At what point in the performance mods do the stock cast iron L98 heads become the limiting factor?

Keep in mind my desire is not to make a race car, but to just have a nice performance boost for my Z. Maybe mid 13's??

Is that ridiculous on stock L98 cast iron heads?

 

Mid 13's can be done pretty easily on the stock heads. They are alot better then people give them credit for, stock they flow almost as well as LT1 heads, and have relatively small combustion chambers (compared to fuelies for example). The true limitation is the TPI setup, it just does not want to make power over 4500 rpms due to the long runner setup.

 

whats the limitations of L98 alum vette heads?

 

Please for any more replies by stock I mean no porting, no spring upgrades, nada. Just as they came from the factory (37,000 miles not withstanding)....

 

Then they are a major performance limiting factor, now.
Right after the stock exhaust manifolds, stock exhaust system, stock camshaft and stock TPI intake manififold and runners.

You're really making life difficult for yourself by not taking advantage of the increased airflow available from porting your own stock castings. Simple physics, more airflow= more power.

Very few or none of the popular aggressive performance camshafts will work to potential without new, better valve springs. Without the proper valve spring, a aggressive performance cam is likely to valve float even at a lower rpm than the stock cam does.

If you want to turn a 15 second stock TPI Camaro or Firebird into a 13second performer you're going to have to make significant performance mods. The heads are a great place to start. All the other addons and mods will work much much better with improved port flow and valvetrain hard parts. There is no downside to porting the heads. Except maybe the time required to do it.
All the wishfull thinking won't overcome simple physics or help push the car down the track.

People have been modding chevy small block cylinder heads for some 50+ years. No need to reinvent the wheel here. Just copy what others have done. All the info is available here in these threads and more in your local library and online on various e-mag articles like Car Craft etc.

 

i would not recommend porting a set of stock L98's, unless they are the alum's....somebody has a ported set of iron L98's for a couple hundred right now in the PARTS FOR SALE section....but i would get some edelbrock heads or something...you'll spend about the same money on completely new heads as you will on getting yours ported, and aftermarkets perform 100 times better...

 

Yes, I understand the much improved potential of aftermarket heads, but I'm not trying to make a race car here.

So, the bottom line sounds like if I upgrade the exhaust, intake/runners, small cam increase, only then I will be to the point of actually NEEDING better heads to make more significant gains.

I would really like to do heads, but that nearly doubles the cost of what mods I'd like to do for now.

If you would, please check my other post "Opinions on this combo for moderate upgrade." and comment.

I think I've read and interpreted enough stuff here to put together some mods that will work well together up to the point of stock head limitations - but that is essentially what I'm asking in that other post.

Thanks for input so far.

 

For $400, tops, you can port and polish your L98 heads as well as have them completely rebuilt. And they will flow like Vortec heads if you are patient and do the necessary work yourself. It is NOT hard to do. Yes you can do it--unless you are a quadrapalegic.

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