There is a short article in the April issue of British Car Mag on
header wrap. Tipically, headers are made out of a relativly thin
material (when compared to the original cast iron manifold). While
passing through the header, exhaust gases cool and thicken,
transforming into a less flowable (new word ?) state. According to
the article, for each 30 degree (F) drop in exhaust temperature,
you lose one second/foot of ehaust velocity. Header wrap helps
maintain the exhaust gas heat, creating a better flow. Another
benifit is the reduction of engine compartment heat; less heat better
efficiency; better efficiency more power.
When header wrap is used for its intended purpose, the fuel mixture
needs to be richened to compensate for the increased flow. Don't use
on a fresh rebuild, work out the bugs frist then apply and adjust.
This same header wrap should work well under the floorboards of
your MGA.
Sources of header wrap given in the article are:
Thermo-Tek
(800)274-8437)
Pegasus Auto Racing Supplies
(414)782-0880 phone
(800)742-0484 fax
It is also availible at local speed shops and J.C. Whitney.
Happy Motoring,
John Fagerlund
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