Cams for Turbos

[Anonymous]

Yet another consideration in the turbo mod system- the cam.

In the world according to Corky Bell (Maximum Boost), turbos hate valve overlap. He actually recommends stock cams over the aftermarket stuff for a lot of applications.

In the world according to Crower, Comp and Crane (judging by their selections of turbo/supercharger cams) they agree with Bell. The cams generally have wide lobe center separations- 112-114 degrees. And a little lower lift numbers than your average performance cam.

Anyone out there have any thoughts/opinions/experience on the topic? I'm thinking one of FSPP's 264 D grinds, maybe with some wider lobe separation, may be a good starting point for my (eventual) project.

--mikey

 

[Anonymous]

For the first stage of your project, I'd stick with a bone-stock cam. It is cheap and will work great with a turbo. You might consider throwing a late-model 250 cam in there -- it might have a bit more lift than a 200 cam, but I certainly wouldn't chase cams until you have your system up and runing right.

I worked on a turbo Coupe engine rebuild several years ago where the owner wanted just a bit more performance out of the engine. We suggested he switch from the Ford turbo cam to the cam for the normally aspirated EFI 2.3 engine, and he was thrilled with the result. IIRC, the n/a cam had a tenth more lift, but the same duration.

Keep us posted!

 

[rbohm]

8) stan is right about the cam. while it is true wider lobe centers are recomended for blown applications, the stock cam also works very well.

 

[Anonymous]

I've run from 114 to 108 on one of my 302's and 106 to 113.5 on a 2.3.
Right now I am using a 110 in my present 302 and it LOVES it!
The last 2.3 SVO I had used the factory 237 roller camshaft which I think was 110. I ran it 2 degrees advanced and it would rev to limiter at 6750 with no hesitation at all.
What I think these guys fail to mention is that the centerline changes the point of maximum power. Yes its true it blows some of the charge out the exhaust at lower rpm but when rpm is above 4000-4500 the engine wants
the added duration to cram the same ammount into it & get it out.
I noticed a .600 second improvement by going from 114 to 110 in my latest 302.
The drawback is that my low range below 3000 feels like the same old N/A 302. This is fine for me because I don't drive it on the street much.
In my case my sicentificly calibrated butt tells me I made a good choice for both engines, however for most people I would stay around 112 or 114 to improve low end performance.
BigTorque

 

[Anonymous]

The following is just speculation, if a turbo cam was to have too much overlap (duration) which I understand too mean that both valves are are opened "together" for longer to assist breathing at high rpm. Then any pressure from the forced induction of the turbo would be largely lost (as it goes in more would go out of exh) . Isnt this the reasoning behind not having too much overlap with a Turbo.
One other thing to consider is that wide Lobe seperation of up too 116 degrees seems to be used for a turbo cam to help get around this.
The lobe sep angle seems to make a greater difference than most would think. C.O.M.E cams have one that is a 217/218 at 50 (CLH 197) duration and they are brave enough to advertise (with that duration) that it will work with stock or near stock converter and gears. It has 114 lobe separation. (wide lobe sep has better vacuum at idle)

 

[Anonymous]

ur pretty much right there tim.

i personly find that most small towing cams is all you need on a turbo assisted car, alternativly you can go for a high lift low overlap style cam.

mine has 206 deg on on intake, 214 on exhaust @ 0.50 total lift is 530 thou and combined with the rockers i have i now have 590 thou lift.

the small toeing style cam works well i had one on my ea ages back, @ 10psi it make 240rwhp@ 6300rpm

then at 15 psi it made 290rwho@6000rpm
22psi it made 345rwhp@5700rpm
then the final 32psi it make 465rwhp@5500rpm.

the cam was a crow cam made to work with the factory ecu computer so it was a baby cam but with the more boost it more power at a lower rpm point and we tried revving it more to see if we could generate bigger numbers and power actually fell of abouve all the above typed rpm points.

cheers.joe.

 

[rbohm]

8) most bulders use wide lobe centers to trick the engine into thinking it has more compression than it really has. that is why rv cams were so popular in the late 70's. they were basically a cam with a bit more lift, baout the sane duration, but wider lobe centers. it was a cheap way to improve power where most people wanted it, and it improved fuel economy because cylinder pressure was higher, and because efficiency was improved.