17 votes
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Scatter Camshafts - What are they and why do I want one?

To understand the question at large, it is first good to know what the application is and how it came about. The engine in question is the older type of 4-cylinder engine used in Series-A Minis (not ...
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Is it right to say that VTEC is solely by Honda?

The Wikipedia article on VTEC should be good at helping you understand it all. VTEC is a trademark of Honda's patented technology (the original patents have expired but Honda have patented newer ...
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13 votes
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Why did Ducati decide to use the desmodromic valve train rather than a more tradition valve train?

Ducati use desmodromic valve systems because it provides for; A more faithful adherence to both; (1A) Not just high speed Valvetrain timing. (1B) But also high acceleration Valvetrain rates; ...
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When does it make sense to replace a camshaft?

Obviously any physical damage; cracked, broken, bearing surface damage, sheared gear, etc... Any catastrophic failure warrants cam replacement without possibility of repair. A warped cylinder head ...
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12 votes

Is it right to say that VTEC is solely by Honda?

VTEC is what Honda are calling their implementation of variable valve timing. Each manufacturer has their own version of it, each with their own name. See here for a list. So, you are right in saying ...
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11 votes
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How would a camshaft start moving during a cold start?

Crank shaft has a pulley or a sprocket at the front end, which turns a cam shaft/shafts through a cam chain or cam belt (timing belt). 1 turn of a cam shaft = 2 turns of a crank shaft. At the other ...
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What are Performance Camshafts?

A cam... in its most generic sense converts rotary motion into linear motion or vice versa using solid egg-shaped actuators (lobes)¹. An engine camshaft... refers to the shaft which houses a series ...
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What is meant by degreeing a cam?

Degreeing a cam is process for installing a camshaft and then verifying it's proper alignment with respect to the crank shaft. If a camshaft is being replaces due to damage or malfunction with another ...
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9 votes
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How does Valve Overlap affect emissions?

During the exhaust stroke as the piston is pushing the burnt gases out of the cylinder the stream develops speed. Since the stream of gas has mass it will develop momentum. This momentum follows ...
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Did the mechanic break my camshaft?

I'm struggling to find the question you are asking here but taking the literal question "Would you assume the mechanic broke your camshaft if your car would not start due to broken camshaft around 30 ...
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Where do the Camshaft Go?

There are a number of different engine designs and these govern not only the location, but also the number of camshafts within an engine. Some terms you will encounter include OHV which means Over ...
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9 votes
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What exactly is a jackshaft?

@Zaid Thanks for contributing this knowledge! I just want to post my own description because it took me more than one read-through to understand your answer. My understanding of the situation: Ford ...
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What is Lobe Separation Angle (LSA)?

Lobe separation angle is affects overlap between the intake and exhaust valves which can effect emissions, performance and efficiency. Example of Lobe Separation Angle Measurement of Lobe Separation ...
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8 votes

When does it make sense to replace a camshaft?

What things could happen to a camshaft that warrant its complete replacement? There are couple of things which I can think of off the top of my head: Performance Gains: The user wants some gains in ...
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8 votes

What exactly is a jackshaft?

Much of the information in this answer is adapted from this excellent forum post In the generic sense A jackshaft refers to an intermediate shaft that transmits rotation/power from one shaft to ...
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7 votes
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Can camshaft seal leaking hurt timing belt and cause sudden engine breakdown while driving? - Volvo XC90

To answer your questions, if there is a real leak, then yes, there is a problem. The oil will cause the belt to deteriorate and possibly slip. When it does, it is catastrophic. Pistons slam against ...
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What exactly is Honda's i-VTEC technology

In addition to Zaid's answer. VTEC - Variable Valve Timing and Lift Electronic Control) In essence, it selects between two different cam profiles depending on the RPM. Here's an animation - This is ...
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Formula 1 valve trains

First, it's probably important to review what valves do and how they're supposed to work on a four stroke internal combustion engine. What valves do Essentially there are intake valves and exhaust ...
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What are crankshaft bearings and how are they different from camshaft end bearings?

The two primary bearing types found on a crankshaft are roller bearings and plain bearings located on the main journals of a crankshaft. There are two types of journals on a crankshaft. Main Journal ...
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7 votes

What exactly is a jackshaft?

Your explanation of the application in the Ford motor is spot on. To answer the original question of "what is a jackshaft?" in a broader context: a jackshaft is simply a shaft that transfers ...
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Can I rotate a camshaft backwards on a Toyota DOHC engine if no timing belt is installed?

It's either in time, or it isn't. You can rotate cams on a non-interference engine in any direction, all you want. However, in general I'd suggest it's best to only rotate only in the natural engine ...
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6 votes

Why did Ducati decide to use the desmodromic valve train rather than a more tradition valve train?

The goal was to prevent valve float at higher rpms. Given the metallurgy of the day it required a lot of spring pressure to ensure that the spring was push the valve closed. The desmo unit ...
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When does it make sense to replace a camshaft?

Other answers have well covered how cams are inspected. This case history makes me wonder if the tech who took this engine apart damaged that cam in some way. The quick discount is suspicious. Dealer ...
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6 votes

What exactly is Honda's i-VTEC technology

This diagram does a decent job of explaining VTEC: In a nutshell (paraphrasing the Wikipedia article), you have two cam profiles, one designed for low-RPM operation and fuel efficiency, the second (...
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6 votes
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Changing Firing Order in a 4 Cylinder Car

Surely, to get a Subaru (or any true boxer engine) to run in this kind of configuration is relatively easy. Bear in mind that you are talking about an engine with two horizontally opposed cylinder ...
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Camshaft problem not sure what needs replacing

I believe this is the part you are looking for: If so, it's called a rocker arm. The most probable reason for its demise is metal fatigue or maybe it just broke. Looking at this forum (and others), ...
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6 votes

How are rotary valves sealed

From the same site, an explanation of the differences between the two types of valves shows theres still a valve seal. I suspect this is the only part where clearences have to be tight.
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5 votes

4 stroke valve timing diagram: if valves are open during TDC, wouldn't they hit the piston?

First, remember that we are talking about four different engine cycles here: Intake; Compression; Ignition/Combustion; Exhaust. Top dead center (TDC) happens between two of these cycles: between ...
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5 votes

Changing Firing Order in a 4 Cylinder Car

Do any of the four cylinder car guys out there run this configuration? Not that I can find, with the simulated exception of some "scatter cams" referenced by @Steve Matthews, and given a great answer ...
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What are Performance Camshafts?

Performance cams have various cam lobe configurations where the valve lift and duration are changed from OEM to provide better efficiency for the combustion process. I would like to make a ...
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