ok, well i was doing some readin on heads. there really difficult for a broke highschool student to make... and if a mistake was to be played out.. well holly hell il be in trouble. anywho i decided to go with a pre-made set of heads. i found these edelbrocks for 650 bucks

SB-Chevy Victor Jr. Cylinder Head
Assembled
215cc intake ports
64cc combustion chambers
2.080'' Int/1.600'' Exh valves
1.550'' valve springs
.650'' max lift
7/16'' rocker studs

now with the 215 intake ports that means i wont have to do any porting.. thats good. now i decided on a cam from comp cams

operating range 2200 - 6200rpm
duration 292 in. and 300 ex.
valve lift .584in and .579
lobe set angle 113 degrees

now i know i will get better preformance out of this upgrade. but will my bottem end handle it? and since the heads can take up to .650 valve lift, should i get them machined down or better compretion? should i replace the valve springs with be hives or are these good enough for my car? lastly, if i decide to go with these heads will these heads even fit my car?

 

For 1300 there's a whole huge selection of heads available. I'd get some TFS heads first or spend 100 more and get some AFR's.

 

i hope youre not planning on using this monster as a daily driver. That's one BIG 'ol cam to be dealing with every day. and with the power potential of that baby i'd be more than a little worried about a stock bottom end. as for those heads, if you're getting them for $650 for the pair, it's a good deal, but if thats for one head, madmax's got a good point.

 

That is a SERIOUS combination...

It won't idle well and will suck more gas than a broke student can afford. Yes, you'll need new valve springs, push rods, and better than stock rockers.

The low end torque will go away with this setup but you'll make lots of power above 3k rpm. You'll also need to do some work on the tranny and converter for this combo to work well.

Cheap doesn't make it the right set up.

 

I think you need to rethink your build taking into account the fact that you are a high school student and build something more prudent for a DD for now.

Maybe take the money you save from this evaluation and buy a nice roller and take your time with a proper build on that.

You also need to take into account all the ancillary costs with a motor such as the one you are planning.

 

ok, well thats good, this is what im after... good opinions.. im not broke, jsut in high school.. and a little broke haha...ok to big... well tahts cool, my second option is comp cams .520 in and .515 ex. will the stock heads work with that? i could always pull the heads off and port them to match me ported plenum, slp runners, and intake. you see i have ported those alrady to make room for somthing better.

so waht is the stock cams specs on the L98?
what is the max lift for the stock heads?
do anyone know the flow # on my stock heads?
stock combusting chamber sice in cc?

if someone knows this info i could make a milder buildup

ps.. 650 for one head!!! wow

 

im not positive what kind of lift the your L98's can handle, but it's nowhere near .520 lift. If it were me, i'd keep it under .470 without some machine work and springs.

on a personal note, im running a lunati voodoo coming in at .468 I and .489 E. i've also got a pair of 416 casting heads I worked over. it's good for ~ 325hp, which IMO is just about right for a DD.

 

naw.. i need more power then that. i want something like 400-450... jsut personal.. anywho i was also told to look at vortec heads.. you got any specs on those... and by the way you should explain the whole chart to me.. i understand the combustion, and intake cc and stuff, but at the bottem.. you should explain that.

im going to be ordering new springs and junk. i will probably re-use the poshrods and lifters depending on that happens

 

The bottom half is a chart. At the valve lift on the left, the different ports at the top flows the corresponding amount of air in CFM.

The percentage beow the exhaust port numbers are is the average percent that the exhaust flows in those conditions of the intake flow. Basically, it's exhaust flow divided by the intake flow.

Keep in mind, they aren't using real valvesprings for this test, which is why they are able to get to .600 lift. In the real world, you'll never get there without machine work.

I've attached the flow chart on a stock Vortec head. As you can see, Vortecs are much better than your stock L98 head, but there are a few problems. I've read plenty of literature saying that they bottom out at about .470" lift. Any more than that and you'll need machine work. Another mayor consideration is the intake. Vortecs have a unique bolt pattern where there are two vertical bolts at each corner of the intake, and making only four per side, rather than the six you're used to.

Now on to your 400 or so horse motor. I'm a little worried about your stock bottom end holding that kind of power for any length of time. A friend and I built a motor a few years back that we dyno'd at 417 ft-lbs and 430-ish hp. The thing got our rubber bumper camaro going in a hurry. Here's what I still remember about it:

I only show you this to give an example of a 400+ horse engine. You really don't have to get that radical. Power is easy to make as long as you think it out. I hear Car Craft has a pretty good database on cylinder heads. If youre gonna splurge, do it on the heads.

With that in mind, you're gonna have to do some a decent amount of modding on your factory TPI to get it to support the kind of power youre looking for. From what I hear, those things run out of air at 4500 RPM on a factory 350, so imagine how bad it'll be on an engine that can actually breathe.




EDIT: This flow chart is from before GM started including a 30* back cut on the valves. If you get a newer pair, the low-lift flow will be a little better than this.