RX8 gearbox into 5a

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scimjim
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RX8 gearbox into 5a

Post by scimjim » Sun Jun 07, 2020 12:07 am

It’s a very common conversion on lots of engines. after a lot of waiting, adaptor plates were finally made. I’ve yet to see an Essex conversion completed though.


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
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philhoward
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RX8 gearbox into 5a

Post by philhoward » Sun Jun 07, 2020 4:22 am

Plenty of pictures of gearboxes bolted to engine blocks. It all seems to go slightly west when you try and have a flywheel and clutch in there too.


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RX8 gearbox into 5a

Post by scimjim » Sun Jun 07, 2020 9:05 am

Thanks to a tip off from CarlosVanDango, I’ve just had a very interesting fb messanger chat with a chap called Quentin Jefferson - who is the only person to have finished a Scimitar RX8 conversion to the best of my knowledge.

After being told that it was a bolt on conversion by the guy that makes the adaptor plates, he quickly found himself in exactly the same position I am now in.

My calculations are almost the same as Quentin’s - the spacer plate needs to be 10 or 12mm instead of 6. Quentin got round this by using the original spacer plate under the adaptor plate and taking 3mm off the flywheel face.

So the next step is to get the plate copied onto CAD and look at getting them made in 10mm steel - with the dowel hole in the right position (as I needed to open it up to fit) and there’s several other modifications that need doing to the plate.
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Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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CarlosVanDango
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RX8 gearbox into 5a

Post by CarlosVanDango » Sun Jun 07, 2020 10:22 am

Jim do you have access to a DTI ? it would be interesting to see the run off on the supplied plate before you CAD copy it

you can take the bellhousing off on the 5 speed RX8 box (not sure on the 6) if you bolt it up and clock it to make sure its ok - from what i read up it should be within 0.12mm

This was my 5 speed bellhousing while i was making my plate
Image
it's a little awkward as the bearing face has gaps in but easily done.

not sure who you got this plate off but i was once at a car show and after an adapter plate for a 2jz (different project) and was talking to a guy who had a stall selling them, he said he could make me one up if i sent him some measurements i asked how he centres them and he wouldn't say, i asked him what measurements he got on the DTI and he said "what's a DTI?"
i didn't bother ordering a plate :lol:



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scimjim
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RX8 gearbox into 5a

Post by scimjim » Sun Jun 07, 2020 10:30 am

Not as easy to remove the 6 speed bellhousing but I have one of each :D

Would definitely need clocking but I think the supplier probably has as he’s sold hundreds for various engines over the years (despite not listening to complaints about the Essex adaptor).


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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philhoward
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RX8 gearbox into 5a

Post by philhoward » Sun Jun 07, 2020 10:33 am

If you need it to be 10 or even 12mm thick, that’s almost thick enough to support threads in Aluminium?

Be about 5kgs lighter too..


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scimjim
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RX8 gearbox into 5a

Post by scimjim » Sun Jun 07, 2020 10:34 am

I’d be worried about the starter - it’s not supported with the RX8 box like it is with the Ford boxes.


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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adamwilkes
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RX8 gearbox into 5a

Post by adamwilkes » Sun Jun 07, 2020 12:42 pm

Just interested: how do you match the bell-housing & plate centres with such accuracy? That's quite a height to travel & keep dead square.


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RX8 gearbox into 5a

Post by efi_sprintgte » Sun Jun 07, 2020 12:47 pm

How much of the drive plate is engaging on input shaft splines with the extra spacing?


JC

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RX8 gearbox into 5a

Post by CarlosVanDango » Sun Jun 07, 2020 1:39 pm

adamwilkes wrote:
Sun Jun 07, 2020 12:42 pm
Just interested: how do you match the bell-housing & plate centres with such accuracy? That's quite a height to travel & keep dead square.
in the photo ive put on the gauge (DTI or dial test indicator) is connected to the end of the crank so you spin the engine round and the DTI reads the run off with great accuracy - its geared you push the plunger in a few mm and the needle spins round a few times allowing you to make minute adjustments
that will give you the centre but if the plate isnt perfectly flat you'll never get it right
for the plate i just used a 10mm plate that i made sure was flat before using it.



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RX8 gearbox into 5a

Post by scimjim » Sun Jun 07, 2020 2:35 pm

efi_sprintgte wrote:
Sun Jun 07, 2020 12:47 pm
How much of the drive plate is engaging on input shaft splines with the extra spacing?
its currently flush (with no spacer) but there’s a trick to getting the release bearing to move further back down the slide (pic with release bearing fully aft)
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And I strongly suspect it involves moving the fulcrum point down
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Which looks like it’ll give me approx 10mm more depth - plus if I take some meat off the flywheel I’ll have even more engagement?


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

efi_sprintgte
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RX8 gearbox into 5a

Post by efi_sprintgte » Sun Jun 07, 2020 3:32 pm

So the input shaft didn’t go into the pilot bearing when I was measuring up (I know in Corkys thread he used a machined extension)

Then the actual clutch drive plate didn’t have much engagement on the input shaft splines, spacing the gearbox away from the engine will make that worse. As will machining the flywheel. I understand however both are necessary to get the clutch to clear the bellhousing.


JC

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RX8 gearbox into 5a

Post by Coupe Racing » Sun Jun 07, 2020 3:45 pm

Silly question but is there any mileage in using the Mazda clutch etc


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RX8 gearbox into 5a

Post by scimjim » Sun Jun 07, 2020 4:27 pm

efi_sprintgte wrote:
Sun Jun 07, 2020 3:32 pm
So the input shaft didn’t go into the pilot bearing when I was measuring up (I know in Corkys thread he used a machined extension)

Then the actual clutch drive plate didn’t have much engagement on the input shaft splines, spacing the gearbox away from the engine will make that worse. As will machining the flywheel. I understand however both are necessary to get the clutch to clear the bellhousing.
im not sure on the 2.8 but the input shaft is flush with the bellhousing on the boxes and the spigot bearing is 15-20mm proud of the block on the Essex.
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Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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scimjim
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RX8 gearbox into 5a

Post by scimjim » Sun Jun 07, 2020 4:30 pm

Coupe Racing wrote:
Sun Jun 07, 2020 3:45 pm
Silly question but is there any mileage in using the Mazda clutch etc
not silly at all - and one of the first questions I asked. Unfortunately the flywheel is really thin (more like an auto flex plate) so I’m not sure it would stand up to the abuse, secondly it would need redrilling for the crank, then balancing, finally it would need a different starter motor - all in all I discounted it as too much hassle 😀

I am looking for the shallowest pressure plate that will fit the 9.5” clutch though, just to give every mm possible.


Jim King

SECURE DRY STORAGE FOR YOUR SCIMITAR

Current: SE5 (8Ball), 1400 1600 1800 Zetec ST170 powered SS1 (G97), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre, TI SS1 (snotty), 1600 SS1 (C686CCR).
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), 1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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