Vortec heads and hp
09-12-2002, 05:11 PM
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Car: 1990 Iroc Z Convertible
Engine: LB9
Transmission: 700R4
Vortec heads and hp
I have an 90 Lb9 rated at 210hp from the factory,Iwant to put 305 Vortec heads and the Scoggin Dickey TPI intake on the car. I also was going to put on headers and a catback exhaust system.I was just wondering what kind of a hp increase to expect from these mods.I was also considering a new camshaft, but I have no idea what to get.
09-12-2002, 05:19 PM
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You've got a decent factory cam, but changing that would definitely help. If you threw an LT4 hot cam in there with those mods and some decent exhaust I could see you gaining a good 50+ horsepower.
09-12-2002, 11:21 PM
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vortec heads
while GM makes heads the come on 305s and denotes them as "vortecs", they are not worth the time and effort to change them out. L31 vortec heads are the desired "vortec" heads and only came on 350's. You can tell them apart from the so called "vortec" heads by chamber design. The L31's have a "fastburn" style chamber thus creating a quicker burn than the smogger style chamber of the 305 "vortec" heads.
09-13-2002, 04:19 AM
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You can fit the L31 Vortecs to a 305, and they seem to work well according to Car Craft. They got 325 HP out of a carbed 305 on the dyno. http://members.optushome.com.au/iroc...5/325hp305.htm
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09-15-2002, 09:52 AM
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Car: 1990 Iroc Z Convertible
Engine: LB9
Transmission: 700R4
bjankuski, did you have to shave the heads to maintain proper combustion chamber size?
09-15-2002, 03:50 PM
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Car: 1988 Firbird
Engine: 406
Transmission: T-56
Axle/Gears: 4.10
I did not shave my heads because I do plan to use them on a 350 or 383 this winter. If I was only going to use them on a 305 I would shave the heads. My 350 Vortec heads came stock with 61CC chambers, they are advertised at 64 CC but mine were 61CC. I then ran the Fel-pro .015 1094 head gasket to try and get some additional compression. I ended up with 8.8 to 1 compression. The stock engine is rated at 9.3 to 1 compression but when I figured out my compression it was 8.9 to 1 stock.
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