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AC Bristol vs Bristol 405 Drivetrain

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BEX1164:
Hello,
 I’m admittedly an AC Bristol newbie so forgive any novice questions.
My question is:  How similar is the engine, trans, overdrive, rear diff from the 405 vs AC Bristol?
What parts of the drivetrain can be swapped between the two?

 I’ve read that the Bristol 100 B2 engine is basically the same at the 100 D2 but with 20 horsepower less.  Is it just cams and timing? Or is the bore n stroke different etc?   Can a 100 B2 be hopped up to the same specs as the 100 D2?

 Thanks in advance for the help and advice.

 

Glen Smytheman:
Hi there and greetings from New Zealand.  I am sure that you will get responses from some of the more technically minded members of the ACOC but you will be pleased to know that the Bristol 100B2 engine was fitted as standard to a number of Aces from new- mine included.  I am not sure when the engine in my car was last reconditioned but it has given me 20000 miles  of trouble free motoring over the last 15 years - some things just get meaner with age...... Engines are basically the same but you would want to check re gearbox 1. Ratios (particularly first) 2. The 405 will have overdrive gearbox and I am not sure if these will fit into an Ace that did not have factory overdrive fitted without adjusting the gearbox tunnel- my car had overdrive fitted at the factory.  Others will be able to tell you on this one.  Either way it won't be difficult.    If you are going long distance touring then overdrive makes sense.  Diff etc I don't think are interchangeable but let me know of you get a surplus 405 diff as my dad has a Bristol 401 that could do with an overdrive diff.  Wishing you lots of enjoyment driving your Ace when you get it on the road.    If you are in the Burbank area in the US then Shawn Thomas would be a good starting point to talk to - let me know if this is the case and I will email contact details. Cheers, Glen

10kph:
Hi,
     The engine is just the same. Same crank, rods,bores, head. The difference is with the cams ,the d2 has "sports" cams and different jets in the carbs. Modern pistons will give 9 to 1 compression with no head machining. Inside the engine is the same polished detail of a Bristol engine. The B2 is a better engine for road use because of the extra torque lower down and does not need to be revved. The gearbox is much the same but some might have had a freewheel 1st gear which can be replaced. The rear end is totally different so of no use for an AC
   Tony
     10kph

10kph:
  Further to my reply.  If the gearbox has overdrive then it will fit if the centre crosstube is moved back. If no overdrive and you want one then let me know because a friend makes the adaptor for the box to take the modern shorter overdrive and gives extra clearance.
     make sure you check the manifold side of the block to see if it is cracked.......but no real problem!
    Tony

BEX1164:
Glen,  Thanks for the reply.  Yes, I am in the Burbank area and would love to find some knowledgeable fellows around me to help with my AC knowledge building.  Please let me know Shawn’s info. I’ll reach out.
 I will post pics of the 405 transmission so you can see the overdrive box it has.  Not sure if it’s the same overdrive box that was fitted to AC’s or not?
 I’ll let you know if I can get the rear diff as well for you.

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