32 valve triumph stag.

[xvivalve]

If the head was on the 'right way round' the chain would cause the one cam to rotate the wrong way.

[soe8m]

You cannot change the direction of a sprint cam in a sprint head so putting the head backwards the camshaft needs rotating the opposite direction than the head what's fitted the "normal" way.

Jeroen

[xvivalve]

...but it's far cheaper to have a special cam made with the lobes in the right positions to work the wrong direction than it is to have a mirror head made?

[soe8m]

That is not possible i'm afraid. You need the original rotation direction. You can change the firing order by making a new camshaft with the lobes changed but that will not solve the rotation issue.

Jeroen

[tony g]

If the second head was fitted with the cam sprocket at the front as normal the cam would turn in the normal direction, the main problem is that the valves would be the wrong side ie the exhaust valves and ports will be in the V and the inlets will be on the outside. This would require major head work to correct including sorting the manifolds out.

Tony

[soe8m]

Then the only option is an extra gear that "reverses" the rotation of the camshaft when fitting the head backwards. Probably the reason why it never has been build.

Jeroen

[tinweevil]

This picture shamelessly stolen from the CT thread should help.

The in the right (normal) head the cam rotates clockwise as viewed and is positioned just after the exhaust stroke and about to open the inlet valves.
In the reverse head whether it is a mirror casting or a normal head fitted backwards the port arrangement is as shown. The cam is between exhaust and intake strokes again so must now rotate anticlockwise in order for intake to follow exhaust.
Normal chain arrangements cannot do this, everything goes clockwise:

You need either:
1) a shorter chain on the left driving a gear that in turn drives the cam.
2) a longer chain on the left with two idler gears so that the cam runs on the 'outside' of the chain.
3) help from M C Escher.

[soe8m]

Or a chain like this:

twist.png (29.77 KiB) Viewed 2026 times

Jeroen

[trackerjack]

You Dutch people cannot resist showing advanced Daff designs

Jonners in this case we are as one

[boss hog]

And what is your solution to have cam drive/timing solved in the reversed head?

I have put the cam on the head in revirse it can work.the rockers will work. the cam lobes on no2,no3 have to be swoped around.

[tinweevil]

I have put the cam on the head in revirse it can work.the rockers will work. the cam lobes on no2,no3 have to be swoped around.

Mr Hog, we know that new cams are needed for both heads, that is not in question. What we are saying is that a new cam alone is not enough on the LH head.

A more practical option 3 - longer rockers that reach across to the far side of the cam on the LH head. Then the cam can rotate clockwise. The problem that introduces is that the longer arm reduces the lift of the exhaust valves. You can compensate for that with bigger lobes on the cam but then the inlets are opening too far. Compensate for that by opening the gaps on the inlets. You might get there that way but it's not going to be quiet (like a sprint ever is).

[jikovron]

Both camshafts would have to be custom made surely as whilst an inline 4 has equal firing of 180degrees @ the crankshaft,, the right bank fires at 180-270-180-270 intervals with the left bank 90 degrees offset

either custom camshafts especially made or a one off flat plane v8 crankshaft would need made first

a chain drive could be fitted as normalish for one side rotation wise and a pair of gears down at the crankshaft end driving a sprocket affixed to the idler gear and a shortened timing chain wouldn't be much work in the grand scheme of whats involved

would be interesting as a concept at least over and above ready made bought engines etc