Technical Punto 75 Cam's

[DJ_Bucho]

There's been quite a bit of talk recently about putting a cam out of a Punto 75 into a Punto 60 engine, thus giving a few etra bhp's

Has anyone actually gone and done this????????

Or like me, is everyone waiting for someone else to do it first, to ensure it can actually be done.

I've been told the Cam out of a Punto 75 is basically exactly the same as some of the performance cams you can buy for the Punto 60, does anyone know if this is true or not, and also is there anything else that needs to be swopped over when changing the cam's, (assuming they can be swopped over) i.e. the shims.

If ANYONE has any information on this topic, PLEASE let me know, as I'm very interested to know if this can be done.

Thanks Very much.

Brian

 

[kebab]

for a cinq 60 conversion? yeah, it would fit on a 60 no problems im skeptical that it would make a noticeable difference but its your time and money.

 

[HP]

As I get it, the cam has slightly longer duration and marginally higher lift. You'd quite probably have to shim the tappets again: fit cam - measure up - buy / swap shims to get the right clearance.

 

[DJ_Bucho]

So what your saying Pete is IF I get the Punto 75 cam you'd recommend getting the shims that go with itl, then when I come to change it over I can take the old cinq shims out and then put the Punto 75 shims and cam straight in???

"kebab" The Cinq head is exactly the same as the one used on a Punto 60 so if the Punto 75 cam fits into a Punto 60 head without problems it WILL fit into a Cinq head without problems.

 

[dave]

So what your saying Pete is IF I get the Punto 75 cam you'd recommend getting the shims that go with itl, then when I come to change it over I can take the old cinq shims out and then put the Punto 75 shims and cam straight in???

there isn't difrent shims for difrent cars, you will need to fit cam first, then measure gaps, some shims you maybe able to just move around, but some will proubly need replacing.

 

[kebab]

"kebab" The Cinq head is exactly the same as the one used on a Punto 60 so if the Punto 75 cam fits into a Punto 60 head without problems it WILL fit into a Cinq head without problems.

try and read what i wrote ! my opinion.

 

[DJ_Bucho]

SO are the shims on the Punto 75 the same thinkness as the shims on the Cinq then????

 

[littleyellowcar]

my understanding of shims are that a shim is a shim - doesnt matter what car they are for, they are just spacers (arent they??) they are available in different thicknesses to take up manufacturing irregularities

im probably wrong tho

 

[dave]

my understanding of shims are that a shim is a shim - doesnt matter what car they are for, they are just spacers (arent they??) they are available in different thicknesses to take up manufacturing irregularities

im probably wrong tho

yep also they are how you adjust valve clearences as wear takes place, if you look up in the haynes manual about valve clearences, you should get an idea of what we on about

 

[DJ_Bucho]

yeah thats pretty much what I understand, but are the shims on the Punto 75 a different thinkness to the ones on a Punto 60 or a Punto 55 (Cinq), and if they are the same, why would I need to change them over?????

 

[littleyellowcar]

they come in all different thicknesses, but the same "size", so if you get the shims with the 75 head, you'll have more to adjust the 54 head with if need-be

 

[DJ_Bucho]

I've heard talk that the cam in the Punto 75 is the same as the one Novitec sell as the performance cam for the Cinq and Sei's. I wonder if those cams come with shims or if Novitec just sumply the cam itself and expect you to use the shims already in your engine???

If they don't supply shims, I can't see why I'd need new shims with the Punto 75 cam???

 

[dave]

I've heard talk that the cam in the Punto 75 is the same as the one Novitec sell as the performance cam for the Cinq and Sei's. I wonder if those cams come with shims or if Novitec just sumply the cam itself and expect you to use the shims already in your engine???

If they don't supply shims, I can't see why I'd need new shims with the Punto 75 cam???

they would have no idea what thickness shims you need

 

[Julio_Scorchio]

they come in all different thicknesses, but the same "size", so if you get the shims with the 75 head, you'll have more to adjust the 54 head with if need-be

How it all works is this:

The cam sits in the cam bearings / carrier and it's axis (centre of revolution) is a set distance from the 'back' of the head, and therefore the front of the head.
The cam will be ground to a set dimension, however the 'base circle' of the cam lobe may be very slightly different from cam to cam, so the distance from the back of the cam lobe to the end of the valve will vary.
The valves may be very slightly longer or shorter than each other depending upon where they were manufactured or obtained from, how old they are or indeed which head they came out of, or which model of car.

As the valve seat is an angled cut, every time it is ground in or if it wears, it moves the whole valve slightly nearer the cam as it settles into the seat, or if it gets carboned up it might move farther away, plus the seats may not be set into the head exactly the same depth / distance from the face of the head. Or the seat may be 'cut' to a different depth. All these things affect the valve clearance.

So first you assemble the whole head, cam, shims and all, making sure the pistons are halfway down the bores. Then you measure the distance between the back of each cam lobe, when the lobe is pointing directly away from the corresponding valve, and write it down (lets say it should be 10thou). If it measures 15thou you take the shim out, measure it, and write it down. Lets say it's 100thou. So you now need to put a 105thou shim in to make the gap right. So you adjust the shims to make the gaps correct. (In the old days of Rally Imps I used to swap the tappet buckets round too, to get the best fit)

So you could do all this without taking the head off, UNLESS:- if the lift on the cam is noticeably more than the std cam, the valves may hit the pistons. Ooops, error.

Which is why you should generally remove the head, put a bit of plasticene on top of the pistons, reassemble the whole thing, and turn it over a couple of times to check how squashed the plasticene is. But that's a lot of work.

One easy way to check is to very carefully turn the engine by hand until the pistons are at TDC, then see how far the valves will push down whilst checking with a trusty dial gauge. However it's not a recommended method, but could do at a push. There is a set safety margin which you should try to adhere to, in order that you don't end up with valve/piston contact at high revs.

Especially if you're thinking of taking it to York.

HTH

Tosh