around 2000 rpm until the rpm no longer increases, then retard it 3 degrees and give us those numbers.

you likely need to buy the mr gasket distributor spring kit and replace the stiff spring only.
.

jwog666

http://chevellestuff.net/tech/articl...r_manifold.htm here is an article on ported vs manifold vacum for advance