Rob, spill your cam knowledge guts here

[87natty]

I'm looking to cam the GN, I've so far looked at two, one being the Edelbrock and the other being an Erson 208. I might go peep out an Isky too, but anyway, we were talking about this piss drunk New Years Eve. I remember the chat, just not the numbers and everything in between.

Spill the beans Rob.

[SuperSix]

Doesn't Leppizzle know a lot about cams?

[87natty]

Maybe web cams?

[Recklessrob]

First off, what are your goals ? Any internal engine mods ? Any work done to your heads in particular ?

[87natty]

OK, back on subject. Stock heads, port matched, bigger valves. I REALLY want to keep it a flat tappet, but a good argument for the roller setup will be heard, definitely. I also have the issue of California smog laws, and while I can get away with any visual inspection, I need to burn clean so I don't want some radical cam profile that sounds like a heart attack at idle.

As far as I remember, no block mods are needed for a roller setup right? I'll also stick with a stock timing setup too. The buy in for the roller is a little steep for me, but finding additives every oil change would be a pain in the ass.

I'll also be using Sylvan's turbo, but I have no idea what size it is, so he'll have to chime in here. I'm also looking at a front mount IC, and 50# injectors soon. I just really want to fuck shit up on pump gas reliably. Daily driver, remember.

[Recklessrob]

Chances are with your heads having oversized intake valves, they likely
have the valve guides cut down as well. That needs to be done to accomodate
any net valve lift over 0.420". If not, flat tappet is your only option since most rollers start around 0.496" net lift. As I told you on New Years, very little cam is
desirable in a turbo car. It is very common to see many who are over cammed.
Too much cam on a turbo car is counter productive as it begins to act like an EGR valve as duration increases. Thus quenching combustion.
My personal cam of choice is the Comp Cams 69-200-8. This is the same cam
that I used in my own build up and in customer's too.
with a stock rocker arm ratio of 1.55 it nets 0.496" of valve lift and 206 deg duration
@ 0.050" Now compare that to Comp Cams 69-248-4 flat tappet cam with a stock rocker ratio. (0.459" valve lift with 206 deg duration @ 0.050") 0.037" more lift at
the same duration. How much better do you think your heads flow with 0.037" of lift ?
Pretty much a no brainer here... On my engine, I took that a little further with the
use of 1.60 ratio roller rockers. Not only do they reduce frictional loss and reciprocating weight in the valve train, they bring net lift to 0.512".  0.053" more lift than a flat tappet cam with a stock rocker ratio at the same effective duration. I
could have used higher ratio rocker arms, but there are some pushrod clearance issues that need to be addressed when doing so. Because roller cams offer faster lobe ramp acceleration and aren't subject to the frictional wear/resistance that a
flat tappet cam has, flat tappet cams have become obsolete. Thats why all the automobile manufacturers have switched. They didn't do it to save production costs,
but because its become a necessity.

FYI; Another testament for low duration roller cams is Grumpy's daughter Melissa's
car. 212 degrees duration @ 0.050" (I don't know the net valve lift) with Champion ported irons- 9.70's @ 138+mph !

[Recklessrob]

I believe Sylvan's old turbo is a PT-51.
Why not run 60s or the new 79s that are high impedience and stock appearing for injectors ?