Camshaft Choice Headaches

[Razkin 0]

The engine:

Wiseco pistons

Block and head skimmed by 0.1mm

At the moment standard headgasket 1.2mm

 

Inlet valve clearance at TDC is 4.0mm. exhaust clearance is a bit more, can't remember and lost the measurements and won't be near the engine for a week...

 

I would like to buy Catcams 4903273

in/ex 2.95/ 2.35mm lift@ TDC

in/out 244/236 dgrees duration @1mm lift

 

That leaves 1.05mm clearance at TDC. Catcams recommends a min of 1mm, but advises 1.5mm and from 5 to 15 degrees before TDC on the exhaust and 5 to 15 degrees after TDC on the inlet.

timing [1.0mm+s] 14/50° 46/10°

 

I do not know what they mean with the above specs, but I think it means that the cams have 1mm lift from 14 to 50 degrees after TDC inlet and 46 degrees before TDC and 10 degrees after TDC?

 

 

Since I do not have the cams I can not do any measurements to know for sure the cams will fit.

I am also considering purchasing a repair gasked by Citroen. There is no thickness mentioned on service box on the standard gasket but it is mentioned by the repair gasket which is 1.4mm.

I can not tell if that is 1.4mm compressed, but it ought to be as standard would be 1.2

compressed?

 

Any advice on the repair gasket/cams?

[stefan 4]

When I go shopping for xu gaskets they always ask me if I want the 1.2mm, or the 1.5mm

[welshpug 1,627]

Payen do a 1.45mm fibre gasket, elring do a 1.35mm gasket, not sure if this is fibre or steel

 

not found a supplier for the 1.4mm item other than peugeot, but this was out of stock for a month and superseded to a very expensive part (circa £60 IIRC, when the 1.2mm is circa £40+vat)

 

no indication if this is steel or fibre, but given the price I'd be inclined to think steel.

 

given its quite an expensive engine build however, and that you will lose compression with a thicker gasket, I would get the pistons valve cutouts machined a little deeper.

 

timing [1.0mm+s] 14/50° 46/10°

 

I do not know what they mean with the above specs, but I think it means that the cams have 1mm lift from 14 to 50 degrees after TDC inlet and 46 degrees before TDC and 10 degrees after TDC?

 

my understanding of those figures is that the valve is open more than 1mm.

Edited February 17, 2012 by welshpug

[Razkin 0]

Forgot to mention its an rfs build and am looking at MLS headgaskets. Without the head and blok skimmed the compression is 11.5:1, so there isn't a negative impact on a thicker gasket, because of the skim the compression is already a bit higher.

 

The bottom end is completely build up already, so would rather not remove the pistons...

[wicked 103 3 Cars]

Don't forget to check the lift of the cams, before you fit the head. Probably you need to machine the head to make them able to rotate.

[petert 555]

 

I would like to buy Catcams 4903273

in/ex 2.95/ 2.35mm lift@ TDC

in/out 244/236 dgrees duration @1mm lift

 

That leaves 1.05mm clearance at TDC. Catcams recommends a min of 1mm, but advises 1.5mm and from 5 to 15 degrees before TDC on the exhaust and 5 to 15 degrees after TDC on the inlet.

timing [1.0mm+s] 14/50° 46/10°

 

I do not know what they mean with the above specs, but I think it means that the cams have 1mm lift from 14 to 50 degrees after TDC inlet and 46 degrees before TDC and 10 degrees after TDC?

 

 

It means that at 14 deg BTDC the inlet valve is open 1mm, on it's way opening, Then at 50 deg ABDCthe inlet valve is 1mm open again, on its way to being shut.

 

Similarly with the exhaust, the exhaust valve is open 1mm at 46 deg BBDC, as it's starting to open, then as it's closing, it's 1mm open at 10 deg ATDC.

 

The overlap at 1mm would be 24 deg.

 

You simply do not have enough clearance at TDC . It will blow up. Either take the pistons out and machine the pockets or fit smaller cams.

 

They're right in saying the closest point will actually occur after TDC on the inlet. If you can't be bothered measuring it properly, subtract 2.25mm from your 4.0mm. That means your maximum lift @ TDC should be 1.75mm.

[Razkin 0]

That makes a lot of sense, thanks for the explanation.

 

Will get the pistons machined to accept the cams.

[Razkin 0]

Can I use that 2.25 at TDC as a rule of thumb? Since the pockets need to be machined I might as wel go for a lumpier cam like the 4903270. The same duration etc, but has more lift.

 

More lift doesn't neccesarily mean better, but is there a way to guestimate if it will be better?