Wanted to share my experience of improving the performance of the stock 305 motor in a 1983 Grand Prix I recently bought with 63K miles. I was not pleased with its "H" version meek performance and set about learning how to improve its performance on the Internet. Found a number of articles on doing so in Chevy performance magizines and selected the one from Car Craft March, 1999 issue - summary follows:
325HP 305 CHEVY, WITH BOLT ON MODS!
This information is a brief summary of an article that appeared in the March 1999 issue of Car Craft magazine.
If you are seriously interested in this build-up, I suggest that you find a copy of that issue.
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. The result was an increase of 20 HP and 24 ft/lbs over stock.
217 HP @ 4,200 rpm. 285 ft/lb torque @ 3,300 rpm.
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. This resulted in no change from the previous mods, maintaining the increase of 20 HP and 24 ft/lbs over stock.
217 HP @ 4,200 rpm. 285 ft/lb torque @ 3,300 rpm.
305 BUILD-UP PART 4.
Added Comp Cams XE262H-10 "Xtreme Energy" hydraulic flat tappet cam. 218/224 dur @ 0.050, .462/.469 lift, 110 deg LS. Set initial timing to 16 deg BTDC. The cam change resulted in a huge increase of 53 HP. Torque was up by 6 ft/lbs.
270 HP @ 5,100 rpm. 291 ft/lb torque @ 3,800 rpm.
305 BUILD-UP PART 5.
Replaced stock cylinder heads with World Products 305 S/R Torquer heads. This gave a 28 HP increase over the stock heads, and the 305 engine now has close to 300 HP.
298 HP @ 5,500 rpm. 308 ft/lb torque @ 3,900 rpm.
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.
Basically, I have done Parts 1 - 4, avoiding the high cost of head work or new heads. I am very pleased with the much improved performance and great sound from the turbo mufflers! My cost was $1,320 in parts, all acquired from Jegs.com and the help of a mechanic who has done this exact type of 305 moptor "wake up" before = $900 in labor. Key was his experience removing all the smog stuff including smog pump,related excess wiring and the many sensors resulting in an early 70's like engine and accessory configuration = no clutter and full access to both sides of the motor!
Key after market parts top to bottom included:
-Jegs #350-9906 Rebuilt Edelbrock 1406 carb
-Jegs # 350-2101 Edelbrock Performer Intake
-Jegs # 555-15950 80gph fuel pump
-Jegs # 555-20412 New timing chain and gear set
-Jegs 40200 High Energy Plug wires
--Jegs 40005 HEI Street Distributor
-Comp Cam -Jegs # 249-CL12-238-2 exact one in Part 4 upgrade
-Jegs cam change kit - #720-4400
-Jegs headers #555-30600 for G body long/black
-50' of header wrap to save the plug wires from melting
-Jegs dual exhaust system kit # 555-30556 -2.5 inch dia aluminized stell with turbo mufflers and all fasteners/hangers
-Jegs # 550-41051 Trans crossmember for 700R4 and dual exhaiust
Jegs was flawless in their assistance in ordering everything correctly and shipping! Everything, including their own parts like the headers and exhaust system installed perfectly. Mechanic said, the exhaust system was the best pre-fab he has ever installed fit and finish. The only alignment problem came up when the trans crossmember bolts did not all lign up on the undercarriage and we had to go with one bolt on each side instead of the original two bolts per side - not planning to race it so adequate support. Watch the timing cover to oil pan joint - mine is leaking oil yet. Also, there were 2 oil pressure related sensors on the block and the left side one had to be removed and the hole plugged for the headers install and the one on top of the motor by the distributor is not giving me an oil pressure reading?
Engine Timing Note: The article mentioned 16 degrees btdc timing on the DYNO (not in a car on the road) in Step 4. I drove it 1,000+ miles down to my winter home that way and found it very hard to start especially when warm on the tirp - firing too early. I am going to dial it back 2 degrees at a time and hopefully find a more roadworthy timing setting.
Trust this information was helpful to you 305 equiped G body owners.
325HP 305 CHEVY, WITH BOLT ON MODS!
This information is a brief summary of an article that appeared in the March 1999 issue of Car Craft magazine.
If you are seriously interested in this build-up, I suggest that you find a copy of that issue.
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. The result was an increase of 20 HP and 24 ft/lbs over stock.
217 HP @ 4,200 rpm. 285 ft/lb torque @ 3,300 rpm.
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. This resulted in no change from the previous mods, maintaining the increase of 20 HP and 24 ft/lbs over stock.
217 HP @ 4,200 rpm. 285 ft/lb torque @ 3,300 rpm.
305 BUILD-UP PART 4.
Added Comp Cams XE262H-10 "Xtreme Energy" hydraulic flat tappet cam. 218/224 dur @ 0.050, .462/.469 lift, 110 deg LS. Set initial timing to 16 deg BTDC. The cam change resulted in a huge increase of 53 HP. Torque was up by 6 ft/lbs.
270 HP @ 5,100 rpm. 291 ft/lb torque @ 3,800 rpm.
305 BUILD-UP PART 5.
Replaced stock cylinder heads with World Products 305 S/R Torquer heads. This gave a 28 HP increase over the stock heads, and the 305 engine now has close to 300 HP.
298 HP @ 5,500 rpm. 308 ft/lb torque @ 3,900 rpm.
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.
Basically, I have done Parts 1 - 4, avoiding the high cost of head work or new heads. I am very pleased with the much improved performance and great sound from the turbo mufflers! My cost was $1,320 in parts, all acquired from Jegs.com and the help of a mechanic who has done this exact type of 305 moptor "wake up" before = $900 in labor. Key was his experience removing all the smog stuff including smog pump,related excess wiring and the many sensors resulting in an early 70's like engine and accessory configuration = no clutter and full access to both sides of the motor!
Key after market parts top to bottom included:
-Jegs #350-9906 Rebuilt Edelbrock 1406 carb
-Jegs # 350-2101 Edelbrock Performer Intake
-Jegs # 555-15950 80gph fuel pump
-Jegs # 555-20412 New timing chain and gear set
-Jegs 40200 High Energy Plug wires
--Jegs 40005 HEI Street Distributor
-Comp Cam -Jegs # 249-CL12-238-2 exact one in Part 4 upgrade
-Jegs cam change kit - #720-4400
-Jegs headers #555-30600 for G body long/black
-50' of header wrap to save the plug wires from melting
-Jegs dual exhaust system kit # 555-30556 -2.5 inch dia aluminized stell with turbo mufflers and all fasteners/hangers
-Jegs # 550-41051 Trans crossmember for 700R4 and dual exhaiust
Jegs was flawless in their assistance in ordering everything correctly and shipping! Everything, including their own parts like the headers and exhaust system installed perfectly. Mechanic said, the exhaust system was the best pre-fab he has ever installed fit and finish. The only alignment problem came up when the trans crossmember bolts did not all lign up on the undercarriage and we had to go with one bolt on each side instead of the original two bolts per side - not planning to race it so adequate support. Watch the timing cover to oil pan joint - mine is leaking oil yet. Also, there were 2 oil pressure related sensors on the block and the left side one had to be removed and the hole plugged for the headers install and the one on top of the motor by the distributor is not giving me an oil pressure reading?
Engine Timing Note: The article mentioned 16 degrees btdc timing on the DYNO (not in a car on the road) in Step 4. I drove it 1,000+ miles down to my winter home that way and found it very hard to start especially when warm on the tirp - firing too early. I am going to dial it back 2 degrees at a time and hopefully find a more roadworthy timing setting.
Trust this information was helpful to you 305 equiped G body owners.
