Page 609 - 2020-2021 Racecar Engineering Drag Racing Parts and Accessories Catalog

2020 DRAG RACING

Competition Series Disc Brake Conversion Kits
Increase braking effectiveness and safety, while reducing critical unsprung weight. Disc brake
conversion kits are sold complete with rigid billet 6061-T6 aluminum four-piston calipers, Big Bite
cross-drilled rotors, performance brake pads, and necessary hardware.
NOTE: Rear disc brake conversion kits listed do not have a provision for parking brake.
SSBW123-25
Part No. Description
Front Disc Brake Conversion Kits
GM, 1964-72 A-Body, 1967-69 F-Body
SSBW123-25 SSBW125-42
And 1968-74 X-Body, 5 x 4-3/4" B.C.
Rear Disc Brake Conversion Kits
SSBW125-42 GM, 1964-81 10- And 12-Bolt Rears, 5 x 4-3/4" B.C.

TECH

The How’s, What’s, Why’s and Where's of Blow-By By Jim Kaekel
The term blow-by certainly isn’t viewed in a positive light, yet each and every internal the engine is overheated as well. During overheating, excessive heat expansion effectively
combustion engine, regardless of brand, builder, or budget, is subjected to it. Blow-by, also tightens piston-to-bore clearance, causing piston scuffing, ring binding, and end butting, all
referred to as crankcase pressure, occurs during the combustion process when burned gases of which seriously compromises cylinder integrity. Lack of lubrication, typically caused by
leak past the piston rings and into the crankcase. The rotation and speed of the rotating running an engine low on oil, can additionally cause piston scuffing, effectively harming
assembly, which not only cause windage, contributes to crankcase pressure, as well. the pistons, rings, and cylinder bores, and can eventually lead to seizing.
Crankcase pressure is released through the breathers, even to the extent of causing Although blow-by is a direct result of the combustion process and is impossible to elimi-
them to drip or blow oil. In a worst case scenario where problematic piston, ring or nate, efforts should be made to keep it as minimal as possible, since any gases that leak
cylinder conditions may exist, the pressure can actually overcome what the breathers can past the rings are a cause for lost horsepower. Minimizing blow-by can be accomplished
handle and cause gaskets to blow-out and begin leaking. by using a set of premium, precision-machined pistons fit to extremely round and true
Even in a perfect world, precisely cylinders that have been honed with a
machined pistons and rings fit to perfectly deck plate in place. The pistons should be
round and true cylinders would still result fit with rings that are correctly sized and
in a minute amount of blow-by, solely end gapped for the specific application.
due to the necessary side (axial), back, The rings should be carefully checked,
and end gap clearance. Clearance must ensuring that each includes the proper
not only exist in the rear and sides so width and radial wall thickness, verifying
that the rings remain free to turn within that they are truly compatible with the
the ring lands, but also at the end gaps chosen pistons. Always carefully follow
so that the ring ends do not butt together. This is the primary reason that it is difficult to the piston ring manufacturer’s recommendations regarding bore prep, ring fitting and end
eliminate blow-by, simply because there are three leak paths for the combustion gases gap specifications.
to follow. Not only can the gases leak between the top compression ring’s end gap and If closer scrutiny of crankcase pressure is desired on an existing engine, it may be
between the cylinder and face of the rings, but they can also leak between the back of the measured using a Blow-By Gauge, such as the available hand held unit offered by B&B
rings and ring lands. These facts illustrate the critical function and importance of the top Performance (BBP40375). Used to check an engine in a car or in a dyno cell, the precision
compression ring, to simply and effectively seal combustion pressure. It’s important to note meter is simply connected to a running engine and blow-by is then measured within a
that although the second ring is referred to as a compression ring, it’s function is solely as range of 1-10 SCFM (Standard Cubic Feet per Minute).
a scraper, preventing excess oil from reaching the top ring, and thereby compromising its Racing engines fit with full length exhaust headers may be affordably fitted with a
sealing ability. crankcase evacuation system to help alleviate crankcase pressure. Available from manu-
Another crucial factor, piston ring end gap is set so that when the engine is up and facturer’s including Allstar Performance (ALL34145), the unit uses breathers paired with
running at normal operating temperatures, it should theoretically become negligible, yet vacuum check valves to reduce crankcase pressure, eliminate oil leaks, and improve ring
sufficient to prevent the ends from butting together. If at any time the rings have butted seal, thereby increasing engine performance. The most effective method in reducing crank-
together, they will have a shiny appearance that is evident during tear down. Extreme case pressure, however, is by employing a racing vacuum pump. Offered by manufacturers
cases of end gap butting can cause the rings to bind in the cylinders, damaging the rings, including CVR and Moroso, a vacuum pump uses negative air pressure to pull air out of the
pistons, and cylinder bores. Similar, binding conditions can occur if the rings have insuf- crankcase, creating vacuum. When selecting a pump, it is important that the chosen unit is
ficient side or back clearance. sized correctly, plumbed, and geared to suit the chosen engine’s requirements.
While excessive blow-by can be caused by pistons and rings that are simply worn-out For applications where a crankcase evacuation system or vacuum pump isn’t practical,
or were improperly prepped during a prior rebuild, detonation, overheating or a lack of such as street or entry level racing applications, Allstar Performance offers a breather sock
lubrication can be culprits as well, quickly destroying an otherwise perfectly good set of (ALL36208) that installs directly over the breather and is designed to catch residual oil,
components. After literally millions of cycles, pistons, rings and the cylinders gradually preventing the dripping and blowing of oil associated with blow-by.
wear, causing clearances to grow, thereby creating a larger leak path for combustion gases. While it’s theoretically impossible to eradicate blow-by, sticking to the basics by select-
Detonation, also known as pre-ignition, caused by running too much ignition advance ing high-quality pistons and rings, ensuring that the cylinder bores have been properly
or operating an engine that is precariously lean, can quickly harm the pistons and rings, honed, and remaining steadfast that the engine isn’t abused will pay dividends in not only
immediately compromising ring seal. The pistons, rings, and cylinders can be damaged if preventing any measurable amount of blow-by, but keeping horsepower aplenty.

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