Building a Chevy 305 engine
by: Cobalt327, Crosley, Jon, LT1Silverhawk
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Contents |
[edit] Overview
Details on building a 305 for performance.
[edit] Car Craft 305 build-up
From "305 Chevy Small-Block Engine Build - 305 Chevy", "Car Craft", March 1999
305 BUILD-UP PART 1.
Car Craft started out with an 80,000 mile (130,000km) 305 LG4 engine from a 1982 Camaro. They removed the engine from the Camaro and put it straight on the dyno with headers, 3" dual pipes to Flowmaster mufflers, and a HEI distributor with 22 deg total advance. This gave a baseline dyno result of:
197 HP @ 4,000 rpm. 261 ft/lb torque @ 3,100 rpm.
305 BUILD-UP PART 2.
Added an Edelbrock Performer EGR intake manifold, but with the EGR blocked off.
217 HP @ 4,200 rpm. 285 ft/lb torque @ 3,300 rpm.
This is an increase of 20 HP and 24 ft/lbs over stock.
305 BUILD-UP PART 3.
Replaced Edelbrock Performer EGR intake with an Edelbrock Victor Jr single plane intake manifold. Replaced Q-Jet carb with a 750 Holley double pumper.
217 HP @ 4,200 rpm. 285 ft/lb torque @ 3,300 rpm.
This resulted in no change from the previous mods, maintaining the increase of 20 HP and 24 ft/lbs over stock.
305 BUILD-UP PART 4.
Added Comp Cams XE262H-10 "Xtreme Energy" hydraulic flat tappet cam. 218/224 duration @ 0.050, .462/.469 lift, 110 deg LS. Set initial timing to 16 deg BTDC.
270 HP @ 5,100 rpm. 291 ft/lb torque @ 3,800 rpm.
The cam change resulted in a huge increase of 53 HP. Torque was up by 6 ft/lbs.
305 BUILD-UP PART 5.
Replaced stock cylinder heads with World Products 305 S/R Torquer heads.
298 HP @ 5,500 rpm. 308 ft/lb torque @ 3,900 rpm.
A 28 HP increase over the stock heads, and the 305 engine now has close to 300 HP.
305 BUILD-UP PART 6.
Replaced World Products 305 S/R Torquer heads with '96 - '97 Chevy truck L31 Vortec cast iron heads, GM P/N 12558060. These are available from GM dealers in the USA for US $408 a pair, fully assembled. The Vortec heads require a different intake manifold, and Car Craft chose an Edelbrock Super Victor. They kept the same Holley 750 DP. Car Craft says that these heads are a bolt on for conventional small block Chevy engines. If your engine is earlier than '87, you will also need a set of self aligning rocker arms, and a pair of "center-bolt" valve covers.
325 HP @ 5,800 rpm. 317 ft/lb torque @ 4,800 rpm.
[edit] Tech comments
With peak torque at 4,800 rpm, the 325 HP 305 would definitely need some stiff rear end gears (I'd suggest a minimum of 3.73 ratio) plus a high stall converter if the car had auto trans. In my opinion the WP Torquer heads are the better choice for a street engine. I think that a 300 HP 305 with 308 ft/lbs torque at 3,900 rpm, would be a nice street / strip combination.
However, it stands to reason that the use of the Edelbrock Super Victor intake mated to the Holley 750 DP carb was a poor choice for this particular engine combination despite the seeming parity between it and the Edelbrock Performer intake and Q-jet carb that was shown in tests #2 and #3. Given the engine displacement, cylinder head flow, cam specs and the effective RPM range of the Super Victor intake, a much more street friendly combination could have been selected. The power "under the curve" and the average power would be much better using a dual plane up to and including the Edelbrock RPM or similar intake manifolds, used with a vacuum secondary or air valve-equipped carb properly sized for the application. Better idle vacuum, crisper off idle response, and better economy would also result from these changes.
The only possible benefit of using the open plenum Edelbrock Super Victor intake and a 750 DP carb would be at the peak of the power curve- if that. This is a tactic that the car mags will employ to give the best peak numbers- but at the cost of the power curve everywhere else.
[edit] Links
[edit] Other articles
"Lunati's 343 hp 305 Build-up"
"150 HP for a 305 Chevy Engine - Hate Me: Add 150 HP to the Chevy No One Likes"
