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Old 10-12-2019, 10:43 PM   #21
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Default Re: Max Compression Ratio

What is the modification? Bore it out some?
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Old 10-12-2019, 11:42 PM   #22
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What is the modification? Bore it out some?
There are a couple ways to do it.
Bore it and make a split sleeve.
Bore it bigger. Sleeve it. Broach a new keyway.
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Old 10-13-2019, 11:16 AM   #23
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Thanks Pete,going to give one a shot.A fella on here claims it helps with a cam thrust issue too.It makes sense,it should.
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Old 10-13-2019, 11:41 AM   #24
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Brent, Some of the OHV's had very high compression, most did not. The last of the aluminum Riley 4-ports were 10:1, Cooks and other racing OHV's were only 6.5 or 7:1 high for the day but considered low today. The diesel conversion that I am aware of was built by a trade-school teacher in L.A. It was an F-head design, OHV on the intakes, exh still in the block. Yes it was very high compression, necessary to ignite diesel fuel. Story goes something happened to the B engine he was running, so he hurriedly built an A block for it for his honeymoon. It worked well for that trip. I once had a set of B rods that he had supposedly built for the diesel, they were double I-beam rods, 2 stock rods welded together, 4 bolts, extremely heavy. I thought too heavy for racing, so sold them to a friend. That friend raced them at Bonneville, and one broke! There was a reinforcing rod in the middle of them! Yes, we are still friends!
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Old 10-13-2019, 01:47 PM   #25
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Thanks Pete,going to give one a shot.A fella on here claims it helps with a cam thrust issue too.It makes sense,it should.
Here is a pic of one. The cam thrust bolt is visible also.
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File Type: jpg B engine damper and mount.jpg (20.3 KB, 103 views)
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Old 10-14-2019, 10:53 AM   #26
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Default Re: Max Compression Ratio

Hi Jim,
Do you sell 7:1 heads?
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Old 10-15-2019, 08:35 AM   #27
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Brent, Some of the OHV's had very high compression, most did not. The last of the aluminum Riley 4-ports were 10:1, Cooks and other racing OHV's were only 6.5 or 7:1 high for the day but considered low today. The diesel conversion that I am aware of was built by a trade-school teacher in L.A. It was an F-head design, OHV on the intakes, exh still in the block. Yes it was very high compression, necessary to ignite diesel fuel. Story goes something happened to the B engine he was running, so he hurriedly built an A block for it for his honeymoon. It worked well for that trip. I once had a set of B rods that he had supposedly built for the diesel, they were double I-beam rods, 2 stock rods welded together, 4 bolts, extremely heavy. I thought too heavy for racing, so sold them to a friend. That friend raced them at Bonneville, and one broke! There was a reinforcing rod in the middle of them! Yes, we are still friends!
I definitely agree with you Jim. Most I think were 'power adders' for AA or BB 4-cylinder trucks to help them keep up with 6 cylinder and V-8 powered trucks. These would not have needed much compression, -just better airflow.
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Old 10-15-2019, 08:38 AM   #28
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There are a couple ways to do it.
.....Bore it and make a split sleeve.
.....Bore it bigger. Sleeve it.
.....Broach a new keyway.

...or just mount it inside the flywheel!
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Old 10-15-2019, 10:32 AM   #29
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Bob, I do, that's the only ratio mine are. e-mail me at jimb4e4@gmail.com and I'll send you details.
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Old 10-15-2019, 11:41 AM   #30
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...or just mount it inside the flywheel!



Adding it to the flywheel does nothing to mitigate crankshaft torsional deflections!

The following is a simple explanation of what a harmonic balancer does and is from https://auto.howstuffworks.com/harmonic-balancer.htm

As the cylinders in your engine fire, they move up and down, generating torque that's transferred into the crankshaft. As you may already know, the crankshaft is what converts the engine's power into rotational movement, eventually turning the wheels of the car.

But consider for a second the forces that are acting on the crankshaft -- they're tremendous. Each time a cylinder fires, a force acts upon the crankshaft, causing it to twist. But this force also causes vibrations in the crankshaft, and at certain frequencies, the shaft can resonate, which makes the vibrations even worse [source: Mach V].

These vibrations from the engine can become too much for the crankshaft to bear, causing it to fail. And when that happens, your car won't run and you'll be facing some expensive repairs.

This is where the harmonic balancer comes in. The circular device, made of rubber and metal, is bolted at the front end of the crankshaft to help absorb vibrations. It's usually connected to the crank pulley, which drives accessories like the air conditioner. The rubber inside the pulley is what actually absorbs the vibrations and keeps them at a safe level. In essence, the device is designed to help prevent crankshaft failure. It's also sometimes called a "dampener."

A more technical explanation can be found at https://en.wikipedia.org/wiki/Harmonic_damper

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Old 10-15-2019, 01:23 PM   #31
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...or just mount it inside the flywheel!



Adding it to the flywheel does nothing to mitigate crankshaft torsional deflections!

Terry, not according to an engine rebuilder from Texas who mounts them there and has argued to many that we don't know what we are talking about when we stated that wouldn't work!

Trust me when I say we have had that discussion here many times and Pete has been involved. (Hence the reason why I put the rolling on the floor emoji.)
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Old 10-15-2019, 01:44 PM   #32
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Brent, mounting a torsional damper on the flywheel end of the crankshaft will make for a smoother running engine, however, it does nothing to minimize crankshaft torsional deflections, and it does nothing to minimize harmonics.

Look at any modern engine designed by engineers and please find one that has a torsional damper mounted on the flywheel end of the crankshaft instead of at the front of the crankshaft, and post your findings here for all to read.
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Old 10-15-2019, 02:14 PM   #33
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Originally Posted by Terry Burtz, Calif View Post
Brent, mounting a torsional damper on the flywheel end of the crankshaft will make for a smoother running engine, however, it does nothing to minimize crankshaft torsional deflections, and it does nothing to minimize harmonics.

Look at any modern engine designed by engineers and please find one that has a torsional damper mounted on the flywheel end of the crankshaft instead of at the front of the crankshaft, and post your findings here for all to read.
Just a side note on the "crankshaft torsional deflections" that Terry mentions here: These deflections are large enough to be easily measured. In fact, every modern vehicle has such a device. It's called a "crankshaft position sensor", and one of its functions is to detect any misfire. It measures this crankshaft deflection every power stroke. If the cylinder doesn't fire, there is no deflection and the ECM records this. After a certain number of misfires in a given time frame, the ECM sets a code and begins flashing the "check Engine" light. The code will indicate which cylinder is misfiring (P0301, P0305), etc.) unless it's a random, multiple cylinder misfire (P0300). Interestingly, in the early days of electronic engine control, driving on a washboard road would rattle the crankshaft enough to upset the ECM and it would set a misfire code!
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Old 10-15-2019, 03:07 PM   #34
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There is an old saying:

Just because you personally don't believe, doesn't mean the laws of physics don't apply.
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Old 10-15-2019, 06:17 PM   #35
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Originally Posted by Terry Burtz, Calif View Post
Brent, mounting a torsional damper on the flywheel end of the crankshaft will make for a smoother running engine, however, it does nothing to minimize crankshaft torsional deflections, and it does nothing to minimize harmonics.

Look at any modern engine designed by engineers and please find one that has a torsional damper mounted on the flywheel end of the crankshaft instead of at the front of the crankshaft, and post your findings here for all to read.
Terry, please go read what I am saying. My comment to Pete was said 'tongue in cheek'. You don't need to try to convince me that it didn't work as we hashed that out here many years ago.
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Old 10-15-2019, 07:17 PM   #36
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Just a side note on the "crankshaft torsional deflections" that Terry mentions here: These deflections are large enough to be easily measured. In fact, every modern vehicle has such a device. It's called a "crankshaft position sensor", and one of its functions is to detect any misfire. It measures this crankshaft deflection every power stroke. If the cylinder doesn't fire, there is no deflection and the ECM records this. After a certain number of misfires in a given time frame, the ECM sets a code and begins flashing the "check Engine" light. The code will indicate which cylinder is misfiring (P0301, P0305), etc.) unless it's a random, multiple cylinder misfire (P0300). Interestingly, in the early days of electronic engine control, driving on a washboard road would rattle the crankshaft enough to upset the ECM and it would set a misfire code!
No it doesnt,the crankshaft position sensor works on hall effect,the passing of a steel reluctor wheel or tone ring (it has teeth,not unlike a gear) above a magnetic pickup.As the crankshaft spins the teeth/space coupled with the magnet makes an impulse,the impulse is read by the ECM.

https://www.samarins.com/glossary/crank_sensor.html
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Old 10-15-2019, 07:22 PM   #37
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The closest thing to a 'harmonic balancer' flywheel is a flex plate/torque converter on an automatic transmission,it provides centrifugal and well as some fore and aft dampening.
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Old 10-15-2019, 07:25 PM   #38
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The closest thing to a 'harmonic balancer' flywheel is a flex plate/torque converter on an automatic transmission,it provides centrifugal and well as some fore and aft dampening.
It is fluid inertia.
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Old 10-15-2019, 08:43 PM   #39
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No it doesnt,the crankshaft position sensor works on hall effect,the passing of a steel reluctor wheel or tone ring (it has teeth,not unlike a gear) above a magnetic pickup.As the crankshaft spins the teeth/space coupled with the magnet makes an impulse,the impulse is read by the ECM.

https://www.samarins.com/glossary/crank_sensor.html

The cited article states: "The signal from the crankshaft position is also used to monitor if any of the cylinders misfires."
Other references state that what is monitored is the slight accelleration of the crankshaft at each firing. If this slight "kick" is not detected, it is recorded as a misfire. Another article mentioned that the system "has to be invulnerable to torsional oscillations" and other 'noise'. So I had things somewhat mixed up! A good reminder for me to check things out first.
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Old 10-15-2019, 09:55 PM   #40
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ummmm, some sensors are hall effect, most are not, just magnetic.

crankshaft position sensor just reports pulses to ECU, and gap, usually at TDC.
if engine has only crank sensor, it fires plugs every revolution
if engine has cam position in addition to crank plugs fire in sequence
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