Welcome to our Site for MG, Triumph and Austin-Healey Car Information.
MG MGB GT V8 Factory Originals Technical - Aluminum versus Steel Flywheel
|I need to decide on a flywheel. Engine is a Buick 215 with 10.5:1 |
compression, Crower 50232 cam (214/218 degrees duration at 0.050" lift,
276/281 advertised duration, 112 LSA, 0.488"/0.490" lift), home ported
heads, 4 barrel carb, Edelbrock Performer Rover dual plane intake, (may
get a single plane or EFI later), tri-y headers, dual exhaust, etc.
Final drive ratio is 3.90:1 and transmission (Rover LT77) ratios are:
I can get either a lighter steel flywheel (22 lbs versus 32 lbs for
the TR8 flywheel) or an even lighter aluminum flywheel. I haven't
confirmed the aluminum flywheel weight yet but I'd guess it's around
16 lbs. I called Buick 215 specialist Dan Lagrou. He sells both and
suggested the steel flywheel unless I was autocrossing. Anyone else
have experience with a set-up like this?
|I'd go for the 22-pounder. You certainly don't need the really heavy one for an MGB ... that's for a vehicle the weight of a Range Rover. I'm not sure I'd get the really light alu one either ... the car would just be too annoying around town. Of course it depends greatly on exactly where the weight is taken off, but 22# sounds about right. (Note that if the flywheel is thinned (pretty common to do this when lightening), you oughta use a longer clutch fork pivot ball ... you know, that little thing that looks kind of like a pawn on a chessboard.) I run a 20-pound flywheel, having converted from the stock 32-pounder, and I couldn't be happier with the lighter feel that the whole car has.|
|With the rotating mass of the motor, not speaking from BOP/R experience, you could get an aluminium flywheel in such a light car. The aluminium probably weighs in around 8 to 12 Lbs and would do fine for a car that cannot weigh any more then 2500 lbs wet. I have other people with lighter cars and four cylinder motors that -should- cause problems, but they run and drive fine as daily drivers. Biggest question is cost as I would think you are talking about a couple hundred more then a stock unit. Our V6 flywheels weigh up to 21 lbs and I have cut some of them down to around 10 Lbs without any driveability issues.|
The only concern is how lumpy is the cam with the 10.5 to 1 compression ratio. If it is fairly lumpy, a light flywheel will exagerate this a little as the flywheels reciprocating weight is what assists in smoothing a motors idle out. I personally like EVERYTHING to be as light as possible on my car and everything you lighten on the driveline means your that much faster.
|BMC Brian McCullough|
|Rather than skim the back of the flywheel, perhaps adding windows to the wheel between the starter ring gear and the pressure plate should be explored.|
Static weight alone is not the issue with flywheels- it's the distance that the weight is from the center of the wheel.
I'm not personally a big fan of aluminum wheels- what with the friction surface being riveted on, differential rates of thermal expansion- not saying they're no good, just saying I'd prerf to use a solid hunk of steel, that has been thoughtfully lightened for best lowest weight
|With the gears and transmission you are running even an aluminum flywheel with a super-light small diameter multi disc clutch setup would pose no problem. You may get tired of 1st gear after awhile but getting off the line will be a piece of cake. If you like responsiveness that combination will give it to you.|
In all honesty Dan, that 3.32 1st gear is borderline with the 3.90 axle. You can however go to a GM T5 and have a very usable combination for spirited driving, or upgrade the axle and drop one or two gear ratios. Either way I think you'll be fine with the aluminum flywheel.
|> Our V6 flywheels weigh up to 21 lbs and I have cut some of them down to |
> around 10 Lbs without any driveability issues.
> The only concern is how lumpy is the cam with the 10.5 to 1 compression
> ratio. If it is fairly lumpy, a light flywheel will exagerate this a
> little as the flywheels reciprocating weight is what assists in smoothing
> a motors idle out.
This will remain to be seen but I think it will be okay.
> I personally like EVERYTHING to be as light as possible on my car and
> everything you lighten on the driveline means your that much faster. FWIW,
I do too. If you do the math, the effect of reducing flywheel mass can be
quite large, equivalent to 500+ lbs of vehicle mass in first gear (reducing
to maybe 25 lbs in 5th gear).
> In all honesty Dan, that 3.32 1st gear is borderline with the 3.90 axle.
> You can however go to a GM T5 and have a very usable combination for spirited
> driving, or upgrade the axle and drop one or two gear ratios. Either way I
> think you'll be fine with the aluminum flywheel.
I thought it would be as well. My car is actually a TR7, not an MGB,
and in addition to the 3.90:1 and LT77, I've got a 3.08:1 TR8 ring and
pinion and a spare Ford Motorsport T5 (2.95:1 1st gear). I'd like to
use the Rover LT77 as it is a direct bolt-in and I thought I'd save the
3.08:1 ring-and-pinion for when I get around to building one of the
stroker motors. I have the parts to do both 266 and 290+ cube strokers
and I probably should forget about the 215 and jump to the 290 but I'm
curious to see how well the 215 will run.
Thanks for all the input guys.
My Olds conversion uses the 50232 Crower cam with 10.25CR pistons and runs with a Weber aluminum flywheel. (The decision for me was easy as the used engine "package " came with the ally flywheel.)
I can say that the engine idles fine and in no way negatively impacts the operation of the engine or clutch. Whether or not the revs come up quicker can be debated - in theory yes, but I think you'd be hard pressed to feel the difference from a light steel flywheel.
As you have a Buick 215 engine, whatever flywheel you decide upon does not have to be drilled for a 3oz-in balance as does an Olds engine (thanks Dan Legrou for the flywheel tech session info!)
> My Olds conversion uses the 50232 Crower cam with 10.25CR pistons and runs
> with a Weber aluminum flywheel. (The decision for me was easy as the used
> engine "package" came with the ally flywheel.) I can say that the engine
> idles fine and in no way negatively impacts the operation of the engine or
What intake manifold and carb are you using? How do you like the 50232 cam?
What sort of rev range does it provide? Are you using the early small block
Chevy valve springs from Dan Lagrou? I also have a 50233 on hand but I think
the 50232 should be plenty for the little 215.
|I have used the heavy steel, light steel & a alu. fly. on a low comp. 4.2 & an alu. fly. on a 11-1 4900 & all I will say is the lighter the flywheel the faster it will hit R.P.M.!!!! I have a trailer hitch on all 3 of my V-8s & thay pull out of a light with a 3,000 trailer just fine. I am going to put alu. flys. on all of my own cars, for the price differance & the way the motor revs up faster I know what I am going to buy.|
I'm running a stock BOP 4bbl intake manifold and a Carter 500cfm carb and with the early small block Chevy springs (as per D&D recommendation). The revs come up quickly with the stock "B" rear and 2.95 T-5 first gear, unfortunately, the tach is still running on 4 cyl pulses, so it's difficult to assess correct rpm. The cam seems to have good overall response throughout low and mid range engine speed and also idles smoothly at 800rpm - it's a good all round cam spec.
There is probably a limit to radical cam profiles with the anemic BOP/Rover stock head porting - stick with a cam recommendation from someone that has "been there, done that"
|Dan J: Using the 3.08 with the 2.95 ford tranny is sort of like a 2.33 first gear with the 3.90 axle. You can get a good feel for what it'll be like by going no lower than 2nd for a few days. You may very well decide that 3.08 is too far in the other direction. A 3.55 might be a much better choice.|
And now a question about flywheels. I missed Dan LaGrou's tech session, was there something about flywheel balance on Olds engines that I missed?
Per Dan's tech session in Townsend, the Olds 215 is not internally balanced and requires that the flywheel have a balance hole drilled at a specific loc'n near the ring gear (I believe the figure quoted by Dan was 3oz-in which amounts to a hole of about 1/4 dia by .8 deep at a specific radial location and about 1" inside the ring gear diameter). The Buick and Rover engines, on the other hand, are internally balanced and do not require this drilled hole.
The other day, I visited Dan and it appeared that, depending on the flywheel/xsmn, the balance hole dia & depth is quite variable.
After this balance hole revelation by Dan, I immediately inspected my aftermarket ally flywheel and discovered two drilled holes about 1/2" dia by .5 deep in the correct location relative to TDC.
|> I have used the heavy steel, light steel & a alu. fly. |
Glen, thanks for the input. I'm sold and will be ordering an aluminum
> The cam seems to have good overall response throughout low and mid range
> engine speed and also idles smoothly at 800rpm - it's a good all round
> cam spec.
Good to hear.
> There is probably a limit to radical cam profiles with the anemic BOP/Rover
> stock head porting
Yes. My heads have larger valves and have been home-ported but your
words still apply. I do have several sets of Buick 300 heads for
the stroker motors. If things work out, I'll have a set of Buick
300 heads on the flow bench for a baseline.
> stick with a cam recommendation from someone that has "been there, done that"
For another project, I'm going to try out a cam selection service recommended
by David Vizard. There's a place that has a proprietary software program
that will optimize profiles based upon your engine information and other
inputs. Cost isn't bad at $40 but it does require cylinder head flow and
other detailed informaton. I have a high-end engine simulation package
(Dynomation) so I should be able to check the results. We'll see how it goes.
That reminds me. Is anyone running a solid lifter cam in a Buick/Olds/Rover
aluminum V8. What sort of clearance change do you get cold to hot? How
does the extra clearance affect the cold start and idle? The engine I'm
using the cam selection software on is also an all-aluminum V8 and I'm told
the block and heads can expand by about 20 thou which is in the range of
the lash setting. The block has a deck height of 9.2" versus a Rover/Buick
deck of around 9" so the expansion should be similar I'd think. Even though
the block is only slightly taller, it'll go to almost 430 cubes due to the
larger Siamese bores. BTW, the block is a Fontana Ford 351W/351C hybrid and
is destined for my Pantera.
> Dan J: Using the 3.08 with the 2.95 ford tranny is sort of like a 2.33 first
> gear with the 3.90 axle. You can get a good feel for what it'll be like by
> going no lower than 2nd for a few days. You may very well decide that 3.08
> is too far in the other direction. A 3.55 might be a much better choice.
I agree. The 3.08's and the 2.95 tranny are an either-or proposition.
If the Rover LT77 transmission holds up, I'll use it with 3.08's when
the stroker motor goes in. I think there are some late TR7 3.45:1 ring
and pinions available should I need the T5.
> Per Dan's tech session in Townsend, the Olds 215 is not internally balanced
> and requires that the flywheel have a balance hole drilled at a specific
> loc'n near the ring gear (I believe the figure quoted by Dan was 3oz-in
Interesting. The balancer should likewise use the same balance factor.
Do they just drll it out also or is there a separate Olds 215 balancer?
The T5 with the 3.45 would be equivalent to a 2.61 1st gear with the 3.90, and the 3.08 and LT77 would be equivalent to a 2.62, either of which should do pretty well for general all around use.
Thanks for the info, I was unaware of that detail. I wonder what causes the difference in balance? Crank perhaps? It's a bit strange that they would do that and it seems a relatively small difference. I've run a Buick flywheel on a couple of Olds engines and never noticed any imbalance.
This thread was discussed between 20/05/2003 and 24/05/2003
This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now