Clogged heat riser tube

Did you unclog it well? What method did you use to clear it out?

In hot weather, you could get away with it! JMHO later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

No harm, but your engine will not run smoothly, and will be hesitant when cold.

~Anthony

A question that I did not see an answer to, but, I take it you need to drill out the heat riser openings on a header in order to make the risers function, right?

-- the Grokdoc Tom Malmevik all that groks is god

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There's a bit more to it than that.

The manifold heating system takes exhaust gases from one of the exhaust stacks and conducts it to a low presssure area adjacent to the tailpipe. (Tear apart a stock muffler and see for yourself.) Plumbing the exhaust from one stack to another stack does not promote any flow between them other than a kind of oscillation. Plumbed in this manner, the heat riser quickly clogs.

The only after-market manifold & exhaust systems that took this into account were manufactuered by EMPI in the late sixties. All others are simply junk aimed at the kiddie trade.

This isn't anything new. A complete explanation of the problem appeared in Bill Fisher's 'How to Hotrod Volkswagen Engines' which was first published in 1970 and similar information has been available on the Internet since at least 1994.

-Bob Hoover

I guess I need to be more clear, Bob. I have a Baja Bug with an aftermarket exhaust header system on it. My new engine has a single dual weber progressive setup that requires the "heat tubes" to attach to the intake manifold. The 2 spots (one on each side) of the exhaust header for the tubes to attach are not a drilled opening into the header pipe. They are welded on flanges. Do I heed to drill the pipe that is visible thru the flange hole to make the manifold heat tubes functional? Is this clearer?

-- the Grokdoc Tom Malmevik all that groks is god

...well yes....and no. You will need to drill out the tubes....which will in turn get you to the exact point that Bob has jnust described for you. with the holes drilled you will still have a very minimal flow....what Bob described as "a kind of oscillation" Ideally you would open one side....shave the other side off anmd re-plumb it to a lower pressure area on the exhaust...thusly creating a proper exhaust flow.

...Gareth

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Dear Tom,

You may drill all you want and wherever you wish but doing so will not make the heat riser functional unless the outlet is at a significantly lower pressure than the inlet, which it is not if it simply runs from one exhaust stack to another.

The exhaust system you are using will cause the heat riser to become clogged because it violates a fundamental law of physics. See the stock system to understand what is involved. Or read Fisher's book.

The long intake runners common to any center-mounted carburetor installation dictate the need for manifold heating. Without it you will experience very poor fuel economy, manifold icing under the right conditions and generally poor performance. That isn't an opinion, it's an engineering fact. When you realize your bug runs like shit the same folks who sold you that disfunctional exhaust system will then be happy to sell you a dual-carb set-up. Being bolted directly to the heads and absorbing heat from them, this will eliminate the manifold icing and poor fuel vaporization. Of course, they will also sell you a mechanical advance distributor, requiring you to jack-up the output of your accelerator pumps since you won't see any ignition advance until the rpm changes. This will make your fuel economy even worse but at least the thing will run. For a while. With an overly rich mixture and air cleaners that are a joke, wear on your rings & valves will be greatly accelerated; how long the thing lasts will depend largely on the climate.

If you follow the typical pattern of young VW owners (and so far you have) it will take you about two years to realize you are being practiced upon by after-market retailers whose only interest is in selling you stuff that ensures a loud and short-lived engine. On the basis of cost-per-mile your 'VW Experience' will cost you more than owning a luxury car.

When you finally come to understand all of this, if you're smart you'll sell your VW to the next youngster waiting eagerly in line, buy yourself a Toyota and get on with your life. And if you think I'm blowing smoke simply check the archives of this list. You are doing (and asking) what dozens of other college kids have done before you. Their Volkswagens remain -- sold to the next sucker

-- but they have vanished from the Newsgroup.

You may find this message a bit harsh. Tough Darts. It describes certain laws of physics and automotive engineering (economics, too) that you can't change no matter what all your buds and the nice man at the VW store tell you.

Now, is THIS clearer?

-Bob Hoover

Clogged after only 300 miles? Hmmmm! Sounds like an awful lot of carbon in your exhaust system. You sure you had it cleared in the first place?

Aw. Now I understand. The "stock" way can lead to trouble with cloging and the way Bob was trying to "drill" into my head is to make it a flow thru system. Am I right?

-- the Grokdoc Tom Malmevik all that groks is god

This I already understand. Since this is an aftermarket motor and exhaust, then my questions

Have a dual weber set on the engine coming out. Went with the single dual due to things I have read here. Figured it would be more efficient that way.

Well lets despell a few more misconceptions you seem to have about me. I have not been a "young" VW owner for many years. I am 50 now and have owned about a dozen ACVW of all kinds since my first one in 1972. These have all been stock and functioned quite well for the purposes I had. When I was young, it was to beat them and pick up "chicks". Now they are for fun. My daily driver is a Motorcycle. This is my first "nonstock Baja VW. Will play with it up in the mountains when I can and fuel economy is very low on my list of concerns. I used to do this with my stock VW's but would damage them a bit. Now I bought an already Baja'd bug to go play in. Have yet to see one with a stock exhaust, and was just asking a simple question about drilling the pipes. I doubt that I will find a reasonable way to fashion a way to run the tubing into the lower airpressure area of the muffler, but I will see what I can do.

Harsh? Maybe to a "young pup" just out of high school, but I ain't him. I have been wrenching my own cars, trucks, bikes, and VW's for many years now. I thoroughly understand the concept of the physical limitations of the universe in which we live and basic automobile engineering, and I have no "buds" around to try and tell me how to be cool. Remember Bob, Not everyone on this list is a "youngster" that needs a lesson like the one you have attempted to give me. But thanks for your input.

Now is THAT clearer??

-- the Grokdoc Tom Malmevik all that groks is god

...well stock *is* a flow through system.....the cheap aftermarket exhausts are not...i9t is far easier and cheaper to just stick two inlets rtight ontop and bolt em up...regardless of the fact that it does not function correctly..

..Gareth

Now lets us not overrate the stock heat riser just because it's an original ACVW part. It's always been problematic - chokes up with crap too soon for my liking, and it's a positive b*ch to clean out. I've reverted to an aftermarket three-piece version because it's easier to clean - and install.

I will save my rant about the muffler makers who can't seem to decide where and how they install the venturi.

I understand that Gareth. Otherwise I would have had no question in my mind. The original motor was the duals so the heat risers were not needed. This is, like I said, the first aftermarket one I have had that needed them for the icing. I have been on this list, though mostly lurking, for about 6 or 7 years, and had always thought that any question was answerable without a need for a lecture......*8-}

And don't get me wrong (no more assumptions please) I have great respect for Bob and his knowledge base. He si good people, but then, so am I.

-- the Grokdoc Tom Malmevik all that groks is god

Yup. Feel free to do what I did.

http://63.230.74.177/baja/page8.html

I didn't work, but at least then I won't have the only engine that looks like that. ;-)

Max

Or what I did.

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My apologies.

However... on the Internet perception IS reality. If it walks like a duck and talks like a duck and is only interested in VW's for 'fun' and doesn't bother to check the archives, where the answer to the question has appeared many times and which you've failed to notice in the six or seven years and uses a Bob Heinlein-coined term as a screen-name in a message posted from the University of Washington servor I think it's only fair that you give me the benefit of the doubt.

Otherwise, the shoe seems to be a pretty good fit.

-Bob Hoover

-(Who still flys a '78 CX500 [world's worst motorsickle] )

OK, I feel _much_ better now. Thanks Shaggie! :P

I've actually had strangers ask me about the strange plumbing on my engine. Maybe I should just blame it on the PO.

Max

-snip-

hehehe, but Bob, a tiny percentage of us ignorant teenagers are stubborn enough to plow through all this crap and stick around for much longer..

This is exactly how I started.. some 17 years ago or so? (Christ.. I need to get a life)

Jan

...not real sure about the 500, but the cx 650 I had was a damn fine wheelie bike. In fact I would have to rate it as one the most entertaining bikes I have owned, even if it was slow and handled poorly, simply for this fact.You could actually leave the line "straight up" and ride it outta sighifairly easilly....a light bike combinrd with lota torque help keep this bird flyin