XU 1900 rally engine rebuild

[Rallyace 3]

I will soon be rebuilding a 1900 XU for use in a Targa rally car. The Targa events that I will be competing on consist of a number of tests, timed to the second. The tests are linked with road sections which are, essentially non-competitive. The tests are short and often have a number of "stop astride", "stop in box" , 360 degree turns around cones and "figure of eight" turns. 

With this in mind, I am far more concerned with torque, quick acceleration and smooth tractable pick up than I am with outright power. 

I will be running an after market ECU, which is likely to be an OMEX 600, if they get a supply of components in the near future. I am allowed to delete the AFM, but must retain the plenum chamber and injection. I have done some basic (well documented) reshaping of ports. I am free to run any cam that I wish and I have a Maniflow four branch manifold and Ashley twin box exhaust. I intend to use a billet steel flywheel, which will weigh in at approximately 3.5 kg. This about half the weight of the standard 1900 flywheel and incorporates the trigger ring for the ECU. The compression ratio isn't established yet, as the valves are being re-cut/re-ground to 3 angle and the head will be skimmed. I will be aiming for something in the region of 11.5:1

I think that I've been lucky with the donor engine, as some of the problems with a 35 year old engine, don't appear to be evident. I will document the build and post here if anyone feels that it would be useful/interesting. If not I'll just lock myself away in the workshop and do it in private. 

Having set the scene I would like to benefit from the combined wisdom of other engine builders and my first question concerns the block and liner seats. The attached photograph shows the liner seat (flywheel end) and I think that this is ok to rebuild. This area has had a light clean up with a brass brush. You may be able to make out a couple of marks that I would describe as "stains".

I would welcome any comments, both on the liner seals and on other aspects of my plans.

[welshpug 1,626]

they look perfectly servicable, no corrosion of the block around the seats, that is more of a concern than the seat itself

[Rallyace 3]

Thank you.

[Tom Fenton 1,526]

As said the seats look fine. What gearbox final drive do you use. For targa I’d go as short as poss. 4.8:1.

[Rallyace 3]

I’m running a 4.8:1 at the moment. I was thinking of going to a 4.4:1 to get a bit more out of the low 1st gear. I do have the 1900 1st gear, but it’s still very short. 

[petert 554]

The 1900 1st gear at 2.92:1, is the longest OEM part there is. Also identical to Mi16 etc. I'd leave the 4.8:1 in there and build the engine to use the revs. AB Motorsport used to put a needle roller bearing on 1st gear so you didn't destroy it on the down change, when 5.1:1 was a common cwp.

Edited February 1, 2022 by petert

[Rallyace 3]

I don’t think that AB Motorsport exists now. Does anyone have a number for the bearing?

[brumster 135 1 Cars]

You have to be pragmatic about where you spend most of your time, and while you're right that 1st is painfully short with a 4.8, how often do you really spend in 1st?

 

I guess with targas you're doing low-speed stuff a bit more, in which case I can kind of understand where you're thinking is, if you're bouncing between 1st and 2nd that would do my head in with a 4.8 on standard ratios. I ran one on stage rallying for quite some time on a 1.9 8v. The lack of rev range and the short 1st were a royal PITA at hairpins/chicanes/etc *but* the 4.8 on a 1.9 box did make the most of 3/4/5th when I was up to speed on the longer parts of the stages - which with stage rallying is really where you spend more of your time. I did end up going hybrid box for the ultimate (stick-shift) set of ratios but whether you want to go that far is another question.

 

Given your limitation on the 1.9 8v being fairly standard I would agree with Tom and Pete, stick with the 4.8 and chase some revs (if you can) to make 1st more useable

[Rallyace 3]

Thanks. You’re absolutely right about the gearing for stage events. Apart from a handful of road events, all of my previous experience is on stage events and the hybrid box makes perfect sense. Unfortunately, there’s no suitable first gear available within the standard boxes. Do you happen to know the number of the bearing that Petert refers to?

[petert 554]

I believe someone at Skip Brown knows the part number for the needle roller. They are hard to get.

[brumster 135 1 Cars]

I'll see if I can find out from AB  dunno if it's 'secret sauce' rated

 

[Rallyace 3]

Cheers.

[brumster 135 1 Cars]

Apparently he could only ever get it from Peugeot Sport France, which is presumably the same as where Skip Brown get them. Special order/part. He never found anywhere else to source them from. So, yeah, probably Skip Brown is your best/only option really

[SRDT 150]

Is this the bearing you are looking for?

 

https://www.pam-sport.fr/arbre-secondaire-bes/176-cage-a-aiguilles-sous-pr1.html

[Rallyace 3]

I’ll follow it up with Del at Skip Brown Cars.

 

[SweetBadger 91]

9 hours ago, SRDT said:

Is this the bearing you are looking for?

 

https://www.pam-sport.fr/arbre-secondaire-bes/176-cage-a-aiguilles-sous-pr1.html

 

Have just had my AB motorsport box rebuilt (the needle roller bearing had got hot and melted!).

 

Couldn’t find the Peugeot sport one, the one above looks just like the one that came out of my box. 60 euros though 

 

this is what I ended up using - 

 

 

from a Vw gearbox.

 

Pinion is machined to 30.8mm diameter to take the bearing and 1st gear inner diameter is 35.8mm

 

Took me a while to find this bearing!

[Rallyace 3]

1 hour ago, SweetBadger said:

 

Have just had my AB motorsport box rebuilt (the needle roller bearing had got hot and melted!).

 

Couldn’t find the Peugeot sport one, the one above looks just like the one that came out of my box. 60 euros though 

 

this is what I ended up using - 

 

 

from a Vw gearbox.

 

Pinion is machined to 30.8mm diameter to take the bearing and 1st gear inner diameter is 35.8mm

 

Took me a while to find this bearing!

Thanks. I really  appreciate the help.

[SweetBadger 91]

No probs.

 

If you go ahead with the needle bearing then the other thing that you might want to consider is how the pinion is machined for it. 

 

My gearbox had the diameter of the pinion reduced right up to the splined section:

 

 

 

This means that you can't torque up the bolt at the end of the pinion to spec because it compresses the whole gear stack against the thrust bearing next to 1st gear.

 

If you machined a slot for the bearing instead it would leave a small collar at the end  next to the splines meaning you can torque up the bolt as originally intended.

[Tima78 0]

Thanks for the helpful information

Edited February 3, 2022 by Tima78

[Rallyace 3]

2 hours ago, SweetBadger said:

No probs.

 

If you go ahead with the needle bearing then the other thing that you might want to consider is how the pinion is machined for it. 

 

My gearbox had the diameter of the pinion reduced right up to the splined section:

 

 

 

This means that you can't torque up the bolt at the end of the pinion to spec because it compresses the whole gear stack against the thrust bearing next to 1st gear.

 

If you machined a slot for the bearing instead it would leave a small collar at the end  next to the splines meaning you can torque up the bolt as originally intended.

Thanks. That’s really useful advice. I’m just looking on the Gearboxkit website. I’ve put the bore and O/D in, but not offering any options. Do you happen to know the length? I’ve also tried the Part number in the “expression” cell.

[SweetBadger 91]

11 minutes ago, Rallyace said:

Thanks. That’s really useful advice. I’m just looking on the Gearboxkit website. I’ve put the bore and O/D in, but not offering any options. Do you happen to know the length? I’ve also tried the Part number in the “expression” cell.

https://rolling.hu/search/F-230742.3*INA

 

Dims there.

 

Bearing available here: https://gearboxkit.eu/product/73340

 

Think I got it from Autodoc from memory... edit: yep - https://www.autodoc.co.uk/ina/7782513

 

Edited February 3, 2022 by SweetBadger

[brumster 135 1 Cars]

Hey Alex - was that my old box where the shaft had been machined too much?

[SweetBadger 91]

2 hours ago, SweetBadger said:

If you machined a slot for the bearing instead it would leave a small collar at the end  next to the splines meaning you can torque up the bolt as originally intended.

This illustrates my point nicely. 

https://www.pam-sport.fr/arbre-secondaire-bes/66-arbre-secondaire-be45-synchros-13x68.html?search_query=Arbre+secondaire&results=204

 

I do wonder if the collar was originally there on my pinion and has subsequently fatigued and broken off  . Would explain the melting of the bearing... And possibly why it's difficult to get 1st on the rebuilt box...

[SweetBadger 91]

6 minutes ago, brumster said:

Hey Alex - was that my old box where the shaft had been machined too much?

Yep that's the one.

 

Although as above perhaps it was machined with a collar which subsequently broke off causing the needle bearing failure - The rebuilt box is difficult to get into 1st unless the car is moving now so something's not right with it. 

 

Miles rebuilt it and said he didn't think that there was evidence of anything breaking off it though so a bit of a mystery.

[Rallyace 3]

I think that I’ll strip down one of my old gearboxes, as the CWP in my box is a 4.8:1 and therefore not one to be experimented on. I’ll have to solve the issue with it being difficult to get into 1st gear. Targa rallying has a lot of 1st, 2nd and third gear use. I think I’ve only used 4th a couple of times on the tests.