Rough running untill fully warm
#2149035
09/06/16 07:03 PM
09/06/16 07:03 PM
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Joined: Jan 2007
Posts: 401 Norway
General 68
OP
mopar
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OP
mopar
Joined: Jan 2007
Posts: 401
Norway
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440, 915 heads, Lunati voodoo 302 hyd. cam, Edelbrock 800 Thunder AVS, Torker 2, FBO ignition, 2" headers, manual trans: Starts easy and idles ok also after choke is fully open but driveability is not good untill engine is fully warmed like after 10 minutes or more of driving. Car needs lots of attention to clutch- and accelerator pedal use to function ok without lugging or bogging down at rpm,s below 2000. Going idle to wot before it is fully warmed will make a huge bog - It completely dies. Acc pump set for longest stroke and a huge .043 squirter still makes this happend. A/F meter reads low 14's at idle and cruise, 13,5 loaded and around 12,5 at wot. Best idle micture setting with the screws out about 1,5 turns. Prior to installing the a/f meter I had bigger jets in the carb but it acted the same when not fully warm. Even when warm it feels like it is on the edge of running too lean and might sometimes bog some when floored. All sympthoms tells me it is to lean but the a/f meter don't... and it has been calibrated. Am I overlooking something? Thinking lifter preload, pcv valve or other not obvious things that can make for thermic problems? Also need to mention that I can not tune away a small lean surge going slowly from cruise to heavier load. Tried different springs and jettings to no vail. Works best with purple spring. What do you suggest?
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Re: Rough running untill fully warm
[Re: General 68]
#2149060
09/06/16 07:43 PM
09/06/16 07:43 PM
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Joined: Jan 2003
Posts: 2,094 central texas
krautrock
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,094
central texas
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that's the way both of my cars are too, no choke. carbs. they are lean until it warms up, they will idle but it's a little slow, then the idle comes around as they warm up. off idle transition is lean so it's a little tricky, if i try to really give them a stab of the throttle then they do the lean backfire or stumble/stall.
to drive them when cold they like to have the rpms around 1500-2000 rpm or so, once they get some heat in them i let the trans shift into third and let the rpms drop...
Last edited by krautrock; 09/06/16 07:44 PM.
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Re: Rough running untill fully warm
[Re: General 68]
#2149181
09/06/16 10:05 PM
09/06/16 10:05 PM
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Joined: Jan 2003
Posts: 5,791 Hamilton, Ontario Canada
Magnum
master
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master
Joined: Jan 2003
Posts: 5,791
Hamilton, Ontario Canada
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It is the intake manifold that must be warm. You can fully warm up the intake and with the short block, oil and even water cold. It will not bog.
I find big port intakes are the worst offenders. You either need to choke the carburetor which Im not recommending or switch to fuel injection.
This is not the solution you are asking for but I think throttling up a cold engine is bad news.
69 Super Bee, 93 Mustang LX, 04 Allure Super
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Re: Rough running untill fully warm
[Re: General 68]
#2149195
09/06/16 10:19 PM
09/06/16 10:19 PM
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Joined: Jan 2003
Posts: 2,094 central texas
krautrock
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,094
central texas
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In some grade yes but this is bad and the driveability is on the edge until it reaches 180-190 F. that sounds annoying, mine are auto cars with holleys. so yes maybe the manual trans and the edelbrocks are just more finicky. or maybe you are the edge of too lean fully warm and that is making the cold driving even worse...
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Re: Rough running untill fully warm
[Re: General 68]
#2149346
09/07/16 01:41 AM
09/07/16 01:41 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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can you borrow another carb to quickly elim or confirm it as the culprit? I would put some thin superformance gaskets on either side of the metal valley pan (vac leak). what is your timing & ported or manifold. there is definitily an issue that I wouldn't be comfortable with
live every 24 hour block of time like it's your last day on earth
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Re: Rough running untill fully warm
[Re: General 68]
#2149394
09/07/16 05:36 AM
09/07/16 05:36 AM
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Joined: Jul 2013
Posts: 1,272 Northern Calyfornua
Sxrxrnr
pro stock
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pro stock
Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
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What are outside temperatures when experiencing your concerns. If 70 degree 'F', engine start and initial performance will be dramatically different than at 5 degree 'F'. I will leave it to you to do the Celsius conversions.
The intake that you are running unlikely will ever give you decent cold weather performance or economy given its lack of crossover exhaust porting to quickly warm it up,,,and is unlikely to ever warm sufficiently for optimum economy.
In warmer weather you should not even need a choke to start the engine. The fact that you indicate that it is closed when starting the engine suggests that your poor performance is occurring in very cold weather. Hence the need for a rapidly warming up intake, which you do not have.
In warmer weather, intake manifold warming even without crossover or heat riser will be quite rapid,,,even with a single plane intake.
Your other option is to leave the choke closed for an extended period of time until engine finally warms up,,,,just not a good option,,,poor performance and economy and rapidly polluted oil and a likely more quickly rusted out exhaust system if you use for a lot of shorter trips.
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Re: Rough running untill fully warm
[Re: General 68]
#2150024
09/07/16 11:24 PM
09/07/16 11:24 PM
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Joined: Jan 2003
Posts: 10,614 Freeport IL USA
poorboy
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,614
Freeport IL USA
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The intake manifold is your biggest issue. Between 40 and 60 is about the worst temp range to adjust a carbed motor. its too cold without a choke, and its too warm for the choke to stay on long enough to get past the lean stumble. Opening up the exhaust crossover in the intake would probably solve most of your problem.
Short of changing the intake, or setting up the choke more rich, the only other option is to introduce warmer air into the intake. A few ways to do that, off the top of my head: 1, If you running an open air filter, get one that is closed for your winter driving. Restricting the amount of cold air available to the carb will help your lean condition. 2 Pull warm air off the exhaust and run it through the thermostat controlled snorkel on the closed air filter housing, if you have a dual snorkel housing, one heated snorkel should be enough to do the job. This will require a vacuum source for the thermostatic air door to open and close, and a tube attached to the header/exhaust manifold duct-ed to the snorkel. 3, If your running a heater core with functioning heat, you can pull a heater hose close to the carb to warm up the carb. 4, Another thought is that maybe you can run a copper tube filled with engine coolant between the bottom of the intake and the valley pan to warm up the intake. This could be controlled to shut off once the engine reaches operating temp.
#1 & #2 are better options. Gene
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Re: Rough running untill fully warm
[Re: General 68]
#2150062
09/08/16 12:04 AM
09/08/16 12:04 AM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
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Posts: 14,889
up yours
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The factory didn't use an electric choke like the Thunder uses. So part of the problem is that it has no idea what the engine temp is.
I ran an Edelbrock Performer on my 64 300, but I used a manual choke. Pull it out, drive till it warmed up and pushed it in. Ran fine in all weather, even below freezing. On my 413 you'd know when it needed pushed in because it would bog with the choke on and it warmed up. Open element air filter (no warm air), stock intake (with exhaust crossover).
Tuning to an AF ratio is not best. Tuning to what the engine wants is best, you can note the AF ratio if you want, but if it needs more fuel, then it needs more fuel. Especially when running an unheated intake that doesn't help fuel atomization.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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Re: Rough running untill fully warm
[Re: General 68]
#2150567
09/08/16 07:42 PM
09/08/16 07:42 PM
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Joined: Jan 2007
Posts: 401 Norway
General 68
OP
mopar
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OP
mopar
Joined: Jan 2007
Posts: 401
Norway
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Actually I wrote something wrong - the Torker 2 HAS heat crossover ports. But on my engine a heat crossover blocking valley pan was used. I guess it is a good idea to open up the heat crossover! With the issues I have it might be worth the hazzle.
Last edited by General 68; 09/08/16 08:18 PM.
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Re: Rough running untill fully warm
[Re: General 68]
#2150591
09/08/16 08:07 PM
09/08/16 08:07 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
About to go away
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About to go away
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Posts: 14,889
up yours
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Well, it couldn't hurt and could be a cheap fix.
edit - I see you have headers, not too sure how well it'll function with headers. But you can try.
Last edited by Supercuda; 09/08/16 08:36 PM.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
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