Tu Engine Build

[calvinhorse 870]

I started off with a tu3s on a saxo vtr greytop bottom end.

i later found out that this combonation makes the compression too high!

so i've bought a 1.6 tu head out of a 306 as this has also got bigger valves and ports.

 

however i think this head is low compession?

 

so how much (if any) can i skim off it to make it the correct compression or a "good" compression?

 

im also using the tu24 cam, weber 40s and a csc manifold (if this makes any difference?) and standard tu3s ignition which i will change at a later date or if needed?

 

thanks for looking

 

c a l v i n h o r s e

[RossD 44]

I'm not sure what lift at TDC the TU24 cam has, but with my CatCam, I couldn't skim the head at all to bring up compression as the valves were too close to the pistons already! (My Cam has approx 2.5mm lift at TDC)

 

You'll definatly need to change the ignition curve if you are running a TU24 cam and a 1.6 head, it will be all wrong to make optimum power.

 

Edit: I've just found the TU5J2 pistons I'm using have a shallower bowl in them to bring compression up, the normal 90bhp 1.6 should have a deeper dish, so you may be able to skim the head.... Only way to find out is to measure it all up.

 

Edit 2: You're using the greytop bottom end... do these have the flat top pistons?

Edited October 16, 2007 by RossD

[calvinhorse 870]

i think they where flat

 

how can i measure how far the valves open?

[trogboy 17]

Plastercine on the top of the pistons is a good way of measuring your clearances if you can fit it all together.

[Sandy 191]

Unless I'm going mad, the TU24 cam doesn't fit the bearings on the 306 head?

 

Later TU5 pistons are damn near flat. You can cut valve pockets with an old valve made into a cutter and a drill/some lubrication. Be careful obviously and do it without the HG fitted so you get clearance on both planes.

[calvinhorse 870]

sandy- i tried the cam in the head and it fits and moves freely with no rattle

or is it that the cam is a fraction to small but not noticable without accurate measurement?

 

so i take it the valves wont clear and the compression is to low?

thanks for the help so far!!

[calvinhorse 870]

just measured the 306 cam (black top engine) and a tu3s cam and they are the same?

 

the tu24 cam works in the tu3s head so the tu24 should work in the 306 (tu5?) head?

 

sandy you may possibly going mad but you are very helpful

Edited October 16, 2007 by calvinhorse

[Sandy 191]

Well, if the bearing sizes are ok, no problem then! The TU3S cam bearing sizes are certainly dofferent to the TU2J2 and TU3J, TU5J2 Rallye and XSi engines. I'd assumed the 306 "big valve" head would be the same.

[calvinhorse 870]

the head came from a roland garos 1.6 if this helps?

[Sandy 191]

Right, it seems to be a bit of a grey area.

[RossD 44]

Could you measure the diameter of the valves? Its very odd, as when I was looking at the early 1.6 blacktops in my local scrappy they certainly had the large cam bearings....

[calvinhorse 870]

i cant remember the exact size but they worked out about 3mm bigger than the tu3s valves.

[RossD 44]

Ah ok, that sounds about right then for a big valve head.