Alright, here is what im working with, a pretty fresh (10k since I built it) 355 with stock style compression pistons (stock for tbi 5.7) 2500 stall, 3:73 gears

Im ditching my tbi setup and going to go with a 427 ecm with maf and for the hard parts, im getting vortec heads, holley stealth ram, and an lt4 hot cam profile cam.

Now my question, i dont want to do the roller lt4 hc for cost reason so im wanting to do a fairly similar hyd flat tappit cam. Whats is one you would reccomend? is there one that may be a little better suited to the hsr and 10ish to 1 comp ill have? lopey idle would be nice and seems the hc has some, im also wanting over .500 lift with 1.5 rockers, not 1.6's.

Spring reccomendations, lt4's i assume?

Thanks, chad

 

There's not really a "fairly similar" one.

The design of the flat-tappet system places a limit on the rate at which the lifter can be raised; i.e., some max # of .001"s per ° of duration. With careful computer modeling of the stresses and such as that (or ALOT of trial and error), it's possible to stretch that limit a little. Not much. This has to do with the "flank" of the cam lobe, and the angle that it meets the lifter face at; if the "flank" is too steep, the lifter won't rotate, and it will fail within a few hundred miles, or less. A larger diameter lifter helps, because then the nose of the cam reaches the lifter face closer to the edge; but this requires $$$$ machine work $$$$ to the block. Costs more than a whole "retrofit" roller system.

Rollers have no such limit. You can build a roller cam to accelerate the lifter as fast as you want, up to the point at which you start pulverizing valve train parts (literally).

Which is why flat-tappet cams with short durations like that little bitty HOT cam, ALWAYS have lower lift than rollers.

To get higher lift with a short-duration flat-tappet cam comparable to the HOT cam, the easiest way is with higher ratio rockers. That sidesteps the lifter acceleration limit.

I don't know why you would have some kind of objection to using 1.6 rockers. Even the HOT cam, if you buy its "kit", uses 1.6 rockers to get its .525" lift.

My suggestion would be, watch eBay for somebody selling the whole factory roller setup out of an engine (lifters, dog-bones, spider, retainer plate, and hardware); and get a roller cam. They're on there all the time. Usually go for $100 or less.

The more aggressive the ramps on the cam (i.e. the more .001"s per °), the more spring you need.

LT4 springs are GARBAGE. They're just yerbasic stock GM crap. Don't even bother, for any kind of lift over about .500". They're still only 1.25" OD, and like any 1.25" OD spring, it's impossible to get enough seat pressure out of them at lifts above .500", without ending up with coil bind, or just breaking them. That's what usually happens to people who use them (including people who bought and installed the HOT cam "kit"): they break. Get the Vortecs already upgraded with larger ones, or with beehives.

 

Thanks for all the good info, i think i may just upgrade to the roller setup after all.

 

crap i forgot to ask. anyone have a suggestion of what injectors i should use?

 

24 #/hr Bosch such as these or these

 

alright, and finally my last question i think, for rockers i am going to go with 1:6's i guess, i dont want to blow my budget on some real expensive rollers, im perfectly fine with non roller rockers, any brands u can trust that arent super expensive? models?

 

Comp 1416

 

Vortecs and stealth ram? Oh yea, they do make a special stealth ram for vortecs right?

Side note, and i've been wanting to ask this for a while - Is it possible (common?) to bore out the lifter holes in the block to use a .904" chrysler (or other?) lifter? Then just get a custom machined SBC flat tappet cam with more aggressive ramp rates?

And on the same token, do the same with roller lifters? Use larger diameter roller lifters and up the ramp rates again?

 

Possible, yes.

Common, not really. Not at our level anyway. A little too much $$$ for what little bang you get, unless you're in a restricted class that's SUPER competitive. Yes, you do need a cam designed accordingly, to get the full benefit. It helps if you use one with larger journals.

Doesn't really help with rollers.

 

those are not self aligning, and if im not mistaken you cant run guid plates with screw in studs.

Plus i dont see it worth the money for roller version rockers. If i had the money...maybe.

 

You are...

That's how you attach guide plates to heads.

Why self-aligning?

If that's what you need, use 1418 instead.

Here's how guide plates and screw-in studs look.

 

i dont think vortecs use guideplates or are setup to run them without machine work, so go with the comp 1418's

i used them for my L98 and they worked great! great price. best place to get them is on ebay from a seller named discountperformanceparts.

http://cgi.ebay.com/ebaymotors/COMP-...spagenameZWDVW

170 with free shipping and a free t shirt summit wants 211 shipped

 

ok my machine shop guy said i could run the guideplates, why wouldnt i be able to??

I can cant i?

 

i think the heads need work to allow guide plates to bolt under the rocker studs and the pushrod hole enlarged. I'm not sure tho but i dont think they ever came stock with guide plates so dont use them since you dont have to. simple self aligning rockers are more than enough

 

The reason im asking is because i am going to do a full roller rocker after all, its either a non aligning rocker, with guideplates, and hardened pushrods, or Self aligning rockers and stock pushrods, it was gonna come down to price or if i could even use the guideplates.