Bristol 411

[Bristol fan]

First, hello from a rainy England!

Second, keen to introduce myself (and project)...and even keener to get your collective advice

So I have purchased a Bristol 411 that is half way through a stalled restoration. Bristol Cars, for those that don't know, was a small, British car manufacturer that unfortunately went into liquidation recently. It has a cool history in that it was established as a car manufacturer at the end of WW2, when the factories/workforce making bombers/fighter planes in Bristol were looking for new ways to stay employed.

You may wonder why I'm posting on this forum - well my car, which dates from 1975, was built with a Chrysler 400 engine (H400-HC10628) and Torqueflite 727 auto (3926-3840). It has a Thermoquad carb and was marketed by Bristol as having a higher lift cam and apparently produced 275hp. I have a fair amount of history and it seems to suggest that it has only done 40,000 odd miles.

The engine is in the car and I'm told was running well prior to being re-installed. That said I'm keen to do a basic "refresh" aiming for two things 1) to genuinely produce around 275hp (!) and a nice level of torque, and 2) to be as reliable and long lasting as possible. From what I can make out the engine is as it left the factory - no mods at all.

I have some ideas (mainly formed by reading posts on this forum) but rather than lead the witness, would love to hear what you would do in my shoes? Again, I'm not aiming for crazy power - just a nice torquey engine - and something that will last (and that goes for the engine as well as ancillaries). I should say that I plan to keep the transmission absolutely stock.

Very grateful for any thoughts or tips. Its not a common engine over here and so I thought best to turn to the experts!! Thanks in advance.

 

[67charger383]

Learn something new every day.
I've heard of the Jensen Interceptor but never the Bristol.

 

[Ruby67]

 

[67charger383]

First, hello from a rainy England!

Second, keen to introduce myself (and project)...and even keener to get your collective advice

So I have purchased a Bristol 411 that is half way through a stalled restoration. Bristol Cars, for those that don't know, was a small, British car manufacturer that unfortunately went into liquidation recently. It has a cool history in that it was established as a car manufacturer at the end of WW2, when the factories/workforce making bombers/fighter planes in Bristol were looking for new ways to stay employed.

You may wonder why I'm posting on this forum - well my car, which dates from 1975, was built with a Chrysler 400 engine (H400-HC10628) and Torqueflite 727 auto (3926-3840). It has a Thermoquad carb and was marketed by Bristol as having a higher lift cam and apparently produced 275hp. I have a fair amount of history and it seems to suggest that it has only done 40,000 odd miles.

The engine is in the car and I'm told was running well prior to being re-installed. That said I'm keen to do a basic "refresh" aiming for two things 1) to genuinely produce around 275hp (!) and a nice level of torque, and 2) to be as reliable and long lasting as possible. From what I can make out the engine is as it left the factory - no mods at all.

I have some ideas (mainly formed by reading posts on this forum) but rather than lead the witness, would love to hear what you would do in my shoes? Again, I'm not aiming for crazy power - just a nice torquey engine - and something that will last (and that goes for the engine as well as ancillaries). I should say that I plan to keep the transmission absolutely stock.

Very grateful for any thoughts or tips. Its not a common engine over here and so I thought best to turn to the experts!! Thanks in advance.

If you can get parts shipped over there, get a mechanical flat tappet Mopar Performance purpleshaft cam , shorty headers, a Holley street dominator intake, a Holley 750 double pumper carb, and a Mopar Performance electronic ignition (now made by proform.) All of this stuff can be had on the US eBay. Great recipe for a mild 383/400

 

[qkcuda]

I just looked up some pictures on line. Neat car. I would probably try and determine what their high lift cam was first. You don't want to over cam it with a stock convertor and rear end gear. You should check the torque convertor size as well.

 

[Budnicks]

welcome & good luck

found a photo one online

I was just curious
sort of a Jenson vibe

 

[68sprtsat383]

Welcome

 

[polywideblock]

g'day from Australia

 

[Hey-O]

Welcome from Missouri!! Learn something new everyday. It does have a little Jenson vibe, I think they used a 440.

 

[Bristol fan]

Thanks all. The advice is much appreciated. My car came with a 400 engine but the earlier cars had 383s. Preference is to keep as much stock as possible but liven her up a little!

 

[33 IMP]

400s had a reputation in the states as something of a dog. This was somewhat deserved because , by the time the 400 appeared, smog devices, insurance surcharges, ratings change from gross horsepower to net, and lowered compression had emasculated the performance cars, compared to the sixties versions. The 383 and 440 had come in performance versions, the 400 was not so lucky.
The primary reason the 400 had a poor reputation was when mopar decided to reduce compression for unleaded gas ,they just lowered the piston in the bore. This resulted in low compression/low performance and yet promoted detonation, meaning even more retarded timing, and even less performance.
The clear solution, if you are willing to go into the motor, is to get the compression back up to around 9-1, 9.5-1, in place of the probable 7.5-1 you likely have. (Mopar is now famous for overstating their compression ratios by at least a half point). That means a piston swap.
The problem is, decent, no, great pistons are available for 400s, but they are all for stroker combinations. A stroker 400, either a 451, 470, or 512 is a wonderful engine that can make serious amounts of power. A stroker kit would be the way to liven her up, a lot! With a little research, you might be able to find decent pistons for a stock stroke 400. I would look at icon pistons (also keith black) or ross. There are others.
To just liven her up a little, i would suggest some thin head gaskets if you can find them, maybe some head milling, to try to bump compression, an exhaust upgrade, depending on your sound regulations, and a mild camshaft upgrade, mild enough to use the stock valvetrain pieces. I would be very surprised if that didnt get you to 300 hp.

 

[Bristol fan]

Many thanks 33 IMP. That makes a lot of sense to me. Are you able to help me weigh up the pros/cons of a 9:1 400 engine vs. a stroked 400? Recognize that cost will be one, but I wonder whether it is one of those exercises where once you have started you might as well do what is best as it is all going to cost a lot! Also i agree with a mild cam - it is "GT" type car, not a racer. Any recommendations on that front? My early thinking was a hydraulic roller, but then got thoroughly confused by the different grinds on offer! My assumption is that what is in the engine is old/worn and should be changed, but perhaps I am getting ahead of myself?

Again, very many thanks to all that have commented and offered advice. It really is appreciated and of great value to me.

 

[F4R/T]

Welcome from southern Il.! Interesting how even the car manufacturers overseas liked Chrysler drive lines.

 

[33 IMP]

Bristol, a stroker can be an awesome engine, but to get the most benefit from the investment in the kit, further substantial investment is required. To feed the extra inches, more camshaft and Lots more cylinder head is recommended, along with improved intake and exhaust.
500 hp is easy, 700+ can be done. None of this is cheap. A good stroker can be 10k euros, tho it can be done for less
From your first post, i think you dont really want or need 500hp for your Bristol. I would just try to warm up what you have, without getting deep into the engine. I would do what i said in my first post. I would pull the heads and get them shaved, hunt up some thin head gaskets, and swap in a (approximately) 215° at .050 /.450 lift flat tappet hydraulic cam at the same time. If they tell you your heads need a lot of work, i would definitely replace them with aftermarket aluminum heads, before spending a lot on the old iron ones. Research into the aluminum heads available is your friend.

 

[Bristol fan]

Thanks again 33 IMP - that is good advice