1592 VS 1725 cc engine flywheels & clutches

[mamoose124]

I have a good flywheel with a new ring gear and a good clutch disk and pressure plate I removed from my 1592cc engine. This is a 10 spline clutch. Will this flywheel and clutch set up bolt directly to a 1725 cc engine or must I use a flywheel for a 1725cc engine? I have read one of the lengthy 2011 threads on this forum regarding the various size clutches and different flywheels for the early Series II & III cars vs the IV and later cars but it isn't clear to me that my current flywheel and clutch setup will not work on the 1725 cc engine. Any clarification will be appreciated.

 

[sunalp]

If I'm not mistaken, the 1592 prior to Series IV had a different flywheel. It was flat and accepted the larger pressure
plate from the Series 1-3. I'm not completely sure that all Series IV's had the same flywheel, but a 1725 flywheel
was stepped to accept the smaller pressure plate. I believe that the splines on the trans shafts were the same.
I know I had a Series IV with an earlier flywheel and clutch on it and it was fine with the later full synchro
trans. You should be able to bolt the earlier flywheel and clutch to the 1725 with no issues. I was actually told
many years ago that the earlier clutch set up was actually a better clutch as it was a bit larger in diameter.

Hope that helps.
Cheers!
Steve

 

[ALC 68A]

My S3 has its original 1600 engine and flywheel, but the non O/D three synchro gearbox had previously been exchanged for an O/D four synchro gearbox from a SV. This works OK with a new, old stock SII/3 type 8" spring type clutch fitted at the restoration. The 7 1/2" diaphragm type clutch normally used with the four synchro box has a different operating lever, so my car still has the original type lever.

Therefore, AFAIK the gearboxes are interchangeable without changing the flywheel, provided you use the correct clutch assembly, unless you have one of the late SV type with the fine spline driveshaft developed for the Hunter (Arrow) range.

 

[spmdr]

Remember there different Throw-out arms and arm pivots (and TO bearings) to go with the different clutch types.

The early bigger clutches have shorter arm pivots.

Later longer arm pivots will hit the early clutches!

DW

 

[hartmandm]

Mike,

Check out Rootes Racers comments in a thread from a couple of years ago: http://forum.sunbeamalpine.org/index.php?threads/1725cc-flywheel-vs-1592-flywheel.25402/

Mike

 

[jumpinjan]

By the way, the Series I flywheel has two locating pins for it's 6-spring pressure plate. The Series II/3/IV has three locating pins and a 9-spring pressure plate. All use the same throw-out lever w/larger carbon bearing. If I were using the early flywheel & 8" plate, I would have a machine shop cut off a few pounds of metal (like what they did to the "Lemans" 1600), those flywheels & pressure plates are pretty heavy combination. The 1725 flywheel/clutch assembly is lighter.
Jan

 

[hartmandm]

FYI - The 7-1/2" clutch and all-synchro transmission was introduced during the series IV.

 

[DanR]

Mike, I can't remember whether my SIV B94103819 4 Sp OD had a Synchro transmission or not, it's been thirty years ago since I drove it.

Should find out soon, it is getting some restoration work done now.

 

[hartmandm]

Dan,

An easy check is the shift pattern on the gear shift knob (if you have the original knob) or just check the gear positions. All-synchro gearboxes have reverse all the way to the right and down. Earlier gearboxes have reverse on the left.



Mike

 

[ALC 68A]

Mike, I can't remember whether my SIV B94103819 4 Sp OD had a Synchro transmission or not, it's been thirty years ago since I drove it.

Should find out soon, it is getting some restoration work done now.

B941xxxxx as a chassis number is for a Series IVa, which means it should have a four synchro gearbox, unless it was changed subsequently for the earlier type.

 

[DanR]

Alc, Based upon my Buddy's communications with me it was all original when He (Kirby) sold it to me.

He ordered it and watched it come off assembly.

I will get under it and take pictures & notes.

It does have the 7 1/2" clutch.

Thanks to all,