A Few General Tu 8v Head Queries...

[Anthony 1,003]

"You're not from round these parts" I hear you cry "this is a local forum for local people don't you know?"

 

Enough of my poor attempt at humour. I've just sold my (anything but) trusty Mondeo, which wasn't proving to be a particularly good daily driver given that it had spent more time in pieces than on the road, and after a bit of thinking decided that a 205 XS would probably prove to be a good compromise as a daily - cheap to buy, cheap to run and maintain, and still enjoyable and have reasonable performance.

 

I stumbled across a suitable car by accident - a nice '89 model that's all original and straight with no accident damage, good few months MOT remaining, four previous owners and 90k odd on the clock. Perfect, except for the minor issue that it's got a snapped cambelt - the price was cheap enough that this wasn't a major concern though and having stripped and built numerous XU engines in my time it should be easy enough to sort.

 

The questions I've got are regarding "improving" the current TU3S engine whilst the heads off the car. I've done a search of the TU section of the forum and it's come up with alot of useful information that's helped alot, but there's some areas of contridicary advice and other areas that I'm a little confused about.

 

1) Given that the standard compression ratio of 9.3:1 is quite low, is it worthwhile skimming the head to increase this say half a compression point to 9.8:1 in a bid to improve efficiency and torque?

 

2) If the worse comes to the worse and the current head and all the valves are mashed, is a TU3 head from a 75hp 106/306 a straight swap, given how plentiful these are? I know the valves are identical and I believe the heads use the smaller cam journals so that I could use the XS cam (which I'm assuming is hotter than the lower power engines) but I'm not sure if the head casting is significantly different/inferior?

 

3) After successfully using an XU10 head on an XU9 bottom end to create a big-valve 1.9 8v that performs really well, I pondered about doing the same with the TU3 by using a TU5 head of sorts which look to have bigger valves as standard. Reading through a few different topics suggest that it isn't really that easy on a TU though, the main problems the different sized cam bearing journals on most TU5 heads, and the lack of compression that either needs 106 XSi pistons/rods or a very heavy skim (that messes up cam timing significantly) to address. Have I understood it correctly, and given I don't want to touch the bottom end or spend significant money would I be better sticking with the TU3S head?

 

4) Do TU3S heads benefit from 3-angle valve seats and a quick tidy of the ports and inlet manifold, or shall I just lap the valves in, replace the stem seals and otherwise leave it as-is?

 

5) A few people mention about TU3 valve springs being quite weak and prone to valve bounce, and TU5 ones being a nice upgrade. There's usually plenty of TU5 engines in my local scrappy that I can strip for the valve springs, but is it worthwhile on an otherwise standard engine - ie has useable power long since tailed off before valve bounce is an issue?

 

I apologise if some of these questions are a bit basic, but I freely admit to not being too clued up on TU engines - hopefully something that should begin to change when I've finished putting mine back together again

[swordfish210 20]

i'm sure there are a few people (you know who you are ) who will give you more information than i can but i'll get the ball rolling:

 

1) Head skim is allways a good idea when the head is off so just get it skimmed down to where it is flat again.

 

2) You could use a head from a 106/306 but if it is a multi-point head then you will have to block off the injector ports. If you want i have a spare TU3-s head that you can have...in exchange for money

 

3) Better to stick with the 3-s head really as you are talking about a lot of work to put a big valve head on and i thought this was supposed to be a cheap daily driver

 

4) I can't be much help on this one as i would let my oppinions cloud my judgement

 

5) The std vlave springs have about a 60,000 mile service life before they become quite subceptible to bounce. You could put some new OE ones in or get some uprated ones from Piper. I just happen to have a set of brand new OE 3-s springs in my possesion that you could have...in exchange for money again

 

I'll have to let the experts fill you in on the rest

[Rippthrough 98]

i'm sure there are a few people (you know who you are ) who will give you more information than i can but i'll get the ball rolling:

 

1) Head skim is allways a good idea when the head is off so just get it skimmed down to where it is flat again.

 

2) You could use a head from a 106/306 but if it is a multi-point head then you will have to block off the injector ports. If you want i have a spare TU3-s head that you can have...in exchange for money

 

3) Better to stick with the 3-s head really as you are talking about a lot of work to put a big valve head on and i thought this was supposed to be a cheap daily driver

 

4) I can't be much help on this one as i would let my oppinions cloud my judgement

 

5) The std vlave springs have about a 60,000 mile service life before they become quite subceptible to bounce. You could put some new OE ones in or get some uprated ones from Piper. I just happen to have a set of brand new OE 3-s springs in my possesion that you could have...in exchange for money again

 

I'll have to let the experts fill you in on the rest

 

1. - Good idea, they come alive with more compression, mines gone from a car that would struggle at the bottom of second to one in which it is virtually impossible stall even trundling along in 5th up a hill at <30mph - I've pushed mine up to 10.4:1 and it's fine on super, which is on an xs cam like yours, although I added a little chamber work to help there.

 

2. - TU3M valves are the same and can be used, I've got an old head sat here from a runner if you want it for a few quid, valves/cams/rockers/pulley, the lot.

 

3. - I'd stick with the 8v as you will end up spending a fair amount that way.

 

4. - They have 3 angle seats as standard, some work can help but I had to do a shedload of work just to get up to 98bhp - and some of that will be the comp. bump - it's fairly good, albeit not perfect.

 

5. - Haven't experienced this yet but mine only goes to 6.2krpm so far, power plateau's at that so I would imagine it wouldn't be much of a problem.

[Sandy 191]

You carb inlet won't fit the TU5 head.

[Anthony 1,003]

Pulled the head off tonight, and a picture paints a thousand words as they say...

 

 

Yup, eight out of eight valves bent. Otherwise it all looks OK - the head casting itself looks fine and there's no play in the guides and the seats look fine, and the pistons I don't think will be adversely affected as the valve marks are pretty minor.

[Rippthrough 98]

Either they're a bit bent, or I've drunk far too much.

[Alastairh 47]

Effort

[j_turnell 137 3 Cars]

Did he say its snapped at idle ha......

[AdamP 0]

I've got eight of those too. I got the head separate from the car though (and no... i didn't pay for it! )

 

Make good paperweights!

[Jrod 7]

Need some valves as I have some here?

[Anthony 1,003]

Need some valves as I have some here?

I was just going to pop down the scrappy tomorrow to strip another TU head, but if you've got a set of valves already out then that'll save me a job - dropped you a PM

[Baz 421]

Pulled the head off tonight, and a picture paints a thousand words as they say...

 

 

Yup, eight out of eight valves bent. Otherwise it all looks OK - the head casting itself looks fine and there's no play in the guides and the seats look fine, and the pistons I don't think will be adversely affected as the valve marks are pretty minor.

 

ERR0R!!!!!!!!!!!!!!!!!!!11

 

Had to be said!

[Sandy 191]

Looks like an Elton John audience

[Anthony 1,003]

With huge thanks to Jordon (Jrod) I now have a complete TU3S head sat on my desk (with 8 straight valves) - you're a star good Sir

 

I'll be getting the head refurbed before it goes back on the car - basicaly cleaned and de-carboned, skimmed, lap the valves back into the seats, and new stem seals etc - and thus I need to make a decision about compression ratio before I give it to the machine shop on Monday.

 

I've made a mental note of Rippthrough's comments on the matter above, but does anyone else have any recommendations on a suitable compression ratio to aim for to find that "sweet spot" before the gains from higher compression are offset by the cam timing being out and the ignition advance being unsuitable and needing the timing pulling back?

 

And as a last point, anyone have any notes of how much skimmed off the head equates to what CR? I've done a few calculations on the back of a post-it note which suggests that I need to lose 1.4cc for 9.6:1, 2.3cc for 9.8:1 and 3.2cc for 10:1, but the shape of the chamber in the head makes that a bit arkward to convert into how much to skim off without measuing it with a pipette.

[christopher 5 1 Cars]

What cam are you going to be running Anthony?

[Anthony 1,003]

What cam are you going to be running Anthony?

Just a standard XS cam.

[Rippthrough 98]

I've a vernier pulley on Anth, but even when set back to standard timing there's only a loss of around 6-7% at the bottom end into the lower midrange compared to the what I'm currently running (couple of degrees advanced).

 

I took 4.4cc out, which equated to just over a 1.1mm skim - not far off the 1mm for a perfect circle, so I'd take the amount for a circle and knock 10-15% off to get you about there.

I wouldn't go any further without tweaking the ignition timing though, I'm fairly lucky with the single point injection because with a couple of tweaks you can have rough control over the timing curve, it's stock at the minute and about spot on through the mid-range.

 

I'd aim for at least 10:1 myself.

[James_R 3]

Stupid question, does the TU deisel Cam pulley work as a budget verniner on the petrol TU's?

[Anthony 1,003]

Stupid question, does the TU deisel Cam pulley work as a budget verniner on the petrol TU's?

After a trip to the scrappy yesterday I had a look into this, and the answer is "sort of".

 

The outer part of the pulley is the same diameter and has the same number and pitch of teeth, and the inner part of the pulley fits the end of the TU cam perfectly.

 

However, the outer part of the pulley is far too wide and fouls against the head, and would need to be heavily machined down to fit - something in the region of about 10mm of material taken from it. Also, the cam timing hole is something in the region of 10-15 degrees offset compared to the standard TU pulley, and would thus be useless for timing the cam up - you'd need to time it up using lift@TDC instead (but that's also the case with most if not all aftermarket verniers)

[Sandy 191]

Late XU 16v pulleys can be milled down for this purpose on the TU 8v.

[macaroni 17 1 Cars]

I once left a TU head at QEP that had enlarged exhaust ports, but needed the valve guides replacing. You, or anyone else, can have that head gratis if a) you want it and Matt can still find it.

I also have a set of rockers if you need them, aswell as a full TU exhaust system, minus the backbox. All yours if you can collect them.

 

I had 3 angle valve seats cut into my TU head and couldn't really tell much difference. The biggest, sensible, improvement I made was fitting a 4-2-1 manifold.

The daftest mod was a 38DGAS carb! Once jetted correctly, it was a monster but, due to the position of the float chamber, made cornering interesting.

 

I had a lot skimmed off my head, can't recall how much, and using a correctly dialled in vernier pulley and hot cam it would rev to 8000rpm very easily.

[Henry Yorke 269 3 Cars]

The K&N pancacke filter that came for the TU3S engine (XS and Citroen AX) also included a replacement jet for the carb. That is how it got its extra 8 bhp which they always referenced. I loved my little silver XS!

 

Also look into what the AX GT and GT500 had in them as they were the same engines. I think the GT400 was injection though. The head you ought to be investigating is a S1 Rallye if it will fit as that was engineered by Peugeot Sport, so I presume more spritely than stock. Sandy will know all about these though and there is probably a good reason why it hasn't been mentioned already!

 

Stu_WOAC on PSOOC knows a lot about these engines as his track car is based on one.

[Toddy 7]

The K&N pancacke filter that came for the TU3S engine (XS and Citroen AX) also included a replacement jet for the carb. That is how it got its extra 8 bhp which they always referenced. I loved my little silver XS!

Stu_WOAC on PSOOC knows a lot about these engines as his track car is based on one.

 

iirc I replaced the secondary 130 jet for a 140 which gave a genuine increase on my AX GT although it did have a ported head.

[swordfish210 20]

I had a K&N pancake filter on mine when it was pretty much standard, made kack all difference even with the bigger jet. I'm convinced it was all a placebo . Get a Weber 32/36 DGV carb on there and see a real difference. IIRC it was the AX GTI that was injected, the GT and GT500 had the same solex carb on them.

[M_R_205 5 1 Cars]

I had a K&N pancake filter on mine when it was pretty much standard, made kack all difference even with the bigger jet. I'm convinced it was all a placebo . Get a Weber 32/36 DGV carb on there and see a real difference. IIRC it was the AX GTI that was injected, the GT and GT500 had the same solex carb on them.

 

Sorry for the slight hijack, will the DGV bolt to the standard manifold? my carbs running a bit s*it so im thinking of replacing it....