What kind of horsepower can I expect? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Chevelle454 · 08-17-2003, 11:36 PM

I am rebuilding my 350 in my '72 this fall. What can I expect with a freshly rebuilt motor with a new quadrajet carb and intake manifold with true dual exhaust?

LonghornJeff · 08-17-2003, 11:43 PM

300-325hp @ the flywheel assuming 9.1 compresson,stock heads (no porting), preformer intake and headers

Chevelle454 · 08-18-2003, 12:00 AM

Really? That much? I know it is hard to guess at what the horsepower would be, but I am just looking for a rough estimate. I was thinking between 200-250 HP. But if rebuilding it with performance intake and exhaust would give me that much, that would be excellent...

Stroker · 08-18-2003, 12:12 AM

I'de guess about 250 with headers based on magazine dynoes of Chevy's goodwrench engines with headers and Q-jet. If using ram horn manifolds knock off about 10 to 20 HP.

LonghornJeff · 08-18-2003, 12:30 AM

The stock 70 chevelle L48 engine was rated @ 300(I think?)
the 72 was 170hp but that engine was unchanged except for the gross/net HP rating and single exhausts.....same lower end as 70 so im assuming 25 hp for the mods.....

the goodwrench engine you speek of is 8.5 to 1 (I think and the heads arent as good).....correct me if im wrong

bpmcgee · 08-18-2003, 12:46 AM

Remember about that time they switched from gross to net horsepower ratings. That would explain the drop from 300 to 170.

I have a book of engine buildups, and they tested the Goodmark GM Crate engine at 234 HP bone stock, I believe. That worked out to 7.4:1 compression ratio, btw.

Brian

Chevelle454 · 08-18-2003, 01:17 AM

I think you might be a little confused. I am rebuilding the 350 in my '72 C20...

smokekiki · 08-18-2003, 08:35 AM

That's kind of a general question.How much do you want to spend.Keep the compression down to 9.1-9.5.You can get a set of vortec heads for 500 and rockers for 170.A good set of headers to help with the flow.Decide how much you want to spend and what you want from the engine.Talk to the cam manufatures,they have a lot of time invested in their cams and a lot of data to go with them.Let them know what you want and how you are buildingthe motor.Even a basic stock engine will benifit from a cam,intake and exhaust.

*Randy70C-10* · 08-18-2003, 10:24 AM

If you want horsepower, it's all in how you build the top end. Do some mild porting on the heads, port match the intake, run a decent cam and you'll be set.

Southpa · 08-18-2003, 12:26 PM

The stock specs for those engines were 255 hp gross or 165 hp net.

08-17-2003, 11:36 PM	#1
Chevelle454 Registered User Join Date: Aug 2003 Location: MN Posts: 380	What kind of horsepower can I expect? I am rebuilding my 350 in my '72 this fall. What can I expect with a freshly rebuilt motor with a new quadrajet carb and intake manifold with true dual exhaust?

08-17-2003, 11:43 PM	#2
LonghornJeff EZEKIEL 25:17 Join Date: Oct 2001 Location: Springfield IL USA Posts: 984	300-325hp @ the flywheel assuming 9.1 compresson,stock heads (no porting), preformer intake and headers __________________ 68 CHEVELLE(HORSESHOE) 69 LONGHORN 396 70 NOVA 454(FOR SALE) 71 SWB 307 71 EL CAMINO 383 72 GMC JIMMY 350 87 BLAZER 350 WIW? http://blog.360.yahoo.com/blog-r5CJt...9_6Orzim4L5uWM Gun control, the theory that 110lb. women have the "right" to fistfight with 210lb. rapists. The reason animal rights activists are more passionate about fur than leather is because it's safer to harrass rich women than bikers...

08-18-2003, 12:12 AM	#4
Stroker Registered User Join Date: Mar 2001 Location: Moore, Ok Posts: 1,149	I'de guess about 250 with headers based on magazine dynoes of Chevy's goodwrench engines with headers and Q-jet. If using ram horn manifolds knock off about 10 to 20 HP. __________________ 72 SWB parts and pieces Oklahoma

08-18-2003, 12:30 AM	#5
LonghornJeff EZEKIEL 25:17 Join Date: Oct 2001 Location: Springfield IL USA Posts: 984	The stock 70 chevelle L48 engine was rated @ 300(I think?) the 72 was 170hp but that engine was unchanged except for the gross/net HP rating and single exhausts.....same lower end as 70 so im assuming 25 hp for the mods..... the goodwrench engine you speek of is 8.5 to 1 (I think and the heads arent as good).....correct me if im wrong __________________ 68 CHEVELLE(HORSESHOE) 69 LONGHORN 396 70 NOVA 454(FOR SALE) 71 SWB 307 71 EL CAMINO 383 72 GMC JIMMY 350 87 BLAZER 350 WIW? http://blog.360.yahoo.com/blog-r5CJt...9_6Orzim4L5uWM Gun control, the theory that 110lb. women have the "right" to fistfight with 210lb. rapists. The reason animal rights activists are more passionate about fur than leather is because it's safer to harrass rich women than bikers... Last edited by LonghornJeff69; 08-18-2003 at 12:32 AM.

08-18-2003, 01:17 AM	#7
Chevelle454 Registered User Join Date: Aug 2003 Location: MN Posts: 380	I think you might be a little confused. I am rebuilding the 350 in my '72 C20... __________________ 1972 C10 1972 C20

08-18-2003, 12:00 AM	#3
Chevelle454 Registered User Join Date: Aug 2003 Location: MN Posts: 380	Really? That much? I know it is hard to guess at what the horsepower would be, but I am just looking for a rough estimate. I was thinking between 200-250 HP. But if rebuilding it with performance intake and exhaust would give me that much, that would be excellent...

08-18-2003, 12:46 AM	#6
bpmcgee Registered User Join Date: Mar 2003 Location: Northern Illinois Posts: 2,181	Remember about that time they switched from gross to net horsepower ratings. That would explain the drop from 300 to 170. I have a book of engine buildups, and they tested the Goodmark GM Crate engine at 234 HP bone stock, I believe. That worked out to 7.4:1 compression ratio, btw. Brian

08-18-2003, 08:35 AM	#8
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,473	That's kind of a general question.How much do you want to spend.Keep the compression down to 9.1-9.5.You can get a set of vortec heads for 500 and rockers for 170.A good set of headers to help with the flow.Decide how much you want to spend and what you want from the engine.Talk to the cam manufatures,they have a lot of time invested in their cams and a lot of data to go with them.Let them know what you want and how you are buildingthe motor.Even a basic stock engine will benifit from a cam,intake and exhaust. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

08-18-2003, 10:24 AM	#9
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	If you want horsepower, it's all in how you build the top end. Do some mild porting on the heads, port match the intake, run a decent cam and you'll be set.

08-18-2003, 12:26 PM	#10
Southpa Registered User Join Date: May 2000 Location: Victoria, BC, Canada Posts: 2,409	The stock specs for those engines were 255 hp gross or 165 hp net. __________________ 1970 GMC 1500 Custom Original 350/TH350 Victoria, BC, Canada You can wish in one hand and crap in the other. See which one gets filled first.

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