The Importance of Dynamic Compression Ratio

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.

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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.

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Rollmaster Timing Chain Failures

The Rollmaster true roller timing sets have been available for a number of years now for the Ford Y-Block family of engines.  These have been a big plus for those engine builders that go to the extra effort of degreeing in the camshafts as the lower crankshaft gear is keyed for nine different camshaft positions.  Before these Rollmaster timing sets came to market, degreeing in the camshafts on the Y involved offset keys or broaching new keyway slots in the crankshaft or camshaft timing gears.  The offset keys were always questionable strength wise regardless if the valve spring pressures were increased or not.  The practice of broaching new keyway slots in the gears is not an exact science when it comes to getting the new keyway in the exact ‘right’ location.  The Rollmaster timing sets eliminates those prior difficulties.

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New Life for a 1955 ‘P’ Code 292 Police Engine

When David Church acquired a 1955 Ford Customline two door sedan, it was found that it was originally ordered as a law enforcement car with the P code 292 and a three speed standard transmission. A little back tracking finds that the car was purchased new in North Carolina and when found by David, still had the 1967 North Carolina license plates on it but was now sitting in a South Carolina field.  It had been well over 40 years since the car had been last registered and state inspected.  Although that car had been sitting in a field for a number of years, a bit of fuel poured into the ‘Teapot’ 4V carburetor and a battery boost gets it started.  It drives itself up and onto a trailer for the trip back to Mississippi.  The odometer is showing 60K miles but when looking at suspension, pedal wear, and general oil and grease build up at various parts of the car, the assumption is the car has 160K miles instead.  More time elapses and now the car is undergoing a complete restoration including an engine rebuild.  The engine rebuild is where I come into the picture.

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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.

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