I'm putting this one here instead of the engine section. It will be especially useful for 305 Caprice owners. It's a mild 305 sbc v8 buildup that is intended to be CARB- and emissions-legal.
A few notes: the engine was tested on an engine dyno, so it probably had no air cleaner, and absent the usual parasitic losses of an alternator and a cooling fan. So in a car, you might see 10-20 hp less at the flywheel (fw)... but that's ok because you'd still be getting 260-270 fwhp, and over 300 fwftlbs. Those numbers would exactly equal a 94-96 LT1 in a Caprice or Impala btw.
Also note that the cam used in the test has specs are very close to a F/Y 92-97 LT1 or LT4 (stock, non-HOT) cam, and a Quadrajet 4v carb was used.
Also note the comparo of
a) open headers (no cat, no muffler),
b) header + dual cat + low_restrict_mufflers,
c) stock LG4 type exhaust with iron manifold, single cat, single muffler.
The dyno test shows that the stock exh system chokes the hell out of the car, but only above around 2500 rpms. So for ordinary mundane driving (under 2500 rpm), the stock system was engineered correctly... and it was probably MUCH quieter (not that any of you would care <g> ).
What I would have also liked to see was the poor man's exh alternative: iron manifold, dual low-restriction cat, dual low-restrict-mufflers. I think that combo would have well.... but it would also show what can be done on a budget, and that might upset the aftermarket header vendors.
Here's the URL:
There are also 340 and 400 hp examples if you probe further:
but the 290 hp article is the most relevant for a street-driven 4000+ car like a Caprice, IMO.
Final note: they talked about that there are "no good" 305 heads, but also that the AFR 350 heads *can* be used. They NEVER said what heads they DID use in the test, so I have to assume that they used the AFRs and milled them to get the compression ratio they wanted. The cr appears to have been around 10.1:1, and that's fine for a 92-octane engine w/aluminum heads.
I further suspect the Vortecs would have done as well; the port volume is smaller on the Vortec than on the AFRs so that would have favored the mild cam, mild rpms, and been better suited for a 305... nevermind that the cast iron Vortecs would have retained the combustion heat better.
The AFRs on the other hand, would flow a bit better at high rpms but this is less of a factor on a 305 vs a 350. They also didn't use as high a comp ratio as they could have w/alum heads, so a AFR to Vortec head comparo (for the test data given) would be close to a wash. IMO.
This is a useful item for 305 owners, and it shows what a mild cam (LT4, $140), cheap GM head (Vortec), and exhaust swap *could* do provided you use a Vortec-matable manifold, and that
a) the ECM were trimmed to provide the fuel needed, and provided that
b) the TBI unit could match the fuel delivery of the Quadrajet used in the test described here. HTH. FYI. - Ken
[This message has been edited by kdrolt (edited March 20, 2001).]