Bristol's Chrysler Engines

[Claude]

In 1995 I bought an engineless LHD 405 from Jim Rogers of New Baltimore Michigan who used to work for Chrysler in a small department that was devoted to their relationship with Bristol Cars. He said that the sales volume to Bristol was less than a single Chrysler car dealership, but the company found the engineering brilliance to be worth maintaining the relationship. He cited one issue related to the early V8 engine where Chrysler had about 40 engineers on it, and when they visited Filton to check out what Bristol had done, they found two blokes with slide rules who were doing more than Chrysler's 40 man team. After that, Chrysler cut a deal in which Bristol would get all the performance stuff they wanted at standard cost, provided Bristol passed on their R&D for free. Chrysler deemed it valuable enough to staff it, and Jim told a number of delightful stories about his visits with Tony Crook and company. For a Michigan boy, England, pubs, fast cars and eccentric ex-race drivers is exotic stuff.

Jim had no reason to deceive. He was retired from Chrysler and was telling stories in a garage as I loaded the 405 on a trailer for the long haul home. What it suggests is that Bristolised may not mean after the engines arrived in Filton that they were changed by Bristol for the 407 to 412+ cars, but that Bristol engineers suggested changes, they were made to the Chrysler product line and then provided to Bristol. It may be that some of the police specials and hot rod parts came compliments of British engineering.

The non-derivative report says Bristol was very important to Chrysler, far more important than the sale of motors would merit. It says that Bristol engineering was superior, and because they provided it to Chrysler with no charge, they got first class handling.

This would suggest that there is more to the story than marketing hype as alleged.

Claude

[potential]

Originally Posted by Kevin Howard

Now having just torn down the engine from my 411 to find a domestic spec Chrysler 400 cid engine with nothing special about it at all (it even still had a cast crank), I concluded that if Bristol were not really enhancing Chrysler engines back in the early 1970s

I think this subject is worthy of a thread of its own. I don't have the experience you do with the cars but my understanding from what I'd read was that the engines were stripped down and 'blueprinted' - no parts changed from factory but rebuilt to aircraft engineering standards with all tolerances and torques at optimum and all the castings cleaned up. It's likely this is an optimistic view of what happened.

Has any mechanic or engineer who worked in Bristol ever talked?

[Kevin H]

Originally Posted by potential

I think this subject is worthy of a thread of its own. I don't have the experience you do with the cars but my understanding from what I'd read was that the engines were stripped down and 'blueprinted' - no parts changed from factory but rebuilt to aircraft engineering standards with all tolerances and torques at optimum and all the castings cleaned up. It's likely this is an optimistic view of what happened.

Firstly I should point out that I have no personal experience with the 5.2 litre engine used by Bristol. However, I think it would be reasonable to assume that Bristol did not “blueprint” Chrysler engines as you describe above, because the cost would have been prohibitive, (it would also be hard to blueprint an engine without replacing some parts). Nor do I think Bristol ever claimed to do this. It's more likely down to some ignorant journalist with an overactive imagination.

As author Rick Voegelin says, "Blueprinting is without question the most used - and most abused - term in engine building."

Originally Posted by potential

Has any mechanic or engineer who worked in Bristol ever talked?

Yes.

Denis Sevier, Bristol’s chief engineer gave a lecture at a Bristol Owners Club meeting in 1976. Mr Sevier apparently explained that when Bristol started using the Chrysler 5.2 litre engine from Canada they (Bristol) installed stronger valve springs, a higher lift cam shaft and a 4 barrel Carter carburetor (commonly referred to as the Power Pack option offered by Chrysler).

He said Bristol also designed a mod for the early Torqueflight transmission extension housing to replace a plain thrust washer with ball bearing race. This reduced heat build up in the bearing on long trips and the mod was adopted by Chrysler.

Mr Sevier’s lecture also covered later cars such as the 411/412 which used the US Chrysler B block engines, but no mention was made of any changes to these engines by Bristol. It wouldn’t have made any sense for Bristol to modify them anyway, because higher spec production versions were available “off the shelf”

Even in basic spec these engines produced considerably more power than the 313/318 A series engines used by Bristol in the 407-410 and it begs the question why didn’t Bristol use the B block engines from the outset.

Originally Posted by Claude

In 1995 I bought an engineless LHD 405 from Jim Rogers …. He cited one issue related to the early V8 engine where Chrysler had about 40 engineers on it, and when they visited Filton to check out what Bristol had done, they found two blokes with slide rules who were doing more than Chrysler's 40 man team.

It may be that some of the police specials and hot rod parts came compliments of British engineering.

Ha ha, that's quite a leap Claude, from a quaint but improbable story suggesting Chrysler’s engineers were incompetent, to Bristol developing some of the higher performance engine mods used by Chrysler. I take it Jim wasn’t actually one of the Chrysler engineers he talked about!

Chrysler were producing "Police Specials" years before Bristol even contemplated using Chrysler engines. The term "Police Special" has also been widely used over decades and applied to all manner of car components.

As for the "hot rod parts", the old A series engine (used by Bristol in the 407-410) was dismissed by performance enthusiasts (because it wasn't very 'tunable') who either used Hemis, or the B block engines that were introduced in 1958, until the LA series engines came long in 1964. The LA smallblocks were used extensively by racers due to their high efficiency and relatively low cost.

As for Bristol’s contribution to Chrysler’s engineering, in his book A Private Car, Leonard Setright mentions the Torqueflight mod devised by Bristol. He also spends numerous pages praising Chrysler's "thorough engineering" and says they were "years ahead of the field". Given that Setright was one of Bristol's greatest fans, I think if Bristol had contributed significantly more to Chrysler’s engineering, then we would know about it.

If anyone wants to read more about the origins of the 313/318 engines I can recommend Automobile Quarterly Vol 32 No.3 in a 16 page article titled "Maple Leaf Mutants - Chryslers North of The Border". It's an interesting article, but it's so difficult to extract the exact facts from it could have been written by Setright, although it wasn't. The article makes it pretty clear that the Canadian Chrysler owned brands were never allowed to be as good a spec as the US cars. So the Canadian Plymouth/Dodge mutants - the "Plodges" - always got engines and other features which were in US Chryslers a year or two before. Although it doesn't specifically say this in the article, I'd say the US simply didn't want the Canadians to have an engine which appeared to be the same as a US engine. So in Canada they made the 313, which was effectively the same engine as the 318 in the US. In another example of this policy, they also made some high performance 303 V8s in 1955/56 in Canada which were exported exclusively for US cars and not available in the local Canadian market. So, while the Canadian Plodges got the Super Red Ram 313 in 1957, the equivalent cars in the US were being sold with the first B series engines. The Canadians got the 245 bhp Power Pack version of the 313 in 1958, which of course the V8 Bristol started using in the early 1960s.

[Markus Berzborn]

If you want to know what Bristol can do to modify the Chrysler blocks, just have a look at the current fuel-injected models.
And if you need more power you have the option of various engine upgrades which are even expressly mentioned on the official website.
It's really no problem to get significantly more power out of these American V8 engines, and it is no secret either.
Aston Martin Works Services offer similar services. They will upgrade your old 5.3 litre AM V8 to 6.3 or even 7.0, if you pay for it.

Regards,
Markus

[Kevin H]

Originally Posted by Markus Berzborn

If you want to know what Bristol can do to modify the Chrysler blocks, just have a look at the current fuel-injected models.

Markus, I think we might be at cross purposes - I was talking about what happened 40-30 years ago.

I assume the current engines are just bought in from Chrysler in whatever state of tune is required.

[Markus Berzborn]

Originally Posted by Kevin Howard

I assume the current engines are just bought in from Chrysler in whatever state of tune is required.

I can't imagine.
Bristol offer upgrades and conversions for all kinds of older models.
This would mean they dismount the engine from your car, and then the engine is sent to Chrysler and back again?
This really does not sound very realistic to me.

Regards,
Markus

[RGSchmitt]

"I can't imagine Bristol offer upgrades and conversions for all
kinds of older models.
This would mean they dismount the engine from your car, and then the
engine is sent to Chrysler and back again?
This really does not sound very realistic to me."

Markus -

I don't think sending the engine to Chrysler is necessary or
feasible. They are relatively simple engines to rebuild or improve,
with many sources of replacement and performance parts (or entire
"crate" engines) from Mopar and others - all the HP you could want
for $7,000 - $9,000, complete, much less for a rebuild. Search the
web for "Mopar crate engines".

I met a Viper engine specialist here who moved back home to Bristol
about 15 months ago. Not sure where he's working now, but I'd bet he
could be turning out stunning engines as a sideline if there's a market.

Bob

[Markus Berzborn]

Originally Posted by RGSchmitt

I don't think sending the engine to Chrysler is necessary or
feasible. They are relatively simple engines to rebuild or improve ,
with many sources of replacement and performance parts

This is precisely what I wanted to say.

But you did not get my quote correct. I wrote: I can't imagine. Period. And then: Bristol offer...

Regards,
Markus

[Kevin H]

Originally Posted by Markus Berzborn

I can't imagine. Bristol offer upgrades and conversions for all kinds of older models.
This would mean they dismount the engine from your car, and then the engine is sent to Chrysler and back again?
This really does not sound very realistic to me.

Regards,
Markus

Oops, perhaps I should have looked at their web site before making some of my recent comments! The home page hasn't changed noticeably in years (true to form) and I didn't realise there was now that great long list of mods and upgrades that they offer.

I wasn't suggesting that they sent engines back to Chrysler. I was going to say that the "upgrades" probably mean changing to the current Blenheim engine and that they probably don't offer upgrades to old engines, BUT, looking at the list of options I see they now offer the following modifications;

High Efficiency Engine Conversion (Sanction 1)
High Output Engine Conversion (Sanction 2)
Competion Engine Conversion ( Sanction 3)
Enlarged Capacity Engines

It seems that Bristol have a new lease of life!

Having had my own 411 engine extensively modified I'd love to know what mods they offer. I wonder if they offer fuel injection of old engines and if so how they are doing it.

Regards,
Kevin

PS. Someone should let them know that Competion isn't a real word

[Richard Levine]

Forgive me interrupting, but would it be imprudent to suggest that one of
you ring Toby Silverton at the Kensington showroom and ask him about the
Chrysler engine modifications performed by Bristol cars Ltd? I have always
found him and his staff to be very friendly and helpful, in stark contrast
to the "old regime".


Regards

Richard

[Kevin H]

Originally Posted by Richard Levine

Forgive me interrupting, but would it be imprudent to suggest that one of you ring Toby Silverton at the Kensington showroom and ask him about the Chrysler engine modifications performed by Bristol cars Ltd? I have always found him and his staff to be very friendly and helpful, in stark contrast to the "old regime".

Regards
Richard

It's good to know things have changed. Last time I rang up the showroom the chap I spoke to wasn't very helpful at all, but then I was asking probing questions about the Brigand as I was thinking about buying one. He did take my details and said he would contact me if one came up. The following day my representative at a London auction was outbid by Bristol on a Brigand. Despite the fact they had just acquired a Brigand I never heard from the chap at Bristol but I suppose they might have already had a buyer lined up.

Last time I was actually in the showroom, with a few fellow BEEFers who had just had lunch in the West End, I don't think the Bristol staff showed any interest in us at all. But then it was probably obvious that we were just a bunch of "enthusiasts". Toby Silverton wasn't there, although I think he was with Bristol by then.

I feel it would be a bit disingenuous if I rang up now and started asking about the available engine mods, given that my own engine is already rebuilt. But if someone is actually intending to spend some money with them it would be interesting to hear what options are available, and at what cost, although I guess that would depend upon the condition of your original engine. In particular I would be interested in V8 "Sanctions 1&2" (sounds reminiscent of Aston Martin DB4 Zagato).

My personal view is that unless your own V8 engine is in very good condition, it would make more sense to replace it with a modern Chrysler engine. If I had my time again that's what I would do, rather than rebuild and modify an old one. The only thing we ended up using from mine was the block! (although it would have been a different story if I'd had an earlier 411 with a pre smog 383 engine).

[legavroche]

Kevin

Would you please expand on the last point you made about the 383 engines, I take it that if you owned one of these you would have considered rebuilding it rather that replacing it with a more modern unit. I have a 411 /S1 with the 383.

Gavin

[Kevin H]

Originally Posted by legavroche

Kevin

Would you please expand on the last point you made about the 383 engines, I take it that if you owned one of these you would have considered rebuilding it rather that replacing it with a more modern unit. I have a 411 /S1 with the 383.

Gavin

Gavin,

I suppose it also depends on what you want to do with it. If you intend to do a basic rebuild/recondition without any improvement (increase in performance) then it wouldn't make much difference. But if you did want to do some tuning then it is more worthwhile on a pre 1971 383.

The main issue is the cylinder heads. The 400 CID engines used by Bristol have a head designed to lower the compression ratio and comply with the pollution controls introduced in the US in the early 1970s. They have a different intake port design so they don't flow anywhere near as well as the early 383 heads, so there's not much point in increasing the valve sizes and doing any porting.

You can of course buy aftermarket heads for the 400 CID engine, but they're not cheap!

I now have a pair of early 383 heads on my 400 CID engine (with larger valves and mild porting). The casting number of the pre smog 383 heads is 2843906, (sometimes referred to as '906 core' heads).

The other benefit of a pre 1971 383 is it will have a forged steel crank shaft, whereas the 400 CID engine has an inferior (cheaper) cast iron crank. This is less of an issue than the heads, although I don't how much you can do with the cast iron crank in terms of welding, machining and polishing.

I was persuaded to "stroke" my engine, so we put a 440 forged steel crank in it, which was "worked" a fair bit to streamline the counterweights.

That said, if you want multi point fuel injection and sophisticated engine management, then it's probably cheaper and certainly a lot less hassle to simply buy a modern replacement engine, regardless of whether you have a 383 or a 400 engine.

[Kevin H]

I came across an article I wrote back in 2001 for the old BEEF mail list, thought it might be of interest to anyone considering a carby change or rebuilding an engine.

---------------------
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 adapter plate!

Kevin Howard
--------------------------

[jimfoz]

I remember seeing a 410 being auctioned at Sothebys in the late 80's or early 90's with a 440. It was well maintained and well used and had a estimate of £10,000. It was also on a set of minilites. It was described as the 'perhaps the fastest road going Bristol' (faster than the turbocharged models?). Haven't seen it in the BOC listings and wonder if it is still on the road???

[Kevin H]

Originally Posted by jimfoz

I remember seeing a 410 being auctioned at Sothebys in the late 80's or early 90's with a 440. It was well maintained and well used and had a estimate of £10,000. It was also on a set of minilites. It was described as the 'perhaps the fastest road going Bristol' (faster than the turbocharged models?). Haven't seen it in the BOC listings and wonder if it is still on the road???

Interesting. Do you remember if it had a modified bonnet?
The 440 was/is an "RB" engine, which some say stands for "Raised Block". Which means it's a bit taller than the 363 and 400 engines used in the 411 and 412. The air cleaner on my 411 with a 400 engine is a pretty snug fit under the bonnet, so much so that it leaves an impression in the under bonnet sound insulation. So unless the 410 had a bit more room it wouldn't be possible to fit a 440 in there with a standard air cleaner.

I was going to say I doubt very much if it was faster than the turbocharged Bristols. For some reason Bristol didn't release power figures in that era, but a Jensen SIII with a 440 engine and would do 0-60 mph in 7.7 seconds. The turbocharged Beaufighter weighed a 1 cwt more than the Jensen, both had 15" wheels and a 3.07 rear axle ratio, but the Beaufighter did 0-60 in 6.7 seconds!

BUT, the 410 was 3.5 cwt (or 10%) lighter than the Beaufighter. Would that 392 lbs (Imp.) make the difference of more than 1 second 0-60 time?

It would be a very close thing!

[jimfoz]

I don't think it did. I say it was a 440, but it was described as a 7.2 which is probably the same thing? Not sure if it was merely an overbored 5.2. I notice Bristol offer an enlarged 7.2 upgrade for the older pre 603 V8's

I will try and retrieve the original catalogue and scan in the picture of the car. It was a well used example so I imagine if the owner has not done much to it since it will be looking very scruffy!

[Sam410]

I seem to recall reading in an old Bulletin about a 412 with a 440 fitted. Does anyone know anything about that? IIRC it had a louvred bonnet to keep it cool.

I have definitely read that Bristol did experiment with using the 440, but decided turbocharging was a better performance / economy compromise.

[Kevin H]

Originally Posted by jimfoz

I don't think it did. I say it was a 440, but it was described as a 7.2 which is probably the same thing? Not sure if it was merely an overbored 5.2. I notice Bristol offer an enlarged 7.2 upgrade for the older pre 603 V8's

440 cubic inch is 7.2 litres, but those small block engines used in the 603 are a thinwall casting and I believe the maximum they can be bored out to is about 365 cid (if my sums are correct). You might be able to get a bit more by 'stroking' it but it wouldn't get anywhere near 440 cid.

However, uprated 440 crate engines are readily available from the US for about USD10k and given that Bristol altered the chassis to accommodate the taller turbocharged engine in the Brigand I'm sure it's not a big deal for them to do the same for any of the earlier V8 cars.