How To Get 500+ More RPM, Without Changing Cam |
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How To Get 500+ More RPM, Without Changing Cam |
motorvated |
Jan 15 2019, 05:50 PM
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#1
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Member Group: Members Posts: 279 Joined: 13-February 13 From: Colorado Member No.: 15,519 Region Association: Rocky Mountains |
2.0 Liter Four. Doing a top end refresh and not planning on splitting the cases or changing the cam. Would stiffer valve springs and beefier pushrods get me there. I'm a little confused when looking at aftermarket springs, as the European Motorworks Single HD springs are rated at 135 psi seat pressure, and stock springs are rated at about 175 psi. Also thinking that chromoly pushrods set at zero clearance cold don't let the valves open fully when hot due to the lower expansion of the pushrod, plus they are a lot heavier than aluminum pushrods. So what can I use to get those elusive extra 500+ rpm? My old stock 1.8 floated valves up near 6,000, which wasn't bad, but I'd like a little more with the 2.0 liter. I'm racing the car in Vintage. Any suggestions.
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Dave_Darling |
Jan 15 2019, 06:07 PM
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#2
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914 Idiot Group: Members Posts: 14,986 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM.
Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.) --DD |
wndsrfr |
Jan 15 2019, 07:55 PM
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#3
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Senior Member Group: Members Posts: 1,429 Joined: 30-April 09 From: Rescue, Virginia Member No.: 10,318 Region Association: MidAtlantic Region |
Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM. Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.) --DD Dave's right on...the cam is going to dictate where your power is, but what you want to pay attention to is the torque curve--dyno your car then do a bit of choosing which size rear wheel/tire combination will gear you down or up depending on the track. You can also consider doing the transmission flip of 3rd & 5th and put in an "S" 4th to get AFKaSZ gearing--I love mine.... |
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