Shotgun Adjustments, Now Troubles

MericaMopar

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Hi guys, I got a '64 361 mopar engine that is entirely stock other than a holley street warrior (4160) 600CFM carb, weiand 8008 intake, and 440 heads. It has a push button auto with 2.76 gears.

I had it running ok at factory specs, 12 degrees of BTC timing, and the carb adjusted just using the idle screw and idle mix screws. It lacked power but would scoot about with no issues.

I then started reading and watching things about getting more performance from adding more timing to the distributor, changing the springs in the distributor, and properly setting transfer slots on the carb (idle mix screws weren't really effective when I first set the carb up). This is where I have run into trouble...

I took the carb off and set the primary butterflies using the idle speed screw to show square transfer slots, they were way to far open before, almost half the slot exposed at idle. On the distributor, I took out the stock heavy spring and replaced it with a black spring from the FBO kit and also used the mechanical advance limiter set to 18 degrees of advance. I then added more initial timing to 18 degrees and set the new idle speed at 1000rpm (in neutral...750 in gear) with the secondary stop screw.

I now have an off idle or off cruise bog....with light to moderate press of the pedal. WOT seems fine and has more power than before. Revving in neutral would result in a backfire through the carb once rpms got to around 3000. Bog is really bad under high load and low rpm. For example, taking off from a stop or letting it shift into 2nd or 3rd while going less than 25mph.

Things I have tried so far:
1. increase pump squirter from 31 to 35
2. changed power valve from 6.5 to 8.5 (vacuum in gear is 17)
3. changed pump cam from orange to blue

These changes have alleviated the carb backfire...and now I just have a bog and the car could still definitely stall out if I didn't do some fancy footwork while taking off or manually shift gears. Past 2000rpm it runs great, zero hesitation when pressing the throttle.


Overall I am confused, mainly because everything I see and read....setting the carb up "correctly" and adding timing is a sure fire thing. Do you guys think this is still a carb issue at this point? I have not tried main jets yet. My feeling is its running lean now because of the timing changes and just needs more fuel now which is why I have been going after the carb. On the flip side, most carb issues are electrical, but I feel the way I have mine set up is pretty normal and should work fine. I know I messed up using the shotgun approach. I did try going back to 12 degrees of timing, but I would have to open up the secondaries quite a lot to get back to a good 1000rpm (750 in gear) idle.
 
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CBODY67

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One thing about some of these changes, you have to consider WHO is advocating them and what their main orientation is. Drag racing (even if its from a red light) or just better street driving. THAT is important.

Back in the later 1960s, it was popular to limit total advance in the distributor and then make up for it with more base timing. Plus the lighter springs in the distributor. Plus removing the vacuum advance operation, too, which usually killed highway fuel economy. In many cases, also, the cars these things were done to did not have anything close to 2.76 rear axle gears, usually more like 3.73 or deeper (i.e., better for drag racing).

But those changes to idle speed are probably where your problems are. With a stock cam, no need for the elevated base hot idle speeds, period.

With the stock cam (which is really not that bad, all things considered) and the stock torque converter (which is usually a little tight for better fuel economy on the highway and works well with the stock cam characteristics), the main place the 4bbl/manifold will work is once the car is moving and the engine can use the additional air flow of the manifold and 4bbl carb.

No external modifications (carb, intake, later model factory cyl heads) will turn a tire chirper into a tire burner, by observation. They can make things more in the tire burner orientation, but usually not all the way there . . . IF that's what you're desiring.

I'd recommend putting the carb BACK the way it came, as to BOTH idle settings of the throttle plates. You can leave the shooter as it now is and see how how that works. THEN get a secondary spring kit and make sure that the secondaries are openning as desired when the engine can use the desired air flow, without bogging when they open.

Remember, too, that your Holley carb is more of a universal-fit carb than OEM replacement. Therefore, you might need to play with the main jetting to get it right for your engine. Just the nature of the deal. It'll be close as is, but not as tailored as an OEM carb for an OEM engine.

But again, with any magazine recommendations, look to see what the orientation is of those making the recommendations. My late machine shop operative used to call them "Tricks of the Week", which he saw many drag racer customers seek to emulate and have little luck getting the same results the magazine claimed would happen. FWIW

Take care,
CBODY67
 

MericaMopar

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But those changes to idle speed are probably where your problems are. With a stock cam, no need for the elevated base hot idle speeds, period.

With the stock cam (which is really not that bad, all things considered) and the stock torque converter (which is usually a little tight for better fuel economy on the highway and works well with the stock cam characteristics), the main place the 4bbl/manifold will work is once the car is moving and the engine can use the additional air flow of the manifold and 4bbl carb.

No external modifications (carb, intake, later model factory cyl heads) will turn a tire chirper into a tire burner, by observation. They can make things more in the tire burner orientation, but usually not all the way there . . . IF that's what you're desiring.

I'd recommend putting the carb BACK the way it came, as to BOTH idle settings of the throttle plates. You can leave the shooter as it now is and see how how that works. THEN get a secondary spring kit and make sure that the secondaries are openning as desired when the engine can use the desired air flow, without bogging when they open.

Take care,
CBODY67

What idle rpm should I be shooting for? I have been targeting 1000rpm in neutral which ends up somewhere around 750 in gear. The carb has a vacuum secondary on it, and I don't think any is adjustable on it other than changing out springs...but when the secondaries are open (WOT or heavy throttle), the car operates fine, no bog.

I know it won't be a tire burner, not what I am after with the 2.76 gears. The cylinder head change was due to the ones on it being toast and these later year 440 heads were cheap and available, and the manifold and carb change were for the same reason, the stock 2 barrel was toast as well (car sat for 30 years).

The bog/stumbling/cutting out is happening when I drive it like a granny would going to church on a Sunday. If I romp on it, it runs fine (albeit, I think on the lean side).

Most of the advice/recommendations I am following are from/for daily drivers that are looking to squeak out just a bit more performance and help improve drivability and throttle response.
 

twostick

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A stone stock 361 should be quite happy to idle at about 600ish.

Are you sure your tach is accurate? Pushing the Drive button at 1000 rpm should make for a pretty harsh engagement and a big lurch forward.

Kevin
 

MericaMopar

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A stone stock 361 should be quite happy to idle at about 600ish.

Are you sure your tach is accurate? Pushing the Drive button at 1000 rpm should make for a pretty harsh engagement and a big lurch forward.

Kevin

Yeah...it lurches pretty good, and by pretty good I mean neck snapping good. So 600rpm in neutral should be fine? setting it to 1000 in neutral correlated to a 750 in gear idle, a 250 rpm drop....would setting it to 600 in neutral not have the same 250rpm drop? I never had the car running with anything other than a 1000 rpm idle so I guess I assumed that was normal?
 

3175375

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Yeah...it lurches pretty good, and by pretty good I mean neck snapping good. So 600rpm in neutral should be fine? setting it to 1000 in neutral correlated to a 750 in gear idle, a 250 rpm drop....would setting it to 600 in neutral not have the same 250rpm drop? I never had the car running with anything other than a 1000 rpm idle so I guess I assumed that was normal?
I believe that he meant 600 in drive.
 

Toolmanmike

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I would guess stock spec is around 550 in drive. A quicker distributor advance curve will pick up more zip for you but watch out for engine ping. Too much too quick and you're back to square 1. If it were me, I would put in a 3.23-3.55 rear gear and then tune from there. (especially if you have changed the original 14" tires to taller 15's)
 

Mike66Chryslers

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Is your distributor's vacuum advance connected to the constant vacuum port or the timed port? Should be on the timed port. Then readjust idle speed as necessary (to the RPM recommended by previous commenters).

If vac advance is on the constant port and you hit the gas hard from idle, you suddenly lose vacuum, ignition timing falls back and you get a big bog before it takes off.
 

MericaMopar

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I would guess stock spec is around 550 in drive. A quicker distributor advance curve will pick up more zip for you but watch out for engine ping. Too much too quick and you're back to square 1. If it were me, I would put in a 3.23-3.55 rear gear and then tune from there. (especially if you have changed the original 14" tires to taller 15's)


Thanks, I do have a 3.31 (if I remember right) 3rd member that just needs to be setup...maybe I will switch my priority around to getting that in first instead of figuring out this bog. I also have 15" wheels with 225/75 tires ready to be installed but was waiting till spring to do that.
 

MericaMopar

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Is your distributor's vacuum advance connected to the constant vacuum port or the timed port? Should be on the timed port. Then readjust idle speed as necessary (to the RPM recommended by previous commenters).

If vac advance is on the constant port and you hit the gas hard from idle, you suddenly lose vacuum, ignition timing falls back and you get a big bog before it takes off.

I do have it connected to ported vacuum. I do not see a change in rpm in idle when I disconnect it (after plugging the now open port on the carb).
 

Toolmanmike

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Thanks, I do have a 3.31 (if I remember right) 3rd member that just needs to be setup...maybe I will switch my priority around to getting that in first instead of figuring out this bog. I also have 15" wheels with 225/75 tires ready to be installed but was waiting till spring to do that.
You are switching to tall tires. That makes a step up in gear ratio disappear. A tall tire with a 3.23 gear will put you back to 2.76 performance.
 

mopar440

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The gears are gonna hurt you, obviously

With a heavy car, you actually want a LONGER shot, so it has fuel for more of the stroke. Try putting in the old squirter and try a longer profile cam. It's kinda opposite of what you think it would be
 

my5thmopar

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Explain. You’re at 18 degrees at idle with no vacuum correct? When you say mechanical locked at 18, then you’re all in at 36 degrees mechanical correct? That’s not with vacuum advance.
 

commando1

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Will everybody STFU and wait for Big John? :realcrazy:

I will not apologize for being brutally honest.
 

MericaMopar

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Explain. You’re at 18 degrees at idle with no vacuum correct? When you say mechanical locked at 18, then you’re all in at 36 degrees mechanical correct? That’s not with vacuum advance.


Yes, 18 degrees of advance at idle, vacuum advance disconnected. The distributor mechanical advance is locked to a maximum of 18 additional degrees, so 36 total mechanical advance, without vacuum advance.
 

CBODY67

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Actually, the hot base idle speed should be about 600rpm in"N" or "P". On our '66 Newport 383 2bbl, that put it at about 550 in "D" with the a/c running. With my '70 Monaco 383 4bbl. I believe it was about 650 in "N", but that increase was mostly for emissions purposes. As I recall, the ONLY car which had a 950rpm hot base idle speed spec was a 340 3x2bbl car in about '71?

The stock distributor on the '66 Newport 383 2bbl had an initial timing spec of 12.5 degrees BTDC. I usually ran it at 15 degrees. With the stock distributor specs for that car, the normal total advance would be right at 38-40 degrees BTDC, which was considered "just right" for any Chrysler B/RB engine. Although some might like 36 degrees better. Even though it was a 9.2cr motor, from new, it liked premium fuel best, so I just advanced the timing a small bit to get a bit more from it.

The "easy" driving you do and have the problem with is exactly in the realm of transition port issues. At WOT, it's all on the main system, with the higher rpm levels. Readjust the secondary idle back down to where it used to be and then re-set the other adjustments back to what they were initially. Make sure the vacuum advance is working, too. A "dial" timing light works great to check timing advance at speeds above idle, to see what's really happening without having to remove the distributor and put it on a disgributor machine.

In the two Holley carb books I mentioned, it states that when at hot base idle, only the idle system is supplying fuel to the engine, but the transition ports/slots are charged and ready for action. As soon as the throttle plates start to open farther, for a bit more rpm, then the idle system and transition system start to work, with the idle system being on the idle speed area and just above it. The transition system adds to that, until the supply limit of the idle system is reached but before the main system is fully operational. If the throttle plates are too far open at idle, the books plainly state that sags/hesitations can occur when the throttle is opened farther and before the main system is fully operational. Reason? Too much fuel, suddenly, than is needed. I suspect that anybody who might advocate for what you did was possibly trying to get past a lean idle situation, for a richer idle mixture? Possibly trying to cover something else they'd done?

In the 1990s, Holley came out with different lines of 4160 4bbl carbs. I never did understand their reasoning other than just catchy names for marketing purposes. Be that as it may, they are still the same basic 4160 design that's been used since 1958 when the original 1850 was OEM with Ford V-8s (332-430cid).

Also be aware that other than the secondary idle speed screw, the secondaries also have a fuel idle system. Allegedly there to help keep fresher fuel in the secondary float bowl. Which is what the two small holes are just below the secondary throttle plates.

Happy Holidays!
CBODY67
 

MericaMopar

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Actually, the hot base idle speed should be about 600rpm in"N" or "P". On our '66 Newport 383 2bbl, that put it at about 550 in "D" with the a/c running. With my '70 Monaco 383 4bbl. I believe it was about 650 in "N", but that increase was mostly for emissions purposes. As I recall, the ONLY car which had a 950rpm hot base idle speed spec was a 340 3x2bbl car in about '71?

The stock distributor on the '66 Newport 383 2bbl had an initial timing spec of 12.5 degrees BTDC. I usually ran it at 15 degrees. With the stock distributor specs for that car, the normal total advance would be right at 38-40 degrees BTDC, which was considered "just right" for any Chrysler B/RB engine. Although some might like 36 degrees better. Even though it was a 9.2cr motor, from new, it liked premium fuel best, so I just advanced the timing a small bit to get a bit more from it.

The "easy" driving you do and have the problem with is exactly in the realm of transition port issues. At WOT, it's all on the main system, with the higher rpm levels. Readjust the secondary idle back down to where it used to be and then re-set the other adjustments back to what they were initially. Make sure the vacuum advance is working, too. A "dial" timing light works great to check timing advance at speeds above idle, to see what's really happening without having to remove the distributor and put it on a disgributor machine.

In the two Holley carb books I mentioned, it states that when at hot base idle, only the idle system is supplying fuel to the engine, but the transition ports/slots are charged and ready for action. As soon as the throttle plates start to open farther, for a bit more rpm, then the idle system and transition system start to work, with the idle system being on the idle speed area and just above it. The transition system adds to that, until the supply limit of the idle system is reached but before the main system is fully operational. If the throttle plates are too far open at idle, the books plainly state that sags/hesitations can occur when the throttle is opened farther and before the main system is fully operational. Reason? Too much fuel, suddenly, than is needed. I suspect that anybody who might advocate for what you did was possibly trying to get past a lean idle situation, for a richer idle mixture? Possibly trying to cover something else they'd done?

In the 1990s, Holley came out with different lines of 4160 4bbl carbs. I never did understand their reasoning other than just catchy names for marketing purposes. Be that as it may, they are still the same basic 4160 design that's been used since 1958 when the original 1850 was OEM with Ford V-8s (332-430cid).

Also be aware that other than the secondary idle speed screw, the secondaries also have a fuel idle system. Allegedly there to help keep fresher fuel in the secondary float bowl. Which is what the two small holes are just below the secondary throttle plates.

Happy Holidays!
CBODY67

I will definitely try to lower the idle back down to what you suggest, seems the easiest thing to try. Then start reversing some of those other adjustments if needed. Thanks for the info!
 
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Big_John

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Will everybody STFU and wait for Big John? :realcrazy:

I will not apologize for being brutally honest.
I have been staying out of threads like this. I don't have the patience these days.

It seems to me that if it doesn't run correctly with the changes made, let's call it point "B", but it ran correctly before, let's call that point "A", it would make some sense to return it to point "A".

One thing that does jump out at me, and is being ignored, is the reference point for timing. Harmonic balancers are known to slip after 56 years of use. The rubber degrades with age and the outside ring slips. Now you have no idea where TDC really is. This is why a lot of guys time their engines by "ear" or "feel" and get a baseline.

I'm also assuming that the 440 heads used were later open chamber, large valve versions. This is gonna drop your compression, for a loss of power and the large valves are going to possibly hurt the bottom end a bit, so again, your timing is going to have to be worked out for what is best for the car.

So... I would go back to point "A", get the car running right again, and slowly creep up on what is optimal. That is the way you do this anyway... What works for one combination in one car doesn't always work for another with a different combination.

But, what do I know?
 

1970cat

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if it were me, i would start by putting the distributor back to where it was. timing, advance, springs, everything. run it, read the plugs to see where your carb is at and go from there. it seems like your changes are each helping to alleviate the previous problem but not addressing the original problem.
 
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