 Obtaining CAM shaft specs without disassembling the engine? |
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| GGerg1186 |
 Dec 27 2020, 05:21 PM
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Newbie  Group: Members Posts: 15 Joined: 28-September 20 From: Dubuque IA Member No.: 24,724 Region Association: Upper MidWest  |
I purchased a used 1.7L engine out of an autocross 914 car. Seller said it had a "performance cam" in it which could mean anything. Planning to pop a valve cover off with a dial indicator and the degree wheel on the front of the engine "spec" my cam. Should be able to get open, close, lift, and calculate duration. Should I put the dial indicator on the push rod side or the valve side of the rocker? Anyone had any success with identifying their cam without engine disassembly?
Next question, any way to determine compression ratio without removing the cylinder head? I am leaning towards removing the cylinder head just to see if I have cast or forged pistons & connecting rods. Ultimately, I want to know whether I can run regular pump gas, what max engine speed should be, and an appropriate carburation system to match the cam. Let me know your thoughts. |
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| bbrock |
Dec 29 2020, 09:13 AM
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains 
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I don't want to hijack but I'm getting ready to do my valve geometry and have a related question, so thought it might fit here.
I have an Elgin 6408 cam and the spec he provides is CAM Lift and also lists intake rocker ratio as 1.3 and exhaust as 1.25. https://elgincams.com/porsche914/ Am I correct that I need to multiply the CAM Lift (in my case .296 for intake and exhaust) by those ratios to get valve lift of 0.385 intake, and 0.370 exhaust to get my reference valve lift for setting geometry? I'll be following Jake's procedure. |
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Posts in this topic
GGerg1186 Obtaining CAM shaft specs without disassembling the engine? Dec 27 2020, 05:21 PM
Mark Henry Pop the oil pump off, most aftermarket cams are st... Dec 28 2020, 07:35 AM mlindner I like Marks idea. but if you want to measure like... Dec 28 2020, 07:54 AM barefoot Cam makers specify valve lift, not lobe lift, so i... Dec 28 2020, 08:36 AM
Mark Henry
Cam makers specify valve lift, not lobe lift, so ... Dec 29 2020, 07:37 AM GGerg1186
Am I correct that I need to multiply the CAM Lift... Dec 29 2020, 12:24 PM |
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