The Stuff You See

by | Aug 2013 | 3 comments

Our man Greg relates some egregious examples of the things that can be done wrong during the building of a high-performance engine. You'll learn a lot of interesting stuff here.

We see what we see and don’t see what we don’t see.  Sounds pre...

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Torque Benders, Part 1: Differential Basics

With RWD, you’re making all that horsepower up front, but you’ve got to make it do a 90-degree turn to spin those tires. That’s got to be hard on the mechanism — downright brutal in any kind of racing. Here’s how to get started putting the pieces back together, and a set-up shortcut, too.

read more

CC Rider, Part 1

What we’re talking about here is a bunch of “C” words — cubic centimeters, combustion chambers, compression, and calculation.

read more

3 Comments

  1. ericred

    Great Article, I’ve been in this trade over 40 years..and I too sometimes just shake my head on some of the things I see. For at least 25 of those years, I ran a Corvette specialty shop, and I can’t tell you how many times I had Vetts come into the shop running awfull, after they had got their car back from a “scheduled” tune up elsewere..The complaint would be rough idle,stalling,backfire on accel..etc.After taking the thing back a few times..with no success..it would land at my shop. After listing to the customer,and the engine..I’d take a look at the distributor hold down,notice how much the dist. had been moved..then I’d rotate it back to its original position,turn back the idle screw(they had adjusted)..and presto..the Corvette was a Corvette again! I’v probably Diagnosed 50 slipped balancers over the years..and it always amazes me how a skilled mechanic, during a regular tune up…would have to RETARD the timing and not question why!
    I do have a question, why does the position of the dist. drive gear have any bearing on the drivabilty?..the gear turns the shaft and rotor..but the ignition timing at the plug is based on the relationship of the rotor& cap..I mean you can drop the distributor in the hole anywhere,index #1 wire at tdc, run the engine and adjust with light(with a good damper)! With the exception of Corvette’s with the tach drive cable..orientation of the housing/gear means nothing….later model EFI w/camsensor in dist as well)
    non the less..great reading!!

    • gmcconiga

      The timing at the plug is actually set by changing the relationship of the distributor housing (stationary element) to the point cam or mag pulse generator teeth (rotating elements.) The cap is keyed to the stationary element, the housing, so the insert in the cap at each spark plug wire moves as you rotate the housing in relation to the rotor, which moves with the rotating member and with mechanical advance. Ideally, on an old Chevy points system, you’d like the leading edge of the rotor tip just overlapping at the trailing edge of the cap insert (clockwise rotation) at idle, no advance. As you speed up the engine the distributor shaft moves clockwise as the mechanical advance weights spring out.. and the rotor tip which is keyed to the distributor shaft also moves clockwise thus moving the rotor tip more into alignment with the cap insert. This alignment is called “rotor register” and is separate from the timing of the engine. Vacuum advance doesn’t affect the physical relationship like mechanical timing does, because the vacuum advance moves the breakerplate opposite rotation. But it will move the moment of arc strike counterclockwise again. Mounting the gear backwards can cause rotor register issues… the rotor may be so far away from the correct insert that it cross fires over onto an adjacent insert. Not always, it depends on how much mechanical advance you have, but it can happen. On race engines with spark sorters we always align the rotor tip with the cap insert at full advance just to avoid crossfire. If you want to observe this register movement first hand, take an old cap and cut a window in it and use your timing light to freeze the rotor motion through the window, just attach the light to a cylinder insert that lies directly in the window. Note where the rotor tip is as you rev the engine, with and without vacuum advance. If you’re like me there’s nothing like “seeing it” to make it easier to understand! Best, Greg

  2. coltjbrn1911

    very informative and ive been building for many years

Trackbacks/Pingbacks

  1. HOT ROD Professional: Digital Magazine For The Automotive Service Technician - Hot Rod Magazine Blog - [...] Playing detective and diagnosing what went wrong in three engine builds. [...]

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Torque Benders, Part 1: Differential Basics

With RWD, you’re making all that horsepower up front, but you’ve got to make it do a 90-degree turn to spin those tires. That’s got to be hard on the mechanism — downright brutal in any kind of racing. Here’s how to get started putting the pieces back together, and a set-up shortcut, too.

read more

CC Rider, Part 1

What we’re talking about here is a bunch of “C” words — cubic centimeters, combustion chambers, compression, and calculation.

read more

3 Comments

  1. ericred

    Great Article, I’ve been in this trade over 40 years..and I too sometimes just shake my head on some of the things I see. For at least 25 of those years, I ran a Corvette specialty shop, and I can’t tell you how many times I had Vetts come into the shop running awfull, after they had got their car back from a “scheduled” tune up elsewere..The complaint would be rough idle,stalling,backfire on accel..etc.After taking the thing back a few times..with no success..it would land at my shop. After listing to the customer,and the engine..I’d take a look at the distributor hold down,notice how much the dist. had been moved..then I’d rotate it back to its original position,turn back the idle screw(they had adjusted)..and presto..the Corvette was a Corvette again! I’v probably Diagnosed 50 slipped balancers over the years..and it always amazes me how a skilled mechanic, during a regular tune up…would have to RETARD the timing and not question why!
    I do have a question, why does the position of the dist. drive gear have any bearing on the drivabilty?..the gear turns the shaft and rotor..but the ignition timing at the plug is based on the relationship of the rotor& cap..I mean you can drop the distributor in the hole anywhere,index #1 wire at tdc, run the engine and adjust with light(with a good damper)! With the exception of Corvette’s with the tach drive cable..orientation of the housing/gear means nothing….later model EFI w/camsensor in dist as well)
    non the less..great reading!!

    • gmcconiga

      The timing at the plug is actually set by changing the relationship of the distributor housing (stationary element) to the point cam or mag pulse generator teeth (rotating elements.) The cap is keyed to the stationary element, the housing, so the insert in the cap at each spark plug wire moves as you rotate the housing in relation to the rotor, which moves with the rotating member and with mechanical advance. Ideally, on an old Chevy points system, you’d like the leading edge of the rotor tip just overlapping at the trailing edge of the cap insert (clockwise rotation) at idle, no advance. As you speed up the engine the distributor shaft moves clockwise as the mechanical advance weights spring out.. and the rotor tip which is keyed to the distributor shaft also moves clockwise thus moving the rotor tip more into alignment with the cap insert. This alignment is called “rotor register” and is separate from the timing of the engine. Vacuum advance doesn’t affect the physical relationship like mechanical timing does, because the vacuum advance moves the breakerplate opposite rotation. But it will move the moment of arc strike counterclockwise again. Mounting the gear backwards can cause rotor register issues… the rotor may be so far away from the correct insert that it cross fires over onto an adjacent insert. Not always, it depends on how much mechanical advance you have, but it can happen. On race engines with spark sorters we always align the rotor tip with the cap insert at full advance just to avoid crossfire. If you want to observe this register movement first hand, take an old cap and cut a window in it and use your timing light to freeze the rotor motion through the window, just attach the light to a cylinder insert that lies directly in the window. Note where the rotor tip is as you rev the engine, with and without vacuum advance. If you’re like me there’s nothing like “seeing it” to make it easier to understand! Best, Greg

  2. coltjbrn1911

    very informative and ive been building for many years

Trackbacks/Pingbacks

  1. HOT ROD Professional: Digital Magazine For The Automotive Service Technician - Hot Rod Magazine Blog - [...] Playing detective and diagnosing what went wrong in three engine builds. [...]

Submit a Comment