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Standard and light flywheel comparison!!

4K views 16 replies 4 participants last post by  GTJIM (R.I.P.) 
#1 ·
HI i have bought from ebay a light flywheel from a 6 cylinder CIh engine which has been reduce its weight to 6kg!!!So i gave my clutch,flywheel,crank pulley and crank to be balanced along with bolts.balanced was ok but the guy told me that he is a bit worried about the wheel that they might took too much out of it and in the end it will just fly off the hood of the car or anywhere else.I have a guide also fitted to it and im planning to replace the stock flywheel rod bolts with stronger ones.I have two pictures on the left is the 6kg wheel and on the right is a heavy stock one!!Can anyone please tell me by looking at it can make a conlusion if this flywheel will hold?Or if i can mesure something please let me know.Thanks!!
 

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#2 ·
Hmmm ... Thinks ....

Your original one on the RHS of the pics looks a bit suspect - there appears to be lots of fine heat cracks in it that make it far more likely to break up.

The six-cylinder one has been extensively lightened! All depends what you are using it for - Road or Racing.

For road use there needs to be much metal kept behind where the clutch disc rubs on the other side to act as a heat sink for the long term abuse a clutch gets on the street .... and this one does look a bit light in this area to me ... though it has been inovativly lightend so the standard clutch and pressure plate can be used.

For Racing use it would probably get by if kept to reasonable revs - say 6,500 maximum - but you need to get it seriously crack tested and balanced before use. Above 6,000 rpm you really need a professionally made alloy flywheel for safetys sake alone.

DON'T rely upon my thoughts - No liability expressed or implied is accepted by me!
 
#3 ·
my race flywheel is similar to yours & it weights 5.7kg
I rev it up to 8500rpm with no problem uptill now,
but I personally consider this is not safe nor wise.
I will therefore set my rev limiter around 7500rpm,
I heard too many severe injuries to leg & foot...
a custom alu flywheel costs about $400,
I think it's better than losing one foot!
Hiro
 
#5 ·
Forgot to tell that.I disasamble the wheel today from the crank after they have balanced it but the guy forgot to make a guide into the flywheel.Should i drill a small hole for the guide or should i leave it as it is in fear i would weaken the flywheel even more??The car will have a 2512cc tunned engine with about 200hp at the wheels or maybe even more about 10-15hp i dont know.The car is street ride no racing in a truck so i guess 7500rpm to 8000rpm will be more than enough.THanks all
 
#7 ·
at least one dowel pin is mandatory with the 2.4 crank for the following reason:
the 2.4 crank does not use the same flywheel bolts as all the other common CIH cranks,
these special 2.4 bolts don't have the positioning shank device that secure the flywheel upon torquing the bolts,
as a consequence all the 2.4 bolts have a significant radial play inside the holes of a classic CIH flywheel,
this is not the case with the 2.4 flywheel which has a completely different design.
Hiro
 
#6 · (Edited)
One Bolt ...

Vargos, One of the flywheel bolts should have a "P" on the top of it. This one is the guide bolt with a fatter shank under the head that fits tightly into one of the flywheek holes to line it up with the crankshaft.
This bolt will usually only fit tightly into one hole in the flywheel - the one clockwise next to the widest gap between the bolts. All the other bolts are equally spaced from each other - this is hard to see but the flywheel will only fit on in one position.

In the attached picture the wider gap is between the bolt marker "P" and thew one below it. Every Manual I have mentions marking it BEFORE removal !! :ugh:

HTH
 

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#8 ·
Vargos, One of the flywheel bolts should have a "P" on the top of it. This one is the guide bolt with a fatter shank under the head that fits tightly into one of the flywheek holes to line it up with the crankshaft.
This bolt will usually only fit tightly into one hole in the flywheel - the one clockwise next to the widest gap between the bolts. All the other bolts are equally spaced from each other - this is hard to see but the flywheel will only fit on in one position.

In the attached picture the wider gap is between the bolt marker "P" and thew one below it. Every Manual I have mentions marking it BEFORE removal !! :ugh:

HTH
Jim this is a 2.4 crank which uses a specific bolt/flywheel assembly,
it is a problem when we want to use this 2.4 crank with a classic CIH flywheel,
because all the bolts have a significant play inside the flywheel holes,
so dowel pins are mandatory here.
Hiro
 
#10 ·
I found the P bolt today jim but they didnt marked when they removed it.But the marked the flywheel where to bolt on to the crankshaft when they balanced so since im gonna replace stock flywheel bolts with ARP ones i think it makes a little difreence.Thenkfully i have HIro pics of crank nad flywheel and i know where to install the new guide.From the look of it i think it is 6mm diameter????thanks
 
#11 ·
Bigger IS Better here!

Try and use pair of 8mm dowel pins if you can fit them in between the bolts - bigger is better here as the dowels will help transmit the power since the flywheel bolts have clearance around them. The flywheel should still only fir one way when the bolt hoes line up - new ARP bolts are a good thing to have too.

Carefully consider a Kevlar Safety Blanket (like the US Drag Racers use wrapped around the bell housing area) - OR a 6mm steel plate arched over the top of the bellhousing and solidly bolted on. Just for safetys sake ....
 
#12 ·
Jim is quite correct, if you are building a high rpm/high power engine than you can't be too safe! While I consider using the Toyota 4AG ARP bolts a good upgrade for most streetable 2.4 engines, if you are regularly revving the engine high (7500+) then I would even consider using three (3) dowel pins for extra strength.

For extreme long-term rpms I would have the crankshaft machined for ARP 7/16"-20 Chevy flywheel bolts. The torque specification is much higher than standard (43 lb. ft.), it is in fact 115 lb. ft.!
I used these bolts with three dowel pins on all extreme rpm engines (9000+ rpm), and would only use aluminium or chromoly billet flywheels for that type of use. No cast iron!

Bob
 
#14 ·
HI and thanks to all again!!!Rallybod the upgrade to the chevy bolts looks very good!!!i might do that.But on the summit web page they have 4 series of bolts.which one is the right for me?Summit Racing - High Performance Car and Truck Parts | 800-230-3030.
item number???
Either the high performance series (180,000 psi strength) 100-2801, or the Pro Series (200,000 psi strength) 200-2802. These fit the 'classic' small block Chevy and Ford engines.
 
#15 · (Edited)
Complete Package

At the risk of repeating myself ....

Stronger bolts will NOT make your cast iron flywheel any "stronger"! You MUST use a flywheel made of far stronger and more ductile material to run above 6,000 rpm reliably and safely.

To fit the 7/16" Chevy flywheel bolts you will have to have the threaded holes in the crankshaft opened out and re-threaded.
10mm = 0.3937" 7/16 = 0.4375" ... and the thread pitches are different!

For the increase in bolt size and strength to be of full benefit the bolts MUST be holding a stronger flywheel on !!
 
#17 ·
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