Starting not so good?

Shamelessly stolen of the Vincent Owner's Club NG!
Peter said -
" Reed vapor pressure. The days of seeing that shimmering mirage over a cup
of gasoline are over. 300 million gallons of gas are lost annually to evaporation at the gas station fuel pump. To stem this, the Fed's have dictated your fuel be less "volatile" in this particular situation - at atmospheric pressure by being less inclined to atomize and turn into vapor. Not a problem for the average car on common rail EFI at injection pressures starting at 40psi and a non issue for direct injection at 2000psi plus. But a huge one for a vintage m/c owners and particular those with lower start off port velocities either due to large size relative to displacement or cam overlap. Essentially that carb tickle now turns into predominantly an unbroken trickle flowing into your combustion chamber with little/no atomization. This is especially evident at ambient temps below about 50-60F with the blends used in the south/south east US. Many a Weber carb'd 911 has become unusable and the trend now is to replace those carbs with a 40-60psi EFI individual throttle body setup.
Over a year ago I started my Shadow after 33 years languishing as basket with exactly 2 kicks, not so this February. Even on a BTH, it wetted the plugs under the original start format. Have now forgone 91 plus octane for mid grade and instead of tickling the original 289's till they foam slightly from the tickle pins at the top, only look for slight moisture at the base of the jet block slot at the gland nut. "
I wonder if this is the case in the UK?
Regards,
Kim Siddorn
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In a nutshell and keeping it very basic, since the demise of TEL (lead) from fuel, refineries have to achieve the correct octane by using a much greater proportion of aromatic (light) fractions and even dissolved propanes. The fuel does the job but has a much reduced vapour pressure and, especially important for all of us with ''summer'' toys, a very poor shelf life. I don't use any fuel that's from last season - I save it for the lawn mower. I have a Jensen with a 500cid stroked Chrysler engine fitted with an 870cfm Holley carb. In summer it won't idle for more than about 5 minutes without the petrol ''boiling'' up in the carb and lines causing stumbling. I fitted a large Facet electric fuel pump at the rear and removed the original engine driven pump - that made a big difference but not a full cure. I'm looking at fitting some pipe lagging this spring..... Good old leaded petrol is available in drums but the price is astronomical :-(
Julian.
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snip
Following on from Johns post.
Now you have the electric pump why not try a T piece at the fuel inlet to the carb with a restricted return to the tank as some Fords did before carbs became a thing of the past.
Also if they are not there already, is it possible to fit a thermal insulator block between the carb & manifold. These used to be very common, I am sure one could be fabricated from hard plastic.
Tony Brooks
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That's a good idea, I had thought about it. One thing I have to remember is that the pump I have is only rated at about 21 gallons/hour, that's a touch marginal and I'm not sure it has the capacity to feed a return line. However I may fit a Holley (rotor cell) fuel pump that would have spare capacity, some nice kit incorporating a pressure regulator and pressure gauge is available for mounting close to the carb to monitor things.

That's a very easy mod, but I'm very stuck regarding bonnet clearance. The engine has Edelbrock alloy heads which raise the inlet manifold, the manifold itself is a bi-plane/single plenum hybrid jobby which is taller than standard. And so I've already fitted a low profile ''drop centre'' air cleaner to get the bonnet to close. Having said that the Chrysler big block uses a valley pan to seal up between the banks and doesn't rely on the inlet manifold to do the job like many V8's - this has the real advantage of not heating up the inlet manifold much at all.
The car is just for fun so I can live with its quirks, mostly!
Julian.
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On Tue, 23 Mar 2010 08:34:31 +0000, Tony Brooks wrote:

I think my Ford truck has one, and that's over 40 years old - not plastic, though. I think it's the same stuff often used for old electrical insulators (presumably it's designed to handle heat well without cracking).
Don't discount the sheer amount of heat radiating from exhaust manifolds, either - often a bit of metal formed (nicely! :-) into a heat shield can help there and stop heat build-up in the wrong places (one of my Stags used to be terrible for it - forget trying to restart on a hot day for 30 mins or so after switch-off).
I think US fuel is pretty horrible stuff, incidentally - in part explaining why US cars typically get such poor MPG figures...
cheers
Jules
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That's one of the troubles, it's a big engine and enormous radiator all shoved into a small space, open the bonnet with a hot engine and it's like standing next to a ''spud-u-like'' open stuck on full power. Everything's gets fried, so much so that people move the ballast resistors and coil forward of the engine, and brake servo diaphragms only last a few years before the heat makes them split. I've stainless headers on my engine - popular at the moment is ceramic coating which seems to help cut the heat down. I'd be happy to wrap it all up in asbestos tape - but B&Q don't sell it now :-)
Julian.
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Should read - ''spud-u-like'' oven!
Julian.
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I'd be happy to wrap it all up in asbestos tape - but B&Q don't sell

Google Exhaust Wrap and there's loads of hits such as this http://www.exhaustwrap.com/default.aspx I like their comment that it reduces underbonnet temperature by 50% without giving the units.
John
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And if you want it off the shelf nearly any inland waterways chandlers will sell several varieties of the modern equivalent. Oh - at a suitable mark up :-(
I have also seen carbs with a thin horizontal baffle below the float chamber to keep the heat away. It seemed to be simmilar to Klingar gasket material.
Tony Brooks
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On Tue, 23 Mar 2010 15:34:12 +0000, Julian wrote:

Hmm, you'd like my truck - I could almost fit two engines in there. I normally just stand inside the engine bay if I'm working on it :-) (they were built with big V8s in mind, so there's boat-loads of room around the straight-6 that mine's got)

Get yourself an angle grinder and homebrew some bonnet vents ;-)

Never have been much of a fan of the tape - just looks messy (reminds me of those quick-fix tapes people wrap around holes in their exhausts, I suppose :-)
cheers
Jules
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Well the SP (440RB with six pack carbs) models got the louvered bonnets. (hoods) Some bright sparks did research and discovered that on the move the louvres, situated in a high pressure area, actually decreased cooling flow through the radiator - and when you park up in the rain the engine gets drenched :-(

I agree. The headers are custom made to fit the car and look nice in stainless and covering them up isn't best (probably like Jordon's you know whats!) Besides, bulking them up with lagging will make changing the plugs completely impossible rather than practically impossible :-(
I think that an uprated Holley fuel pump and a fuel return line from the carb makes the most sense.
Julian.
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One other aspect of injection is they have a presure relief pipe back to the tank. That means the fuel doesn't sit in a hot engine bay for long. Fuel vapourisation isn't a modern problem. I remember it on mother's A35 back in the 60's.
John
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