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old gh bug
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Joined: February 22, 2013
Posts: 197
Location: UK
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 Posted: Tue May 11, 2021 7:47 am Post subject: Kadron DP Manifold Modification |
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I have read on here (but can't find it now) that someone had modified there DP alloy manifolds to enable better idle flat spot etc,
what they said was that they cut the centre web out of the manifold and only left about 20mm and this solved the problems of the typical Kad flat spot etc.
What I would like to know has anyone done this and does it work, I would of thought if this was a good fix everyone would be doing it ?? |
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Max Welton
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Location: Black Forest, CO
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Brian_e
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Joined: July 28, 2009
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Location: Rapid City, SD
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| Posted: Tue May 11, 2021 9:07 am Post subject: Re: Kadron DP Manifold Modification |
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I allows more of a plenum under the carb, and keeps the "charge robbing" to a minimum making for a smoother idle.
Brian
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APPLEGREENVW
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Joined: November 30, 2003
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Location: Seekonk,Massachusetts USA
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Alstrup
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Location: Videbaek Denmark
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spencerfvee
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Joined: August 19, 2004
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| Posted: Tue May 11, 2021 10:13 am Post subject: Re: Kadron DP Manifold Modification |
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| Alstrup wrote: |
| The above was a test. The enlarged plenum up top works better |
..........................................................................what alstrup says is very true it all ways worked for me spencerfvee |
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old gh bug
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Joined: February 22, 2013
Posts: 197
Location: UK
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| Posted: Tue May 11, 2021 10:30 am Post subject: Re: Kadron DP Manifold Modification |
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| spencerfvee wrote: |
| Alstrup wrote: |
| The above was a test. The enlarged plenum up top works better |
..........................................................................what alstrup says is very true it all ways worked for me spencerfvee |
That’s good information, I have a spare set of manifolds that I might try .
Would this also be ok with SVDA mod to carb?
Thanks |
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Max Welton
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Alstrup
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Joined: July 12, 2007
Posts: 7212
Location: Videbaek Denmark
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| Posted: Tue May 11, 2021 1:10 pm Post subject: Re: Kadron DP Manifold Modification |
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The manifold vacum for an SVDA is not affected to anything worth mentioning. Remember, the vacum is only activated at X amount of throttle opening. So the engine is already making suction. - Or at least it should be.
The off idle transition - can - be affected by this, but not more than it can normally be compensated for with different ignition timing. (Easiest with a programmable of course, but doable with an SVDA.
Now, regarding off idle stumble. Here is a little information, which is also a small commercial. I hope it is accepted by the moderators.
I have been developing a velocity stack for Kadrons that fit inside a stock Kadron aircleaner and is easy to install. It will be released within the next month or two. The reason why I am menthioning it here is that during testing I have borrowed some cars wchich had Kadrons installed on top of more or less interesting engine combo´s and engine displacements. Apart from the power increases we saw, we also noticed another side benefit which we did not expect at all. It was exactly that - reduction of off idle stumble. One engine was a no frills 1641 engine with a C25 cam, stock heads, 8,7 CR, regular 009 distributor, Kadrons on Empi manifolds and a Sebring style muffler. Apart from the 2,5 hp and 4 Nm powergain almost across the board the engine suddenly became more responsive off idle to the extend that the "non mechanical" owner noticed it.
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jimmyhoffa
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Joined: February 16, 2014
Posts: 1056
Location: St. Louis
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| Posted: Tue May 11, 2021 1:14 pm Post subject: Re: Kadron DP Manifold Modification |
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I have a version of both of these modifications on my Single IDF 1915 engine. Conceptually speaking, there is a good bit of overlap between a Kadron and Centermount double barrel with isolated runners. A Centermount IDF is basically Kadrons on REALLY tall manfiolds. Like, a foot tall.  Most accurate Kadron setup advice also applies to a single IR Centermount double barrel installations (Dellorto/IDF/Zenith) including cam/head configuration practical limits and rough venturi sizing.
I have my stock end castings "windowed" through the divider like the picture of the Kad manifolds, as well as 5" velocity stacks.
As advertised, the cross-port windows in my stock end castings really help idle quality, and the tall velocity stacks on top of my IDF make it possible to get off-idle crispness. Without both tricks, it is impossible to achieve both goals.
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old gh bug
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Joined: February 22, 2013
Posts: 197
Location: UK
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| Posted: Tue May 11, 2021 1:42 pm Post subject: Re: Kadron DP Manifold Modification |
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| Alstrup wrote: |
The manifold vacum for an SVDA is not affected to anything worth mentioning. Remember, the vacum is only activated at X amount of throttle opening. So the engine is already making suction. - Or at least it should be.
The off idle transition - can - be affected by this, but not more than it can normally be compensated for with different ignition timing. (Easiest with a programmable of course, but doable with an SVDA.
Now, regarding off idle stumble. Here is a little information, which is also a small commercial. I hope it is accepted by the moderators.
I have been developing a velocity stack for Kadrons that fit inside a stock Kadron aircleaner and is easy to install. It will be released within the next month or two. The reason why I am menthioning it here is that during testing I have borrowed some cars wchich had Kadrons installed on top of more or less interesting engine combo´s and engine displacements. Apart from the power increases we saw, we also noticed another side benefit which we did not expect at all. It was exactly that - reduction of off idle stumble. One engine was a no frills 1641 engine with a C25 cam, stock heads, 8,7 CR, regular 009 distributor, Kadrons on Empi manifolds and a Sebring style muffler. Apart from the 2,5 hp and 4 Nm powergain almost across the board the engine suddenly became more responsive off idle to the extend that the "non mechanical" owner noticed it. |
Any pictures of the plenum chamber in the manifolds |
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earthquake
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Location: SANDY VALLEY, NEVADA
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| Posted: Thu May 13, 2021 1:21 am Post subject: Re: Kadron DP Manifold Modification |
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I am not sure when VW did the milled slot between ports on DP housing ends, does any body know if it made a difference? I am going to try this someday.
eQ
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spencerfvee
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| Posted: Thu May 13, 2021 6:04 am Post subject: Re: Kadron DP Manifold Modification |
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[quote="earthquake"]I am not sure when VW did the milled slot between ports on DP housing ends, does any body know if it made a difference? I am going to try this someday.
.............................................................................................................................................i dont know when vw started the slot between the ports . i have seen some stock dual port end castings .that did not have the slot between the ports .why they did this i think it helps to balance the two ports . i have run both type on my motors i like the ones that do not have the slot when i port the end casting . spencerfvee |
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modok
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Joined: October 30, 2009
Posts: 26781
Location: Colorado Springs
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| Posted: Thu May 13, 2021 5:41 pm Post subject: Re: Kadron DP Manifold Modification |
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| Max Welton wrote: |
So having a better idle makes the transition off-idle better?
Max |
More like.... making the idle worse.... but more even, keeps all the cylinders hot, which probably helps response.
I don't agree with any of the ideas about shortening runners or windowing them together.
WOULD it idle more even? probably yes... at the expense of something else.
IMO.....Better to embrace the weirdness, and enjoy the boosted torque and MPG........
if you want an even idle then get a different setup.
ANd/or there are other ways to improve response. Look at where the acc pump aims. Texture the inside. Get the temps right. and of course.... COMPRESSION, exhaust tuning. Hotter spark |
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