Why do L92/LS3 heads tend to disappoint so often?

[Ianosh]

From the very begining ive never understood the 'hype' about the new GM ls3 engine, ten years after the gen III ls6 making 400hp, GM came out with the 6.2liter brother making 426hp. 26 more horsepower with 30 m ore cubes just doesnt strike me as that impressive to begin with, that being said, the biggest change to this version of the ls3 engines is the 'l92' head that they come with. With 260cc intake ports, big valves, offset rockers and excellent flow numbers even from the factory, you'd think these would be the head to have. The more time i spend online and at the track, the more i find guys going no faster, or even going slower when swapping these heads onto various LS2 and 6.0 variants from the old cathedral port style. I know this is a very broad and vague question, but what comes to my mind is back in the 70's when the 4v cleveland heads were supposed to be the 'hot ticket' but many of the guys that switched to them saw no improvements. Anybody have any thoughts as to why this seems to be so common https://mechanicfaq.com/ls3-intake-manifold/ ?

[66vairguy]

Not really Corvair related. That said head and camshaft design can be a classic numbers game. Do you want good low end grunt, or high RPM power - always a compromise. This reminds me of the old 1990 Vette L98 at 245HP, then in 1992 the 300HP LT1 came out. Yes modest today, but after the awful 1980's this was hot stuff. So 50 more HP to advertise - WOW. Well in real life very little difference --- in the quarter mile the 1992 was just slightly faster vs. the 1990 - almost a tie. Why? The L98 was had a lot of torque and launched ahead of the LT1 off the line, but at higher RPM the LT1 caught up - just barely. That said a L98 was a great engine off the line and left a number LT1 owners surprised.

Old automotive saying "You advertise HP, but you drive torque". Now if you want the best of both worlds, then a well designed turbocharged system is the answer.

[MtnVairMike]

I think you answered your own question. Owning a 72 350 small block and an 93 LT1 I can tell you there is a lot of difference between the old design and the LS design that I drove just the other day

Us gear heads recall when it took special parts and tricks to top 400hp net on old school small blocks. The LS design does it right out of the box.

Heads cam headers and a few tweaks sees 500-600 hp. Try that with an old Chevy small block.

Time marches on

Mike



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