UN1 dowel pin location

[Andy]

Noticed a significant mis-alignment of the UN1 to the engine.
The hole in the copper bush on the crankshaft is oval which looks strange to me...
For sure I miss some dowel pins.
The small top dowel pin on the gearbox picture is something I trial fitted myself (looks to be 8 mm on the gearbox side) but not sure if it needs to go there.
Does anyone know which dowel pin are missing
and what dimensions these dowel pins have are so I can have them fabricated ?

 

[Eddie]

Andy,
You may have movement on your flywheel...so the oval bearing...you definately have the WRONG bolts... A2. 8.8 stainless are not strong enough & the washers are the wrong size...you MUST FIT PROPER 12.9 FLYWHEEL BOLTS & no WASHERS.
EDDIE.

 

[Mike Pass]

Hi Andy,
Definitely change the flywheel bolts for ARP ones. I have seen what happens when the flywheel comes off - pretty scary. If I remember correctly the holes in the crank for the flywheel bolts go right through so some threadlock may be needed.
It was on the dyno when it came off - it sawed through the engine stand, hit the floor - came out through the dyno room metal door - went across the workshop smashed the bench opposite and then shot up out through the roof and ended up 50 yards up the road! Nuff said. Not my engine or build!
Here are a couple of pics of when I upgraded the clutch. The dowell pegs seem to be in the adaptor plate on my car and not the bellhousing. I don't know what size the dowell pegs are. You can see one at top right in the pic.

I have a needle roller spigot bush on my car not the phosphor bronze solid type.

If the gearbox is not aligned correctly then the spigot bush, release bearing, clutch fingers and the gearbox mainshaft bearings will be damaged and the clutch action may be affected. The best way to check the alignment is to borrow a magnetic dial gauge. Clamp it onto the flywheel centre and the rotate the crankshaft and check the positioning of the adaptor plate and bellhousing. Once you are happy that it is correctly centred you can redrill and redowell/pin it so it will go back in the same place if you take it off again.

I replaced the relese bearing and carrier ( Chris Cole items) as the original Renault items are a bit crap.

Cheers
Mike

 

[Andy]

Hi Eddie, I was planning indeed to replace the bolts but good you point it out. At the end I will also replace the clutch and flywheel since i do not like all the holes in the flywheel weakening it. The guy who built it before me used on the suspension parts even stainless steel bolts which snapped during removing the nut. Therefore I decided to take the complete car apart and completely redo it properly and use all correct grades of bolts.

Mike, looking to your adapter plate, it looks like the dowel pin goes where I was thinking it should go. The gearbox side is 8 mm but the adapter side is tapered in my case from 7,2 mm to 6,5 mm holes. Probably best to drill the adapter plate through with 8 mm drill and weld 8 mm studs in place after checking the alignment.
Scary story about the flywheel, if this happens in my cobra I can say goodbye to my legs, in a gt40 we sit safer from this perspective ;-)

Thanks guys
Andy

 

[Graeme Stebbing]

Hi Scorpion, I just checked some UN1 boxes I have, and on the gearbox side none have any solid dowels, there is a hollow one next to the starter bump it measures 12.7 od on all boxes, but its the only dowel. I removed these boxes from donors, and none have any other dowels, and I have not removed them so they must be mainly on the engine side.

 

[Andy]

Drilled the 2 x 6.5 mm pilot holes open to 8 mm.
Using 2 drills of 8 mm as dowel pins, have now a snug fit of the adapter on the gearbox. Checked also the alignment of the adapterplate towards the gearbox axis and looks perfect.
Checked also the gearbox axis and measured a 0,004" deviation during turning it around. Looks acceptable.