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Lightened flywheel options

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I am about to have my flywheel done next monday by my local Healey specialist, along with other work such as sorting out the crank plugs, one came loose and cut a nice groove in the shells of number 2 big end. I am also getting a porosity kit installed, along with a fast road cam, a rebore and new pistons and a balance - going out to plus 1.02 mm - fourth bore, so it will be sleeves after this but not in my life time I hope! I will let you know how I get on.

:cheers:

Bob
 
Hoghead said:
If you could post a drawing of how the flywheel is done it would be greatly appreciated
Click to expand...

Tom's Import Toys provides lightened stock flywheels on an exchange bases. Here's a photo, he has material removed from the front outer edge.
https://tomsimport.com/new/parts/parts.asp?sect=14&new=1
Mine was done by a shop in Cali and they remove all the material from the rear outer area. The final weight totaled 15lbs. Sorry no picture, it's in the car...
 
thanks for the pic and an interesting way to do it.

My car is in Vancouver (the other one) and getting it across the border and back will cost as much as the machine work. I was hoping for a drawing so that I can get it machined at a local machine shop and balanced along with the other reciprocating bits
 
What is the weight of a stock flywheel as I see both 30 and 26.8 lbs posted here.
Mine is still on the engine and the car and I are 1/2 a world away or I would weight myself

Toms Import Toys advises that his lightened flywheel is 24.65 lbs with all the machine work done on the clutch side

Randys pic of his flywheel shows 20.2 lbs.

At what point is it "too light" for street use and what is the optimum weight for a BJ8 street car?
 
My stock unmachined BN4 flywheel weighs 28.6lb.

On the car I have a lightened flywheel, the amount I'm uncertain. It was a case of remove as much as possible without really trying to, i.e. the large chunk inside the ring gear on the engine side and the periphery on the clutch side outward of the bolt circle. Generous radii were left and it would have easily been possible to take a fair bit more off.

The result is a free-er revving engine at the expense of easy gear changing. The rpm falls so quickly back to idle that I have given up trying to get 3rd gear when taking off from the lights, instead going straight from 2nd to 4th. I can live with that.

My advice would be don't go crazy trying to get the last bit of weight removed as it will become more annoying to change gears gently. Also, if you are going to lighten it without disassembling the engine then get the flywheel balance checked beforehand and the imbalance noted, then when you have lightened it have it re-imbalanced back to the same as previously. The factory balanced the entire crank/flywheel/clutch assembly as one and they are not necessarily in balance individually. Some folk do not know this and have their flywheel resurfaced during a clutch overhaul which removes the "1" marking and therefore gives them a 1 in 4 chance of getting the flywheel back on the right orientation. Mark the orientation of the flywheel to the crank first before disassembly.

Andy.
 
The flywheel I just removed was 21 lbs and that still seemed heavy and did not affect tickover or smooth running in any way. You can safely go down to 20 lbs for a street BJ8. The number I hear most for the original is 28lbs.
 
it is not about the weight of the car -> that is the wrong assumption.
Think about rotational speed.

It is about getting a disc or weight to spin. Just try to spin a bucket with 15 litres of water spinning at 'idle' and accelarate it to max rev.
Do the same again with 10 litres or 5 litres of water, you will experience that less water means you are able to spin it up easier.
 
Is there an easy way to determine if I have a stock or lightened flywheel in my BJ8, without taking the car apart to see.

When shifting from 1st to 2nd, RPM drops so quickly that I'll need to increase the RPM when the clutch is in to get it into 2nd. And even then the car needs to drop in speed for that to happen.
Other Healey's, 1st gear, clutch in, slides right into 2nd, no drop in speed, no gas on the pedal until after it's engaged.

Transmission was rebuilt and I helped the professional do it. Even after the rebuild, it doesn't always want to go into 1st every time.

Complete stop, shift into 2, 3 or 4th, then into first. Sometimes it just will not slide in. Makes me very nervous when someone is behind me at the light. While waiting, I'll test it a couple times, works fine, then when it's time to move, it will not go into 1st and I end up starting in 2nd. But every time, going into 2nd, RPM drops very quickly and once in 2nd the car has slowed down for that to happen. If I try and force it in with more gas, the car will buck once in. A friend drove my car yesterday and mentioned, that's not right. I think you have a lightened flywheel and that's why you aren't carrying momentum thru to 2nd.

On an up note, very happy with the way the car speeds up very quickly on the freeway, when in 3, 4 and 4th overdrive. Really a fun drive. Maybe that's what Healey's do, or maybe because I have a lightened flywheel?

Is this a flywheel or transmission issue?

Thoughts?
 
Last edited:
I sometimes have the same issue getting into 1st. I always put it into 2nd first and then 1st and it works most of the time. It seems the only time it won't go into 1st easily is when there is someone on my tail that seems in a rush......and I'm trying my best to jam it into first. Usually wind up leaving in 2nd.
I don't have a lightened flywheel so can't speak to that part of you question.
 
Hi All,-

Andy makes a couple of points, I must admit, I was not fully aware of:

1. The Factory balanced the crank/flywheel/clutch-assembly as a unit and not individually.
2. The orientation "1" mark on the flywheel was meant for crank/flywheel balance realignment.

As with the rear brake drums, how many have removed their flywheel for such purposes as resurfacing or to install a rear engine seal, or have even changed the clutch and pressure plate, assuming the units were individually in-balance?

How many have recognized the alignment "1" on the flywheel and not lost it to resurfacing?

How many have lightened their flywheel thinking it would make the engine more responsive and never considering the effect it would have on shifting?

Over the years, this is the type of information I have gleaned from these discussions that help me better understand what I am experiencing in my Healey. As a result, I am put in a position to be better able to understand, anticipate, and address issues. Thank you Andy and "All" that contribute their knowledge and help.

Last, consider this. If the standard flywheel weighs 28.6 lbs. and Tom's Toys lightened flywheels are 26.6 lbs. , it would be reasonable to assume that the difference of 2 lbs. or 7% should result in minimal adverse shifting issues while providing some additional engine responsiveness. However, when removing as much as 8 lbs. or 28% from the 20-21 lbs. as Derek suggested is safe, I would expect greater engine responsiveness but with equally greater consequential negative effects.

So, is it worth lightening the flywheel if you are only going to reduce weight by 2 lbs.? Why would you take the potential negative effects of an 8 lb. reduction on a Healey primarily used as a cruiser/casual-driver?

Just my thoughts,
Ray(64BJ8P1)
 
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Ausmhly, most of us do not us 1st gear unless at stop preparing to go up hill. So, why sweat down shifting to first? Lots of pulling power in 2nd gear. Down shift when the car is not moving if needed.
 
Thanks guys, however my question is related to 1st to 2nd. Not 2nd to 1st. (I just mentioned 1st pointing out the tranny was rebuilt. This relates to tranny or flywheel?)

What I asked was:
When shifting from 1st to 2nd, RPM drops so quickly that I'll need to increase the RPM when the clutch is in to get it into 2nd. And even then the car needs to drop in speed for that to happen.

But every time, going into 2nd, RPM drops very quickly and once in 2nd the car has slowed down for that to happen. If I try and force it in with more gas, the car will buck once in. A friend drove my car yesterday and mentioned, that's not right. I think you have a lightened flywheel and that's why you aren't carrying momentum thru to 2nd.

Is this a flywheel or transmission issue?
 
Sounds more like a worn 2nd gear synchro than flywheel issues to me.

It shouldn't matter much about rpm drop if the synchro is good - the synchro is basically a metal-to-metal brake and is intended to cause the two gears to rotate at the same speed so they will engage without grinding, and if good should do that whatever the speed is.

Do you have the same problem going up from 2nd to 3rd? 3rd to 4th? (you have the same weight flywheel and similar rpms in those gears too when you shift)

​
How easy is it to downshift from 3rd to 2nd? That is where it can help to blip the throttle (and/or double clutch) to get the gears similar in speed before the synchro finishes the job of matching the gear speeds.

Just food for thought

Dave
 
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