Bristol Engines

[UK6]

Enthusiasts,
If you are keen to build a cost effective 2.5L "Bristol" engine which looks very much like the "real deal" then you may like to consider the following:

1. Utilise a Triumph 2500 block and crank - strong,affordable,4brg mains, 75bore by 95mm stroke.

2. Cast a "Bristol" style - cross pushrod head utilising 3 IDA webbers (a la 12 port racing Bristol head) or 3 ICH carbs. Recall that BMW retrofitted their std block in the same fashion to arrive at the legendary 328 hemi head arrangement. In essence, you would be going down the same pathway!

170 bhp and suitable torque would be guaranteed- at a reasonable price.
The key point being that the engine would look like a Bristol product!
The bonus being that aftermarket TR to Celica or Supra bellhousings already exist.


Brett

[Geoff Dowdle]

Why dont you just fit a TR engine , saves the cost of the expensive alloy
head, just don't open the bonnet at the Annual Concourse.

Who will spend big money fitting a replica 2 litre engine to a Bristol
saloon , I'd say no one . There are plenty of good used ones around from
cars that have been wrecked.
Only AC , Frazer Nash and Cooper owners might spend big money on a engine ,
but they are more likely to buy another tatty 405 and sent it to its
grave for just a few engine parts that they will probably never use.
Original blocks are always repairable , new cranks & other moving parts are
available , original heads can be repaired . I think this forum talk about
new replica engines will lead no where, but good luck anyway.
When I got the Bristol bug about 35 years ago the BOCA members said it was
impossible to get a 100 series engine , let alone a 100D engine . Within a
few years I had 2 D engines and a 100A fitted in a Ace , Aceca and my 400 ,
then later a 100A for a engineless 404 .
The same still applies , if you want one it's only a matter of looking , now
it's so much easier with a computer & Forums like this.
Save the planet and use existing parts.
Geoff
Geoff

[UK6]

Geoff D,
I agree that that the most cost effective approach to re equipe an
engineless Bristol saloon would be to hunt down original gear and restore
it. A couple of people on the forum broached the topic of a big bore 6 cyl
Bristol engine ie 2.5/3L. My suggestion is just that - if you want a
significantly bigger engine that looks something like the original without
having to build the bottom end you may consider starting with something like
a TR bottom end and fit a specially cast Bristol type head ( not an original
Bristol head). As you well know, even Jack Brabham or Mike Hawthorn could
not overbore a std block to 2.5L and get it to hang together! I would take a
guess that a fully engineered 2.5L 100D2 engine (which I don't think exists)
would require at least 40 000 pounds.
A specially cast oversized head (for the sake of the argument, lets call it
a 2.5L head) may cost 10 000 pounds. I know that I am oversimplifying the
engineering problem and indeed ,the market/volume/unit price problem, but
the TR route would have to save 30 000 pounds!

I reiterate Geoff's question, how many people really want a bigger 6 cyl
engine which looks like a Bristol if the complete engine and modern 5 spd
box is going to cost (at a guess) upwards of 12 000 pounds? (engine and box
not fitted to your car)

Brett

[Geoff Dowdle]

Brett,



maybe I did not express my self clearly , but what is the point of a 2.5 -
3 litre TR block with a very expensive oversize copy of a Bristol head that
will not fit in a Bristol chassis with major surgery , removing the gearbox
X member and cutting the firewall & floors , new engine mounting brackets
etc .
The cost of all that would be greater than buying a 2 litre engine from one
of the many wrecker / specialists . If you went the TR special head route
you would only end up having re engined special that would be worth far less
than one fitted with the correct Bristol six.


The others that imagine they can make a 2 litre Bristol into 2.5 - 3
litre (and retain the same external dimensions) had better get their
measuring tools out and have a good look at a 2 litre six's bore spacings ,
centre main sizes , crank , head design etc .

I believe Bob Gerard in the late 50's removed the liners from a 2 litre
block and ran special pistons straight in the block , giving about 2.3
litre . He used this engine in his rear engined Cooper Bristol with 6 port
head running on methanol and reportedly produced about 190 - 200 bhp . Ivan
Glasby in Sydney has this Cooper and engine but is now back to 2 litre , I
doubt that Gerard could make it reliable.

Geoff

.

[UK6]

Geoff,
I am fully aware of what you outlined - I only offered a technical
alternative to acheive a larger bore "Bristol" engine for those who
expressed an interest. I am not arguing with you re relative costs of
staying original vs the "big block" idea - I agree with you that staying
original is cheaper -see my previous post. Re cutting x member etc, let's
not forget that the 405's got the "gas axe" treatment from the factory to
allow the installation of the laycock overdrive.

Brett

[Bellerophon]

If one was thinking about producing a new block and head one should
consider the weak points of the existing design and if it would be possible to
improve on this without building a complete new engine.
One point to think about is the amount of land between the bores especially
between number five and six cylinders.(a hot area) If Bob Gerard removed
the liners to increase the size of the engine it would have made the
reliability a serious factor. Percy Kemish (responsible for the racing engines)
told me the head sealing to the block gave them a problem with the racing
engines although he did find a way to make the engines last the length of a
race but this was always at the back of this mind.
Food for thought.
Bellerophon

[Geoff Kingston]

Geoff
We don't really have to do the imagining on the 2.5Litre engine because Peter Jaye of Jaye engineering is already producing new cylinder heads and tells me that another very well known and well respected firm is or are about to produce new blocks for a 2.5 litre. version of the engine, which his heads will fit with, if memory serves me right, he said minor modifications.
As to second hand engines these are neither as plentiful and certainly nowhere as cheap as the were years ago and while blocks and heads can be repaired and built up it does not get over the fact that the original casting are 50 to 60 years old
and if nothing else weakened by years of use and probable corrosion of waterways etc.
I don't see that producing. a replica engine or even the major parts to build one ether in standard or modified form for cars of the age is a waste of any ones time or effort. If you look at specialists supporting the Rolls Royce and Bentley market the practise is both widespread and well established. and for those of us who like to use. there cars frequently and enjoy their performance to the full the knowledge that people are making these parts, some to a better design that the original components and more able to stand up to modern road conditions is a great comfort.
Geoff.