What cams to use?

[FORZALANCIA]

Hi Guys,
I have just rebuild a 2L bottom end & have now started on the head. We grinded out the combustion chambers as well as both the inlet & exhaust ports as well as giving them a good polish. I have obtained some cams & i was wondering if you could tell me what you think? They have a much longer lobe then normal & are 81/51 duration. Is this too much for me to use with my supercharger setup?
Comprised of the following:
Sidedraft 45 weber
1.2L roots type supercharger running pulley ratio 1:1.32
2L motor running 8.9:1 compression (standard pistons) with 1.6mm copper head gasket
Will these cams work well with this setup?or are they way too lumpy? & is it better if i only use a lump inlet one & a standard exhaust cam?
Thankyou,
Antony

[VX131R]

I think as the theory goes if you have a high lift intake and exhaust on forced induction engines, you end up blowing all the boost straight throught and out your exhaust when overlap occurs, everyone I have spoken with suggest standard exhaust or close to it and higher lift intake to enable more air/fuel to get crammed in there. You'll be best with adjustable cam wheels to play with cam timing to get the best out of it.
Plenty of people in here know more about it than me, not up to that stage yet myself.
Sounds like a great project :D

[VX131R]

I think as the theory goes if you have a high lift intake and exhaust on forced induction engines, you end up blowing all the boost straight throught and out your exhaust when overlap occurs, everyone I have spoken with suggest standard exhaust or close to it and higher lift intake to enable more air/fuel to get crammed in there. You'll be best with adjustable cam wheels to play with cam timing to get the best out of it.
Plenty of people in here know more about it than me, not up to that stage yet myself.
Sounds like a great project :D

[Pope1]

Don't know much but that theory sounds reasonable to me. My car has the standard VX exhaust cam but the inlet one was changed to the one from the 2L IE to improve breathing at higer revs.

[Fingers]

You have to be careful with the amount of lift aswell, apparently any more than about 0.5 mm more than the standard lift and you'll need to dry build the engine to check the valve to piston clearance, standard for the VX engine is 9.2mm actual lift, not effective, effective is probably about 9? Please correct me if that's wrong. But yeah, I've always heard that it's better to do just the inlet cam, and those cams you have sound pretty good.

Pope1, has the Beta IE cam made a big difference, I was going to try this but got A GC IIIA for a good price. I'm interested to hear. Did you fit the cam yourself?

[Pope1]

I knew someone was going to ask the before and after question.

Don't laugh, but the answer is I don't know because I never drove the car in its stock condition. I saw the car advertised in the UK and got a friend there to buy it for me. Then it went off to GC for some mechanical restoration and it was only after that had been done that I went to the UK and drove it before shipping it back here. I should add here that I had owned a Beta coupe' some years before, when I lived in the UK, so I had a pretty good idea of what I was getting. What I can tell you is that it was GC's idea that the IE cam should be fitted to compliment the head work that he had done on it. Apparently it was standard practice for him when building a fast road VX.

[Fingers]

Bugga, never mind, just curious, I've met so few people with a VX let alone any that have done any mods.

[Hamish]

As the saying goes - been there done that - but not with an IE cam, only a 130TC inlet which made an appreciable difference. I've only heard good things about the GC111A cam, so should be an interesting add-on.
Fingers, send me a PM, have something coming which might interest you..... :!:

[Wallace]

And I would think way to high a compression ratio. Unless you have a cheep source of high octane that is .. .