924Board.org

[jody in georgia]

need some input from someone who's done v8 conversion. one is it seems every one is using chevy clutches and bellhousings .I need to know if you are welding a part of the input shaft from chevy to the porsche shaft is this how you all are hooking it up. I know I have to cut tube and make adapt. to fit bellhousing. second are you using slave cylinders or hydraulic throwout bearing. any input is greatly appreciated as I'm fixing to embark on my conv. soon and want to get some info from you all who's already done it.

[Adie]

Ok here's the low down, Summit do a hydraulic center throwout bearing for about $85, I always use the porsche bellhousing so I can use the original clutch and s/motor. if you want to use the Chevy bellhousing all you need to do is first measure the engine once it is square on the torque tube with the correct spiggot bearing, then using a spare bellhousing you make a spiders web and find the centre of the flange that fits to the engine. Once you have a datum for that (it's the centerline the torque tube would rin through) you can mill the back off the bellhousing to the depth you measured earlier, take off an extra 10mm and weld a 10mm thick flat plate on the rear that has just been milled, and re-mill it flat as it will have warped slightly with the heat. as you can replicate the center of the bellhousing you can make a datum point and redrill the mating flange to the original torque tube. naw all you need to do is drill and tap the 4 holes to bolt on the summit throwout bearing and hook up to your existing m/cylinder.
Another way of finding the centre is having another bellhousing and bolting the 2 together, then you have 2 reference points for a dowl to mark the new centre of the where the torque tube goes. However as Rick will point out, i know nothing and this will cost somewhere in the region of $8000, reality would show that if you have access to a mill, welding plant and basic engineering measuring tools it will cost nothing. the 10mm plate is common construction of boilers and road side maintainence and I used to obtain mine late at night. Last time I brough a piece (24inches by 32 inches it cost £6 or about $10. leaving $7990 to shove up ricks arse) expect to pay an engineer about 3 hours work to mill reweld and re-mill and punch the large holefor the torque tube to fit through. (I used to be £25/hour for basic machineine work (rebores/crank grinding/valve seat replacing/ flywheel skimming and the like so add a bit of for being silly enough to mention its going in a porsche and call it $50 an hour). the clutch splines are the bit I can;t help you on, the Rover V8 uses the same as the 944 so I could use either, a good clutch company can match your requirements with a decient clutch, i.e. your size with the correct hub/splines. If it's any help the 944 has the same splines as the Ford Granada/Sierra Cosworth/v6 essex engines, I'll take a guess at Mustangs and anything that used the T5 5 speed and indeed the T5 tremec rear tailed box found in TVR's. They may fit in the chevy flywheel. I'll be over at the other forum if you want any further help, I just cant stant certain posters on this forum to give any additional help.
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924 zero cylinder race car,

[PORSCHEV]

Hey Adie...I like the concept of the way you decribe your adaption...I was just wondering how far ahead the engine would sit in the engine bay with that set up. Where I used the chevy bell housing, cut of 10 cm from the torque tube to allow the eninge to sit farther back and also so the drive shaft would reach the farther through the bell housing and into the pilot bearing. Your method sounds much easier..but at the time I didn't have a computer and the resources I have NOW!
When you used the hydraulic throw out bearing....what do you use for a master cylinder to operate it and how was it set up to the pedal? When I made mine I had to gear up all new pedals and put in the master from a 94 chev truck to match the slave. That was worse then fitting the engine!
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1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

[Adie]

The summit one works from the stock cylinder and was perfect, used everything as it came from the factory, the displacement require for the throwout bearing was equal to 1.2 inch travel on a .625" master cylinder, the porsche one is pretty much the same. the throw out bearing usually requires spacing forward to work as there's usually to much depth as there's no arm to get in the way. In theory you could mount the bearing to the flat plate, bolt it to the torque tube, dummy fit the engine with a clutch and flywheel on the input shaft (I guess as its a torque tube its an intermediate shaft) and measure the distance between the back of the block and the plate, this would give you the dimension you need the bellhousing to be, Index the bellhousing and mill to depth. I'd add +5mm for clearence and space the bearing out accordingly. This way the datum point does not change, the torque tube inner shaft is still at the same place in the engine as it would be (unless you made the inner shaft shorter as well!!!) so you basically change the dimensions of the bellhousing to suit the components that fit inside.
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924 zero cylinder race car,

[PORSCHEV]

The car I converted was a 76 924 with the cable controlled clutch...no hydraulic master.
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1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

1978-#53 "D" track racer.

[Adie]

????? my race car was/is a 76 but it had hydraulic, it's a left hand drive also. However I've been doing this type of conversions on 1955 fords for 15 years so refabrocating a new pedal box isn't outr of the question, the easiest way I can see is to extend the priginal pedal with an ear, make a falkrum for the end of the push rod and thread it so it's adjustable, reweld a plate of the bulkhead where the cable used to go through and have a plate on the other side to strengthen it. I'll have to relook at my 924 as I'm sure it had a hydraulic clutch but it was a long time ago and I have done so many different cars since, they all seem to merge into one another theese days. I'll be over at the hybrids forum site trying to got that established so I can chat there. I only pop in here to see if a certain member has been around.
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924 zero cylinder race car,