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sxuxrxf
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Joined: May 18, 2005
Posts: 1338
Location: Oceanside, CA
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 Posted: Wed Dec 17, 2008 3:16 pm Post subject: Custom Heat Riser Location? |
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I need to add the heat riser mounts to my header and am wondering if there is a better place to put them.
I came across a suggestion for putting the right side in the standard location, but putting the LEFT side near the collector. What would be the benefit of this?
Any thoughts?
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KevinAlbrecht
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Joined: March 07, 2002
Posts: 990
Location: Ocean City > Boca > Pompano > Kirkland > Eugene > Sarasota
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| Posted: Wed Dec 17, 2008 3:23 pm Post subject: Re: Custom Heat Riser Location? |
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| sxuxrxf wrote: |
I need to add the heat riser mounts to my header and am wondering if there is a better place to put them.
I came across a suggestion for putting the right side in the standard location, but putting the LEFT side near the collector. What would be the benefit of this?
Any thoughts? |
I think I read that from Bob Hoover. I have no welding skills, but would love to do it. The point of it, is by relocating the one side downstream, you create a negative pressure towards the side downstream. Thus drawing the exhaust from the positive pressure side flowing down to the negative side.
Would help heat the intake and prevent clogging.
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Kevin Albrecht
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sxuxrxf
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Joined: May 18, 2005
Posts: 1338
Location: Oceanside, CA
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| Posted: Thu Dec 18, 2008 12:20 pm Post subject: |
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thanks, I'll give it a shot.
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KevinAlbrecht
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Joined: March 07, 2002
Posts: 990
Location: Ocean City > Boca > Pompano > Kirkland > Eugene > Sarasota
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| Posted: Thu Dec 18, 2008 2:10 pm Post subject: |
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| sxuxrxf wrote: |
| thanks, I'll give it a shot. |
Please share your progress. - Kevin
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Eaallred
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Joined: May 18, 2003
Posts: 5756
Location: West Valley City, Utah
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| Posted: Thu Dec 18, 2008 5:26 pm Post subject: |
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The way the heat risers work with an aftermarket header, the exhaust gases end up flowing back and forth, rather than flow through like it would on a stock manifold.
Relocating one side down near the collector will make it perform like stock.
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Bob Hoover
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Joined: December 14, 2004
Posts: 64
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| Posted: Thu Jan 01, 2009 10:58 am Post subject: Re: Custom Heat Riser Location? |
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| sxuxrxf wrote: |
I need to add the heat riser mounts to my header and am wondering if there is a better place to put them.
I came across a suggestion for putting the right side in the standard location, but putting the LEFT side near the collector. What would be the benefit of this?
Any thoughts? |
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Lotsa benefits. Better fuel vaporization is the biggie.
It would help you understand the situation if you can get your hands on a rusted-out STOCK muffler. Put a thin grinding wheel into your angle-head grinder (both avail. from Harbor Freight) and cut the belly out of the big 'can' (it's actually an 'expansion chamber.' the only 'muffling' is being done by the peashooters). Once you can see the INSIDE of the 'muffler' you will see that the heat-riser is damn near 4 feet long! It takes the OUTPUT of the heat riser and dumps it into the throat of the right-hand side outlet. The length plays a role in the muffling qualities but you can cheat a bit and no one will notice. When VW de Mexico began running juicers, which need CLEAN oil, they copied the Subaru oil pump/filter adapter, and stuck the oil filter over on the left-hand side. This made it kinda tricky to install the stock muffler so they moved the hear-riser OUTLET over to the RIGHT-hand side of the 'muffler,' putting the INLET on the LEFT. With regard to the engine's heat-flow nor carburetion -- as with any other 'flat' engine using a single center-mounted carb, VW's need a LOT of carb heat. VW de Mexico simply did a right-to-left swap.
Then someone comes along with an after-market exhaust system and FAILS to provide a proper OUTLET for the heat-riser system. Car doesn't run for shit and all the guy's buds tell him he's got to install dual carbs to fix it.
Welll.... actually, he don't. What he's got to do is to provide a PROPER OUTLET for the heat-riser system. And cutting open a stock muffler will show you what's involved in a PROPER system.
Basically, you have to put the OUTLET in an area of LOW PRESSURE, such as just in front of one of the outlet pipes. One way to do that is to use a step-drill to put a HOLE in the bottom of the COLLECTOR of your after-market system and use it as the outlet from your heat riser. That is, you tack-weld that small-diameter pipe from the stock muffler into the hole you just made then heat & bend it about a dozen times until you've the flanged fitting up to where it's a good fit with the flanged fitting on your intake manifold (HINT: It's a good idea to clean your heat riser before doing all this. Stock heat-riser tends to clog after fifty, sixty thou.)
So why do all the after-market exhaust systems come with the heat-riser outlet welded to the #4 exhaust stack? Actually, they don't. The GOOD ones, like the old EMPI, run the heat riser just as I've described above. And that puppy worked a treat! But at about $200, the typical VW owner simply couldn't afford it. So they bought one of those after-market POS jobbies... and found they'd just bolted a lot of problems onto their engine.
The heat-riser system isn't any mystery. Nor does it reflect any kind of 'trick' system, it's just basic physics ...and good engineering.
-Bob Hoover |
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sxuxrxf
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Joined: May 18, 2005
Posts: 1338
Location: Oceanside, CA
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| Posted: Wed Jan 14, 2009 6:51 pm Post subject: |
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So, I'm ready to tackle this project this weekend. Here's a pic:
Can the right side use either #1 or #2? I'm guessing #2 is hotter = better. I was just thinking for easier/cleaner install.
Since the right side will be the inlet, instead of coming off the header at 90°, maybe make it more of a "Y" than a "T" to scoop up the exhaust.
For the left side, can I enter the collector anywhere? I was told that after-market set-ups use #2 and #4 for a pulsing effect. We are tying to create more of a one-way flow, right? I would like to enter either on the left side or top - does it matter? I will join the tube at an angle so that the return "feeds" into the exhaust in the same direction.
What do you think of wrapping the pre-heat tubes with the muffler wrap to hold in the heat better?
I just got my new manifold also. The pre-heat tube goes all the way to the carb, rather than just flowing thru the base.
Thanks for all of your input. I'll post pics of the outcome next week.
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KevinAlbrecht
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Location: Ocean City > Boca > Pompano > Kirkland > Eugene > Sarasota
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| Posted: Wed Jan 14, 2009 7:33 pm Post subject: |
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sweet, keep us posted.
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sxuxrxf
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Joined: May 18, 2005
Posts: 1338
Location: Oceanside, CA
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| Posted: Sun Jan 18, 2009 11:59 pm Post subject: |
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It's finished! It will be a while before it runs, but at least the hard part is done.
I had to cut up the stock heat tubes and add metal to get them in the right position so that the connections would be under the tin. Now the tin slides around the tubing. I still need to make a couple of small sections to cover the slots.
Hopefully this keeps the manifold nice and hot!
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KevinAlbrecht
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Posts: 990
Location: Ocean City > Boca > Pompano > Kirkland > Eugene > Sarasota
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| Posted: Mon Jan 19, 2009 2:02 pm Post subject: |
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| sxuxrxf wrote: |
| It's finished! |
Looks awesome!
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Kevin Albrecht
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Bob Hoover
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Joined: December 14, 2004
Posts: 64
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| Posted: Mon Jan 19, 2009 8:41 pm Post subject: |
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| sxuxrxf wrote: |
It's finished! It will be a while before it runs, but at least the hard part is done.
.
Hopefully this keeps the manifold nice and hot! |
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It should.
-Bob Hoover
PS -- Nice job. You owe yourself a cool one :-) |
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Scott Novak
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Joined: October 12, 2004
Posts: 1586
Location: Minneapolis, Minnesota
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| Posted: Mon Jan 19, 2009 9:47 pm Post subject: |
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The question I have is how do you go about cleaning out the carbon that will eventually clog the heater passage inside the intake manifold?
I would that periodic cleaning before it completely clogs with carbon would be in order.
Has anyone had any experience cleaning the carbon out of this type of intake manifold?
Scott Novak |
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Runboy
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Joined: September 19, 2007
Posts: 298
Location: Antioch Ca - Soon to be Crescent City Ca
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| Posted: Mon Jan 19, 2009 10:27 pm Post subject: |
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In my opinion they are cheap enough that should they become clogged, just toss it and get a new one.
That is my plan on my "mileage master" intake.
I don't believe anyone that says they can completely clean an original manifold out! 
I have played around with that a bit, cut one open etc.
I have also been wondering if the buildup will be not so bad on modern pump gas vs the old leaded that original manifolds would have run on.
Mike |
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Runboy
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Posts: 298
Location: Antioch Ca - Soon to be Crescent City Ca
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| Posted: Mon Jan 19, 2009 10:29 pm Post subject: |
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Also, how about using one of those "turbo hats" and fabbing a hot air pickup up to the single IDF for clod weather running?
Mike |
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Bob Hoover
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Joined: December 14, 2004
Posts: 64
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| Posted: Tue Jan 20, 2009 5:18 pm Post subject: Heat Riser |
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| Scott Novak wrote: |
The question I have is how do you go about cleaning out the carbon that will eventually clog the heater passage inside the intake manifold?
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Somewhere between 50,000 and 70,000 miles of service, in association with some other task that requires dropping the engine and removing the heads, the heat-riser is cleaned using abrasives and a flexible wand, such as rubber tubing.
Some dealers had enough business to support a full inventory of 'exchange' parts, literally overhauling the old/used part and swapping it out against the customer's part. In that case, the entire intake manifold would be overhauled by removing the gross carbon build-up using abrasives, followed by cold-tanking the part repeatedly until the heat-riser was perfectly clean. The part was then primed & painted, often with decals or other markings that identified the dealer.
-Bob Hoover |
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Eaallred
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Joined: May 18, 2003
Posts: 5756
Location: West Valley City, Utah
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| Posted: Tue Jan 20, 2009 5:26 pm Post subject: |
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sxuxrxf, that looks great!
Now if only header manufacturers would offer something like that. Well done!
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Eric Allred
You have to remember something: Everybody pities the weak; Jealousy you have to earn. |
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Runboy
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Joined: September 19, 2007
Posts: 298
Location: Antioch Ca - Soon to be Crescent City Ca
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| Posted: Tue Jan 20, 2009 9:40 pm Post subject: |
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I have done three similar setups and am glad that the word is getting around about the "fix" for proper heat riser performance.
I would sure like to hear back how that single IDF with the modified heat riser runs for you.
I would like to do a larger carb setup on my bus but the dual carb tuning/linkage just ain't happening on my daily driver.
Mike |
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sxuxrxf
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Joined: May 18, 2005
Posts: 1338
Location: Oceanside, CA
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| Posted: Tue Jan 20, 2009 10:29 pm Post subject: |
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| Eaallred wrote: |
sxuxrxf, that looks great!
Now if only header manufacturers would offer something like that. Well done! |
Thank you very much! 
It will be on the dyno soon for tuning.
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Mongo63
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Joined: February 15, 2007
Posts: 1358
Location: prison city, IL
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| Posted: Wed Jan 21, 2009 1:14 am Post subject: |
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| Scott Novak wrote: |
The question I have is how do you go about cleaning out the carbon that will eventually clog the heater passage inside the intake manifold?
I would that periodic cleaning before it completely clogs with carbon would be in order.
Has anyone had any experience cleaning the carbon out of this type of intake manifold?
Scott Novak |
A length of clutch cable in an electric drill works well for this, picked that up from 80's Yamaha dirtbike manuals. 
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TallKewl7
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Joined: November 28, 2007
Posts: 95
Location: Sandy Eggo, CA
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| Posted: Wed Mar 04, 2009 7:30 am Post subject: |
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I read this thread a while back. I'm running a single Dellorto DRLA 40 on my 1835 in a Baja. I've been having carb problems up the wazoo. (Kids, don't put a carb up your wazoo. I'm a trained professional with the proper safety equipment.) So I decided to implement this modification to my car. I started the fabrication last night. It's still pretty rough, but you get the general concept.
Right side:
Left side:
At the collector: (I plan on making a slip connection here. Take the springs off the collector, raise the collecter enough to slip the preheat tube in and slide it back down, trapping the preheat tube in the process)
Marshall
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