The Dynamic Compression Ratio (DCR) is not to be confused with the Static Compression Ratio (SCR). The SCR is the compression ratio number that’s most often referred to when talking compression ratios but it is not the final say in determining if a particular engine is going to be pump gas friendly or not. While the SCR value may get you in the ball park, it is not accurate enough on those engine combinations that are built on the ragged edge for pump gasoline use versus needing a blend of higher octane fuel and/or racing fuel. The SCR value is simply the calculation that is the result of the difference in values of the piston being at bottom dead center versus the piston being at top dead center. Camshaft events and piston connecting rod lengths do not play a part in the SCR calculation which is where the DCR comes into play.
Continue reading “The Importance of Dynamic Compression Ratio”Category: Engines
Ford Y-Block Exhaust Testing
When the question came up as to how well some of the various exhaust and header designs perform on the Ford Y-Block family of engines, the 312 dyno mule was again put to work in doing an extensive exhaust system test. Twenty-four different exhaust systems ranging from single exhaust to stepped headers were tested with each system being tried in a variety of configurations. Where possible, the different exhaust systems were also tested with and without mufflers and a variety of head-pipe lengths. When mufflers were used, they were sized according to the pipe size going into them which required having a variety of chambered mufflers on hand for this test. Except in the case of where the headers used for the 2010 EMC competition were used, mufflers were a deterrent for making additional power. While there are mufflers out there that are not a detriment for power production, those simply were not on hand for this test.
Continue reading “Ford Y-Block Exhaust Testing”Roller Rocker Arm Geometry Checkers are back!
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Degreeing in the camshaft – Part I – Finding TDC
Part of the blueprinting process during any engine buildup will include degreeing in the camshaft. This operation is performed to insure the camshaft is phased or installed at the desired position in relation to the piston sitting at TDC. While degreeing in the camshaft during its installation may seem to be an activity reserved just for the race engines, the fact remains that it’s just as important on the daily driver applications as it is for high performance engines.
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Degreeing in the camshaft – Part II – Phasing the camshaft
Part I of this article went into detail as how to find exact TDC. With that now behind us, the actual process of checking the camshaft and how it is currently phased within the engine can begin. For this, a 1.000” travel dial indicator will be required that can measure the up and down motion of the lifters. While the number one cylinder is customarily the cylinder of choice in which to check the camshaft, any cylinder can be used to degree in the camshaft once TDC has been found for that cylinder. In fact, later in this operation another cylinder will be checked in which to both verify the results obtained off of the first cylinder check and also insure that the camshaft is at least consistent in values on two different cylinders. For now, the number one cylinder will be used as a reference.
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Degreeing In the camshaft – Part III – It’s twelve pins between the marks for the Ford Y
Most camshaft timing sets for the Ford Y family of engines (239/256/272/292/312) requires that there be twelve pins between the timing marks on the sprockets and for those marks to be on the oil filter side of the engine when doing the initial chain installation. The exception here is that this only applies to Y engines that actually use a timing chain and does not apply to right hand or reverse rotation marine engines that use a gear to gear setup. While the Y is not the only engine to use the pin or link count between gear marks to time the camshaft, most V8 engine families simply align the timing marks on the cam gear and crank gear with the centerline of the engine. Due to the infrequency of engine manufacturers using the pin or link count for camshaft timing, it does leave the door open for mishaps by those not familiar with this.
Oil Viscosity and Its Effect On Engine Power
It’s pretty well known that engine oil with a higher rated viscosity tends to rob power from the flywheel end of the engine. It’s this mentality that has the new car manufacturers using lighter weight engine oils in which to increase the fuel efficiency of their engines as well as pick up some additional power.
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Intake Manifold Plenum Slots
In dyno testing the different intake manifolds on various engines, it’s found that the intake runner and plenum designs are main players in determining what the power curve for a particular engine combination will look like.
Y-Block, 585HP without a supercharger or other form of power adder
While a dynamometer is a great tool for sorting out engine combinations, there are those instances where some of the data provided conflicts with other data also being recorded. A case in point here is where the EGT’s (exhaust gas temperature) do not match up with the results of the oxygen sensors. Continue reading “Y-Block, 585HP without a supercharger or other form of power adder”
Cylinder Head Milling for a 1cc Reduction
In the course of milling cylinder heads for a specific decrease in combustion chamber volume, it becomes necessary to know exactly how much a cylinder head must be milled for a 1cc (cubic centimeter) reduction. Continue reading “Cylinder Head Milling for a 1cc Reduction”