I would like to know some of your opinions on the maximum amount of lift that I can get out of my lo3 heads.The motor was purchased from s&s engine remanufacturing, so I know the heads have been machined for new valves and shaved down a bit,Not sure on how much though.They told me that if I wanted to exceed a lift 0f 480, then all I would need to do is get stiffer springs is this true?

 

Stiffer springs don't have much to do with lift- spring rates are matched to the cam.

The hard limiting factor on lift is either the point of coil bind on the springs (when they "flat stack" and won't compress any further) or the point at which the retainers hit the valve guides/seals. You don't ever want to get any closer than .050" from either of those events. On a set of dead-stock L03 heads I pulled from a 92 Camaro the retainers would hit the guide seals at only .440-.450 lift (surpisingly low!). The stock springs could actually take much more lift, but didn't have the necessary tension (spring rate) to control anything like a "performance" cam.

 

Can I Hi-jack this thread? Two Questions.

What is the Maximum Lift for a 1988 L05 Head?

I want A better cam than what i have(Stocker).. I was looking at 270 Duration, and around a .480 lift.. Is that too Big for a computer controlled engine?

Thanks, Nick Hall

 

Without knowing the full specs, Id say that it will likely cause interference, and may be too big for the motor. In addition, the stock heads flow like crap, so youll strangle the motor at higher RPMs where the cam makes its peak power.

 

I couldn't say for sure, but like I said, above, my stock/original LO3 heads off a 92 had the retainers hitting the guide seals at less than .450" lift. Plenty of room with a stock LO3 cam, but not nearly enough for anything but a very very mild performance cam.

Not all heads are the same. Most factory SBC heads will take around .470 without modification (limiting factor, again, is usually when the retainers hit the valve guide/seal), but that's not a guarantee on any given set of heads. Obviously, my L03 heads would not have taken that much.

Stock springs can take about .500" lift fairly easily without binding in most cases, but they lack the pressure to control a performance cam at higher RPMs (they can barely keep up with a stock cam).

 

ok, thanks I just wanted to get some good info from great people such as yourselves. I'm not really sure on the specs for the heads
either the only specs I know are the cam,which is 203/450 and that the block has been bored 30 over.

 

Actaully, thats a fairly good cam for a stock engine. So long as the overlap is ok for EFI, it should run fairly well. Keep in mind that you will need to tune the ecm.

 

What about the duration, Should it be safe to go into the 220-230 range? I just want more of a noticeable idle.

 

When the heads were re-worked did they replace the stock press in studs for screw in units? if not I would spend the money now to have that done. Cams with lift past .480" really require it or your chances of pulling a stock stud out of the head with a high lift cam increases.

 

I'm not to sure about that I'd have to call the company that I bought it from to find out.I think that 480 is where I want to be with lift, so now the question is the duration of the cam. I want something that will give me a little bumpty bumpty .

 

Now that I actually have a LT1 cam out in the garage, what's the lift on the LT1 cam ? With 1.5 or 1.6 rockers.

Yes I have stock LO3 heads, hmmm and I suppose 305 TPI heads are the same way ?

 

305 TPI heads are limited in the same way. There were different cam specs for the LT1 throughout the years. Refer to the LT1 cam digest up top for links that chart the specs as the years went on.

 

hrmmm I'll have to look at the cam or the box to figure out which one I have, i.e. which LT1 cam I have

But, with 1.6 rockers, I shouldn't have any problem with stock LO3 heads ?

 

I would not risk it. I would stick with the 1.5's. Although you may not exceed the stock lift (you should measure since cast heads can range from .450" to .490") you will be have a high likelihood of pulling out the stock pressed in studs. Lifts that near and exceed .480 (which you can't do on stock untouched heads) really require screw in studs.

 

Shifty, I think he is talking about 1.6:1s on the factory peanut cam. If so, it will make it something like a stock 350 cam, .37x, .41x lift.

 

Oh maybe I miss understood him. If that is the case than Fast is right. 1.6 rockers on the stock cam will be fine, will yield nice results, and work on stock heads.

 

Is there anything to worry about more duration other than tuning?

 

Actually I was talking about 1.6 rockers together with the LT1 cam.

So besides screw in studs, what else would be needed to be done to the LO3 heads ?


For some reason I'm not getting any notification about new posts in the thread hmmmmm

 

What about duration on the lo3 head?

 

What's needed to be done, in order to run a LT1 cam and 1.6 rockers on a LO3 head ? Any machine work ?

 

You ran run just an LT1 cam on your stock Lo3 heads with nothing more than a new set of valve springs and retainers.
However, if you want to run an LT1 cam and 1.6 rockers you will need to have the valve guides cut to accept higher a lift cam (stock heads are limited from .450" to .480" max lift). On top of this, as you noted, you would also want to have the pressed in studs removed for screw in units. The cost of these two processes to your heads out weighs the gains by adding 1.6 rockers. You would be better off putting that money towards better tuning software.

 

Cutting the valve guides huh ? ouch how much does that usually run ?

I'm looking into all options right now, quite a bit to look into, for instance I've heard one can get valve springs cheap, and then I hear stay away from the "Z28" springs ?

Is this is also the case for aluminum L98 heads ?

 

I think the aluminum L98 heads are different and can accept cams with a higher lift.

As for machine cost having the valve guides cut isn't that much. I want to say it ran me only like $100 or so for both heads. It is around $200 to have the studs replaced for screw in units.

People say stay away from the "z28" spring because they are prone to failure. Any comp or crane spring that matches the cam will suffice. That will run you around $60 or so.

 

So unless I can find some aluminum L98 heads (not even sure where I would find them, if anyone knows, let me know) I guess I'll go with the cam and springs only and leave the rockers alone for now.

 

If you are also new to tuning I would go this route. A cam alone will give you enough to worry about for a first time tuner. Practice on the stock set-up first and really get good with just a cam swap. From there I would look into different heads and such.

 

so to add to this discussion, my stock 88 305 (LB9 engine) had the common 1.94, 1.5 valves. im lookin to get my block bored .060" over, shavin .010" off the heads and porting/polishing the manifold. .350 int .384 ext is the stock lift 179 int, 194 ext is the stock duration, i will upgrade my pushrods and rockers but they will stay the same length and same ratio. now u know my engine and situation, and without getting another computer chip or reprogamming the computer(because the stock one is impossible to reprogram), what is the biggest cam i can put in that engine?

Gramps