Bristol Engines

[technicaltom]

Hi , I have been thinking more about these Bristol cylinder heads( 6 cylinder) , in a previous post i suggested a" modular " head might be easier cheaper to make, castings mold patterns etc. would be less complex , also machining would be less complex,
A futher thought occured to me ,why not have the easy part of the head,the lower half machined from a solid blank of alloy .this may sound like a lot of work,but it is not nowadays when you consider the number of engineering companys that have CNC Milling machines and very highly trained operators,
The CNC program only has to be created once.
Regards Tom

[Hal]

The CNC idea is a possibility. However, once again i would need an engine to play around to determine best way forward.

[technicaltom]

Hi, Just to add a few more observations regarding past attempts to enlarge the Bristol 6 cylinder engines by the likes of Bob Gerards , Jack Brabham Mike Hawthorn ETC.

My suggestion that a modern engine and cylinder head built to almost exact Bristol original specs.needs some clarification,When i suggested that the "New"2010 engines dimensions be altered a little i was well aware of the limitations that existed in the say 50s even 60s ,and those were no modern synthetic oils no computer aided design .less empirical knowledge ,This list could go on and on.

One other area that has improved dramatically is the balancing of engine components by computer aided machinery. Some of the engine designers of the 40s50s60s era were incredibly clever futuristic engineers who in my opinion were at least 50 years ahead of their time, imagine what they could do with all the modern computer help/metallurgy that is now available.

The engine i visualise if it ever happens would be externally identical to the present engine and would be available in more than one capacity,the customer could choose standard bore and stroke at one price and bigger bore or stroke at another price.

There are endless examples of engines that have been made " big bore" and it was thought that the limit was found, using a Ford crossflow as an example at 1760 CC Only to discover later that someone managed to make them 1970 ccs.And who would have thought a 3500cc Rover V8 would eventually be more than 5 litres.

Tom

[UK6]

Tom,
Re overboring cylinders whilst keeping the external dimensions of the
block the same - I think that you will have insufficient sealing area
between the bores. The original engine is already marginal in this area!
The other issue, as correctly pointed out by Geoff Dowdle, is that a
substantially overbored block from say 66 to 75mm diameter would
encroach/erode your main bearing area of your block.
In short, if you increase your bores to enable 2.5L or more you need a new
longer block casting and crankshaft. Hence my TR 2500 engine block and
crankshaft suggestion earlier. Can I suggest that you have another look
inside any block and you will see what I mean.

I guess you could design a "modular" engine with different stroke
crankshafts and vary the rod length. Unfortunately the 6cyl Bristol motor is
already substantially undersquare and thus increasing the swept volume by
increasing the crank throw and fitting shorter rods would be a backward step
in efficiency. I think that most designers just set out to optimise the bore
to stroke ratio and allow say, a 3mm overbore capacity.

Regards,

Brett

[Jonathan Lingham]

Might this new fangled 3D printing provide a cost effective way for fabricating patterns for heads and blocks? Anyone embraced this technology yet?

[James McClure]

I must admit that I've been thinking of selling the motor and gearbox from my 401. Then possibly installing a 2.4 Jag motor, which I have. Hopefully not much weight added, as the 2.4 is lighter than a 3.4, though I have no info as to how much less.

Then the 401 would be driven more, with less chance of being stolen and gutted for a fake Ace, etc.

[Kevin H]

Originally Posted by Jonathan Lingham

Might this new fangled 3D printing provide a cost effective way for fabricating patterns for heads and blocks?

I don't think plastic blocks and heads would work very well

Originally Posted by James McClure

I must admit that I've been thinking of selling the motor and gearbox from my 401. Then possibly installing a 2.4 Jag motor, which I have. Hopefully not much weight added, as the 2.4 is lighter than a 3.4, though I have no info as to how much less.

The Jag engine and manifolds would need to weigh roughly the same as the Bristol engine. Isn't the 2.4 a small V8? lovely engine but would it fit width wise?

Then the 401 would be driven more, with less chance of being stolen and gutted for a fake Ace, etc.

How does that work - would you have a sign on it saying "Not worth nicking cos it has a Jag engine" ?