360 Questions.. pardon my ignorance.

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Gotchya. Just my personal advice, but I would disable and remove the OSAC valve.
Its gone, vacuum hooked direct from carb to distributor.

Came here because I have pretty much the same truck, same setup. '74 D200 truck, 360, Holley 2210. My setup runs PERFECT, so I wanted to let you in on where I ended up with it, starting with square transfer slots:

10 degrees initial, limited to 33 all in
Ported vacuum advance
mix screws 2.25 turns out.

This equals a 700rpm idle.

For what it's worth.
Ok that sounds like I’m not far off. How did you limit the all in timing? What port on your 2210 is your advance hooked to? I feel if I bump up my base timing from 5 up to 10 I’d probably be in the vicinity of 650-700rpm for idle.
 
Forget about the vacuum advance for now. Plug the damn port and get a base tune up in the poor thing. Then worry about vacuum advance.
 
Forget about the vacuum advance for now. Plug the damn port and get a base tune up in the poor thing. Then worry about vacuum advance.
So what’s your basic method then? It seems everyone has an opinion on what’s “correct”.

Carb is set to a baseline 2.5 turns on the idle mix screws, idle speed screw is set to achieve a square transfer slot. Initial timing is 5 degrees at 650rpm (on the last step of fast idle cam, shop manual calls for TDC). Once it comes off that cam to regular curb idle it wants to stall unless I give it a little throttle.

So where would YOU go from there?
 
So what’s your basic method then? It seems everyone has an opinion on what’s “correct”.

Carb is set to a baseline 2.5 turns on the idle mix screws, idle speed screw is set to achieve a square transfer slot. Initial timing is 5 degrees at 650rpm (on the last step of fast idle cam, shop manual calls for TDC). Once it comes off that cam to regular curb idle it wants to stall unless I give it a little throttle.

So where would YOU go from there?
Give the engine what it wants, stop worrying about trying to hit a specific number or target for timing, turns of idle mixture screws ect. Don’t be afraid to adjust the idle speed screw a little from a square transfer slot either way, give it the idle timing it needs to maintain a smooth idle and not slam in to gear, and make sure to limit the total timing once you establish what it wants for initial if it’s above what the distributor was originally curved for. And the best piece of advice I’ll give is this, once you set one thing, don’t be afraid to re do it once you change something else. All of these adjustments can affect each other.
 
You need a vacuum gauge. You can use that to zoom right in on the air screw adjustment and to see where the engine wants the timing to be.
 
Give the engine what it wants, stop worrying about trying to hit a specific number or target for timing, turns of idle mixture screws ect. Don’t be afraid to adjust the idle speed screw a little from a square transfer slot either way, give it the idle timing it needs to maintain a smooth idle and not slam in to gear, and make sure to limit the total timing once you establish what it wants for initial if it’s above what the distributor was originally curved for. And the best piece of advice I’ll give is this, once you set one thing, don’t be afraid to re do it once you change something else. All of these adjustments can affect each other.
I’m expecting to set things a few times and tinker a lot. So questions about the process..

With it stumbling at hot idle should I first adjust the speed screw or the base timing?

Once base idle is established do I adjust the mixture screws for best idle/vacuum before bringing the vacuum can back in?

After all that, I confirm my total timing and limit the distributor weights if necessary?

You need a vacuum gauge. You can use that to zoom right in on the air screw adjustment and to see where the engine wants the timing to be.
I have a gauge, I used it in an initial setup where I got the truck running OK from a non-starter when it came home. Now I’m to the point with the truck I’m really digging in and doing the proper process to actually start driving and using it.
 
I’m expecting to set things a few times and tinker a lot. So questions about the process..

With it stumbling at hot idle should I first adjust the speed screw or the base timing?

Once base idle is established do I adjust the mixture screws for best idle/vacuum before bringing the vacuum can back in?

After all that, I confirm my total timing and limit the distributor weights if necessary?


I have a gauge, I used it in an initial setup where I got the truck running OK from a non-starter when it came home. Now I’m to the point with the truck I’m really digging in and doing the proper process to actually start driving and using it.
You should continue using the vacuum gauge.
 
With it stumbling at hot idle should I first adjust the speed screw or the base timing?
That’s fuel related.

Once base idle is established do I adjust the mixture screws for best idle/vacuum before bringing the vacuum can back in?
The vacuum advance will have zero effect on idle if on ported vacuum (where it should be for a relatively stock engine) so you’d want the idle fuel and timing sorted out prior to adding it back in to the equation.
After all that, I confirm my total timing and limit the distributor weights if necessary?

Yes and adjust the curve with springs. And I’ll add that once vacuum advance is added back in, you might have to delay it with the screw in the can to avoid detonation on early tip in at cruise.
 
So with the vacuum can disconnected I settled at 10 degrees initial, it’s a bit back from rough running and a bit higher than sounding lazy. Idle is stuck around 500-550rpm, mix screws are 2 turns out and I had to put a turn and a half into the idle speed screw. Vacuum on the gauge has a little bounce to it but not dramatic, shows to be in a good range. RPM only drops 100-125rpm when put into gear.

Here’s the issue I’m on now.. when I bring the vacuum can back in I’m at almost 50 degrees of advance at about 750rpm. It is firm going into gear but I wouldn’t say it’s slamming gears.

I measured the spark port on the carb, it show vacuum all the time, increasing with engine speed. The only other ports are on the firewall side, one for PCV and one that I believe is the heated air hookup for the air filter. Which leads me to, I’m sure, a wildly incorrect train of thought..

With those variables could I not set the motor back to TDC timing like the shop manual states and rely on the vacuum can to apply the timing? That appears to be how it would have been originally setup?
 
Sounds to me like you’re either using the wrong port on the carb or the carb base plate is cracked allowing vacuum where it shouldn’t be. A true ported vacuum gets its source from above the throttle blades and has zero vacuum until the throttles are opened.
 
Sounds to me like you’re either using the wrong port on the carb or the carb base plate is cracked allowing vacuum where it shouldn’t be. A true ported vacuum gets its source from above the throttle blades and has zero vacuum until the throttles are opened.
I’m starting to wonder on the carb too.. I sprayed around the base of the carb and where the intake meets the heads and didn’t find any noticeable leaks. I’ll check the back port when I have more daylight and confirm it’s not a ported source. On the curb idle should I just put another turn into the speed screw to raise the idle to 750? I can imagine that will be exposing quite a bit of that transfer slot..
 
Sounds like, for whatever reason, the t/blades are open too far at idle which is causing the vac adv port to be operating at idle, adding timing.
For 'whatever reason' could be a myriad of things such as a vac leak, very low compression etc.....
 
Its gone, vacuum hooked direct from carb to distributor.


Ok that sounds like I’m not far off. How did you limit the all in timing? What port on your 2210 is your advance hooked to? I feel if I bump up my base timing from 5 up to 10 I’d probably be in the vicinity of 650-700rpm for idle.
All in was limited with a FBO plate that I modified to my needs.
Timing is on ported vacuum.
 
What does
Initial timing is 5 degrees at 650rpm (on the last step of fast idle cam, shop manual calls for TDC). Once it comes off that cam to regular curb idle it wants to stall unless I give it a little throttle.
the fast Idle cam have to do with anything?
Of course it's going to stall coming off the step, cuz the T-port got slammed shut.
The T-slot exposure is set using the curb idle screw on the curb-idle stop, the absolute most closed the throttle can be, with absolutely NO interference by the fast idle system.
Where did you get the idea to use the lowest step of the fast-idle cam?
Start over
 
Here’s the issue I’m on now.. when I bring the vacuum can back in I’m at almost 50 degrees of advance at about 750rpm. It is firm going into gear but I wouldn’t say it’s slamming gears.
Fifty degrees should be as good as impossible.
Something is not right.
The absolute MOST, your Vcan would be able to bring is 24*, with most of the stops filed off. Thus, at idle, with full-manifold vacuum, and with 5* initial, the absolute most you could get would be 29*.
Typically the VA will max at around 13>15 degrees. More than that will require modification.
If in fact you are truly getting 50, then, either;
1) The throttle opening is enough to bring in full signal to the sparkport,
2) or the advance springs have to be not functioning correctly or not at all. AND/OR
3) the VA return spring has malfunctioned. Which I've never seen; or
4) something else is wrong that I have not thought of
SO
1) Check your curb idle transfer slot exposure! if that is correct, then;
2) Pop the cap and rotate the rotor against the spring pressure as far as it goes then quickly release it. The rotor should snap back to the starting position with a good deal of authority. If this does not happen, set your crank position to TDC #! Compression and pull that beotch outta there and lets get to the bottom of that bad boy.

BUT
if the rotor pops back nicely, then it must be a faulty signal to the ECU, and the only way mine ever did that was with the polarity reversed.
SO
Check your pick-up colors. the Small-block CW rotating Distributor needs a Pick up with one ORANGE wire on it. I forget the other color, maybe black.
If your pick-up has a Violet wire, it belongs to CCW rotating distributor.
Now, Go look where that pick-up connects to the ECU wire. The orange wire should go straight thru the connector without changing colors. I have seen polarity-reversing patchcords plugged in there, that look factory, about 6inches long. I seem to remember the wires being gray and black. If you see one of those, unplug it, Reconnect the P-Up to the ECU, and see if the engine will start. The timing will be all wrong, so you'll have to start over. I'm sorry, but I can't remember which way the timing went, So, if it won't start; pretend it's a new distributor install.
THUS:
Set the crank to TDC #1 compression, then advance the crank, BACKWARDS, CCW, to ~20 degrees. Push the V-Can CW until it hits the firewall, then pull it off the firewall to align the P-up to the nearest reluctor vane, center to center. Then install the rotor. With the rotor properly parked, mark the outside of the distributor as to where the tip of the rotor is. Install the cap. Find the mark; it better be close to or right under a tower. That tower will be your #1 cylinder, so plug #1 wire into it. Then follow CW in the firing order.
Now fire it up and reset your Idle timing. Then verify that the Strobing is without drama.

If it should happen that at 5* Idle-timing, the Engine needs a lot of throttle-opening to idle, My guess is that the engine has a mechanical problem, either;
1) a cylinder has gone down, or
2) the cylinder pressure is poor, or
3) the valve-timing is more than just a little off, or
4) the idle AFR is extremely off,

happy hunting.
 
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