Detonation vs. Pre-Ignition
(Editors Note: the following is in response to Greg Goss’s entry in the August 2012 issue)
A sharp point or edge that can glow in a combustion chamber or on a piston top does not cause detonation. Mr. Goss inadvertently was referring to pre-ignition. Detonation and pre-ignition are two distinctly different terms and are often misused, misquoted and misspoken. Ever hear someone say, “Pre-Detonation?” No such phenomenon exists.)
Detonation occurs when the fuel does not possess enough detonation- resisting chemicals, thus enabling the compression heat to set off the end gasses before TDC, which tries to knock the piston, rod and crankshaft back down the hole backwards. Pre-ignition happens when a hot glowing spot or incandescent sets off the air/fuel mixture prematurely. This confusion comes primarily because both terms can seem similar.
Rock & Roll Engineering
Grand Terrace, CA
Removing Debris From Cylinder Head Coolant Chambers
No matter how much cleaning and blowing you do, sometimes cylinder heads will still have debris like glass beads, chips, grindings, rusty crumbs, etc. trapped in the water jackets.
It is a nasty situation when you install the head and debris falls (hopefully detected) onto the clean deck and or into the oily cylinders. I could not tell you where I learned this trick if offered a million bucks. Perhaps I thought it up myself. I would like to think so. It is one of those things I always seemed to know.
The tip: Fresh, stiff shaving cream. Use just enough to close the water openings. No need to fill the water chamber. Squeegee any excess off, making sure the openings are still sealed, then clean and dry the areas around the sealed openings. Carefully install the head and voila! The shaving cream will evaporate and if used sparingly, it will not affect the coolant.
You can use the rest to shave with!
Animal Jim Racing
‘Mag’ Testing Cast Iron Performance Oil Pumps
If you have a drag race engine, you must be sure to “magnaflux” any cast iron oil pumps you use. The pumps can crack at the base and the result is total failure. In my lifetime I have seen a few pumps crack.
The pump body will often crack due to vibration. This is mostly due to a prolonged ignition miss, an out of balance engine, or the driver doing John Force impersonations during his burnout. A quick “mag” can save you and your customer a lot of headaches.
Jeff “Beezer” Beseth
Beezer Built, Inc.
Newtown Square, PA
4.6L Cadillac Cylinder Head Block Dowel Removal
Using an old style slide hammer to remove a 4.6 Cadillac cylinder head block dowel has always been a pain. I have come up with a slick tool that cuts the job down to about five minutes for all four dowels.
Here are the parts needed:
A 9/16?-12 tap, a 3? piece of 9/16? coarse all-thread (we actually use a 460 Ford head bolt where we took a die and added a few more threads on it), a 9/16? coarse thread nut, a 9/16? thick flat washer and a steel bushing 1-1/2? long x 1-1/4? diameter with an .800? diameter hole (we use two Chevy pilot bushing adapters welded together).
Tap the block dowel approximately 1/2? deep and put the bushing over the dowel. Then thread the nut onto the bolt or threaded rod and slide the washer onto the bolt and insert into dowel. Hand tighten, then walk the dowel out with the nut.
The puller is similar to a power steering pulley puller. We now do these jobs in less than five minutes and the dowel is reusable.
Michigan Motor Exchange
Manufacturer Shop Solution:
Natural Gas Engine Valve Train Parts Selection
With recent legislation encouraging over the road engines to be converted to natural gas, many rebuilders want to know: What do I need to do to ensure long life of an IC engine using natural gas?
Natural gas fuel may be in either liquid petroleum gas (LPG) or compressed natural gas (CNG) form. Either fuel creates problems with extremely hot exhaust temperatures and excessive wear on the valve seat and valve face. These fuels are considered dry fuels, and have few hydrocarbons that deposit layers of protection on internal surfaces, increasing wear on these surfaces.
QualCast recommends replacing the valve and seat materials in these engines. Valve guides, valve stem seals, springs, etc., can be kept to OE specifications.
Valve Seats: The exhaust seat must be cast in a high-nickel alloy. Typical nickel alloys contain 40-50% pure nickel (Ni) content. QualCast alloy has 46% nickel, 29% Chromium (Cr), maximum 8% iron (Fe) and other elements used for wear protection.
Valves: Both intake and exhaust valves should have Stellite (Cobalt based alloy) facing on the seat area. The exhaust valve may have the head forged in 23-8N (23% Chromium/8% Nickel) stainless steel as long as it has a Stellite facing. For a longer lasting exhaust valve the head may be forged in Inconel (high nickel super alloy that is much more expensive). For well head or unrefined natural gas, certain marine, or other extreme heat applications, Inconel and Stellite are recommended.
Seat contact area: Many natural gas valves come with a 20 degree seat angle and valve seats come with a 20 degree starter angle. The lower angle allows for an increased seat contact area. If using 30 or 45 degree valves, ensure the seat contact area is .100? to create a larger contact surface to transfer heat from the valve head to the seat. The ignition system and/or fuel mixture may require adjustments. n
QualCast Technical Department
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Engine Builder Staff
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