Torque converter affecting idle question

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7dart0

7dart0

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Is it possible that my torque converter could bring down the idle in gear too much?

I have a 360 magnum motor with unknown cam, eddy dual plane intake, 670 holley street avenger (new), tti step headers, tci 904 trans.,3:23 gears, but i'm using the stock /6 torque converter.

I've been trying to chase it with carb adjustments but it never seems to change just stays around 500 rpm in gear and in Park and Nuetral it idles up at 1200 RPM.
 
Not only possible, but probable. It is one of a list of most critical components in your combination, and one that will give you incredible bang for your buck. I would strongly suggest that you use a custom built converter from Precision, Ultimate or one of the other builders recommended by the veterans on this site.

It may cost a bit more, but the results, day-to-day enjoyment and satisfaction of driving with a well-matched converter can not be overstated.
 
700 is a HUGE difference in RPM from neutral to in gear. Where is your timing at? Why is the cam unknown?
 
cam is unknown because the long block i bought from a guy lost the cam card and couldn't remember what was in it.
 
i haven't had time to double check the timing but I do have the butterflies on the primaries set per holley specs. so there isn't too much of the transfer slot shown.

I did not however adjust the mixture screws in gear as my ebrake doesnt work and i have noone to help me yet. I just did it in park. I wouldn't think doing it this way would have that much affect on the idle in gear.
 
Is it possible that the vacuum advance is active?
If the primary butterflies are too far open, this can happen. Then in neutral/park idle will be high; and when in gear, as vacuum drops the advance drops out and the idle falls into the basement.

The transfer ports should be square to very slightly rectangular UNDER the butterflies. The carb has to be removed to set this. If the engine idle is too slow in N/P after this is set, then, either the idle-timing is insufficient. or the engine wants air from another source; such as the PCV or the secondary cracking screw.

If the vehicle is sluggish on take-off,and the timing systems are working, the TC may be bad, but if take-off is brisk, I imagine the TC is good. Take-off is the the first second or two from a dead stop. A faulty TC will also show up as a lazy motor ,in traffic.
 
not sure about the vacuum advance being active. I do have it plugged into ported vacuum on the carb.
 
If the carb is brand new, I wouldn't fiddle with it until you get the timing where it needs to be. Put a light on that thing! I'd also be popping off a valve cover and figuring out approximately what cam is in there
 
What MR.mopowers means, is that you will have to fingerprint the cam to see how big or how little the cam is. This is useful information, upon which some better understanding can be gleaned from your combo.
Since you are not familiar with the process,and from some of your answers, I take it you are not really a gearhead.

Since an engine spends so much time at idle, and/or driving away from an idle, it is very important to get this idle figured out. I have a shortcut for you, that requires zero tools.

1) First,with the engine running, unhook the vacuum advance. If the idle speed did not change, then the vacuum advance was not active.
2) Set the T-port sync as described in post 8:The transfer ports should be square to very slightly rectangular (that is taller than wide) UNDER the butterflies.Once this is set do not change it; we will set the idle speed using another means. Completely close the secondary butterflies, but make sure that they do not stick closed.The carb has to be removed to set these.
If,after this is set,the engine idle is too slow in N/P then either the idle-timing is insufficient, or the engine wants more air from another source (such as the PCV, or the secondary cracking screw.) If the idle speed is too fast, the timing is too far advanced.
3) Make sure the PCV system is hooked up and working.
4) Start it up and warm it up. At this point the idle speed may need changing. The N/P idle speed should have fallen to between about 500 and around 900, using the above system. A small nearly stock cam will want to idle at 650 to 750. A raunchy street cam may like 900 or more. So,depending on the size of your cam, you will need to ballpark the idle speed in there somewhere.Since you didnn't mentioned idle problems at 500 in gear, Ima guessing the cam is stockish. So lets target a 750 rpm idle speed in N/P. So, loosen the dizzy hod-down bot a little bit, and grab the dizzy and advance the timing by pulling the V-can towards the front of the car. That would be CCW as viewed from the top. Just keep pulling, for as long as the engine rpm continues to rise. As long as the rpm is rising, the engine is liking it. Okay what rpm did this achieve?
If it is under the target 750; We are maxed on the timing, and nearly maxed on the primary cracking screw.If we need more rpm we are going to have to get it from the secondary cracking screw. But first how close are you and what is the quality of the idle? Fine tune the mixture screws. If the idle is 700 or more, perhaps we can get to target with up to 1 more turn of the curb-idle screw. But if that won't get it, put it back where you found it, and crack the secondaries instead.Do it.
But on the off chance that the idle speed has risen to more than the target 750,with the T-ports synced, and the secondaries closed, and the PVC working, and no vacuum leaks, then the only way to slow it down is to retard the timing, until the target is reached. Do it.
5) The in-gear idle test. Okay lets see what happens. One foot on the brake, pop it into manual low.
 
Late to the game. But could the wrong flex plate converter be the problem or part of it? The 360 magnum is externally balanced. Could an out of balance combo play havoc at low rpm? Or if the converter wasn't bushed to the proper size. The converter could be offset.
 
With info given, I'm guessing vacuum leak or throttle plates not closed at idle
 
Blind Squirrel said:
Late to the game. But could the wrong flex plate converter be the problem or part of it? The 360 magnum is externally balanced. Could an out of balance combo play havoc at low rpm? Or if the converter wasn't bushed to the proper size. The converter could be offset.
Click to expand...

No. Don't know anyway how that could affect it. It'd only cause it to vibrate if the balance was off. No clue what you mean by "bushed to the proper size"???
 
My slanty TC is pretty tight, which behind the slanty that idles sweet at 500 in gear, 550/600 in Park is no biggy. And it has the torque to pull away at that rpm.
But I can see that TC being a chore if the N/P idle HAD to be 1200.
But I've never had a cam in a sbm,with under 250*@050,that couldn't be tuned to idle at 750ish,or less.
 
AJ/FormS said:
But I've never had a cam in a sbm,with under 250*@050,that couldn't be tuned to idle at 750ish,or less.
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Same here. My 408 has a Racer Brown solid FT with 240 at .050 on a 108 LCA and it idles fine at 700 in gear. It'll idle down to 600 in gear but the plugs don't burn as clean so I run it at 700. By the OP's description it sounds like a tuning issue
 
i ended up bringing the initial timing to 20* with a mechanical advancement limited to 14* with an FBO plate. I plugged the vacuum can as it was advancing to much at cruise and popping out the exhaust.

It idles in gear at about 900 rpm and about 700 in drive and reverse.

Thank you guys for all the suggestions and comments
 
mopowers said:
700 is a HUGE difference in RPM from neutral to in gear. Where is your timing at? Why is the cam unknown?
Click to expand...

mopowers said:
Initial timing?
Click to expand...

mderoy340 said:
X2
Click to expand...

70aarcuda said:
That
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Give these guys a ribbon!

Funny that the cheapest solution, twist the distributor CCW, helped to solve the issue. The engine may want more initial timing, but, you got it to a point where it works well.

I bet the exhaust at idle doesn't smell nearly as rich as it did before.

Good job!
 
If the Vcan was making it pop, Ima suspecting rotor phasing is the issue. It would explain all your woes.There is no way that at cruising, say 2200 rpm,it should be popping, and most especially not out the exhaust. Even if you had an exceptionally fast curve, and an exceptionally generous can, that would still still be about 45-48** total cruise timing. I have run my combo deep into the 50*s at 2200, with nothing but a thank-you from my 360S.
Popping out the exhaust is usually a rich mixture continuing to burn in the header or a little further down. It has to have fresh air for this to happen, which usually points to a leaky gasket (or rust-holes), at the flange or the collector. If you fix the holes/leakage, and lean it out a tad, you will be able to reconnect the Vcan, and enjoy the benefits that brings.
The TTIs have pretty good header-flanges, but they only have a 3-bolt collector. Also, if they are over about 5 years old, and not ceramic, they are subject to rusting in the area where the pipes enter the collector,up top,between the pipes. I've had to repair mine there several times in 15 years, and they need it again. Moisture collects there.

A simple test for rotor phasing is to rev the engine up,(N/P) to a little higher than where the mechanical timing is all in, and then begin adding the Vcan timing. The engine should respond to that, by building more rpm, until it's too much. But I doubt you can reach that point, because typically the all-in rpm is 3200 +/- 400, and will be about 34*+/-2. The Vcan will typically bring in 12 to 16 more, for a total of 34 + 14 = 48 +/-4. That's 44* to 52*. Easy-peasy for the SBM. But if it begins to pop or missfire or actually loose rpm, then you need to rephase the rotor.

If I'm wrong, it'll cost you a bit of time to prove it, and nothing else.
If I'm right, then after the rotor is rephased or the exhaust is sealed up, or both, then you can begin to zero in on the timing that the engine is wanting,perhaps craving.
 
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