Xs Or Xsi?

[R.G_205 0]

i am doing my engine rebuild for my rolland garros and i have used the xsi 1.4 internals in my tu3s alloy block and was wondering what head to put on to top off the build? is there any noticeable differences? i can see that the exhaust ports are bigger on the xsi head but the inlets 'feel' smaller (i say feel because my feeler gauges are out of battery's) any advice would be great

 

Roddy

[GeorgeXS 32]

Well given that a 106 xsi produces nigh on 20bhp more as standard and has virtually the same head as a 106 rallye if i remember rightly? then i'd say the xsi head would be a better bet!

[RossD 43]

Well given that a 106 xsi produces nigh on 20bhp more as standard and has virtually the same head as a 106 rallye if i remember rightly? then i'd say the xsi head would be a better bet!

 

Yep, the XSi (TU3J2) has bigger inlet and exhaust valves than the XS (TU3S) but bare in mind the stud patterns on the inlet side are different between the two heads, so you have to either use the XSi injection system or fabricate a manifold if you use the XSi head.

Just make sure it is a genuine XSi head - You say you've measured it and the ports seem smaller, this doesn't sound right!

 

Edit: Ah, seem smaller, correction!

Edited July 14, 2011 by RossD

[Lan 24 1 Cars]

exhaust valves will always be smaller no matter what engine it is are you sure you're not confusing the two?

[R.G_205 0]

Well given that a 106 xsi produces nigh on 20bhp more as standard and has virtually the same head as a 106 rallye if i remember rightly? then i'd say the xsi head would be a better bet!

 

so the xsi head is almost the same spec as the tu24 head?

[trogboy 17]

so the xsi head is almost the same spec as the tu24 head?

 

Almost. - inlets spacings are slightly different, as are the valve sizes (by a smidgen). TU24 also has no holes for the injectors and makes use of 8mm stem valves rather than the 7mm stem valves of the later large valve heads.

 

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[R.G_205 0]

right i think im being retarded....but i compered my measurements from my xsi head to my xs head.. my XS head has bigger inlet ports and smaller exhaust ports compared to my XSI head?? any one help? and the xsi head has a larger cam so i think i will just put that cam in my xs head, it looks like it will fit but will take it out tomorrow and have ago thanks for the help so far!!

 

roddy

[GeorgeXS 32]

right i think im being retarded....but i compered my measurements from my xsi head to my xs head.. my XS head has bigger inlet ports and smaller exhaust ports compared to my XSI head?? any one help? and the xsi head has a larger cam so i think i will just put that cam in my xs head, it looks like it will fit but will take it out tomorrow and have ago thanks for the help so far!!

 

roddy

Hmm the xsi ports should be larger as said above.

You say the cam is larger, in what respect?

Xsi and similar later Tu heads have larger camshaft bearings if i remember rightly and as such the cams arent interchangable.

Sounds like you have a head off a lower power late Tu engine, ie off a 306/ZX etc to me.

[trogboy 17]

As above. The XSI cam shouldn't fit as the bearings should be too big to go in the XS head. In addition it shouldn't have a lobe to drive the fuel pump that you'll need if you are not going for an electric one.

 

The TU3S ports may well be wider at the manifold mating face as the length and profile of the inlet runners is going to be different for each stock set-up.

 

Post up some pictures so we can have a look.

[R.G_205 0]

okay well i will try and get some pics up loaded tomorrow and the cam fits in the xs head so i must have a different head

[burr_2000 1]

hey roddy, get us some numbers either from head ,cam or even donor engine. Whats even more worrying is if you have supposedly bought a XSI engine to mix and match parts, so what do the pistons look like? The engine may not be a xsi from the start. if you say the cam fits a xs head then your donor engine could of been using carbs, ie 1.4 309 iron block engine etc. im interested to see whats happened here.

[R.G_205 0]

hey roddy, get us some numbers either from head ,cam or even donor engine. Whats even more worrying is if you have supposedly bought a XSI engine to mix and match parts, so what do the pistons look like? The engine may not be a xsi from the start. if you say the cam fits a xs head then your donor engine could of been using carbs, ie 1.4 309 iron block engine etc. im interested to see whats happened here.

 

sorry late reply iv been on holiday

 

the engine code on the block is a cast iron 100bhp block as i compared it to auto data and the pistons have dome on the top but the xsi head doesnt seem to match everything i have read (bigger ports cam wont fit xs head and doesnt have the out cut to fit a distributor to it) and it had all the injetor hols and coil packs the lot. but ill take som pics of everything tomorrow hopefully thanks for the help too!!!

 

roddy

[christopher 5 1 Cars]

so the xsi head is almost the same spec as the tu24 head?

The TU24 has similar Valve diameters to the XSI. But the port spacings and stud patterns are different. Although on the face of it they might look similar, the TU24 hugely outflows the XSI out of the box.

Edited August 12, 2011 by christopher

[batespeed 0]

sorry to hijack this thread, but i didnt realise the tu engine had two different vave stem diameters, 7 and 8 mm . i asume there is different valve stem seals for each ?

only asking as my 3s head had reground valves and new valve stem seals fitted but was burning oil from day one (i dont know what the rings were like as the engine was lying in my shed for nearly 3 years before i put it in, but i dont remember it burning much oil before) it didnt help that i blew a radiator hose after about 100 miles of driving, and gave it a good roasting.

could it be that i fitted the wrong seals and this is why its burning lots of oil ? or is it more likely to be the rings ?

 

the head came out of the scrappies years ago , off an ax gt, but it might not be the original one, it has 3s cast into it at the front ,and no visible guide wear.

 

any distinguishing marks on the cam to tell if its an tu3s one ?

 

i will try to do a wet and dry compression check at the weekend, and measure the valve stems, and check the seals are still in one piece

 

again , sorry for hijacking the thread but its all related stuff...

Edited September 21, 2011 by batespeed

[trogboy 17]

Yep - different valve stem oil seals. As far as I know only the TU24 had 8mm stem valves so I'd be suprised if someone managed to accidentally source some and fit then to you TU3S head, Besides if thy were that much over sized you'd probably be puffing serious clouds of blue smoke when engine braking.e

 

You don't say when yours is burning oil, under load, at idle, on over run/engine braking, only after it's been sat for a while. The symptoms will give us a clue.

 

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