75 HP Bristol engine.

[Lewis]

I own the HRG 2 Litre. The one and only. An experimental chassis built by HRG in about 1948/9 for a Bristol engine. Having got as far as a rolling chassis with an engine borrowed from Bristol Cars, the penny dropped when HRG realised everyone else was using this engine for racing. The engine was, very reluctantly, returned and the chassis ended up with a cousin on a New South Wales sheep station.

To complete the car I found an early 400 engine near Melbourne. It is engine number 1065, stamped 400/75 on that brass plate on the offside rocker cover.
Now the Oz Bristol gurus don't acknowledge the existence of a 75 HP engine outside early Filton development cars, so what have I got?

I wrote to Tony Crook a few years ago but did not receive a reply. A pity because long ago when I married in London he lent me a 403 for a weekend.

Does anyone out there know whether 75 HP engined cars were sold by Bristol and if so how many and to whom?

Lewis.

[johnelfixit]

Well, my 400 instruction manual suggests that the "touring engine"
produced 75 bhp at 4500rpm and was equipped with a single dual port solex
carburetter, whilst the sports engine (with special camshaft) produced 85
bhp and had three downdraught SU`s. This sports engine is usually referred
to as the 85A. The engine and was then fitted with three Solex carbs,
became the 85C and was used in the 401. The single Solex was fitted to a
special manifold connected to the water circulation system.

John P

[brianjgkidd]

> I had an early Bristol 400 - still in existence, but not with me, unfortunately.

The Bristol Parts list (I still have it) which came with the car shows a SINGLE
Solex twin choke carburettor with a separate induction manifold. It also shows
three SU carburettors, attached directly to the head, to make it an 85A engine,
but with a catalogued power of 80 bhp.

My engine was subsequently fitted with three Solex carburettors to turn it into a
85AC engine, with a catalogued power of 85 bhp.

I'm sure an engine fitted with a single Solex would have given less than 80 bhp,
and Setwright's book refers to early 400 car engines giving 75 bhp. But how many
of these were sold, I don't know.


Best wishes,

Brian Kidd> > > > >

[Geoff Dowdle]

Lewis and others,
It is interesting that this engine is marked 400/75

The 400- 403 Workshop Manual states "Type 85 engine is 75BHP at 4200rpm
fitted with single Solex30 AAPI

85A is 80BHP at 4200 three SU - D2

85C is 85BHP at 4500 three 32 BI

You all would have known this , but there is no mention of a type 75 engine
( it could have been a special engine producing less than 75 BHP )

Of the First series 400's delivered to Australia the BOCA has record of
eight 85 series engines , most have been converted by fitting 3 SU's or 3
Solex
Lewis your 75 series engine is the only one of it's type that I have heard
off . I can only assume it produced lower bhp by lower compression or change
of
camshaft although there is no mention of those parts in the 400 Parts Book .

If you look at Ashley's website www.jel450.com there is a Register I
compiled of all known 400's .
Engine 400/75 #1065 was originally fitted to a first series chassis # 530
which is Car# 266 ( one can assume the 166th type 400 of approx 420
produced ) ,
although the engine I assume was the 65th produced & unlikely to be a
development engine.
Chassis 530 is currently owned by Nick Wood in Perth , W.Australia it would
be interesting to find out what was stamped on the bulkhead ID plate.
BAC did not assemble type 400's , chassis # , engine # or Car # in any
order , its a real jumble , unlike later models .
I believe that the standard Filton bodied 400's were produced in Car#
sequence and Chassis and Engines were just selected from a stock at random.

The Blocks of the early engines were different to later 400 engines . At the
rear of the block there is a screw in welsh plug rather than a bolt on alloy
plate ,
Lewis does you engine have this feature ?
What engine number is stamped on the block near the starter motor mounting
? Does it have a prefix ?

We can all have our theories , but as time passes facts & knowledge pass
with men that produced the cars.
All the inaccuracies printed in the past by so called experts are reprinted
and eventually become fact.

Regards
Geoff Dowdle

[Geoff Dowdle]

John,
The sports engine you refer to is a 85B having Sports Cam & 3 SU Carbs
producing 85 bhp

85 , 85A & 85C (or 85AC) all had the same touring cam but different carbs ,
Geoff D

[johnelfixit]

Geoff,
You could well be right, however my workshop manual for the 85A engine and
gearbox clearly shows an engine with three SU`s and quotes 80 BHP at 4200
rpm. The instruction manual (the book supplied with the car) quotes power
output figures at 4500 rpm which are 5 BHP higher. Early marketing speak??

John P

[Geoff Dowdle]

John,
Standard Engines available for 400's (from 1946 to 1951)were as follows
85 Single Solex STD Cam 75bhp
85A 3 SU STD Cam 80 bhp
85B 3 SU Sports Cam 85bhp
85C 3 Solex STD Cam 85bhp
85AC 3 Solex STD Cam 85bhp
( Note the 85AC engine is possibly a 85A upgraded to 85C spec with
change of carbs
from 3 SU to 3 Solex. I have never seen reference to this 85AC designation
in any BAC produced
manual , handbook, partsbook, etc . The only reference I have seen is in the
BOC Register .
Does any one have a 400 with a 85AC engine fitted who can confirm the
stampings on the bulkhead plate ,
rocker cover plate and engine/head stampings.)

There were at least two 400's fitted with a FNS engine from new ,
number FNS1/5 for the Aldingtons of AFN Ltd.
Prototype #2 (Regn# NHX115) which I understand was destroyed in a rally
accident . This engine was then fitted to a
new car Chassis 600 , but it is not currently with that chassis . Does
anyone know of it's current location?

Chassis 500 was ordered by W.H. Lowe on Melbourne , Australia in 1948
with a Special Sports engine ,
with designation 85BS/1592 . It is possibly a FNS type engine stamped as
a BS (Bristol Sports) engine .
I have not seen the car or engine for many years but believe it has a
counter balance 2 in main crank, sports cam ,
higher compression, 3 Solex carbs ,STD 85 sump and possibly larger valves
with about 120bhp(similar spec to the FNS engine 126bhp at 5500 rpm).
This engine predates most of the other BS engines by a few years and is
unusual that it has 2in main journals .
Although in the" Bristol 2 Litre Sports Manual" there is reference to
BS1/SC & BS1A/SC engine types which have 2in main cranks .
(SC for Small crank ) and other specs similar to the BS1 and BS1A type
engines that were fitted to Cooper Bristols , Tojerio's, etc in the early
1950's.

As for the 400/75 designation , it is a bit of a mystery . It could have
been a mistake by a BAC staff member stamping the rocker cover 75 instead of
85
or another special order engine .
Geoff D

[Lewis]

Thank you all for the interesting speculation and forgive me for not responding more promptly. We have been shepherding the youngest son through Year 12 exams and, frankly, mounting a takeover for BHP would be easier. His school days over, he will be concentrating on the pursuit of young women and booze.

I bought this engine from Graeme Lowe of Mornington (?), Victoria. It was the usual heap of boxes filled with almost unrecognizable bits of metal. There were no carburetors, manifold or crankshaft. A bloke in Geelong had just made two crankshafts, at the request I believe of Will Bailey who bought one and I was able to buy the other. Colin Young supplied three Solex carburetors and manifold.

It looks as if mine was the "Touring" engine with a single carburettor, although as it seems likely to have been the 65th made, not a particularly early one.

Why would anyone want to buy a Bristol with a less powerful engine? One presumes the cars were originally bought, as now, by people who generally
wanted something better and faster than the usual run.

I cannot see what is at the rear of the block. The body is a tight fit and the block is only an inch or two from the bulkhead with the lip of the bonnet rim blocking vision. I'll see what I can do next time the car is serviced. The number stamped on the block by the starter motor is 1065, no prefix.

Perhaps Geoff's suggestion of a mistake by the man who stamped the plates is correct. I don't think we'll ever get to the bottom of this.

Regards,

Lewis

[Lewis]

I need some advice.

Could somebody post a short, simple, chlld's guide to tuning triple Solex downdraft carburettors. I suspect Geoff Dowdle may not be able to resist.

And nobody is to fall about laughing. I have done it before. When I bought my first 403, back in 1965, I had one of those marvelous carburetor balancing devices and used to happily play with mixture and throttle settings, but the device was sold with the car and I have never found another.

Reason for all this is the alteration of the linkage from accelerator pedal up to the carbs to eliminate most vibration when I hit a bump. Inevitably carburetor balance has suffered and I would like to confidently go back to square 1.

Regards,

Lewis

[Ashley James]

Until Geoff recovers from his trip to Thailand you could try the
workshop manual, which is a download from www.jel450.com
Hopefully you'll be starting with the correct jets which was more than
I had. It months and guidance from Geoff to get my 5000 rpm!
Ashley

[Brian Cuddigan]

Hi Lewis, There are balancing devices available from Holden. I had the
Balance meter SD/090.33 and there is also a carburettor synchroniser
SD/090.043.
Go to www.holden.co.uk The only problem with the balancer was that there is
not enough room beneath the bonnet for-aft bar so I had a rt. angle plastic
pipe joint to use it sideways! Brian

[Lewis]

Thank you Ashley James. www.jel450 was exactly what I wanted. Having read the relevant bits of the manuals I now remember what it was I did so many years ago. Now if my youngest son (who is at that wonderful age where he knows everything) will spare a moment to persuade my computer to correctly size the pages for printing I will be in business.

Regards,

Lewis

[Lewis]

And thank you Brian Cuddigan. Christmas is early this year. I recognise Holden's carb. synchroniser and will have no trouble using it as my small bonnet lifts off, no hinges. I will discuss synchroniser and balancer with my local garagiste. A wild man in his youth (once apprehended by police for driving to work at 130 mph in a 60 zone; having set up roadblocks to catch him they couldn't prove his speed and he got off) he has endured years of servicing Japanese jelly moulds and was intrigued when I came along with the eccentric HRG Bristol. He now looks after six Bristol engined cars, says they are beautifully built and easy to work on and plans to expand his business. Minions will endure the bread and butter work while he plays with proper cars.

Regards,

Lewis

[Geoff Dowdle]

Lewis,
it is quite a lengthly process to try and correct 50 plus years of abuse on
those old Solex . The most important things to look for before you start
tuning as per the manual is ......

1. Are the 3 carbs the same , especially the throttle bases, make sure they
all have the same number of progression holes ie 2 for 401 - 405 , 3 for
406 & D2 . All faces must be flat including the adapter the carbs bolt to.

2. Float levels MUST be at 16mm down from the top of the main body when the
engine is idling, this can only be measured by making up an external plastic
sight tube attached to a spare main jet holder.
The levels are adjusted by shimming the needle & seat unit in the carby top
. Note machining of the carby tops can be different different for different
Solex applications.

3. Make sure the jetting is correct , ALL JETS & Emulsion tubes. Check the
diameters with various size metric drills. Many original jets have been
incresed in size over the years by drilling out .
As a rule you should need slightly leaner jets than STD as the quality of
modern petrol is so much better than the very poor petrol of the late 40's
and early 50's

4. I usually replace the nice brass AMAL throttle rod ball joint
ends(usually badly worn) with new ones to allow the throttle butterfly's to
go back evenly on the adjustment screws.

5 Although not directly related to Carby tuning , valve clearance must be
correct, distributor MUST be in good working order , advancing correctly .
Very few Lucas distributors work well even when new, they were poorly made.
(BAC used Delco Remy twin point for all the BS engines) I usually replace
the Lucas with a modified Malloy twin point unit, thats is fully adjustable.
There is no point in converting your Lucas to electronic operation while the
advance curve is no where near correct. You must have a TDC make on either
the flywheel or fcrankshaft fan belt pulley to operate a timing light .

6 Unless you do most or all of the above you will never get a 6 cylinder
Bristol running nicely.

Must go, Good Luck
Geoff Dowdle
I

[Claude]

This Needs To Go In The Bristol Car Owners Book!!!

[Ashley James]

It's taken me months of alternating between Geoff and Samaritans
before I got it somewhere handy. At one point i think Geoff wanted
Samaritans number too!

Ashley

[Lewis]

Panic over. The little HRG Bristol is running like a Swiss watch. I downloaded
the JEL450 Bristol Carburetor Tuning manuel and employed the Holden Vintage and Classic UK balancer that arrived in the mail this morning.

The years fell away and I was back playing with my first 403 in 1964. So simple; disconnect everything, wind it all back to scratch, factory settings, reconnect linkages identically with finest possible tolerances, a little adjustment and I might have a turbine under the bonnet.

Only two snags, the local garagiste, who is now caring for four Bristols, has appropriated the balancer and I have had to order another from Holden, who are terribly excited and have sent me twenty emails in as many minutes.

Lewis.

[Ashley James]

I just bought one! I've the car almost perfect but know from
balancing motorcycle carbs how important it is to get the throttles
exactly the same. I was going to use a Morgan Carbtune through holes
in the pilots jets, but this is easier.

Holdens are the most expensive company on the planet along with
Frosts, but they do sometime have things you can't find elswhere.

Ashley

[Geoff Dowdle]

To tune the Solex correctly you have to balance the air flow of each carb
, and balance the vacuum on the idle system with in each carb .
If you have a 404/405 Workshop Manual there are details on how to do this .
Most owners use a Holden type air flow balancer and then just screw the
idle mixture screws in or out until the beat of the engine changes then
screw it out about half a turn ,this gets the idle mixtures pretty close.

But the 404/405 manual has detail instructions of how to make your own
triple Manometer , using this the airflow of the three carbs can be adjusted
together (as adjustment of the airflw of one carb can slightly adjust the
air flow of the other two ) . Once the airflows are matched you use the
triple manometer to balance the vacuum at the pilot jets , this is adjusted
by screwing the idle mixture screws in or out .
Then if the carbs are a matched set , jetted correctly and in good condition
you have a chance of tuning the old Solexes correctly .
IT IS WELL WORTHWHILE TAKING THE TIME AND VERY LITTLE MONEY TO MAKE YOUR OWN
TRIPLE MANOMETER.
Every 6 cylinder Bristol owner should have one.

Geoff

In my experience, it is important to assure that there is not an air leak
around the butterfly shafts
of the Solex carburetors.

Bill Watkins