Bristol Engines

[technicaltom]

I have been following this thread with interest and would like to add an observation regarding engine capacity.The cylinder head at present when as standard has a certain intake port capacity/volume usually described in cubic centimeters( CCs)and has an ability to flow so many cubic feet per minute(CFM) All very basic stuff that applies to any engine.So if a new block was manufactured with a little more room/clearence for a longer throw on the crankshaft,or larger diameter cylinder liners , or both, then extra capacity maybe up to or even more than 3 litres would be possible.
Now the cylinder head with its siamesed inlet tracts will need to be able to flow more CFM to feed the extra capacity therefore the new head will need a slight redeseign to allow it to breathe better, all this = more hp.
With some careful research its possible that con rods could be sourced from another engine,as Brabham did many years ago on their Repco FI engines,if memory serves me right those con rods were standard Daimler Dart 2.5 V8 items.Pistons are not an issue as custom pistons are available from numerous manufacturers and relatively cheap.The crankshaft could be sourced from many countrys nowadays. I look forward to others views . Tom

[Geoff Kingston]

Kevin,
The last time I looked at Bristol Cars website in the section covering upgrades there was mention of a. 2.5 liter engine, I assumed that this was a conversion of the existing engine but when I was speaking to Peter Jaye about his new cylinder heads he told me this was going to be based on. new block castings. made or about to be made by IN Racing and that his heads would fit this block.
Bristol Cars obviously think these problems can be overcome quite probably with the other additional new parts you outline, but I would certainly be interested in the larger engine option if it were available.
Another thought but what about a project based on the Larger BMW engine that the Aldingtons wanted Bristol to use instead of the 328 unit, that must have been designed to fit the same type of chassis layout as the smaller unit, same probably goes for the post war BMW V8 though that may be even shorter supply than the Bristol unit.
Geoff.

[Kevin H]

If you are going to vary the capacity and design of the new engine you should probably look at incorporating this into any survey of the potential market, because purists may be put off by something which moves too far away from the original.

Kevin H

[Geoff Kingston]

--- On Tue, 9/3/10, Bristol Cars - Owners and Enthusiasts Forum <webmaster@bristolcars.info> wrote:

From: Bristol Cars - Owners and Enthusiasts Forum <webmaster@bristolcars.info>
Subject: RE: [6 cyl Bristol cars-t-396] Bristol Engines
To: geoffkingston15@btinternet.com
Date: Tuesday, 9 March, 2010, 20:46

(Please type your reply below this line!!)
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Kevin,
.I think for this exercise and in respect of the survey you are probably right most will probably want to stick to the basic original specification but if Bristol themselves are going down the route of a 2.5 engine it has to be worth considering as an option.
Otherwise as long as its based on one of the 100 series engines and does not cost an arm and a leg I am seriously interested in what develops out of all this.
The BMW meanderings especially the V8 were based more on past than present thoughts.
Geoff




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CURRENT MESSAGE FROM: Kevin Howard

If you are going to vary the capacity and design of the new engine you should probably look at incorporating this into any survey of the potential market, because purists may be put off by something which moves too far away from the original.

Kevin H



______________________
PREVIOUS MESSAGE FROM: Geoff Kingston

Kevin,
The last time I looked at Bristol Cars website in the section covering upgrades there was mention of a. 2.5 liter engine, I assumed that this was a conversion of the existing engine but when I was speaking to Peter Jaye about his new cylinder heads he told me this was going to be based on. new block castings. made or about to be made by IN Racing and that his heads would fit this block.
Bristol Cars obviously think these problems can be overcome quite probably with the other additional new parts you outline, but I would certainly be interested in the larger engine option if it were available.
Another thought but what about a project based on the Larger BMW engine that the Aldingtons wanted Bristol to use instead of the 328 unit, that must have been designed to fit the same type of chassis layout as the smaller unit, same probably goes for the post war BMW V8 though that may be even shorter supply than the Bristol unit.
Geoff.

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[Hal]

Originally Posted by Kevin Howard

If you are going to vary the capacity and design of the new engine you should probably look at incorporating this into any survey of the potential market, because purists may be put off by something which moves too far away from the original.

Kevin H

I read on the BOC site about the Bristol Sports engines. So how about using the Bristol Sports engines as a starting point, which i think used the 100 series block.

Could this be a way of gaining the extra power without sacrificing any originality ?

Is this possible / feasible or barking up the wrong tree again.

[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