360 Questions.. pardon my ignorance.

[CoolDave]

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.

 

[RustyRatRod]

Its gone, vacuum hooked direct from carb to distributor.

Probably a good idea. Even if it was in working order, it's just less to go wrong.

 

[volaredon]

The "osac" port on the carb IS the (ported) vac advance port.

 

[TT5.9mag]

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.

 

[CoolDave]

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?

 

[TT5.9mag]

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.

 

[RustyRatRod]

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.

 

[CoolDave]

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.

 

[RustyRatRod]

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.

 

[TT5.9mag]

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.

 

[CoolDave]

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?

 

[TT5.9mag]

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.

 

[CoolDave]

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..

 

[Bewy]

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.....

 

[emmett442]

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.

 

[AJ/FormS]

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

 

[AJ/FormS]

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.

 

[CoolDave]

What does

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

That was for a point of reference. Like I said, off fast idle it wanted to stall. I’m not using the fast idle cam for anything different than normal.

Last night I pulled the carb again and yanked off the baseplate. I didn’t find any cracks or anomalies so I cleaned it and reinstalled it with a fresh gasket. Set transfer a lot to a square and mix screws to 2.5 turns. Ported vacuum now reads almost zero at idle and jumps up when you crack the throttle so I think the gasket fixed that problem.

Here’s where it gets weird.. now with the vacuum can disconnected I’m reading about 20 degrees advance at idle, which is still a LOW idle. So I’m assuming either my distributor is trashed (quite possible, parts store special), my timing light is going haywire or I have something internal to the motor with more slop than it needs.

I think my first step is going to be turning the crank by hand and watching for slop in the turning of the distributor rotor.. then I’ll move on to pulling the distributor out and inspecting it and reset it in the motor from scratch.

 

[AJ/FormS]

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,

If it should happen at a TRUE 20* Idle-timing, I'd just go straight to cam-timing.
This can be checked close enough without taking the timing cover off, but, one valve cover will need to come off.
The idea is to put the cam on one of either #6 or #1 split overlap and reading the advance off the balancer. It's just that easy.
Split overlap is when, near TDC, both the intake and the exhaust valves are open equally, the one closing while the other is opening. For this test, you don't have to be super accurate, BUT you gotta be sure that the lifters are not bleeding down while yur doing it. And, if your timing chain is really stretched, you gotta do the test with the slack taken out from the "pulling" side.
Ideally, the cam will be in a few degrees advanced.
As to cam-timing
As the cam gets more and more retarded, it takes more and more throttle-opening to idle.
As the cam gets more and more advanced (which does not happen with chain stretch), it takes less and less throttle-opening to idle.

As to ignition timing;
at idle, the engine will always like a bunch of timing, usually into the thirties and more .... at idle.
The more advance it gets, the higher the idle speed will climb.
The more retarded it gets, the lower the idle speed will fall, until it stalls.
>This is why after the Transfer slot to mixture screw adjustment is finalized, Idle rpm is set with Idle-timing. It's the only other option left.

In your case, with the sparkport already being tickled, and the idle-timing pushing 20 degrees, it seems obvious to me, that the engine has a mechanical problem, and the most obvious is cam-timing. But could be other, such as;
1) internal friction, a crank spinning in a very high oil-level, or a dragging convertor, or
2) like very low cylinder pressure, or something I haven't thought of, or
3) like dead cylinders, which could be; bad plugs, bad wires, a bad cap, or even crossed plug wires. Numbers 5 and 7 are occasionally messed up.

 

[CoolDave]

Last night I pulled, cleaned and reassembled the distributor. Restabbed it and retimed it. Mechanical is set to around 8-10 initial and about 36-38 all in. Idle is stubborn at 500-550rpm but it eases into gear without stalling or slamming, its running cool and the oil pressure is good even at idle.

When I find time I’ll run it up and down the street but idling around the yard it seems fine. I guess we will see.

 

[volaredon]

Nother 360 question
Why did they castrate every damn one of them with low compression and DISHED pistons???

 

[AJ/FormS]

possibly cuz it already had 20 cubes over the 340, and 42 on the 318?
But more likely to keep that girl sucking gas so the oil-barons could keep on getting richer.
My second combo was the 11.3 Scr combo with the Hughes 270/276/110 cam at .028Quench, that with a manual trans geared for 65=1600/ 85=2100, got about double the mpgs that the stock engine did when geared 65= 2500 with an automatic. That sorta revealed to me that something ugly was going on in the world as regards the profits of gasoline.
Even in todays world, it seems no matter what the manufactures do, fuel economy is barely creeping up. The typical engine of the mid 2010s , being a direct-injected, 4-pot, 2.5l, DOHC, VVT, mpfi, engineering marvel with all of 160 hp, still only gets mid to high 30 mpgs.
Whereas I bet most of us can squeeze a 318, to get that economy at a similar cruize-rpm, with nothing but closed chambers, a bit of squeeze, and computerized ignition advance, and still make way more than 160 hp.
So then, how far have we really come in the last 50 years? They're dumbing us down, and we know it.

 

[Bewy]

To meet emissions targets....

 

[CoolDave]

Carb on the motor is junk.. peeked down the barrels and inside the intake was wet with fuel. Pulled the top off it, tweaked the float level and put it back in.. it fired up and ran for less than a minute, inside the barrels are slick with fuel and I got a big puff of smoke out of the carb when it stalled out. Thing is just dumping fuel. I tried spraying carb cleaner around it and squirting it in the front drivers-side corner caused an almost stall so there’s also apparently some kind of vacuum leak there too.

So truck will be on the backburner for a bit, I don’t have funds to be buying stuff for a project that I don’t need running immediately. I’ll plan on buying a new or verified replacement.

 

[CoolDave]

So I have an update on this in case anybody is interested…

Long story short I got drastic but it paid off.

Basically after overthinking this truck and tinkering on and off for so long I decided to scrap everything I had read or memorized and started from scratch on my troubleshooting and setup..

First problem was the vacuum leak in the carb, I had seen the baseplate mentioned a few times but that wasn’t my issue at all. The main body of the carb had some distorted tabs for the baseplate screws to where the if you took the gasket out and just matched the faces together the left/right edges would touch but you could see daylight straight through the middle. Considering it was potential scrap anyway I simply took a flat file and leveled the tabs down to get a better face on the main body. Threw it all back together and tried spraying the carb like I did to initially find the problem.. fixed.

Next I moved onto the timing again. The motor has been replaced in the truck so I found the date code and it’s a ‘75 motor. Pulled out my shop manuals, both ‘73 and ‘75 called for TDC timing, I went a little higher and locked it in around 8-10. Lo and behold with the vacuum advance hooked up and the transfer slot set about square the idle speed landed around 700rpm.
Call that good.

Last was idle quality and off idle stumble.. I reset the idle mix screws to 2 turns out and it was decent but with an odd miss here or there so an extra half turn out and no more stumble.

I still have to road test it but it’ll crawl in gear, has no more stumble at part throttle and it will throw rooster tails in the yard so I’m calling it good. Sure, it probably is a little fat and lazy but considering it will just be for cruising into town on weekends it’s more than sufficient for my needs.