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  VW Parts Catalog > Exhaust & Mufflers >

PreHeat Modification Labor to VW Headers (For Center Mount Carburetors)
PreHeat Modification Labor to VW Headers (For Center Mount Carburetors)


 

PreHeat Modification Labor to VW Headers (For Center Mount Carburetors) was developed since all the VW Aftermarket headers had non-existent or poorly engineered pre-heat flanges, so we spent weeks figuring out what worked (and why), and now offer it for you! As usual, with manufacturers incapable or unwilling to make these headers properly, we had to spend the time and money to do it ourselves!

This is the labor ONLY to the header you buy at the same time from Aircooled.Net, the header must be purchased separately. Because we do not do any ceramic coating, we strongly recommend that you only do this to "RAW" headers from us, or you will have a ceramic coated header that will rust where we have performed the work and welding.

We feel that this modification is a MUST for anyone that wants to run a header along with a center mount carburetor, whether it's an On or Off-Road car, Weber IDF or Dellorto DRLA, Weber/Holey Progressive, or even a stock Solex!
Now many may think to themselves, "My header has preheat flanges on it on cylinder #2 and #4, what's wrong with that?", which is a very good question. Flow always goes from high pressure to low pressure, right? With flanges placed normally on cylinder #2 and #4 primaries, the pressures are the SAME, they just alternate back and forth as the engine cycles. This provides a pulse, but not a FLOW from one side to the other. We put a flange on one side, but the other side is routed to the collector, which is a low pressure area. This flows hot exhaust from the primary, through your intake manifold, then to the collector.
Increased preheat will cause the engine to run significantly richer with the carburetor jetting unchanged, since the metered fuel is not falling out of suspension (condensing). Not many people know that liquid fuel is not flammable, only the vapor is. There is a significant amount of heat required to change any liquid into a vapor, this characteristic is well knwn as the "Latent Heat of Vaporization" in chemistry books. You can experiment with this in your Kitchen. Put a pot of water on the stove, and turn the burner on, with a Candy Thermometer in there. The water temperature will increase until it reaches the "Boiling Point" which is when non-pressurized water turns to steam. At this point all the heat you are adding, does nothing but turn the water to steam, WITH NO MORE INCREASE IN TEMPERATURE OF THE WATER! The temperature will stay at the boiling point until all the water is boiled off, THEN the temps will rise!
Conversely, if you have steam, when it changes back to water it releases a lot of heat. This is why a burn from steam will be far worse than from hot water! This effect is also how the human body cools us, via perspiration.
The same principle applies to gasoline metered from the carburetor. Every drop of fuel requires a LOT of heat to change from that liquid to a true vapor (instead of just small droplets). We can keep adding heat all we want, and until it all the fuel is vaporized, the temperature will not climb much at all, but they WILL stop getting "so cold". This is also why a VW Intake Manifold can have ice on it, despite ambient temperatures over 70F!
Another way of viewing preheat is to visualize what happens without it. If the heat is NOT provided, you must deliver more fuel to compensate for all the fuel that will be condensing on the way to the cylinder (remember, liquid fuel won't burn, and it puddles in the intake manifold and carbons up your valves and combustion chamber). This is a problem even in temperatures over 100F! Expecting the intake manifold to "stay warm enough" without providing heat to it is crazy! You MUST provide heat to prevent the condensation.
The easiest measure of "Proper Preheat" is to measure the temperature of the intake manifold. If the intake manifold is colder than ambient temperature, then you do not have enough pre-heat!
When we first started, we added more and more heat to the intake manifold. This will NOT cause your engine temperatures to go up because all we are doing is vaporizing the available fuel. We had to go through many "versions" of our preheat modifications, before we reached an acceptible level of pre-heat that actually did the job properly. As in the boiling pot of water, it took a LOT of preheat to actually vaporize all the gasoline that was being run though the system.
After all this McGyvering, we decided to make it available to Aircooled.Net customers that purchase a header from us. We will do this work on street headers, or even big off-road headers that commonly run center mount 2 bbl carburetors.
You do not have to worry about "Too Much" preheat. If the intake manifold actually got HOT (it won't), you simply change the size of the hole in the preheat gaskets to regulate the flow of exhaust. You may run the big ones in Winter, but in the heat of the Summer find that a smaller hole works better for you. But this control is certainly better than NO PREHEAT that you had before!
Work typically takes a couple weeks, and we do NOT offer any coating services after our work is done, if you want that done you will have to do it locally.
Price: $109.95
Restrictions: DISCOUNTS/PROMOCODES DO NOT APPLY TO LABOR
Country of Manufacture or Origin: MADE IN USA

PN: EXHAUST-PREHEAT-MODIFICATION


Modification Not Currently Offered, Sorry!
Product Overview
 
PreHeat Modification Labor to VW Headers (For Center Mount Carburetors) was developed since all the VW Aftermarket headers had non-existent or poorly engineered pre-heat flanges, so we spent weeks figuring out what worked (and why), and now offer it for you! As usual, with manufacturers incapable or unwilling to make these headers properly, we had to spend the time and money to do it ourselves! We feel that this modification is a MUST for anyone that wants to run a header along with a a center mount carburetor, whether it's an On or Off-Road car, Weber IDF or Dellorto DRLA, Weber/Holey Progressive, or even a stock Solex!

This is the labor ONLY to the header you buy at the same time from Aircooled.Net, the header must be purchased separately. Because we do not do any ceramic coating, we strongly recommend that you only do this to "RAW" headers from us, or you will have a ceramic coated header that will rust where we have performed the work and welding.


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