When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I've watched videos and combed through the posts on here but I'm still a little confused on the procedure; mainly where to hook up the gauge and what to cap. I have a 71 Cutlass S 350 with a edelbrock 1406 and HEI. The distributor is hooked to the left side of the carb(facing the front of the engine) and another hose hooked to the right side. Disconnect the hose on the left and there's no vacuum unless the throttle is increased. Right side at idle there is around 15(not completely steady but in that range) plugged into the carb port. No change in idle when I disco left side but idle increases when disconnecting right side. So, should I be taking readings off the right side carb port or left and what should be capped off while doing so?
The port that does not have vacuum at idle is the one for ported vacuum for the distributor (if you choose to run vacuum advance off of ported vacuum). The other port is full manifold vacuum. You must connect the gauge to manifold vacuum. People loose a lot of sleep over this, but there is NO difference among any of the manifold vacuum ports. That one on the carb is exactly the same as one that comes off a runner on the manifold. Connect your vac gauge to one of these when adjusting the idle mixture screws. If you choose to use manifold vacuum for your vacuum advance instead of ported vacuum, cap the ported vacuum port on the carb and tee the distributor into one of those manifold vacuum ports.
Thanks for the info. So cap the X and move the line over to T into the right port going into the carb? Is there a performance difference if I kept it how it is? I mean, why are they both hooked up now?
If I do as above, gauge goes to right carb port and I need to cap the hoses for accurate readings?
The only real difference of running manifold vacuum advance is the engine will run a bit cooler at idle. If you put a T in the line on the drivers side to run the vacuum advance, when you perform a tuneup simply unplug the vacuum advance and plug in your vacuum gauge as the vacuum advance needs to be disconnected any way to set timing.
Manifold vacuum is the best and the one you want. Just study up more on it and you will see the light. Engine runs cooler and is more responsive off the line. It really sinks in by just trying both and messing with adjustable vacuum cans and distributer springs. Just keep your total advance under 38 degrees at all times just to be safe.
There are pros and cons for using ported vacuum for the distributor. Use the one that the engine likes best. Note that you will need to change initial timing depending on which way you go. Straight manifold vacuum can sometimes cause pinging if you don't have the distributor configured properly.
More importantly, from your photo, it appears that the line connected to the ported vacuum was the transmission modulator, NOT the distributor vacuum advance. That is completely incorrect. Whoever installed that carb had no clue as to what they were doing.
Joe I think the OP has the vacuum gauge hooked where the modulator was plugged in to. He should not have to adjust anything but the curb idle a bit lower if he goes to manifold vacuum.
Joe I think the OP has the vacuum gauge hooked where the modulator was plugged in to. He should not have to adjust anything but the curb idle a bit lower if he goes to manifold vacuum.
Yeah, but I assumed that when the OP said "left" and "right", he was referring to conventional nomenclature (left meaning driver side). If he's actually referring to the orientation of the photo, then yes the modulator is correct.
Yeah, but I assumed that when the OP said "left" and "right", he was referring to conventional nomenclature (left meaning driver side). If he's actually referring to the orientation of the photo, then yes the modulator is correct.
sorry for the confusion but yes, the drivers side port line looks to be going down to the transmission. The passenger side is going to the distributor.
The only real difference of running manifold vacuum advance is the engine will run a bit cooler at idle. If you put a T in the line on the drivers side to run the vacuum advance, when you perform a tuneup simply unplug the vacuum advance and plug in your vacuum gauge as the vacuum advance needs to be disconnected any way to set timing.
Ok so passenger side port will be permantenly plugged, the dist and tranny line will be T'd to the drivers side carb port? During tune, disconnect T line and hook up gauge to carb port. Should I cap the T while doing so? Permanent cap on passenger side?
T tranny and distributor to driver side? Nothing hooked to it
Also, any idea what the part coming out of the manifold is for?
Capping ports is performed with a rubber cap. Using the T installed on the drivers side for tuneups requires you to unplug the line off the T going to the distributor and plugging in the vacuum gauge in its place.
The item on the manifold is a temperature controlled switch. Apparently not used (typical) and can be removed and a pipe plug installed in its place.
Capping ports is performed with a rubber cap. Using the T installed on the drivers side for tuneups requires you to unplug the line off the T going to the distributor and plugging in the vacuum gauge in its place.
The item on the manifold is a temperature controlled switch. Apparently not used (typical) and can be removed and a pipe plug installed in its place.
Great thanks! I got them T'd off and will try to do the adjustments tonight.
Is there a recommended place to order a shop/repair manual for our cars? I assume Haynes and Chiltons aren't really preferred
I'll need all the help I can get. I've been messing around with the timing since I bought the car but not much has changed and at idle it won't go past 12 degrees and that's with the distributor maxed out clockwise
Mossy, to add to Eric’s reference of lar’s material. Lars recommends that anyone interested in his work contact him directly as he likes to provide info of his that has not been floating the web.
I'll need all the help I can get. I've been messing around with the timing since I bought the car but not much has changed and at idle it won't go past 12 degrees and that's with the distributor maxed out clockwise
Is it because there is interference with the vacuum advance hitting somewhere? If yes you need to pull the distributor and move the rotor one way or another a tooth until you get full adjustment.
Is it because there is interference with the vacuum advance hitting somewhere? If yes you need to pull the distributor and move the rotor one way or another a tooth until you get full adjustment.
You are correct. It is hitting a plug on the intake
Drain some coolant out of the radiator until the level is below the manifold. Install a male pipe hex socket plug in that ones place. Take your old one to match the size of the new one to a local hardware store if you want to leave the distributor where it is at. Or. you can restab it so the vac can is on the other side (where it belongs) and rewire accordingly. Either way will work.
I'd like to put it where it's supposed to be. So it's meant to be on the passenger side of the carb? I wonder if it's on the driver side because of that other piece(part of the AC?) was in the way?
It looks like moving it 180 degrees is going to put the dist vacuum manifold close to the firewall and there won't be much room for adjustment in the clockwise direction if needed
It looks like moving it 180 degrees is going to put the dist vacuum manifold close to the firewall and there won't be much room for adjustment in the clockwise direction if needed
I have a GM HEI on my car with a factory vacuum advance canister and I had plenty of room to set the timing anywhere from 10º to 20º.
Green mark is 0, orange is factory balancer line. Before I checked TDC, current setting was 12 degrees at idle with no more physical room to move the distributor clockwise
According to the finger test, this is my TDC. Any suggestions as to where I go from here? I didn't adjust the distributor before the test.
Shouldn't the line on the balancer line up with 0 on the timing tab on the compression stroke? If so, why isn't it? I need to replace the balancer anyway
Its possible the outer ring has spun on your balancer. You've come to this conclusion means that this is possible. Double check your work, and start looking at a replacement. Dorman brand comes to mind, but there are others too.
I have a pic or two of Olds balancers with a check mark. I'll post it as soon as I find it. I don't know if the factory did it or previous owners, but its a sign its spun. It needs to be very clean to see them, as they very faint. I hope this helps.
Last edited by don71; Aug 27, 2018 at 09:15 PM.
Reason: ad pic
I got the balancer pulled off and don’t see any other distinguishing reference marks. I figured as rusty as the thing is it would be the original but I’m guessing they weren’t made in China back then....that’s what it said under the surface rust.
Since I don’t know if the ring slipped I guess I’ll order a new one
Since I don’t know if the ring slipped I guess I’ll order a new one
You also don't know if the new one is accurately marked. You don't know if the keyway on the crank is accurate. You don't know if the timing tab is accurate. This is why people actually check TDC rather than throwing money and new parts at it. Your old balancer was fine. You could have bought a simple piston stop for a tiny fraction of what the new balancer cost you and actually checked TDC on the old one. You still need to check the new one, by the way.
You also don't know if the new one is accurately marked. You don't know if the keyway on the crank is accurate. You don't know if the timing tab is accurate. This is why people actually check TDC rather than throwing money and new parts at it. Your old balancer was fine. You could have bought a simple piston stop for a tiny fraction of what the new balancer cost you and actually checked TDC on the old one. You still need to check the new one, by the way.
That is correct; I used my finger for TDC and recently realized that’s not exact. So I ordered a piston stop tool the same time as the balancer.
Capping ports is performed with a rubber cap. Using the T installed on the drivers side for tuneups requires you to unplug the line off the T going to the distributor and plugging in the vacuum gauge in its place.
The item on the manifold is a temperature controlled switch. Apparently not used (typical) and can be removed and a pipe plug installed in its place.
Is this what was originally supposed to be in its place? Either way, it’s not needed?
