I was at Twin city speed in brewer Maine today To order another Crane 2-272-H cam.
I wanted that cam and they kept trying to sell me different cams, lifters, springs and other stuff I didn't need/wouldn't realy need untill I told them I P&P, assembled and intstalled what valve train componets I had gathered from ebay and summit with no "cam help line", blue printed and machined them my self. Then they knew they couldn't trick me onto buying stuff I didn't need.
I have ordered stuff from them over the phone from Japan and I figured it was an import place. I go in there and 7/8 of the stuff there is chevy stuff or genaric stuff like valve traine parts or ignition stuff that could go on domesic SB and BB engines.
They had a box there that had crane gold lifters in it and just thought I would ask what they were for.
They are for chevy 60*-V6's, and they wanted to get rid of them because the guy that ordered them didn't have the money for them and that was like a year ago.
There a half 1.5 and half 1.6 set.
So I was thinking put the 1.6's on the intakes and 1.5's on the exhaust.
Sound good?
That way I don't have to machine the heads (my self) to deal with the lift if I put 1.6's on both sides and had .511'' lift on the exhaust.
That would give me about .480'' on the intakes and .480'' on the exhaust with the crane 2-272-H cam.
They only thing I need is the rocker studs from crane, I would have ordered them but I think I'm am running low on money till the next pay day.

 

I have never heard of anyone trying to mix different rocker ratio's on a valve train. Doesnt mean it can be done. Just curious it it would cause any problems since the exhaust valves are smaller than the intake and now not opening as much either. As well as any difference the cam makes. Let me know how it works. Didnt know there were any fellow 3rd gen'ers up in the Bangor maine area.... Cool

 

It's actually a common practice.. likely it was a mixed ratio kit from Crane, not just a jumble of rockers. Sounds like a plan... good find!

 

It is a more commen thing for ford guys to do.
You can get half and half kits made by crane and comp from summitracing.
The exhaust valves are smaller but normaly open as much or more then the intake with both lift and duration.

 

Its really common for anyone to do, but I was always under the impression you put the higher lift to the exhaust side. Because that is the weaker of the two.

 

No.. exhaust is usually of little concern. Think about it, the piston is forcing air out of the chamber via the exhaust. If it starts to slow down, the chamber builds pressure and increases the velocity forcibly, and by the time the piston is at the top of its stroke there's very little room for spare gasses... the chamber has no choice but to vent almost all exhaust gas. The intake side, on the other hand, is attempting to draw air in using a vacuum and a relatively large volume. Doesn't take alot for the cylinder to fail to fill to 100% capacity, thus freeing up flow is far more critical.

 

you should be able to order the studs separately from crane or comp cams. they have thier own p/n in the catalog, (caint find it now )

 

You need the flow on the intake because the air has to be drawn in, the exhaust is pushed out.
They put more work onto the intake side.

 

If that is the case then why do dual pattern cams favor the exhaust, if the intake is what is so important.

 

usually it's for emmisions, as most factory Poncho mills have the duall pattern cam.

 

Its definately not mostly for emmisions, because most performance cams are dual pattern also.

 

Is there an improvment by doing this? Or is it the same as using the same ratio for intake an exhuast?

 

Just curious- with a cam already in, will the computer have a fit?

 

Dual pattern cams are for engines where either added exhaust (PMD motors, that's why extra exhaust duration) or added intake (more intake than exhaust) duration is required for better flow on that side.

 

There will be an increse just from useing roller rockers over stock.
If I had it my way I would use 1.6's on both sides but these were cheap and they had them right then and there.
In my case there will be in improvement over useing both 1.6's be cause if I used 1.6's on the exhasut in my case I would have to remachine the valve guides. With 1,5's I don't have to.
This isn't making it duel patern because the duratoins are different for the for the exhaust and intakes.