Mast sells a small bore LS3 head p/n 510-301, it uses all LS3 valvetrain parts and accepts a stock LS3 intake.

Good call! I forgot Mast came out with their own head castings recently. I wonder how it compares to LS6 heads though?

Ok, if you have to pass smog that changes things. Is it a sniffer test or just a PCM check?

Since you're a T56, do you have higher than 3.42 gears like 3.90 or 4.10? That's a fun way to use your power better.

I'm going to be putting a stroked LS1 on the dyno in the next few weeks with a set of these heads on it and can report the results if anyone cares.
Here's the flow numbers from Masts site.

Flow Data w/3.900" Bore Plate



Lift Intake Exhaust

0.100 72 55

0.200 148 107

0.300 224 155

0.400 282 203

0.500 322 214

0.550 338 222

0.600 342 227

0.650 346 231

0.700 353 257

Those sound like impressive heads, do you have the link to them?

Very cool, so you can run square port or LS3 intakes with these?

Yep, LS3 rockers, valve springs, and intake.

Sniffer and visual smog test

How would ya interface the LS3 TB to the ecm - or would you need a different ecm ? Sounds interesting !

Converting a Gen IV TB to run on a Gen 3 engine just requires an adapter cable.



I've got nothing now, Ned. I've never had to deal with smog so the only suggestion I could make would be to go with a small stealth cam or maybe a Z06 cam.