Bristol Cars - Owners and Enthusiasts Forum  

Go Back   Bristol Cars - Owners and Enthusiasts Forum > Bristol Forums > 8 & 10 cyl Bristol cars

8 & 10 cyl Bristol cars From Type 407 onwards

Hot starting issues/boiling fuel

Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 01-05-20, 06:49 PM
Join Date: Mar 2015
Posts: 14
Default Hot starting issues/boiling fuel

We've always had what we called hybrid cars in the family, european cars with US engines, not always Chrysler but a few. A Facel Vega (383), a Monteverdi 375L
(440) and I still have my father's 1975 Interceptor (440).
They all suffered (as did the Bristol) from hot starting issues. All cars had at some point had their intake manifolds changed to aluminium ones which made the issue worse. If the car had a Holley carb the problem was less pronounced. Aluminium is a good heat conductor so no wonder the carburettor gets a lot more heat after switching off. The holley's fuel chambers are further out from the centre of the intake manifold and get a bit less heat than a Carter/Edelbrock. The problem (and the solution) are somewhere else and very easy to fix.
The Chrysler big blocks cylinder heads have so called heat crossover ports in the centre with a channel running through the intake manufold under the carburettor from one side of the engine to the other conducting hot air across.
This is to warm up the carburettor in cold weather. In hot weather after shutting down the engine, it will easily boil the fuel in the chambers resulting in vapour lock and ridiculously long starting times. All the above cars had it and it was solved by exchanging the valleypan gasket with one that has blocked heat crossover passages, easily available at places like Summit.
I then usually cover the valley pan and the underside of the intake manifold with insulation material. Oh and if the car does not yet have an electric fuel pump install one while you're at it.
Probably preaching to the converted here but when I mentioned this to a well known Jensen specialist it was news to him and he immediately ordered a bunch of gaskets. So hope this of some help
Reply With Quote
  #2 (permalink)  
Old 03-05-20, 01:55 PM
Join Date: Jul 2008
Posts: 52
Default Heat

Itís one thing at modest speed. The draft takes the heat away. Stationary, the Chrysler V8 has 2 caspt iron exhaust manifolds weighing c 50meach. The cast iron takes ages to cool. Then the cast inlet manifoldq and the rest of the engine. Itís no wonder the heat builds up and explains why we see many Bristolís on a hot day parked with the bonnet popped up. Add that huge Rotomaster to the mix and itís no mystery that all that insulation has been added. I found that steel tubular manifolds were a good place to start.
Reply With Quote
  #3 (permalink)  
Old 04-05-20, 12:15 PM
Join Date: Apr 2015
Posts: 69

I second Peter Kents comment re tubular manifolds. My 410 now has free flow, four into one, each side, a fine piece of knitting, and the under bonnet temperature is markedly reduced. The standard cast iron manifolds concentrate heat right up underneath the heads, about as far out of any airflow as it is possible to get.

I have started to get interested in air intake temperatures to the carb and there are now temperature indicator strips dotted about the inside of the air filter casing and we shall see what we shall see when I get a chance to drive it again.

I suspect a supply of cool air to the filter intake might prove advantageous but how to achieve this is not obvious.

Martin Barnes put me on to something that is well worth knowing re hot running and starting issues and handed me the solution free of charge. This was a new pair of float valves. He told me that the float valves wear over time, resulting in over full float chambers and too rich a mixture particularly at idle. After I'd fitted them I realised that the slow running jets had been screwed further and further in over time in an attempt to compensate for the overfull chambers until they were effectively up to the stops.

The slow running jets are now well out and can be adjusted effectively and sensitively.

The car now starts on the button when cold, after a very few turns of the starter when hot AND now behaves impeccably in hot slow moving traffic, whereas previously there was always a risk that it would stall as one moved off.

Hope this may help somebody

Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT. The time now is 10:34 AM.

This is the live site

Search Engine Friendly URLs by vBSEO 3.6.0 PL2