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Original FUEL HOSES - Petroflex -- FU-109

This article will be of interest to concours enthusiasts intent on having things perfectly original. These pictures show the flexible fuel lines at the MGA carburetors.

wrapper tag
Original manufacturer's wrapper tag.

The first picture is an original manufacturer's plastic tag which was wrapped around the hose identifying the manufacturer. "Smiths" is the manufacturer's name. "Petro-Flex" is a registered trade name for their fuel hose products. The band had been stretched a bit on the hose before being removed for scanning. Otherwise it would be straight, flat, and wrapped on the hose as a cylindrical tag.

OEM fuel hose
Original Equipment Manufacture fuel hose.

This is a picture of an OEM fuel hose, new and never installed. Notice the smooth configuration of the crimp collar. Also note that the yellow plastic brand name band does not include "REGD" as seen in the previous picture. This may have been eliminated from the tag some time after the cars were built when replacement parts were being produced. The free spinning flare nut is a steel machine part with a brass crimp collar securing the hose to the hose barb. The steel braid was most likely originally bright finish but has weathered with time to the current dark bluish-gray appearance. The braid is composed of 4 small wires per band in a 2 over and 2 under weave and 12 lateral steps in one revolution. This means there are 96 wires in the weave.

Original braid coverd fuel hose
Period replacement fuel hose with blue tracer tape in the stainless steel braid.

This picture shows a period replacement hose, not made by Smiths, but very similar except for the blue plastic tracer in the braid. The blue tracer stripe is another manufacturer's trademark unique to a single manufacturer (believed to be American origin) and not part of the original Smiths fuel hose.

End fittings are brass, originally bright finish but commonly weathered to a dull patina with time. The hose barb is secured to the hose with a thin brass crimp shell. Notice the indented crimp pattern different than the original part. The low pressure hoses of the day were plain rubber covered with stainless steel braid for abrasion resistance and maximum service life, best as this was possible. As long as the hoses were in regular service they seemed to hold up quite well. If the car was left to sit for a few years the hoses could dry out and break up internally with no visible sign of external deterioration. The next time the fuel pump was switched on the hose might leak profusely in multiple locations, not unlike a lawn sprinkler hose.

Modern motor fuels are also tough on original type rubber fuel hoses. With time and the elements and new fuel formulations it is very unlikely that any original fuel hose would still be serviceable today. For a quick field fix you can cut off the brass crimp shell to remove the old hose, install the original flare nut and hose barb fitting into a new 5/16 inch fuel hose, and secure it with a screw type band clamp.

close up of braid pattern
Close up of the braid pattern.

This is a close up picture of the cover braid. The blue tracer is helpful in identifying the braiding pattern and the number of individual wires in each braid. Here the weave pattern has 7 thin wires per band. The bands are interwoven in a double basket weave going over 2 and under 2 and staggered. As the blue stripe plastic band does one 360 degree rotation it steps laterally 12 bands (11 in between). With 7 wires per band this requires 168 wires to make the weave. Thanks to Mark L. Lambert for the pictures above.

Some modern replacement parts may use plain rubber hose. Most will have original style stainless steel braid covering. The better modern replacement hoses will have a Teflon inner lining which is very resistant to any modern fuel formulation. These Teflon lined hoses often come with a lifetime guarantee. I have a set of them on my car which has now done over 200,000 miles in 20 years since being restored, and the Teflon lined fuel hoses are still in very good condition.

close up of  Moss braid pattern
Close up of the Moss Motors part braid pattern.

This is a picture of a Moss Motors supplied replacement hose with stainless braid (and Teflon lining). This has a braid structure using 4 thin wires for each band with the 2 over and 2 under basket weave and 12 lateral steps for one rotation around the hose similar to the OEM part. Here the wires may be slightly thinner or more tightly packed together. With slightly narrower bands it has a shallower angle for the braid wrap, more crosswise of the hose and a shorter distance along the hose for one rotation. For one band this shows 2-1/2 rotations around the hose in the length of this picture (30 lateral band steps). As a point of casual interest, this hose has been in service for 20 years and is still looking pretty spiffy.

As a side note, the smaller flex hose on the other side of the engine for the oil pressure gauge signal line was also originally a Smiths hose. Modern replacement parts commonly have construction similar to the fuel hoses with stainless steel braid covering, but original parts were much different. The original oil pressure hose had cloth braid on the outside of a small bore rubber hose, then had a steel wire spiral wrapped around it for protection and form holding (similar to the temperature sensor tube). One of the brass end fittings was stamped with the maker's trade name "Smith's Super-Flex".

Original Smiths oil pressure hose
Original Smiths Super-Flex oil pressure hose

On 06 April 2017, Garry Kemm in Victoria, Australia wrote:
"S.Smith & Sons (England) Ltd. was a parent company and their subsidiary companies included Petro-Flex Tubing Co. Ltd.   Petro-Flex manufactured both petrol and oil tubing. ... Sometime late 1950's the design was changed to a steel braided version which was the same (at least externally) as the petrol hoses. The Smiths PetroFlex oil hose part number is PFP 195. The attached photo is of an original oil hose from a 1959 MGA Twin Cam, and it can be seen that externally it is the same as the original Petro-Flex petrol hoses, that is braided zinc plated steel".
Original Smiths oil pressure hose, Updated

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