[DeTomaso] 73L dying

[MikeLDrew at aol.com]

In a message dated 8/6/07 13 56 33, JDeRyke at aol.com writes:


> Second, add your external fuel filter to the output line from the fuel 
> tank,
> not to the output line from the fuel pump. 
> 
> >>>This is how I had originally plumbed my Pantera, which is why my fuel pump 
conked out in Las Vegas.   I thought I was doing the fuel pump a favor by 
putting the filter between the tank and the pump.   In Las Vegas, I learned from 
John Christian (25 years experience at Roush Racing, doing everything from 
NASCAR crew chief to developing the new Ford GT engine, and now at GM racing in 
charge of their drag race engine program) that this is NOT where the filter 
needs to go.

The reason is that the fuel pump is designed to pump--NOT to suck.   He 
likened it to using a straw--is it easier to suck liquid in, or blow it out?   He 
said that putting an ordinary fuel filter in front of the fuel pump makes the 
pump work MUCH harder than it is designed, and leads to premature failure.   
Earl's and other companies make special 'pre-filters' which are much less 
restrictive (and less effective) and are designed to go between tank and pump.   But 
ordinary fuel filters go upstream of the pump, between pump and carb.

Jack's warning about the vulnurability of fuel filters is worth paying 
attention to.   The plastic filters are 'safer', in that they are less likely to 
break, but they should be mounted securely, and away from any excessive heat 
source (i.e. exhaust systems).

Jack also wrote:

The little factory
filters in Holley, Rochester and Carter 4-bbl carbs are too small so they
plug up rapidly with trash. Remove & throw away as your external unit is not 
only
much bigger, its a better filter.

>>>That's not very smart advice.   It's true that you should definitely not 
rely on these as your ONLY fuel filters.   But these things are basically 
post-filter-filters, designed as a last line of defense, protecting your 
carburetor.   Think of it this way--if these screens plug up and your car stops, they 
are doing their job.   A few minutes on the side of the road, fishing out the 
junk from the screens, and you're on your way again.   Remove these screens, and 
that junk goes into the carburetor instead, resulting in a full carburetor 
rebuild.

I got to spend many hours broken down on the side of the road in the middle 
of France because the fellow I was riding with had failed to fit these filters 
on his Holley.   He was using old fuel line, which broke down and fell apart 
internally, upstream from the fuel filter.   The bits of fuel line plugged up 
the carburetor, the car quit stone dead, and as a result I had one of the 
finest meals in my life in a delightful little bistro.   

Well, that was actually a good thing.   

But the car wound up going back across the English Channel on the back of a 
tow truck, which wasn't.   Proper fuel filtration would have turned this 
episode into a momentary delay, instead of an ordeal.

Mike


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