Can I use those aluminum L98 heads on my 305. If I am not mistaken, don't these heads use 1.94, 1.50 valves, just like what are in my stock cast 305 heads? I have a TPIS Big Mouth Base, SLP runners, Ported Plenum to match the runners. I am also thinking about just using a L98 cam, do you think it will be enough with 1.6 rockers? And what size injectors would be better to use, the 19 or 22? I have both. I would like to break into the 13's with this setup.

 

Of course you can. I've used them for almost three years on my 305.

You are correct about the valve size on the Corvette heads, but the stock 305 heads have 1.84/1.50 valves.

Your plan for mods is very similar to what I've already done. I have the 52mm TB, TPIS runners, base and ported plenum.

The L98 cam is identical to the 305/5-speed cam (and with G92 in the later years). If you're running an automatic, you've got the peanut cam and it definitely needs to be replaced. If you're going to go with a different cam, go with something a healthier than the stock L98 cam. I'm running the Crane 2032 (214/220 @ 50, 452/465 lift with 1.5 rockers, 112 LSA). I am using 1.6 rockers for a valve lift of 482/496.

Everyone seems to think they need larger injectors with the slightest of mods. This is a major misconception. Larger injectors become mandatory only when O2 sensor voltage cannot be maintained over ~850mV with a reprogrammed prom and adjustable fuel pressure regulator. This can only be determined by scanning your O2 voltage at WOT. Look at my results with my stock 19 pounders. If I can run 12-flat with puny 19 pounders, I can conclude that you won't need larger injectors either.

------------------
Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous).
http://members.optushome.com/au/downunder1/rides/willie/willie.html

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

[This message has been edited by Willie (edited December 09, 2000).]

 

That was absolutly beautiful. Every single questioned answered. I personaly want to thank you for taking the time and giving the advise. I can't wait until spring.

 

You left out one thing. The L98 aluminum vette heads dont have heat risers. Will be a problem for emissions.

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92 Formula
305 TPI 5speed
1LE package
Mods: SLP headers,SLP catback,SLP air foil,ported plenum,K&N, Crane AFPR (47psi),MSD6AL, MSD wires, AC DELCO cap/rotor/plugs, Bosch O2sensor, 3:73s,JET fan switch, Macewen white face gauges, Intellitronix Digital Gauges

 

True, they do not. BUT it's inconsequential. I installed everything back on the engine (including the EGR valve) as though the heads have a heat riser. In Arizona, we go through an annual emissions check (visual and tailpipe). This tailpipe test is performed at idle and cruising speeds. My results (hydrocarbons and carbon monoxide) are as low as the previous year with stock heads. If you want my specific results, e-mail me and I'll provide the proof. Please note in my signature under my original reply that I state my car is "emissions-legal". I'm emphatic about this fact.

The performance advantage to not having heat risers is that the exhaust gases don't have any nooks and crannies (through the heat riser) to restrict flow.

The weight difference is also significant. Stock 305 heads weigh 44 pounds. The Corvette aluminum head weighs in at 19 pounds fully assembled. You couldn't ask for a better head for a 305.

Willie


[This message has been edited by Willie (edited December 09, 2000).]

 

Willie,
just wondering. The ecu doesnt shoot out any codes?

I'd love to have those heads. I came close to buying them a few months ago.
Hell, I'd get them strictly for their weight!

 

I should have mentioned this in my previous post: NO CODES IN ALMOST THREE YEARS OF DAILY DRIVING!!! Think of it this way. The heat riser sends exhaust gases through a passageway in the intake manifold (base, if you will). The EGR has a temperature sensor which senses the exhaust gas temperature which is one parameter used to turn the EGR on. Without a heat riser passageway in the head, the passageway in the base contains "dead air". This "dead air" can never heat up as hot as the actual exhaust gases, therefore never triggering the EGR. The EGR will always sense a much lower exhaust gas temperature than it actually is. In essence, you're faking out the EGR into thinking the exhaust gases are much cooler than they really are. So there is no way a code can be set.

I also didn't mention that I gained 0.8 seconds with these heads and a Crane 2032 cam. Bottom line: These heads work great on a 305!!

Willie

[This message has been edited by Willie (edited December 10, 2000).]