Ok, getting the final paperwork done on the Iroc. It is 85 Iroc with LB9.

I am going to start modding this car like crazy over winter. I need some advise on what to do.

This is what I have in mind:
1. Mach Underdriver Pulleys
2.SLP Headers
3.Custom true dual exhaust, with c/o after the heads
4.Air foil
5.Homemade cold air intake
6.Possibly LT1 Intake

Here is where my question comes down to, the heads on the LB9 are supposed to be very restrictive, so I am going to go with a set of Aluminum L98 Heads. I want to get the heads port and polished, because most likely I will be stripping the TPI setup off the LB9 and dropping in a L98(w/o setup) and swapping the TPI back on the L98. But this is a long way down the road, probally more than a year, if I even do it.

What would be best to go with a set of port and polished L98 heads? It has really come down to either a LT1 or LT4 Hot Cam. I think that the LT1 would do just fine, but my freind thinks that I would get more power out of the LT4 Hot Cam.

And with those mods what kind of times would the car be capable of pulling at the track?

 

<h1>Ern,</h1>
(That's "Big Ern" for the rest of you...)

Before you spend a dime on the underdrive shaeves, ask around for some real data on the HP gains and timeslip improvements from the change. I think there are a lot more cost effective ways to get 2HP. Don't believe the advertised claims - get some dyno sheets and/or time slips.

Ditto on the throttle body air foil. Unless you can pick up a used one really cheap, don't waste your money.

A LT1 intake will significantly change the torque curve on your engine, and will affect the optimal cam selection, so you really should decide if you want to do that before anything else. Installing the LT1 base will negate the need to port the plenum, runners, etc., but NOT the heads. If anything, it will expose the weak flow of the heads even more.

The larger chambers of the L98 heads will lower compression on your 305, and you will get valve rim interference with the smaller bore. The net result is that you will at least shroud your valves (if you don't crash them into the deck) and lose power from lower flow AND lower compression.

The '416 and '061 castings can be made to flow well if you spend some time with them. The money you would have wasted on an underdrive setup could purchase a die grinder and burrs to open up the ports. You can increase the valve face sixes on the 305 head castings to 1.94/1.56 if you're careful about shrouding.

And if you get a die grinder, you can improve the restrictions in the plenum right behind the throttle body and get a lot more gain than an airfoil would provide. You can also gasket match the plenum, runners, and intake base for even better flow (if you don't change to the LT1).

If you don't want to port your own heads, at least check out the World S/R torquer 305s.

The headers and dual exhaust are going to make an improvement that is worth the cost. It would be good if you could install a balance pipe somewhere behind the cats for best scavenging and flow.

Keep doing your homework. You're on the right track. Just don't overlook the cam and fuel delivery after all the other changes are calculated.

 

i have the world products s/r 305 heads that have been poted and polished along with the hot cam and a fully ported tpi setup. i still have the stock chip so, but the car runs cosiderably better. when I get the chip I will be able to start tuning. i will post with the results.