Which Flywheel

[tonyabacus]

Does anyone know or have experience of fitting a flywheel from another six bolt engine such as a 711 block fitting or perhaps a Formula Ford, BDA application

If its possible to fit a six bolt flywheel from another application, if so which, would it require modifications or machining, looking also to lighten the flywheel for a fast road application, nothing too light but enough to make the engine sweeter.
Thanks
Tony

[2cams70]

The 711M flywheel is a lot heavier than the LTC and it's drilled for a pressure plate that's a smaller diameter than the LTC. Your best bet is to get a steel flywheel from either Burton's or QED.

It's risky lightening the standard flywheels because they are cast rather steel.

[StressCraxx]

Correct about machining a cast iron flywheel to lighten it. There are steel ones available from US Formula Ford that will fit. About 17 years ago, the Sports Car Club Of America after much input from several engine builders' analysis agreed to allow a lightened steel flywheel/ring gear assembly weighting 16.5 lbs. The reason was reducing the torsional resonance stresses that caused the crank to break between the third and fourth crankpin throws.

https://iveyengines.com/parts/

[HCA]

How are you defining ‘fast road car’ - a car that is on the public road all the time, or a car that alternates between touring and competition? Also, what cams do you plan to use?

Too light a flyweel with a higher cam will not be tractable at lower rpm/speed and certainly not good when it comes to touring on hilly roads. My experience admittedly is with MGBs where the engines are very sensitive to light flywheels, but my advice is to tread carefully.

I am also about to build a ‘fast road’ engine with Q420 cams and opting for a non-lightened flywheel….

Are you planning distributerless ignition? If yes, try QED as they have a natty one with trigger teeth incorporated..

[RichardHawkins]

Tony,

I wanted to fit a pre-engaged starter, and as the pinion enters the ring gear from the front of the car rather than the rear as does a bendix type starter, I wanted a flywheel with the restraining diameter at the back of the flywheel. I chose a flywheel from a crossflow engine, I don’t recall which one, and as two cams points out the clutch is different. I re drilled and doweled the flywheel for the correct clutch, which was the most difficult part of the job, machined the flywheel to the same weight as the Lotus item and then had it balanced. For the time taken I probably should have bought a new steel flywheel. My engine has not run yet.

Hope this helps,

Richard Hawkins

[tonyabacus]

The spec will be more than a Sprint, but with about 135/140 bhp, the cams will most likely be Kent cams, as stated I want something that can be used mainly on the road, but could be used in the occasional hill climb or track day.

Thanks Richard the experience you described makes it debatable as to whether time spent against new purchase would make it viable. Has anyone had experience recently with Ark Racing who specialise in flywheels. Many years ago Derek Matthews who originally ran the business was a font of knowledge and produced a flywheel for me on a BDH, which was a work of art, but I know he retired and I have not heard much about the business since.

Thanks to all who pitched in, any other alternatives to Burtons anyone?
Tony

[2cams70]

Just source yourself a standard Twin Cam flywheel in that case and leave it standard. It's perfectly fine if you are keeping largely within the engine's standard RPM range. Ford/Lotus already thought about things when they originally designed it and made it lighter than their other flywheels.

Truth be told the Burton's/QED steel flywheels are about the same weight as the standard one (I know because I bought one). Steel has a greater density than cast iron. They are only useful if you are using more than standard RPM's.

Worthwhile putting a dowel in though and not just relying on the 6 bolts for retention.

[RichardHawkins]

2cams70,

How to fit a dowel to a 6 bolt flywheel defeated me, do you have any advice?

Richard Hawkins

[HCA]

Slow speed drill….?

[rgh0]

Personally I am not a fan of using dowels on bolted assembly except to ensure alignment. On a properly fitted flywheel the flywheel is a light press fit on the hub for cylindrical alignment. Bolt alignment is not critical but with properly fitted bolts and machined hub and flywheel the bolts will tight fit in the flywheel. The flywheel is secured by the bolt clamping force not by the bolts or any dowels in shear if assembled properly.

The original 4 bolt crank especially in a developed twin cam with an iron crank appeared to be marginal on clamping force hence the dowelling and later moves to six and 12 bolt cranks. However a 5 bolt Datsun crank appears good in any circumstances in my experience. So a good quality crank, good quality bolts and good quality assembly means most options will work.

As for flywheel weight I don't think a somewhat lighter steel flywheel is unacceptable in a road Elan and definitely needed in a competition engine both from bursting strength at high speed as well as from quicker engine acceleration. it is not just flywheel weight but where that weight is in the flywheel that's important as its rotational inertia that matters not just weight

cheers
Rohan

just my personal opinion

cheers
Rohan

[2cams70]

If you are just using a standard clutch there's really not much point in reducing the weight of the standard LTC flywheel or the Burton's/QED steel one that's for the standard clutch because a lot of the rotational inertia is in the clutch and pressure plate and not just the flywheel. Different story if you are moving to a small diameter racing clutch.

Although the Datsun crank uses only five bolts they are of much larger diameter than the Ford bolts so this setup is not really directly comparable.

[HCA]

Ah - is he talking a dowel in the crank or dowels added to locate the pressure plate..?
I assumed the latter, but only because thr crank and flywheel from QED is drilled for dowels at crank connection so assumed this is standard. The pressure plate though is not…

[2cams70]

2cams70,

How to fit a dowel to a 6 bolt flywheel defeated me, do you have any advice?

Richard Hawkins

The standard flywheel I removed from my LTC engine and the crankshaft I removed from my engine already had a dowel fitted. I'm not sure if that was original or not.

The standard crossflow engines (also 6 bolt) on the other hand normally have the crankshaft pre-drilled for a dowel but no dowel is actually fitted and there's no hole drilled in the flywheel to accept a dowel

If you need to drill a dowel hole best to have it done properly by a machine shop if you don't have the necessary fixtures to hold things in correct alignment.

[RichardHawkins]

Rohan,

Thanks for the advice, I had assumed that the six bolts are designed to produce enough friction between the crankshaft and flywheel, however I was concerned that there was a dowel hole in the crankshaft but not in the flywheel.

Thanks for setting my mind at rest,

Richard Hawkins

[RichardHawkins]

2cams70,

My Lotus flywheel did not have a dowel, but like you I don’t know if my flywheel is original. This seems strange to me that Ford went to the trouble of putting a dowel hole in the crankshaft and not using it. I am an old man now and fast driving is behind me, so I will settle for six bolts.

Richard Hawkins