5.7 cam selection
Joined: Mar 2014
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From: South Ms
Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: 5.7 cam selection
My last third-gen I ran stock Vortec heads with a flat tappet cam 218 218 465 lift and never had an issue revved it to 5500-5700 RPM. Stock valvesprings. Looking back now I should have changed them as a $100 insurance but ran the car for years no troubles.
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From: Bright, IN
Car: '86 Bird, 96 ImpalaSS, 98 C1500XCab
Engine: LG4, LT1, L31
Transmission: 700R4, 4L60E, 4L60E
Axle/Gears: 3.73 Tors, 4.88 spool, 3.73 Eaton
Re: 5.7 cam selection
It's probably not so much the mass of the roller lifter as it is the more aggressive valve motion that the roller lifter permits over that of a flat tappet lifter.
Joined: Jan 2005
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From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: 5.7 cam selection
Which is likely exaggerated by the use of a higher rocker ratio in my case. Due to the 1.7 rocker ratio change the springs exert even less force on the heavy lifter. My springs were also considerably under the stock specifications because of the use of 0.100" longer than stock valves. That being said the LS6/Comp787 upgrade worked out very well. I shimmed the springs to the correct LS installed height and the results were very nice.
Joined: Sep 2003
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From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: 5.7 cam selection
More rocker ratio amplifies the spring rate on the lifter side. Pushrod side length of rocker shortens so you get more spring force on the lifter
Joined: Jan 2005
Posts: 10,420
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From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
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From: 53.0907° N, 113.4695° W
Re: 5.7 cam selection
What roller cam is out there that has .450"-.480" lift? And not a lift rule cam.
Are we limited to the Magnum line?
EDIT:
Valve train control notwithstanding, can you fit this lift under stock seals/guides, springs and retainers? From the replies in this thread, the answer is yes (with at most tapping down the OEM seals to seat further on the guides).
XTREME ENERGY™ Hydraulic Roller Camshafts (CARBURETED) HYDRAULIC ROLLER − Good for towing, excellent
mileage, smooth idle. Will work with stock converters
and gears.
Hyd. 600 to 4600 rpm, XR252HR, 252/258, 200/206, .472"-.480", 110° LSA. (compression ratio value pending).
Would you consider running this with new OEM Vortec springs? It is a lot quicker than the 268H I had success with which has less lift and more duration (which I ran with new stock springs). This might fall into the ramp rate that 86LG4Bird touched on earlier. Not coincidentally, the recommended spring is the 26918. (I may have answered my own question).
Are we limited to the Magnum line?
EDIT:
Valve train control notwithstanding, can you fit this lift under stock seals/guides, springs and retainers? From the replies in this thread, the answer is yes (with at most tapping down the OEM seals to seat further on the guides).
XTREME ENERGY™ Hydraulic Roller Camshafts (CARBURETED) HYDRAULIC ROLLER − Good for towing, excellent
mileage, smooth idle. Will work with stock converters
and gears.
Hyd. 600 to 4600 rpm, XR252HR, 252/258, 200/206, .472"-.480", 110° LSA. (compression ratio value pending).
Would you consider running this with new OEM Vortec springs? It is a lot quicker than the 268H I had success with which has less lift and more duration (which I ran with new stock springs). This might fall into the ramp rate that 86LG4Bird touched on earlier. Not coincidentally, the recommended spring is the 26918. (I may have answered my own question).
Last edited by skinny z; Mar 2, 2018 at 07:20 PM.
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