Re: Rough running untill fully warm
[Re: Supercuda]
#2150861
09/09/16 06:43 AM
09/09/16 06:43 AM
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Joined: Jan 2007
Posts: 401 Norway
General 68
OP
mopar
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OP
mopar
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Posts: 401
Norway
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I see. Experience with this anyone? How is the head cross over port shaped/constructed? Is it just a channel through the head? Then it won't lead much heat up to the manifold but maybe enough to cut the warm-up time some?
Last edited by General 68; 09/09/16 12:19 PM.
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Re: Rough running untill fully warm
[Re: General 68]
#2151472
09/10/16 03:34 AM
09/10/16 03:34 AM
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Joined: Jan 2003
Posts: 10,609 Freeport IL USA
poorboy
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Yes, the crossover is a rectangle shape at the intake manifold edge of the heads (below that curved hollow at the center of the head) and intake, but changes shape as it passes through the head to the exhaust ports, and also changes shape as it passes through the intake manifold itself.
When the weighted and spring loaded flapper valve (heat riser valve) on one exhaust manifold (I believe its the right manifold, its been a few years) closes, it sends the exhaust back through the port on the head, under the pendulum on the intake, through the port on other head, and into the exhaust. If the flapper valve doesn't close, or isn't there, the exhaust heat drifts up (heat rises) to the intake. Over time (generally 8-10 years), the carbon from the exhaust plugs up the ports under the intake and at the intake manifold end of the heads. That carbon needs to be dug (chiseled) out of the ports.
As long as the ports are clean, there should be enough heat passing into the intake to help the cold running condition for several years. Gene
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Re: Rough running untill fully warm
[Re: poorboy]
#2151481
09/10/16 05:21 AM
09/10/16 05:21 AM
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Joined: Jan 2007
Posts: 401 Norway
General 68
OP
mopar
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OP
mopar
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Norway
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Good reading Poorboy. How does the exhaust enter the crossover - I know where it comes out of the head an into the intake but how is it routed from the combustion chamber and into this channel? Part of the reason why I ask this is that I know my crossover ports are carbon plugged and need to be cleaned out. Never bothered to do this as this function not was going to be used.
Last edited by General 68; 09/10/16 05:26 AM.
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Re: Rough running untill fully warm
[Re: poorboy]
#2151482
09/10/16 05:29 AM
09/10/16 05:29 AM
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Joined: Jul 2013
Posts: 1,272 Northern Calyfornua
Sxrxrnr
pro stock
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pro stock
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Northern Calyfornua
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Op has stated that his installed valley cover pan has the close the cross over option. It was suggested very early on in this thread that his intake may not have this port,,,,blocking with the valley pan will give indentical results,,,,a cold or very slow to warm up intake.
Again I repeat, this is not recommended for a normal street driven engine. The lack of early and adequate heat to his intake manifold as oft repeated in this thread is a leading candidate for the erratic running issues that he had described.
The factory installed these ports for a good reason. Not anticipating they might be disabled by some tuner with a better idea.
Last edited by Sxrxrnr; 09/10/16 05:30 AM.
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Re: Rough running untill fully warm
[Re: General 68]
#2151742
09/10/16 05:47 PM
09/10/16 05:47 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
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The center port in the head ties into the exhaust port, the flapper in the manifold routes exhaust from that side, thru the intake to the other side till it warms up and the flapper opens. With headers the flapper is moot since headers do not generally have them.
A vacuum and a screwdriver is all you need to clean those ports out.
I, personally, have never seen it plug up and I've been fooling with Mopars for 30+ years. Some say it happens, I wonder why?
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]
#2151797
09/10/16 08:07 PM
09/10/16 08:07 PM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
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In the head, just one port if I recall correctly, I haven't played with a big block in 20 years. However, in the stock application the passenger side manifold, with the flapper in the outlet port directs all 4 cylinders exhaust thru the intake.
I can't find a good drawing of how it works.
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: Sxrxrnr]
#2151902
09/10/16 10:51 PM
09/10/16 10:51 PM
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Joined: Nov 2010
Posts: 3,696 jersey
Spaceman Spiff
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jersey
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Op has stated that his installed valley cover pan has the close the cross over option. It was suggested very early on in this thread that his intake may not have this port,,,,blocking with the valley pan will give indentical results,,,,a cold or very slow to warm up intake.
Again I repeat, this is not recommended for a normal street driven engine. The lack of early and adequate heat to his intake manifold as oft repeated in this thread is a leading candidate for the erratic running issues that he had described.
The factory installed these ports for a good reason. Not anticipating they might be disabled by some tuner with a better idea. what about all the aftermarket heads that have no crossover? my 526 has RPM heads, and a holley 1000cfm hp carb, with no choke housing. no issues with cold start/warm up.
526 cubes of angry wedge, pushbutton shifted, 9 passenger killer!
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Re: Rough running untill fully warm
[Re: General 68]
#2152044
09/11/16 01:20 AM
09/11/16 01:20 AM
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Joined: Oct 2007
Posts: 3,903 Oregon
hooziewhatsit
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Oregon
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Robert: Forgot to answer one of your Q's: I run 20 degrees initial on manifold vacuum. Distributor is set up for that and if I remember right it will idle at 28 degrees. It will instant drop to 20 when opened up. Total is 35-36 all in by 2.500 rpm. Your distributor is hooked up to manifold vacuum, and not ported, correct? What is your vacuum in drive? At what vacuum does the vacuum advance start advancing? If vacuum in drive is below where the vac advance engages, you will have issues, particularly when cold. If that's the case, you'll need to use a hex key in the nipple of the vacuum can to lower the point that it engages, to prevent that overlap. Easiest way to test this is with a mity-vac and timing light, or just take the distributor cap off and watch for it to move.
If you ever find yourself in a fair fight, your tactics suck.
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Re: Rough running untill fully warm
[Re: Spaceman Spiff]
#2152131
09/11/16 06:09 AM
09/11/16 06:09 AM
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Joined: Jan 2007
Posts: 401 Norway
General 68
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mopar
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Norway
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what about all the aftermarket heads that have no crossover? my 526 has RPM heads, and a holley 1000cfm hp carb, with no choke housing. no issues with cold start/warm up.
Yes what about that? Supercuda: Norway yes! Hoozie: Running manifold vacuum - not ported. No vacuum reading in drive as it is a manual. Idles at 12hg vacuum. Not sure at which vacuum the advance kicks in but should be well under 12 hg as it is all in at idle.
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Re: Rough running untill fully warm
[Re: General 68]
#2152134
09/11/16 06:31 AM
09/11/16 06:31 AM
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Joined: Jan 2003
Posts: 3,575 The Netherlands
BigBlockMopar
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Edelbrock carbs and open/single plane Torker-intakes don't always like to play well together. Try installing a 1", or better, a 2" spacer under the carb and see how the engine likes that. (But make sure the spacer has 4 holes, not the 'open' type.) The spacer mostlikely will improve the engine's vacuum-'signal' to the carb and it in turn, will react much better and quicker to changes in the throttle.
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Re: Rough running untill fully warm
[Re: General 68]
#2152186
09/11/16 10:45 AM
09/11/16 10:45 AM
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Posts: 5,444 Indiana
YO7_A66
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Indiana
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General 68: If you are running the FBO manifold distributor like I do, I know mine specifies a minimum of 12" vacuum per Don. I tested mine and my timing at idle stays solid down to 11.5", then below that the timing drops off. You might be right on the edge unless Don did something different with your setup.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Rough running untill fully warm
[Re: General 68]
#2152193
09/11/16 10:57 AM
09/11/16 10:57 AM
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Joined: Sep 2007
Posts: 14,889 up yours
Supercuda
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Ok, running manifold vacuum is one of the problems.
As you open the throttle manifold vacuum drops and timing backs off causing a similar problem to what you are seeing.
As a test run ported and see if that helps.
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]
#2152505
09/11/16 07:15 PM
09/11/16 07:15 PM
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Joined: Oct 2007
Posts: 3,903 Oregon
hooziewhatsit
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Yep, that low of vacuum at idle is most likely the problem. Mine idles at 17", and sits at 14" in drive. Vac advance doesn't drop out until 10".
Like supercuda says, I bet you're right on the edge of advance. As soon as you put some load on it, the advance goes away and your idle drops. This would be exacerbated when it's cold.
If you ever find yourself in a fair fight, your tactics suck.
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Re: Rough running untill fully warm
[Re: General 68]
#2153092
09/12/16 03:15 PM
09/12/16 03:15 PM
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Joined: Jan 2007
Posts: 401 Norway
General 68
OP
mopar
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OP
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BINGO! (I think). Plugged the vacuum advance and it acted better on the choke. No sure how well it drives after that as it was still touchy during warm up but needed more trottle opening from the idle screw (ofcourse, after losing 8 degrees vacuum advance) and readjusting the idle mixture. Runs super when warm. Had already put back the bigger jets. Needs some more testing but all in all it is a lot better. I was debating the manifold vacuum with Don a couple of years ago but didn't get any love. Can't wait to see how it drives at next cold start! Thanks a bunch all!!
Last edited by General 68; 09/12/16 04:36 PM.
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