BadSS

The question of how much streetable power one can make with the 305 comes up occasionally as does the 305 verses 350 debate. For those that need to see some documented results, I was weeding through some of the old magazines and ran across a few dyno articles that might help shed some light.

The 325 horse Vortec 305 option (as seen below) should be very appealing to those with a good condition 305 short-block wanting immediate results and planning on a budget 350 (or larger) build later. The 350 Vortec build (similar build, built around the same time and dynoed at the same facility) should give those some idea of what to expect when or if the 305 is swapped for a 350 later.

With $1500 AFR heads (that I don’t believe are still available) the 9:1 compression 305 (as seen below) generated very impressive numbers, but horsepower and toque still falls short of a 350 build with $500 Vortec heads. Regardless, there is little doubt with more compression the “Potluck 305” could have passed the braggadocios 400 horse mark!

Here are the short list specs on the engines:

305 Vortec – Dynoed at Westech
“305 CHEVY” – March 1999 Car Craft by Marlan Davis
Stock 1982 LG4 305 – 1 5/8: headers into dual 3” Flowmasters
197HP @ 4600 rpm and 261TQ @ 3100 - Baseline
Added:
L31 Vortec heads milled .045” (55cc chambers) w/.015 head gasket for 10:1 compression
XE-262H10 (218/224 .462 / .469 – 110)
Super Victor intake (made better power than the RPM) - 750 DP
Peaks - 325HP @ 5800 rpm and 317TQ @ 4800 – it made fractionally under 325 HP at 5500 and 5800 rpm, but dropped like a rock past 5800 rpm
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305 Air Flow Research – Dynoed at Bonded Motorsports
“Potluck Buildup” – December 1993 CHP – by Mike Magda
8.87:1, .030 over 305 – AFR190 “305 heads” 58cc chambers
1.99” intake / 1.55” exhaust – 245cfm intake / 174cfm exhaust @ .500 lift
AFR hydraulic flat tappet (218/223 .491/.501 w/1.6 rockers – 110)
Performer RPM with Carb Shop modified 650 DP (approx 730cfm)
Peaks - 387HP @ 6000 rpm and 368TQ @ 4000
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350 Vortec – Dynoed at Westech
“Tearing the Envelope” – August 1999 Hot Rod by Terry McGean
9:1 350 with L31 Vortec heads – 1 ¾”headers into dual 3” Flowmasters
XE-268H10 (224/230 .470/.480 – 110)
Super Victor intake – 750 DP
Peaks - 395HP @ 5700 rpm and 400TQ @ 4800

urbanhunter44

iTrader: (3)

Awesome info! That vortec 350 is very close to my build, nice to see some good numbers coming in. Those are stock vortecs right?

89IrocZ350TPI

Ive seen this info somewhere before. Interesting