ziggy89

So building another motor. Doing it on a budget for a strip only car. Have everything to put a 383 together except a rotating assembly. Was wondering my where my 062 vortecs will stop breathing at rpm wise. Curious so I can pick a cam. Was hoping g to shift around 6k. Thinking comp xr274r-10 which is a solid roller 236/242 duration and .564/.570 lift. That too much for vortecs? Valve guides already machined. Any thoughts appreciated.

sofakingdom

iTrader: (1)

Hard to say. Probably about 6k, give or take, on a 383, assuming the CORRECT porting has been done: which is, the LEAST POSSIBLE required to remove casting irregularities. Meaning, the basic shape and size of the intake port is left TOTALLY UNALTERED. All you're going to do is, clean up those funky steps and angles right behind the valves where the factory just kinda jammed the seat cutter in, and MAYBE, if it's REAL BAD, take out the parting line between the parts of the casting. The exh port is just like any other stock SBC exh port though; whatever your head specialist does to any of those, will work just as well on 062s.

Depends on how, and how much, they were machined.

Pop acoupla valve springs off and see how far the valves go before bad things start to happen.

You're going to need some SERIOUS valve springs for that; they'll have to be 1.550" OD, or, you'll have to go with some of the more $$$ beehives. Aka, LS6 stockers won't cut it. You need something in the 180 - 200 range on the seat and 450ish over the nose. Stock valves also aren't gonna cut it: they're way too soft for the forces they'll have to face. Get ones with longer stems. Which will also ease the guide clearance issue.

ziggy89

Don't have a head specialist. Just always gone by a rule of thumb the stock heads with minor touch up work like a longer duration for the exhaust. I just don't want to run this thing out of breath at 5k rpms. I'll sell what I got and buy some cheap aftermarkets of that's the case.

sofakingdom

iTrader: (1)

I should also add, Vortecs are said to experience "port stall", wherein once the lift gets too great, and the restriction created by the opening ceases to be the factor that limits the flow, turbulence RAPIDLY sets in. You should consult with somebody that knows ALOT more than I do about this sort of thing and make sure you stay out of that kind of trouble.

Or, instead of an off-the-shelf cam, you could go with a "custom", such as from Bullet. You could use something like a R260/375 intake and R270/363 exhaust. The idea being, keep the lift low, the exh duration about 10ish° more than the intake but lower lift, and optimize it for torque rather than RPM. Another tactic might be to look through the Comp catalog at circle-track cams and pick out one for short, tacky tracks with tight corners. Or even something tried & true like the good ole 288AR6.

cardo0

Well it becomes complicated when using stock electronic fuel injection. Stock ECM's seem to behave better with a 112 degree LSA or wider. But your stroker and stock vortec heads would perform better with a 106 LSA. And the vortecs are a pretty modest lift head where over 1/2" valve lift doesnt increase much flow. If you are ignoring street manners Isky has a cam on the shelf with modest lift and tight 108 LSA, the RR-490 ROLLER:http://iskycams.com/cart/index.php?m...roducts_id=281
And it revs past 6000 RPM. I would install that cam with 1.6 rocker arms.

For a ECM friendly 112 LSA I like the crane cams SR-228/338-2S-12 IG using 1.5 rocker arms.

This kinda puts your comp xr274r-10 in between those two doesnt it? The comp cam has possibly a little bit too much lift but more than likely a harmless amount.

Hope this can help.

ziggy89

I'm not worried about computer tuning. Car is getting a carb. I'll look into those cams. Don't mind a tighter lsa because again carb and track only. Big part of looking at that xr284 is the numbers are almost identical to my xe274 that I have in my 91. (383 with 195 eliminators)