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uhhrace Samba Member
Joined: March 24, 2014 Posts: 6 Location: San Diego, CA
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Posted: Mon Nov 23, 2015 11:06 pm Post subject: No heat risers? |
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Bought a new exhaust that doesn't have any flanges for the heat risers to bolt onto. Can I just block off the heat risers? And will it noticeable affect how the car runs? I know it brings warm air to heat the carb, but I live in San Diego so I don't know if it ever really gets cold enough for that to be an issue. |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11739 Location: Redding, CA
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Posted: Mon Nov 23, 2015 11:50 pm Post subject: Re: No heat risers? |
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If you have dual carbs, it's not an issue. But a single carb? Now that's another animal.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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andk5591 Samba Member
Joined: August 29, 2005 Posts: 16754 Location: State College, PA
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Posted: Tue Nov 24, 2015 5:29 am Post subject: Re: No heat risers? |
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Outside temp is not that relative when it comes to a fairly high velocity mix of gas and air. On a hot day if you blow on your wet arm, its still feels cold. You will see icing on the outside of the intake.....even with risers, you will still see some.
X2 what Tim said. I just converted a future buggy to dual carbs for one of those reasons. _________________ D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them... |
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volksworld Samba Member
Joined: November 26, 2011 Posts: 2525 Location: formerly NY currently NC
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Posted: Tue Nov 24, 2015 7:20 am Post subject: Re: No heat risers? |
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even exhaust systems that HAVE flanges are a problem...including stock mufflers that arent designed correctly internally to actually allow a FLOW of exhaust through the heat riser |
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vamram Samba Member
Joined: March 08, 2012 Posts: 7276 Location: NOVA
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Posted: Tue Nov 24, 2015 8:04 am Post subject: Re: No heat risers? |
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volksworld wrote: |
even exhaust systems that HAVE flanges are a problem...including stock mufflers that arent designed correctly internally to actually allow a FLOW of exhaust through the heat riser |
Does anyone make a stock exhaust that is designed correctly for the heat risers flow? _________________ Eventually, "we are what we pretend to be.’”
Give peace a chance - Stop Russian-Soviet Aggression!!
'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
Click to view image
Save the Supers!! |
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air-h2o-air Samba Member
Joined: January 25, 2015 Posts: 579
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Posted: Tue Nov 24, 2015 9:04 am Post subject: Re: No heat risers? |
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Dansk that i have is correct |
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uhhrace Samba Member
Joined: March 24, 2014 Posts: 6 Location: San Diego, CA
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Posted: Tue Nov 24, 2015 10:32 am Post subject: Re: No heat risers? |
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andk5591 wrote: |
Outside temp is not that relative when it comes to a fairly high velocity mix of gas and air. On a hot day if you blow on your wet arm, its still feels cold. You will see icing on the outside of the intake.....even with risers, you will still see some.
X2 what Tim said. I just converted a future buggy to dual carbs for one of those reasons. |
So icing on the outside of the intake, will this freeze the gas/liquid inside the intake, or just slow it down on its way into the engine? |
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Volks Wagen Samba Member
Joined: February 13, 2013 Posts: 2926 Location: Germany
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Posted: Tue Nov 24, 2015 10:45 am Post subject: Re: No heat risers? |
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uhhrace wrote: |
andk5591 wrote: |
Outside temp is not that relative when it comes to a fairly high velocity mix of gas and air. On a hot day if you blow on your wet arm, its still feels cold. You will see icing on the outside of the intake.....even with risers, you will still see some.
X2 what Tim said. I just converted a future buggy to dual carbs for one of those reasons. |
So icing on the outside of the intake, will this freeze the gas/liquid inside the intake, or just slow it down on its way into the engine? |
It cause the fuel to drop out of vapour type form and condense in the intake, which will lean out the vapour but might gather to give globs of fuel droplets at times, so you'll get rough running. _________________ 1973 1303 with AB-motor - sporadic
reconstruction as time permits, 1986 ex-Bundeswehr Doka - on the road again.
I'm definitely, probably, the worlds greatest lover.
Aithníonn ciaróg ciaróg eile. |
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OLD VW NUT Samba Member
Joined: February 23, 2011 Posts: 2776 Location: High Desert of Washington 98823
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Posted: Tue Nov 24, 2015 11:04 am Post subject: Re: No heat risers? |
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The stock style heat risers help to keep the fuel atomized on its way to the heads and intake valves. Carb icing usually shows up at the outside base of the carb first - once you see icing on the outside you can bet there is more than that on the inside. Severe icing will plug jets and even interfere with the throttle butterfly. The car will either run like crap or not at all.
Very few manufacturing clones of VW stock mufflers build into their product the proper plumbing that will allow enough exhaust gases to heat the intake manifold to prevent icing. Some do.
Check out the pic below - a grab from the gallery. That little tube on the left will likely create more exhaust flow than simply perching the riser connection on top of the #4 exhaust port. There is very little flow from those - usually found on mass produced headers. You can make your own heat riser setup by putting one heat riser next to #2 or #4 exhaust port and run the other side to the exhaust collector on a header setup. If you are looking for a stock muffler find one plumbed as this one is.
Aircooled.net sells mufflers that are close to OEM. One with left hand preheat and one with right hand preheat. I have no idea if one is better than the other. Ask John about that.
http://vwparts.aircooled.net/Muffler-GERMAN-1966-71-Type-1-LH-Pre-heater-p/113-251-053ak.htm
http://vwparts.aircooled.net/Muffler-EUROPEAN-1966-71-Type-1-RH-Preheater-p/113-251-053aj-rh.htm
_________________ 71 Ghia Coupe - stock body - no rust! Powered by a 2110 W/Dual HPMX 44's - Rancho Pro Street Transaxle - A/C by Gilmore
Other car - 2013 VW Golf TDI |
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morymob Samba Member
Joined: November 09, 2007 Posts: 4683 Location: east-tn
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Posted: Wed Nov 25, 2015 4:27 am Post subject: Re: No heat risers? |
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Easy to check if yours is working, after eng gets warmed up check temp of the heat tube on both ends, if u can hold one end u r getting no flow of exhaust gas. On orig good ones i used to swap the 'cooler'end flat gasket 4 one with the small hole in summer to drop intake runner temp as hotter temp isn't needed then. |
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volksworld Samba Member
Joined: November 26, 2011 Posts: 2525 Location: formerly NY currently NC
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Posted: Wed Nov 25, 2015 9:55 pm Post subject: Re: No heat risers? |
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vanram the leistritz muffler pictured by old vw nut was the best one on the market but they are no longer available... what you cant see in that picture is that the heat riser tube ended directly in the center of the left tailpipe opening...this allowed the flow of exhaust through the tailpipe to "siphon" exhaust through the heat riser tube....ernst mufflers were not set up like that and were terrible...i've seen kadrons like that but the steel was very thin and they didnt fit very well...never tried a dansk...40 years ago real empi headers ran the heat riser tube directly into the center of the collector but i havent seen anyone do that since then |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11739 Location: Redding, CA
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Posted: Wed Nov 25, 2015 11:58 pm Post subject: Re: No heat risers? |
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One thing not mentioned: the exact placement of your pea shooters is very important. If you stick them in too far in some mufflers, you can interfere with the gasses going to the heat riser. Check your Bently for the measurements when installing the pea shooters.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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talljordan Samba Member
Joined: January 10, 2012 Posts: 954 Location: San Francisco, CA
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Posted: Fri Nov 27, 2015 8:13 pm Post subject: Re: No heat risers? |
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Tim Donahoe wrote: |
One thing not mentioned: the exact placement of your pea shooters is very important. If you stick them in too far in some mufflers, you can interfere with the gasses going to the heat riser. Check your Bently for the measurements when installing the pea shooters.
Tim |
This is one thing that has always bugged me. Why couldn't VW and the aftermarket folks just add a little stop tab.... _________________ 1972 Super Beetle, Parked until adequate restoration funding is acquired in restoration!
Wanted: Male computer diagnostic plug end |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11739 Location: Redding, CA
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Posted: Sat Nov 28, 2015 12:41 am Post subject: Re: No heat risers? |
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Jordan, I guess they just figured people wouldn't be keeping these cars for decades, and didn't think it necessary to provide a fail safe tab to prevent the issue.
The information is in the Bently, though.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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