Fuel Pump in earlier V8s

[Kevin H]

Originally Posted by GREG

I can understand having standard service items as spares,although none are rare on a V8, but I do not understand the logic of keeping items like fuel pumps.

However, what do I know !

The EFI system for my 411 (which is in boxes in my garage at the moment) has two fuel pumps, just in case one fails!

[john smith]

1969 383 - 411 (S1)
Some years ago I fitted the Edelbrock carburettor, fuel pump (model 1723)
and inline filter.
All work like a dream.
From the Edelbrock item description:
"Performer RPM Street Fuel Pumps
Designed for use with all Edelbrock carburettors used in Performer or
Performer RPM applications. The unique valve design improves flow quantity
and quality, and will support engines up to 600 hp. High-volume, 3/8" NPT
inlet and outlet surpasses the capacity of conventional models. Produces 6
psi and does not require a regulator. For gasoline only. Clockable lower
housing can be rotated for best inlet/outlet alignment."
JEVS

[geo]

Originally Posted by john smith

1969 383 - 411 (S1)

"Performer RPM Street Fuel Pumps
Designed for use with all Edelbrock carburettors used in Performer or
Performer RPM applications. The unique valve design improves flow quantity
and quality, and will support engines up to 600 hp. High-volume, 3/8" NPT
inlet and outlet surpasses the capacity of conventional models.

Glad it works well John, but unless one has increased the performance of the engine, does it ever experience fuel starvation? Not necessarily your usage, but many electric pumps fitted by people as after-market bolt-ons do what it says on the box, but then the inlet valves to the carburretor prevent one from wasting all that precious fuel!

George

[pasini s]

> Hi Sam,
>

just a question: did you have to fit a fuel pressure regulator after the
1404/1405 pump? If you did install one, what did you use? Thank you!

Stefano

>
>
>
>
>
>

[Sam410]

The SU pump was already fitted when I bought the car. I don't think there is a regulator fitted, but I am not certain what it would look like or be located so if anyone can tell me I shall check.

[john smith]

Geo
Thanks for your contribution, but I am not sure what you are trying to say!
Some twenty years ago I started to 'update' my 383 engine (from 12 miles per
gallon).
I replaced a lot of items and today I am getting 20 (+ or - 2) miles per
gallon depending on the traffic and my temperment.
Remember - the Canadian '383' was manufactured for use in California which
then had very tight emission controls + lead free fuel.
This engine was fitted with a Carter Four Barrel carburettor which met those
emission controls by restricting the airflow through it.
The Four Barrel Weber carburettor allows some 40% more air (cubic feet per
minute).
I have a 360 degree unrestricted air filter + new intake manifold fitted.
No modification to the bonnet is/was required.
The Edelbrock fuel pump was only part of that updating process.
I have three 1950's Carter mechanical fuel pumps which broke down - the
Edelbrock pump uses a different method of pumping and is self regulated at 6
psi as required by the Weber and is much quieter.
Some years ago, the 'leaded' fuel disappeared from the market.
To date, I have not re-tuned for that loss.
My email is jevs@iol.ie if you would like more detailed info.
JEVS

[Nick Challacombe]

My 313 Canadian Plymouth/Dodge engine had no emission controls and was
designed to run on leaded fuel.
It has always had a Carter 4 barrel carburettor and a large circular air
intake to the carburettor.
No modification has been made to the fuel side of the engine at all apart
from changing, for convenience, from
the std Carter mechanical fuel pump, to a Facet electric fuel pump situated
by the servo under the offside front wing.
The Facet comes with an adjustable regulator attached. I also put in a dual
point distributor and an inline fuel filter.
I have now done 30,000 miles with this set up in the last 11 years with
19mpg on runs, no sign of any valve seat wear,
the older the engine gets the better it gets.
The 407 was renowned for overheating but since I rebuilt the radiator 10
years ago and kept the right amount of anti-freeze
in summer and winter, no problems.
Keep it simple I think is the answer.

Nick

[Kevin H]

Originally Posted by john smith

Geo
Remember - the Canadian '383' was manufactured for use in California which then had very tight emission controls + lead free fuel.

This engine was fitted with a Carter Four Barrel carburettor which met those emission controls by restricting the airflow through it.

The Four Barrel Weber carburettor allows some 40% more air (cubic feet per minute).

John, are you sure about this?
Where was your 383 made? (what's your engine number?)

I thought Chrysler only started making changes for the emission standards late in 1971, when they started to restrict air flow in the cylinder heads.

383's manufactured from 68-70 (and possibly into 1971) would have had the heads with a casting number 2843906. These were a relatively high performance head with very good air flow, so I can't imagine why Chrysler (or Bristol) would put a restrictive carb on a 383 engine with these heads.

As for air flow and carbs, I'm no expert but I did a bit of research on the topic a few years back and wrote this on the old BEEF mail list;

----

There must be many a V8 Bristol out there with a tired or non original carburetor, so for those who are thinking about fitting a new carburetor I thought I might share a few facts I which learned recently about carburetor selection, and possibly explode a few myths in the process. This is a fairly simplistic view but it should at least point people in the right direction!

Carburetors are rated according to the airflow capacity, that is the volume of air which they can supply or 'flow' in one minute, this is measured in Cubic Feet per Minute or 'CFM'. The air of course combines with a measured quantity of fuel on the way through, which ideally will be vaporized by the time it gets into your engine's cylinders.

There is a 'rule of thumb' formula which can be used to match carburetor size or capacity to engine size;

engine capacity (CID), multiplied by maximum engine speed (RPM), divided by 3456 = Carburetor CFM

CID x RPM
__________ = max CFM
3456

For example for a Bristol 411 series 4 or 5 the formula would be (400 x 5500) / 3456 = 636 CFM

However this formula assumes 100% volumetric efficiency (VE), which means the 400 CID engine actually consumes 400 cubic inches of air/fuel mixture for every two revolutions. Which in the case of a normal 400 CID Chrysler engine produced in the 1970's, it doesn't. In fact of the Chrysler V8's used by Bristol, the 400 CID engine, fitted to the 411 S4 & S5 and 412 S1, probably has the lowest VE because of the anti pollution, or 'smog' measures in force in the USA at that time. It is effectively 'de tuned' and probably has a maximum VE of about 70%. All other V8's used by Bristol probably have a maximum VE in the region of 80% to 85%.

An engine's VE varies with engine speed and is highest when peak torque is produced. So taking into account the VE of the 400 CID engine fitted to Bristols, it really only NEEDS a carburetor which flows about 445 CFM.
CFM ratings are only a guide and it is possible for a four barrel carburetor to flow at least 20% more air than it is rated.

At the other end of the scale they can of course flow a lot less, in fact the secondary throttles on some four barrel carburetors are activated by manifold vacuum controlled air valves (commonly known as 'Air Valve Secondaries'). If these are working properly the carburetor will only flow the amount of air required by the engine (Manifold vacuum varies with engine speed and load).

However, most carburetors are fitted with jets, metering rods, etc, which provide a fuel supply in keeping with their air flow rating. So the greater the CFM rating the bigger the standard jets will be and vice versa, (to allow the correct maximum air/fuel mixture). Jets are of course changeable (as are often metering rods ) so there's nothing stopping you from re-jetting a carb that is slightly too small or too large for your engine to make it more suitable. There are however, other specifications which may need to be modified to achieve optimum performance from a wrong sized carb. Including but not limited to; metering rods, air valve adjustment, inlet 'needle and seat' size, air bleed, float level, float drop, accelerator pump adjustment, enrichment circuit timing. Most of these modifications should not be attempted by anyone other than an experienced specialist.

When a carburetor is significantly larger or smaller than the engine requires, these issues are exacerbated because the manifold vacuum becomes too high or too low. Larger carbs, for example, have larger throttle bores and venturi area, which means the manifold vacuum will not reach anywhere near that which the carb is rated at WOT wide open throttle (1.5-inch/Hg), unless the engine is highly tuned to a greater volumetric efficiency and probably higher maximum engine speed. Generally speaking any significant variance in manifold vacuum from the standard at which a carb is rated will make carburetor tuning very difficult.

Many people have been, and probably still are, led astray by the carburetors fitted as standard by American muscle car manufacturers in the 1960's. According to the formula given above, it would seem they fitted oversize carburetors to some particular production model Corvettes, Camaros and Mustangs. Well they did! But that's because these cars were frequently entered in sanctioned competition events where the standard equipment carburetor had to be retained. So when competing they tuned the engine 'up to' the capacity of the carb.

The moral of this story is, if you need a new carburetor for your Bristol, unless the engine has been seriously modified for performance, use the formula above to correctly size your carburetor and it will likely work very well 'straight out of the box' with very little alteration.

NB: Carter, and most other manufacturers of 4 barrel carbs, made different models for different engines (Chevrolet, Pontiac, Ford, Chrysler etc). Make sure you get the correct one for your engine or the throttle linkages won't be correct, the choke actuation will likely be incorrect, and it probably won't fit your intake manifold without an adaptor plate!

Kevin Howard