View Full Version : TR4/4A Flywheel... Lightened or Stock, that is the question

06-04-2014, 01:06 PM
I have a 1963 TR4 that I am rebuilding the engine from the block up. I have a new Findanza aluminium flywheel. I am increasing the bore to 87mm, and installing a very mild cam, otherwise it is a stock engine. What are the pros and cons of the lighter flywheel?

06-04-2014, 02:34 PM
Concerning the issue of the flywheel; the lighter flywheel will allow the engine to rev up faster,
taking less power from the engine to do so. It'll be a little easier on the synchros as the revs drop a bit faster.
To really get the full benefit you would need to do a whole bunch more work on your engine proper. Balancing
crank,connecting rods,pistons,flow the head & more. I did most of what I just said; but wanted to maintain the reliability.
Lightened the existing flywheel a bit so when I dropped it on my foot only 2 toes would break !
You'll get a bunch more responses.
Good Luck

06-04-2014, 04:43 PM
I am balancing everything crank, rods, pistons, however, I can not find a shop that will flow test my head, so, I'm probably leaving it stock. I want a peppy, smooth running engine. A fun weekend street car. Will the lighter flywheel affect the idle? Suggestions

06-04-2014, 04:44 PM
I have that basic set up on my TR4a, noticeable and nice difference. I shaved my flywheel but similar end result.

06-04-2014, 05:06 PM
I did not see much hair on my head, so did not have it shaved.

Will the lighter flywheel affect the idle?

I did have my flywheel lightened per Hermans diagram and installed the larger pistons/liners. I think it's peppy enough but wonder if my idle would not be a little smoother with the added weight on the flywheel. The idle has no lope, but does flutter up and down a little -probably due to the significance of the mechanical advance at low RPMs. If I turn it up a few hundred RPMs (to over 1000 or so), it smooths out very well. Since I never drove the car before the changes, I can't say what difference it made, or if I'd do it again. The 'roughness' of the idle doesn't really bother me much, and most probably would not notice it, but it's just one of those things I find myself wondering about.

06-05-2014, 10:36 AM
Would you mind telling me what size pistons, 87mm, 89mm or... and did you change the cam, if so, what are you using, did you remove the heavy "weights" fan extension, on the front of the crank and replace it with an electric fan and a harmonic balancer? or any other modifications. The main reason I'm asking is that I do not want an engine that has a lope to it.
Any advice is appreciated

06-05-2014, 11:54 AM
I think the major con of the lightened flywheel will be a more sensitive clutch at low speeds and lower rpm.If you like keeping the revs up you may not mind.
How do plan to drive the car.
I have more hod rod friends than sports car friends but some similarities are that I am surprised at the expense,not just money but dercreased longevity,milage,etc., that some go thru,that didn't drive the car to the max when stock.If your racing different story.
Have fun,


06-05-2014, 12:18 PM
When I rebuilt my engine I went with the 89mm pistons, had the flywheel balanced & lightened, crank balanced. Went up on the
cam just a little bit. Fancy new connecting rods and pistons. Like my race engine I try to make the bottom end as bullet proof as possible.
I'm using a Macy fan to keep things cool. With the oversize liners it tends to make the engine run warmer. Probably no advantage with
the 89mm. Very very little done to the head and intake. It does not lope; but kicks in strong around 2000rpms. Don't forget you've
got and old gearbox and rear diff back there.

06-05-2014, 12:34 PM
Harry, did you use the uprated Moss Motors cam or TS Automotive's "torque" cam or something else? Do you recall the lift and duration? The TS Automotive cam is suppose to be a mid RPM torque cam. And, are you saying that the 89mm pistons are not worth the extra heat in the engine. Would you have rather gone with the 87mm?

06-05-2014, 01:26 PM
All my engine build up material is not readily available(out of state).
But believe it was the Moss cam. If I had to do over would go with the 87's esp. since you already have them.

06-05-2014, 02:11 PM
This is helpful. Thank you

06-05-2014, 07:25 PM
I have 87mm pistons and a stock TR4 cam. I have a plastic yellow fan (mounted backwards) on the stock extension, as well as an electric fan controlled by a thermostat (but it does not block the crank hole in the radiator). I have 3/8" push rods installed. 5lbs was removed to make my flywheel weigh 14.5lbs. I have a pair of H6S's (not H6's). I have a uprated (DOT5 tolerant) hydrolic T-O bearing in my HVDA 5-speed. I have 195-65-R15 tires mounted on TR6 wheels.

I can dump the clutch without giving gas to pull out, but generally rev a little and feather the clutch to make it smooth. I can rev it up a lot, dump the clutch, and spin the wheels easily. The last time I auto-crossed, I stamped the brake so hard at a hair pin turn, that I killed the engine. I didn't notice until I let off the brake, and noticed the engine had to restart before taking off again. My course times were very good (I was only behind a TR3B and a TR6 -both driven by excellent drivers) -and not by much.

Although I have yet to drive in Texas 'hot' weather, I have not overheated in temperatures around 90.

I am happy so far, but am looking forward to a real test in heat. I drove it to Pa last fall and am planning a longer one later this month. I'll let you-all know how it goes and hope this information is useful.

06-06-2014, 07:54 AM
Which T/O bearing did you use in the HVDA that is Dot 5 tolerant?

06-06-2014, 05:53 PM
Which T/O bearing did you use in the HVDA that is Dot 5 tolerant?

I wish I could answer that more specifically, but I don't really know. I do know I spoke with Herman about it, and he knew the (original stock) one I had would not stand up to DOT5. I think the new one he sent specifically warns against DOT5, but I was assured it would work. -Something about a difference involving a square cut o-ring, and a round one. I'd imagine the material it's made from is different too. The bearing I used required shims, instead of turning a collar. I see a lot of "not for dot5" warnings, that seem to be ignorable. My issue in the TR3, was the single can reservoir, and I really wanted it all to be DOT5. The bearing cost a little more, but I think it was worth it. I also have the McLeod (TR6) pressure plate Herman recommended.

6,000 trouble free miles so far... And today I was caught in some red light traffic, humid, 90 degrees in the hot hot sun... so I got to see the temperature go up a little for the first time.

06-07-2014, 08:15 AM
McLeod? 1st generation used the shims, 2nd generation bearing used in the HVDA kit uses screw in out method (MUCH easier) for setting the clearance. Clearly "not for Dot5" by the manufacturer's instructions. Reason: I don't know why but not recommended so I still use Castrol GT LMA in mine.