Since I’m at work, I’ve got time to think about things like “isn’t it possible to use 1.7 rocker arms with the stock Fiero camshaft?” and things of the sort.

So, how about it? If my stock camshaft lift numbers are right: 0.410 exhaust, 0.394 intake—and my numbers on the Crane H272 camshaft are right: 0.484 exhaust, 0.454 intake—then why would it not be possible to use 1.7 ratio rocker arms with the stock camshaft? The word around these forums is to use 1.5 ratio arms with the H272, which—by my numbers—would equal 0.72 and 0.681 exhaust and intake valve movement (respectively), which is still more than the stock camshaft would produce with 1.7 ratio arms (0.697 exhuast, 0.6698 intake).

Am I missing something here?

yes, if you can find them, you can use them.
the higher ratios do add extra load to the cam shaft & pushrods.

You have to use Crane rocker arm studs p/n 99148-2 to convert to the 3/8" thread and then you can use and FULL ROLLER chevy small block V8 rocker arm you want.

I bought Summit's 1.7 ratio aluminum full roller rockers for $16 a piece.

I thought about doing the same mods, but I now have desktop dyno and this program is very addictive.

I ran the extra lift and it didn't seem to gain much as far as peak or powerband goes. Lou did you notice any increase? i have a comp 260 which has .440 lift and with 1.7s the lift would be .498 and the gain was like a few rpms a powerband and a couple hp/tq. So is this program reall y accurate because if so the best cam is the carne 272 instead of the 1.7s on a stock cam.

my motor isn't assembled yet

it's a roller cam 3400 block with Fiero intake

Just out of curiosity. What other modifications do you need to make to run a bigger cam? Does the engine computer need to be reprogrammed, bigger injectors, or something else? How would the computer know there is a bigger cam without a MAF sensor?

I ran the Crane H260 cam .427/.452 with 1.52 rockers with perfection ... see the second graph ... with no changes to the computer, Tomco FieroStore injectors and and adjustable fpr set at 45psi at idle.

With the roller cam from the 3400 and 1.7's I'll have .464/.464 inches of lift and a peak at 5200 rpm right where I want it for a potent street motor.

[This message has been edited by lou_dias (edited 06-18-2006).]

quote Originally posted by SCCAFiero: Just out of curiosity. What other modifications do you need to make to run a bigger cam? Does the engine computer need to be reprogrammed, bigger injectors, or something else? How would the computer know there is a bigger cam without a MAF sensor?

If you put a big enough cam you need to tune it to get the max out of it. The ECM will not compensate for WOT. Increasing fuel preassure will do some. I did get 146hp with the stock 3.4 cam with poor mail order tunning.