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 Post subject: Re: Clutch Coupler?
PostPosted: Fri Aug 07, 2020 6:35 am 
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Joined: Tue Mar 23, 2010 9:56 am
Posts: 116
Hi Al,

Engine is 1600cc... Ex-GT4 motor with driver/car/engine being fairly successful on the West Coast in SCCA/NASPORT. its supposed to be a high reving, high lift engine (Bertelis/Robello built)... but in GTL trim may need some adjustment due to SIR. I'm still seeing if I can make what I have work (at least drive it and see), but agree if it's to much of a risk... going back to something more stock in design may be beneficial (as others have suggested as well).

After some careful measurments it looks like my input shaft "adapter" when all put back together just enters the back of the crank to the tune of about 3/16 of an inch on the adapter, actually riding up on the beginning of the slope of the splines on the adapter. It also appears the back of the crank has been machined to remove ~ 2.5 mm to accommodate this fit. The splines on the adapter do not go into crank (1 mm too fat). This is either good or very bad.... Suggests some type of pilot bushing could be used with some modification (extension, machining) to the adapter.. Alternatively, this will be an area of metal to metal contact...w/wo bushing causing ???

Other issue is that the trans case/engine block really does not have any index dowels to align trans housing.... and the 5 bolts that hold it all together (including the 1 ' spacer) are a little sloppy. Thus, by now supporting the tip of the input shaft adaptor (with a pilot bushing)..I may be introducing greater stress on the input shaft if the trans case is not indexed (centered) on the shaft....where as before w/o a pilot bushing (stock VW design) there was no such stress.

Neil


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 Post subject: Re: Clutch Coupler?
PostPosted: Fri Aug 07, 2020 7:00 am 
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Joined: Sun Jan 23, 2011 4:54 am
Posts: 2089
If you can't accurately and repeatably align the trans/input shaft with the clutch, it sounds like a recipe for constant trans and clutch problems to me... I would take a step or two back from this spacer thing and rethink how that's going to reliably work.

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 Post subject: Re: Clutch Coupler?
PostPosted: Fri Aug 07, 2020 10:17 am 
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Joined: Wed Oct 28, 2009 9:24 am
Posts: 931
Neil -

Not sure if you are familiar with the stock VW design but that used two "ring dowels" (concentric rings) around two of the engine/transaxle bolts to align things. That's important with or without a pilot bushing. If the crank and trans input shaft aren't aligned, the pilot bushing or the clamped-in-place driven disk will lock the front of the input shaft to the (much stiffer) crank and make short work of the input shaft or bearings, as Matt notes.

Hopefully both your block and transaxle case still have the counterbores for the alignment dowels.

With a 1.6 engine and a light touch I think you can probably make a stock 5th gear work, but again do the gearing math and see what the revs will be doing.

When I typed about the tight press fit on 5th - that takes care of the splines but does nothing for the fine teeth of course. Both can be failure points. But a 1.6 can't have more than so much torque and as mentioned it's torque not RPM/hp that breaks things like gears. And as our friend Mike Ogren notes, a stock type clutch disc cushions things quite a bit in terms of shock loading.


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 Post subject: Re: Clutch Coupler?
PostPosted: Sun Aug 09, 2020 3:29 am 
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Joined: Wed Jul 06, 2011 3:48 am
Posts: 708
Location: Florida
Matt's comment probably the best since all this started. Wiped out two new $1,800 input shafts on our Ford T-4 box before we found the alignment pins on the bell housing were .048 off. One more $1,800 custom made input shaft and $600 plus shipping to fix it finally solved all the problems. Also destroyed two Tilton 5" clutch discs along the way. Taylor, of Taylor Race Engineering had to get a block and machine it into an alignment tool to accomplish the fix. The transmission guru Scott I referred you to earlier was there too as Operations Manager. When in doubt go to the experts.

Bob

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