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PostPosted: Thu Jun 20, 2019 8:25 am 
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2 BBL ''SuperSix''

Joined: Mon May 25, 2015 9:23 pm
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I have this '81/225 that I finished tuning. It ran OK when I bought it, so I just did the standard tune up and maintenance. I runs like crap when it is cold- bog, low power. When it gets to temp all those issues go away. A start about 10 minutes later will result in a bog or flat spot, maybe a stall. A minute or 2 down the road and everything is good. Summertime and the second issue is more prevalent. Winter time both are issues. I remember all those /6's from the 60's never started up right when hot in the summer. I guess the intake over the header, routing of the fuel line and lack of some type of carb insulator is the cause for those ills. Since the car itself is in great condition with A/C, PW, etc., I'd like to keep it as a daily driver. No vacuum issues. I can deal with the start up issue right now while its summer but winter is a different story. Any thoughts?


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PostPosted: Thu Jun 20, 2019 9:13 am 
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Joined: Fri Feb 29, 2008 10:49 pm
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Location: Salem, Oregon
Car Model*: 58 Plymouth Plaza 2dr, 63 Valiant Signet 200 2dr
Has the choke plate been calibrated correctly and is the thermostatic spring assembly in good working order? Are you using an electrically assisted thermostatic spring assembly?

~THOR~

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PostPosted: Thu Jun 20, 2019 3:00 pm 
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2 BBL ''SuperSix''

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Yes. Never a problem to star when cold. Choke assembly and electrics work. I'm assuming the the hot start is from the fuel, e-10, evaporating too quickly. Is there a difference between the pre smog specs and the 1981 smog specs, timing,jet size?


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PostPosted: Thu Jun 20, 2019 4:31 pm 
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Location: Salem, Oregon
Car Model*: 58 Plymouth Plaza 2dr, 63 Valiant Signet 200 2dr
MR. DIPLOMAT wrote:
I[t] runs like crap when it is cold- bog, low power.


MR. DIPLOMAT wrote:
Yes. Never a problem to star[t] when cold. Choke assembly and electrics work.


So, color me confused :?:

MR. DIPLOMAT wrote:
When it gets to temp all those issues go away. A start about 10 minutes later will result in a bog or flat spot, maybe a stall. A minute or 2 down the road and everything is good.


I assume you mean immediately after restarting, which isn't uncommon. There are modifications that people have made to try and lessen the effect of fuel boiling in the carburetor. One of those is the fuel line mod: http://www.slantsix.org/forum/viewtopic.php?t=15778

MR. DIPLOMAT wrote:
I can deal with the start up issue right now while its summer but winter is a different story. Any thoughts?


I'm still confused by the earlier statements regarding how it runs cold. Can you clarify?

~THOR~

_________________
1958 Plymouth Plaza 2 door Club Sedan
1963 Plymouth Valiant Signet 200 HT - "CL4P-TP"
Licensed Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing


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PostPosted: Fri Jun 21, 2019 6:52 pm 
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2 BBL ''SuperSix''

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Cold start sequence- crank motor twice, pump accelerator pedal twice and the motor starts with high/cold idle. I'll let this go on for 30 seconds(the cat will heat up fast) and then I tap the pedal and the motor hits the 2nd choke cam step and is idling around 950 rpms. Let the car warm up for 2-3 minutes(195* stat) and try to pull away. Try to push down on the pedal and it will hesitate or bog until sufficient momentum and the motor will respond to light throttle pressure but will break out into a hesitation or bog if the load is increased. Once it is at operating temp, no issues. I thought that the hot issues were fuel line and/or fuel boil over related. your post indicates same.


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PostPosted: Sat Jun 22, 2019 9:02 pm 
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Joined: Thu Jan 24, 2013 3:39 pm
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Location: Houston, TX
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Mr Diplomat: one thing I guess might help us to understand a description of what you did in the standard tune up and maintenance. (i.e. did you touch the carb? put a new carb kit?, just spark plugs and cables?). I guess your car is a Diplomat, and I would guess it had the Lean Burn System from factory (was it removed/hacked?, maybe damaged during the tune up?). It has a cat converter, so maybe all the systems are still there. Please, let us know a little more on how the engine conditions are.

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PostPosted: Sun Jun 30, 2019 8:28 pm 
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2 BBL ''SuperSix''

Joined: Mon May 25, 2015 9:23 pm
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No lean burn. Cap, rotor, wires , plugs,air filter. I have same car with 318-2 and it runs w/o issue. In that car I changed the tune specs to that of a 1973 318 and have never had an issue since I tuned it. Thought to do the same with the /6 but thought I'd try to get an answer here.


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PostPosted: Mon Jul 01, 2019 2:02 pm 
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TBI Slant 6
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Location: Houston, TX
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Ok. I would try to use old cap, and try old and new rotor (new caps&rotors can be crap). Spark plugs gap (0.35 to 0.45), probably 0.40 as yours should have Mopar electronic ignition, or whatever value is in the service manual (I hope you have one). Check also that the exhaust manifold heater riser valve (http://www.slantsix.org/forum/viewtopic.php?t=12454) is not frozen, so the carburetor base can heat quicker, and the valve can close after warmup. I have not had your problems, my car is 69, with a Holley 1920 single barrel Carb (do you have a 2 bbl? or a Holley 1945?). I might also play with how much gas the accelerator pump is sending to the carb (you can graduate the strength of the shot, there are a set of holes to pick). Why this was not happening before the tuning? I don't know, but I view some faults on crappy replacement parts.

By the way, old cat(alytic) converters with no lean burn probably requires to check the cats/replace them. Some reference to replacement cats (if you what to pursue that way in the future) are here: viewtopic.php?p=446622#446622

Good luck, hopefully the old parts in the distributor can do the trick.

Whatever you do, do one thing at a time to get sure what helped.

CP

PD: maybe you can try to use the old air filter, being dirty might have caused a change in the air-gas ratio (as a test, not a permanent solution. If the old filter works, a different jet might help, you don't know what you get with an old car). Also checking fuel level inside the carburetor might help.



Any other comments about this answer, or the problem, are welcome.

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PostPosted: Mon Jul 01, 2019 5:49 pm 
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Turbo Slant 6

Joined: Sat Feb 18, 2006 2:19 pm
Posts: 888
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https://www.ebay.com/itm/1981-Chrysler- ... SwDkdakkqU


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PostPosted: Mon Jul 01, 2019 6:39 pm 
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Turbo Slant 6

Joined: Sat Feb 18, 2006 2:19 pm
Posts: 888
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Have that book in hand, much info,good place to start.Reading it now. What is your carb number? Is dual pickup distributor switching from start to run? Electric assist choke system, time temperature senor may be bad. Choke comes off too quick. Choke vacuum pull off may need custom adjustment. Idle screws still sealed? Book has how to on that. Carb heat shield still there? Vapor return fuel filter should be there for 81.Book has float adjustment-on vehicle gas in the bowl how to,quite interesting. Get book.


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PostPosted: Tue Jul 02, 2019 8:42 am 
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TBI Slant 6
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Joined: Thu Jan 24, 2013 3:39 pm
Posts: 174
Location: Houston, TX
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matv91 wrote:
Have that book in hand, much info,good place to start.Reading it now. What is your carb number? Is dual pickup distributor switching from start to run? Electric assist choke system, time temperature senor may be bad. Choke comes off too quick. Choke vacuum pull off may need custom adjustment. Idle screws still sealed? Book has how to on that. Carb heat shield still there? Vapor return fuel filter should be there for 81.Book has float adjustment-on vehicle gas in the bowl how to,quite interesting. Get book.


+1. I have a service manual, and it tells you a lot of good stuff. You have a 318 also, so it will be worthy for both cars.

Just wanted to add that even when I have not suffered a similar problem like yours, the carb my car came with was not working properly, causing bogs when accelerating from stop. After trying a rebuilding and a cleaning, I decided to buy a NOS carb in ebay, as carbs can deteriorate with time and ethanol gas... (there might be better options to where/who to buy in this forum, but never buy a rebuild from a general autopart store, unless you really want to test your luck); car has been running beautifully since.

Since your car is newer than mine, and Matv91 has already pointed to stuff my car does not have, going by the manual can help a lot.

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/6 Dodge Charger 69

Image...there's nothing like using the "Search" link above to solve most of your problems...


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PostPosted: Mon Jul 08, 2019 6:37 am 
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2 BBL ''SuperSix''

Joined: Mon May 25, 2015 9:23 pm
Posts: 14
Car Model*:
Accelerator pump issues would be most of the time. This is just a cold run issue.


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PostPosted: Mon Jul 08, 2019 6:10 pm 
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Joined: Mon Mar 31, 2003 1:04 pm
Posts: 7484
Location: Oregon
Car Model*: 2018 Eichman Digger
A slim chance, but still might be worth checking that your manifold is torqued properly. If it's "A little loose" You could be experiencing a vacuum leak cold that goes away once the manifold heats up and seals. The OEM spec for the manifold is 10 ft-lb. This allows the stack to float on the head as it experiences the temperature delta from start up to operating temperature. If it's reached this point, the manifold gasket should likely be replaced.

If the timing shifts a bit with the cap and rotor/plug change out, you can experience an effect not unlike mixture change. If it tends toward lean take a little timing out. Just changing the plug gap a little can create this effect. A slight change in gap can move your timing incrementally, and create the effect of richer or leaner running state. Certainly not as much as a jet change.
The BBD uses ported vacuum signal to move the metering rods in the main jets. A slightly lighter spring tension will lean the main circuit, (Shallower vacuum to pull the rods down into the jets. Higher spring rate fattens the circuit up.) Verify the setting is correct. SlantSixDan and others have shared the BBD manuals from time to time. If you dig around in this section's Frequently Asked Questions links you will find the manual.
When a tune up is done, the vacuum the engine operates at can improve. (Especially when valve lash is corrected in the case of a mechanical valve train.) Deeper vacuum will fatten the circuit up. Tight valves can cause poor vacuum signal. Normally, the setting on the metering rods doesn't get messed with. A poor setting can be masked by other measures. Your car should use hydraulic lifters so would not be an issue unless someone previously swapped the Hydraulic top end for a mechanical one.

Just a few thoughts. In most cases, the simplest explanation is probably the right one. I like the idea to try the old cap and rotor. It's hard to find good parts these days. I quit trying, and installed a Mallory Unilite. (Not the simplest, nor the least expensive way to skin a cat.)

CJ

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PostPosted: Sun Jul 28, 2019 2:43 pm 
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Turbo Slant 6

Joined: Sat Feb 18, 2006 2:19 pm
Posts: 888
Car Model*:
https://www.ebay.com/itm/1981-82-Chrysl ... 1059!US!-1


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PostPosted: Sun Jul 28, 2019 3:01 pm 
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Turbo Slant 6

Joined: Sat Feb 18, 2006 2:19 pm
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If that is the choke vacuum pull off on your carb, it needs different adjustment procedure .There is no rod to bend,just a screw up in side to turn.


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