what are the basics to look for when selecting a blower cam? any popular choices for a hydro roller cam?

 

Depends on what you're after. For a mild street setup you want to keep the lobe separation pretty wide (~114) and quite a bit more exhaust duration than intake (+10-14*). That will help the engine be EFFICIENT with the boost you give it and not blow a lot of mix right out the exhaust during overlap. With small blowers you don't want to waste any of the precious airflow they provide by letting it flow right out the exhaust.

For a real high performance application or racing that's got a blower with plenty of flow potential you can go tighter on the lobe separation and not such a big split in duration. More like a N/A engine that can really move some air in the upper RPMs. Yeah, you waste a lot of boost right out the exhaust, but you just pulley up the big blower some more to compensate for it.

 

Like Damon said it depends on what set up you are going to have: FI vs Carb, small blower vs big blower, amount of boost, street vs strip and so on..... compcams has blower cams listed Here with short descriptions for application hope this helps!

 

yes, EFI or carb?

 

EFI, its an 88 TPI mas air system (i know it sucks, but its what i got) on a so far stock 305, my setup will be basically the same as JY89Turbo's, cept im using slightly larger turbos... im trying to get my hands on a set of the T-bird .60/.48's as i type this. its more of a street strip setup, i've heard that the stock TPI/LT1 cams are actually pretty good (cept for the small lift), but i really want a cam with a decent lope in it, even if it doesn't help my performance... as long as it doesn't hurt it... and i do have 4.10's gears, and a 2600 stall so if i lose a little bottom end i should still be ok... this is in an S10 BTW

 

hows the zz4 cam?

dur @ .050.... 208/221
lift................. 474/510 (1.6 rockers)
lobe sep........ 112

i realize this wont give me much of a choppy idle, but it fits my budget at $130 off ebay, and so far it matches your requirements... 13* more on the exhaust dur, the lobe sep is only 112, instead of 114, but it should be ok right?, and i think its got more than enough lift

BTW i plan to push 10 psi, turbos should be spooled by about 2000-2500 RPMs

 

First thing that you have to understand in selecting a blower cam is that in most cases it's just a matter of compensating for the deficiencies of the engine (mostly heads, intake, exhaust…) and secondly pressure management.

If your heads are ported to match the optimal requirements of the engine typically you'll have the best/broadest power band with something approximating a small, single pattern cam.

That being said, for most blowers (roots or centrifugal) the closer the rest of your setup is to right, the more the cam will look like a normal, NA cam, large splits and greater LSA's are there to cover up other inefficiencies. Typically with centrifugal blowers used in street cars there is also some "lets make more low end where the blower sucks and let the blower make up for the small cam up top."

With a turbo the equation changes a little since the turbo effects the pressure in both the intake and exhaust ports. Since in most cases (unless you're talking about a killer exhaust setup)there is 1.5-2.5x the pressure in the exhaust port you'll usually gain some by a reverse split duration cam, where the exhaust lobe is actually shorter then the intake lobe and some extra LSA helps to prevent harmful overlap.

For the most part, a cam that works well with a turbo will not have any thump to the idle unless the engine is intended to run A LOT of rpm, MUCH more then a comparable NA cam