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Re: 1300/1500 engine
Posted: Sat Sep 03, 2022 8:46 pm
by soe8m
Ok, the gearbox of the 1300 is fine. Is it possible to use the mainshaft of the 1850 box, fit the 1300 gears on that shaft and all what is behind the housing like adapter and overdrive?
To simplify the question, can I mix? Use the 1300 gears and gearboxhousing and the 1850 mainshaft and fit the o/d externals to the 1300 casing?
Jeroen
Re: 1300/1500 engine
Posted: Sat Sep 03, 2022 9:16 pm
by cliftyhanger
1850 and 1300/1500 single rail OD boxes both use the RKC767 mainshaft, so yes, should be able to build a 1300 overdrive box.
Re: 1300/1500 engine
Posted: Sat Sep 03, 2022 9:53 pm
by DOLOMITE 135
To simplify the question, can I mix? Use the 1300 gears and gearboxhousing and the 1850 mainshaft and fit the o/d externals to the 1300 casing?
If both gearboxes are single rail then as stated above this is possible, as I have done it (the three rail gearbox has a smaller tip on the mainshaft where it fits into the input shaft and is a different lenght as the three rail uses the same version of the J type overdrive as the sprint and as such is not compatible).
Two observations if you do this, the first I have learned from experience is to always replace the circlip TKC6444 on the mainshaft even if you only intend to replace the gaskets and reuse all the bearings etc, I now never reuse them. The second point is that the higher the engine power the higher the overdrive operating pressure needs to be, the unit I built (which was fitted in a Spitfire 1500) used an unaltered 1850 overdrive unit, this meant that engagement was much slower than the 1850's and Sprints I have been in as once engaged it would need to build up the pressure a bit. For us this was seen as minor as it was for mainly motorway use, but depending on your type of driving you may need to have the operating pressure lowered to activate the overdrive in a more timely manner.
A little further info on operating pressures is included here:
https://www.canleyclassics.com/?archive ... -overdrive
Re: 1300/1500 engine
Posted: Sun Sep 04, 2022 6:41 pm
by soe8m
DOLOMITE 135 wrote: ↑Sat Sep 03, 2022 9:53 pm
If both gearboxes are single rail then as stated above this is possible, as I have done it (the three rail gearbox has a smaller tip on the mainshaft where it fits into the input shaft and is a different lenght as the three rail uses the same version of the J type overdrive as the sprint and as such is not compatible).
Thank you, then that will be the plan.
Jeroen