Rally X1/9 - Prototipo style

yep you need the input shaft plus the fifth gear on it's end and all the gears from the cluster shaft, the gears are matched pairs, so no mixing and matching is possible (except for a pair of fifth gears that you know run together)

Yes you could reuse the CW and pinion of the X19 5 speed trans, but as I've already said that will be a poor choice for stage rallying, a shorter final drive while it may limit top speed, increases the torque applied to the wheels as gears are "torque multipliers", you want to be 3/4/5 as much as possible, but still have a useable 1/2 for very tight turns and switchbacks which is what makes the 105TC trans preferable to the 100s - you'll have a useable first.

The next thing to note is any transmission that was mated to a dohc engine like a 100s regata or a 105 ritmo will require the input shaft splines to be shortened, as the twin cam input shaft is longer.

And you definitely want to save up for a limited slip differential centre. The standard five speed cast iron diff carrier is the "weak link" in the five speed transmission. The cast iron isn't that strong and has some big holes cast into it, these are the weak spot. The diff carrier will crack and then takes out the trans casing with a big bang. An aftermarket LS differential centre will be machined from a far superior grade of metal and won't have this problem

The gears themselves are not the weak point, anyone that says so really doesn't know what they are talking about. The standard gears use a high tooth count, this is to make them as quiet as possible during operation (and possibly for less frictional losses) A coarser tooth (lower numbers per gear) is stronger than a fine gear tooth (like in a stock X19 trans) so the gear set from a 125/130 ritmo would be stronger than the 105 gear set due to this (but AFAIK and from pictures the 125/130 looks like it still uses the same diff carrier)

Finally for competition use a transmission oil cooler would be a wise investment, my lemons build thread details how I went about designing a suitable transmission oil cooler setup.

SteveC
Been a little while since last update

Gearbox dilemmas now resolved


Good progress is being made with gathering parts and engine machining

Gearbox dilemmas are solved - I bought a competition Bacci Romano 5 speed box. So standard X19 5 speed case, close ratio dog box with limited slip diff and choice of FDs

Keeps the gear change mechanism and driveshafts standard and simple.

Brake set up is also decided with 280mm discs front and 270mm at the rear, both ventilated.

Lightweight steel flywheel and racing clutch is on order, 200mm size which is rated to 270 lb/ft so plenty capacity.

Engine is progressing, pistons are getting machined along with the block. That should be the final time at the machine shop before I then build up the bottom end.

I picked up a titan dry sump pump and am currently working on producing a dry sump pan.

Then I need to move onto the cylinder head again, some porting work and valve train needs sourced as well are working out how to take valve clearance measurements.

All go!
 
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Sounds spicy! Please tell us more. Pics please.
Do you have the gearbox parts yet? If so, did it take long to receive it?
What clutch did you choose?
For a dry sump pan you could mod a 128 pan. They are sheet metal so not difficult to cut and weld.
 
Sounds spicy! Please tell us more. Pics please.
Do you have the gearbox parts yet? If so, did it take long to receive it?
What clutch did you choose?
For a dry sump pan you could mod a 128 pan. They are sheet metal so not difficult to cut and weld.
Gearbox was built by Bacci Romano, looks like a standard X19 boxq but clean. With it being a standard H pattern it helps with entering some of the lower categories in rallying for me.

The sump pan is going to be an alloy part, CNC produced locally

I will add some more pictures when I build up the bottom end. Other than that I have a mountain of parts building up ready to fit once the car enters the garage next year

Picture is measuring the head cc while working out the static compression ratio which cam out to be 15:1. Machining work will bring that down to 12.7:1
 

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Owning 128's and X19's, plus doing my apprenticeship and then working on / selling spares for these cars for over 40 years tends to get a few facts to stick...

SteveC
I would be very interested to get your input on the cylinder head / ITB set up.

The cam spec I am running will be 11.2mm and 10.7mm lift along with 282 / 272 duration (@.2mm).

I am thinking of tapered ITBs with the injectors in the ITBs and then a air horn. Thinking of matching the ITB size with the final head port size (Multipla head needs opened out a lot)
 
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