Alfa Pages

[rsfruitbat]

Does anyone know how to tell the difference between the inlet and exhaust cams if you have no marks and no pulleys fitted?

[tvatavuk]

Partnumber on them?
Hmm one of those two had missaligned cams (one cam was sharper, other looked more like worn) for later opening of secondary valves.
_________________
Tino Vatavuk
Little black dress which replaced Alfa Romeo 33 S 16v Permanent 4 GMo

[john 33_16v]

Hi,

The inlet cam has the staggered valve opening.

John
_________________
If it aint broke, fiddle with it until it is!
- - - - - - - - - - - - - -
93 33 16v Mirtle Met
08 Fiat Grande Punto Exotica Red
90 Yamaha FZR600 Genesis- Silky white/red/blue

[rsfruitbat]

This is where I get confused. Cams have no part No's. I am trying to compare with a set in a pair of heads. I had been told that inlets are in line. Looking at the cams neither are in line and both have slightly different shaped lobes. Inner inlet (cam) lobe looks asif it is a lot "fatter".
Any ideas?

[john 33_16v]

Hi,

I have a new inlet camshaft in front of me.

The lobes are in pairs with one lobe of each pair starting fractionally before the other. One lobe is sharper, and the sharper lobe has a slightly shorter lift.

The 2 pairs are at 90deg to each other.

The shaft has light red paint 'splash' on it.

hope that helps.

John
_________________
If it aint broke, fiddle with it until it is!
- - - - - - - - - - - - - -
93 33 16v Mirtle Met
08 Fiat Grande Punto Exotica Red
90 Yamaha FZR600 Genesis- Silky white/red/blue

[stedee]

yes thats right, the inlet valves open at slightly different times to aid the mixing of petrol and air
_________________
brum brum

[rsfruitbat]

Thanks for guidance on the inlet cams, do you know how this shape differs from the exhaust cam?

[hugh jinjin]

inlet cams have one fat lobe and one pointy one per cylinder, exhaust cams have 2 pointy ones!

[rsfruitbat]

Thats the kind od description a simple bloke like me understands. Ta.

[richard33]

Not trying to confuse - but I understand that the cams described above are pre-cat. I believe that post-cat cams (not so powerful) do not have the stagger.
Out of interest, I recently rebuilt a 16v engine for racing, and had to check through 4 sets of cams from 4 different engines, just to find 2 inlet and 2 exhaust cams with lifts at, or higher, than minimum spec. Some were abysmally worn. It was easy to check the lifts with a head on the bench - but even checking the overall height of each cam indicated which were lemons!

[rsfruitbat]

Thanks. I'll keep an eye out for that. Out of interest what did you do with your cam followers? did you stay with hydraulic? If so what do you rev to. If you convereted to solid could you please tell me what you did and the cost. I am building a 16V for a 33 rallycar.
Regards

[richard33]

I retained the hydraulic lifters (again by careful pre-selection of dozens of the little buggers) and bled them as previously described on this forum.
If you are using standard profile cams, there is probably nothing to gained by fitting solid lifters - which both expensive and fiddly/time consuming to shim.
Again, if you are retaining the standard Motronic ECU, then as you probably know, this has a rev limiter built in, to cut in at about 6800. The hydraulic lifters are certainly OK for this and quite a bit more - the standard cams are running out of puff at around 7000 anyway. So unless you are running uprated cams and a modified ECU, solid lifters are a bit of a waste of time and money. If you do have your ECU modified to eliminate the rev limit - a chip with a revised map is required, as the standard Bosch chip simply retains the settings required for 6800.

[john 33_16v]

[rsfruitbat]

Thaks for the response on the hydraulic valves. I am going to be running a DTE engine management system. I am fitting the 16V heads onto a 1350 blockas there is a 1400cc capacity limit in rallying.
As engine cc's go down so the same cam in effect becomes "wilder" i.e a road cam in a 1700 would be a road rally cam in a 1600 or a full race cam in a 1186. So using the std cams but hoping they will provide more puff than 8V heads. To get the most out of the engine I would benefit from being able to rev higher which is where my question comes from. Ideally the rest of the engine is being built to take 8500rpm.
Will std hydraulic lifters take this? Any ideas ?

[richard33]

I take your point about the cams characteristics when used in a smaller capacity engine - as the lifts are proportionally higher, but as the durations are the same, doesn't that mean that the rev band will be unchanged ? If so, won't they have run out of puff long before 8500?

[rsfruitbat]

My understanding is that it has a similar effect. As the piston is smaller the amount of air drawn is effectivley increased. This is the same for the duration the smaller engine doesnt need the same amount of air so the same cam will have the effect of a longer duration. My understanding is that the cam is designed to allow a certain amount of airflow at a certain rpm. To flow the same amount of air that a 1712 does at 6800, a 1400 would have to be revving at 8315rpm.
Ultimately I'm not sure. there are a lot of question marks on this build but a 16V has got to a better route long term than an 8V. The proof of the pudding will be on the rollers.
Thanks for advice and will take it on board. I will let people know how it fares but its a few months off yet.

[Serpent33]

For anyone's future reference.

INTAKE
opening BTDC- 8deg/35deg lift 9mm / 9.5mm
closing ATDC- 48deg/48deg

Exhaust
opening BTDC- 52deg/42deg lift 9.2mm / 9.2mm
closing BTDC- 12deg/22deg

To add to id of intake cams, only on the intake lobes you can find the ramps to be of same plane and highlinted (can be visualised). Coupled with the fat lobe with sharp lobe combination, it should make id'ing the intake cams easier.
_________________
Each time I speed I say, "Dear lord, make me fast and accurate..."