(Login PatSignorino) Members from IP address 12.229.203.118
Hi All, 1st post! I'm glad I found this message board!
I recently had a 351c 4V with C6 Auto rebuilt, the engine is stock and in great shape, but the secondary systems are in worse shape. Last week, I bought an Edelbrock Performer 600cfm Carb, and got that running ok now. I also got a Pertronix ignition just to bring a little more simplicity to the setup. I posted some questions to other Mustang Specific message boards, so sorry if some of you are seeing this more than once.
When I pulled the old Holley Carb off the engine, there was one hose on it hooked to the outside canister on the distributor. I've tried to hook this up to the Edelbrock on both ports (using a timing light to set the timing with the hose disconnected and ports plugged first), but the car runs really bad when the hose is placed on either port.
One port retards timing when you put the car in gear so much that the car won't move more than 5 feet before dying. The other port advances timing to full 40? degrees by 1,500 rpm.
I have the hose disconnected now, and timing at 14BTDC. The car drives great like this. Advance is laggy but seems to work when I rev the engine, and watch it on the timing light.
My question is, what is that hose supposed to do? Retard or Advance, and how much and when? A book I have called Ford Performance says I should hook it up to Manifold Vacuum, but it acts just like I mentioned above where timing retards so much it kills the engine when in gear.
The vacuum advance unit is adjustable. You need to limit the total advance under vacuum. You adjust the unit by inserting an allen key (I do not recall what size, try several until one fits) into the front (some have two) hose nipple. Turn it one way or the other (been a while, obviously) until total additional vacuum advance is about 10 degrees. Your engine will like this.
In my daily butt hauler I run manifold vacuum advance. The car is a 1973 Mercury Montego four door. It's a pretty big car, about 4200 lbs. The engine is a 351 Cleveland 2V, it has a PAW/SSI 11339 (194/204 @.05, .458/484), a Performer intake, a 600 Holley and duals. I use a Pertronix Igniter in a Ford dizz with a Ford Duraspark coil. The Holley has a light sec spring, so it cuts in quickly.
I run 12 degrees initial advance, use the stock curve and use manifold vacuum for the vacuum advance unit which is adjusted to provide only 10 degrees additional advance. The result is that at idle, the engine runs smoother with the ac on (York comp that does not cycle, unless you count when I have to turn it off when the core freezes. I could store meat in that car). The vacuum provides an increase in efficiency at cruise (18 MPG with 2.75s). Being that it is manifold vacuum, the amount of additional advance is reduced when I push into the throttle. Acceleration is easy and effortless, especially in the 2-5K range where Clevelands run great. The greatest advantage of this set-up is the reduction of advance under acceleration. The US 2V Cleveland heads have an open chamber. That chamber coupled with the dished pistons of 1973 create a great deal of surface area. Detonation is a real problem here, but I am able to run the car on 87 octaine with no problems, even on hot SoCal days with the AC on. When I was trying ported vacuum, I could get it to run well but detonation on acceleration was a problem. As it is, the car runs very well.
I'm pretty sure I have the canister hooked to the correct vacuum source on the carb now.
If I hook the canister up to either the manifold vacuum or the vacuum port on the right side of the edelbrock, my timing advances really high even at idle. I think there is too much vacuum on those ports.
If I hook it up to the port on the left side of the edelbrock carb, timing stays the same (14 degrees) until you flick the gas, then timing advances very quickly to 40-45 degrees BTDC. The marks on the balancer stop at 30BTDC, so I'm guessing on the 40-45, but I'd say that's accurate if the scale would remain the same size further on the balancer.
I found an alan wrench that fits in the vacuum can, and turned it clockwise and it stopped at about 4 turns (it was fully tight). I rehooked it up, and checked timing, still goes to 40-45. I then took the alan wrench and ran it counterclockwise 5 times, checked again, still 40-45. I gave it another 5, same result, and another 5, and the threads popped off the bolt hole inside the canister same result.
For right now, I'm still running without the vacuum hooked up.
I'm pretty sure I have the canister hooked to the correct vacuum source on the carb now.
If I hook the canister up to either the manifold vacuum or the vacuum port on the right side of the edelbrock, my timing advances really high even at idle. I think there is too much vacuum on those ports.
If I hook it up to the port on the left side of the edelbrock carb, timing stays the same (14 degrees) until you flick the gas, then timing advances very quickly to 40-45 degrees BTDC. The marks on the balancer stop at 30BTDC, so I'm guessing on the 40-45, but I'd say that's accurate if the scale would remain the same size further on the balancer.
I found an alan wrench that fits in the vacuum can, and turned it clockwise and it stopped at about 4 turns (it was fully tight). I rehooked it up, and checked timing, still goes to 40-45. I then took the alan wrench and ran it counterclockwise 5 times, checked again, still 40-45. I gave it another 5, same result, and another 5, and the threads popped off the bolt hole inside the canister same result.
For right now, I'm still running without the vacuum hooked up.
I'm assuming your messing with the stock dual diaphram advance. It has springs and spacers to adjust advance. The heaver spring the more vacuum it takes or the more shim will limit the total vac advance. The retard side was more for emisions so the factory didn't have to run a thermactor pump. My car has the imco system which used the thermal vac switch on the water pump then into the speed sensor under the dash which decided to retard or not. My car is a 1970 351 4v mustang.
I haven't touched anything in the distributor itself yet. I'd like to run just vacuum advance if possible.
I found this quote doing a newsgroup search...
"I recurved my distributor a number of years ago but did a great deal
of research before doing so. Here is what I found.
When you refer to 36-38 degrees of total advance that is based solely
on the initial advance and the weights. The vacuum advance(I use an
adjustable crane type) kicks the advance up to as much as 60 degrees
under load. If you doubt either of these numbers wrap timing tape
around your harmonic balancer(on my tape degrees are displayed all the
way around) and watch the numbers while you give it gas; with vacuum
advance and without.
This sounds severe but it's not unless you are wide open. You need the
vacuum to help under part throttle initially but once RPMs are pretty
high the weights are doing the job. That's why with timed advance you
have no vacuum at full throttle. In other words, when you are going
flat out all you have is mechanical advance."
That sounds sort of like what I'm looking at when I hook my vacuum can up to ported vacuum. Is what he's saying above at all accurate (the 38 degrees total advance I'm shooting for being the figure for mechanical plus initial and not including vacuum?)
I've pretty much got the problem down to the vacuum can. The car is running pretty good without it hooked up.
When I do hook it up, I have way way way way way too much advance, we're talking 60+ in the 3,000 rpm range. I hooked it up anyways, and drove around the block. The car had great response, but was pinging at anything more than the lightest throttle. So, I disconnected again
I'd like to either limit this can's max advance (I've tried the hex wrench in the nipple, but the full extremes of adjustment don't change the advance nearly enough). What other adjustment can I make? I'll open it up tommorrow and peak inside. I just bought a vacuum tester gun, so I can give it vacuum and see what happens inside.
