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Horsepower difference ?
Heres a dumb question...........the first ZR1's had 375 hp , then it jumped to 400 hp, what change or addition made the difference in horsepower gain ?
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Re: Horsepower difference ?
I believe you are correct, porting and some change in cam grinding , gave it the 30hp gain . I know chevrolet used to retard cam timing years ago for emissions and hp reduction to meet standards.
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Re: Horsepower difference ?
improved intake port alignment. Bit better heads and cams, improved exhaust and header/cats.
405 hp blocks also had 4 bolt mains and all of them were made in 1993 |
Re: Horsepower difference ?
>Mild port/polish on intake and exhaust ports.
>better blending of the ports just above the valve seats >Three-angle valve seats >"Sleeve spacer" between the head and injector housings to improve alignment >Revised cam timing but cam profiles remained the same >Revised calibration >New exhaust manifolds...which actually cost 5-hp but went to production to solve a problem with the engine ingesting debris if the cat converter substrate failed at high rpm. |
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Referred to as catalyst reversion. Occurs during engine de-celleration, i.e. lifting throttle with clutch engaged at high rpm. All that's left of the Oil Control Ring lands, is that short section on the left end.:eek: https://cdn10.bigcommerce.com/s-nkg9...-damage-02.jpg |
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Some of that info came from GM press info that was distributed in the 1993 long lead book. The rest of it came from a conversation I had many years ago with Graham B. |
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