Camshaft dial in

[rockiemosley]

I just lifted the cam cover on my 1974 GTV 2000 (Spica) and found the cams 105200320000. It would be great to fit some more performance oriented cams, but there is alot of other things I want to buy right now, so I am trying to maximixe the performance of the stock cams. According to The Alfa Romeo Owner's Bible by Braden...Performance on the 2000 can be improved by advancing the intake cam 5 holes or 7.5 degrees and retarding the exhaust 1 hole or 1.5 degrees. Anyone have any comment on those numbers? Can I go a little more? According to my info the stock cam is

Intake opens Intake closes exhaust opens exhaust closes
22 70 51 27
after Bradens tweaking...according to my calculations...
Intake Opens Intake Closes exhaust opens exhaust closes
29.5 77.5 49.5 28.5
so I compare those numbers with the what is perhaps the hottest Spica car the early 1750 in stock format---
IO 37 IC 61 EO54 EC 30

So my question is...are Braden's reccomendation about all the power I can coax out of the stock cams, should I leave well enough alone?


Thanks

[Alfar7]

You won`t get much from those cams. Changing LCs as suggested by Pat will move power up a minor amount at higher revs. But you will also loose a little 2000-3500 torque (drivability suffers).
If you have the VVT sprocket it is advancing from 114 to 10o which is as far as the cam should be set. The 10548032000-01 is a better "performing" cam foe Carb motors with more lift & duration. There is one on the BB for sale that I listed this week. You have about the last year for good Spica pumps. It would improve things but you would need to adjust the FI a bit.
Rj

[rockiemosley]

Thanks Richard...just to clarify, Ive got no VVT sprocket on the 1974 GTV and Spica injection, so what cam would be best? Or should I not fix it if it aint broke?

[alfaparticle]

I think that the lobe centers are 114 intake and 102 exhaust for 1974 cars.
Richard, wouldn't it be an improvement to move the intake to 102 and leave the exhaust alone?

[Alfar7]

Download the cam cap template from Centerline to be sure you know what mark is on your cam cap on the intake side.
I would suggest setting the cam (non VVT) at 102, but if drivability feels less in the normal driving range move it to 104. The top end on these cams are nothing much. The car would be better with a vvt modified to open at 2500 RPM or so.

[rockiemosley]

OK I got the template and checked my timing marks...Intake side appeared to be marked at 114 degree center, and exhaust was marked at 102 center...I made a new mark on the intake side at 102. (its a 74 gtv2000) Anyway, after doing the tweaking per Braden (Advance intake 7.5 degrees and retard exhaust 1.5 degrees), my exhaust cam is pretty close to the stock 102 mark,,, and my intake cam is way advanced past the 102 mark. ( I only moved it 5 holes) Just estimating based on position of 114 mark in relation to the new 102 mark...im guessing Ive got the intake cam centered on 90 or 92. This is making me think that the intake cam must have already been advanced, although I swear the marks lined up before I started fiddling. I am thinking I need to get some dial indicators and start over... find true TDC and adjust crank mark and put it all back stock and go from there, maybe setting intake cam on a 102 center, but honestly with the small bit of play in the chain and the few degrees of crankshaft rotation where the TDC mark appears to line up, there seems to be some room for inaccuracy. Anybody got a more percise method of cam timing other than lining up the marks? The difference between 102 and 104 is so small it could be that the angle from which you are viewing the marks could be the difference. Part of the confusion here... the intake cam mark lined up at the 114 center mark before I advanced the cam 5 holes...and now it is way on the other side of my new 102 mark, which makes me think advancing the cam 5 holes equates to more than the 7.5 degrees I thought I was moving it.

I guess part of my open ended question here is this- Are the marks on the cams a constant, and lobe centers are altered at the factory by moving the timing mark? Any help?

Thanks

[alfaparticle]

Make sure that you only rotate the engine forwards while you are checking the valve timing. If you do that, there should be no chain slop. It is true that the marks are close together, but it is not hard to estimate 2 degrees.

[1166]

Remember to check TDC. I have had several cars where the pointer is bent or the adjustable style pointer is in the wrong place.