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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.

There are two basic methodologies in checking the camshaft phasing. One would be to check the opening and closing events of the intake and exhaust lobes and comparing those to the camshaft specification card. Most checks performed with this method for aftermarket cams will be done with the lobe opening and closing events being measured at 0.050” off the heel of the camshaft. For instance, lobe lift is measured at 0.050” after the lifter starts to rise and again at 0.050” before the lifter comes to a rest at the end of its closing event. Some of the older oem Ford grinds use 0.100” for the check so be sure to know what the spec card or manual calls for when checking a camshaft using the opening/closing specs methodology.

Because of manufacturing variances and/or excessive lubricant on the lobes and tappets themselves, there tends to be some error introduced into this checking method that can make it difficult to obtain accurate readings. Be aware that most high viscosity cam lube is to be used only on the tappet faces and the lobes and should never be used on the lifter stems or lifter bores; also do not use camshaft specific lube on the engine bearings. While working with lobes and lifters that are simply oiled would give more accurate results, doing it this way would require that the cam lobes and lifter faces be removed to properly lube them for the final engine assembly. Doing this then increases the risk of the camshaft being reinstalled incorrectly if not re-performing the degree in process again.

Another method which is also my method of choice involves checking the lobes as measured from their centerlines. This method works for a majority of the camshafts out there and only gives issues when the lobes are special ground to the point they are not symmetrical on the opening and closing ramps at the top of the lobes. The following detailed instructions will be using the lobe centerline methodology.

Lobe Centerline Methodolgy –

At this point the camshaft, lifters and timing set are already installed. If the crankshaft gear has multiple keyway slots, then use the ‘zero’ position slot as a starting point. Many camshafts already have a given amount of advance built into them and in most instances starting with the ‘zero’ slot will have the camshaft much closer to its desired installed position. Second guessing the camshaft and pre-adjusting the crank gear more often than not ends up having the camshaft being installed way off of the mark when performing that first check.

With the dial indicator firmly attached to the deck surface and so that its stem can contact the intake lifter for the number one cylinder, the engine is rotated until that lifter is at full lift as indicated on the dial indicator. Placing the indicator stem at the outer edge of the lifter rather than in the pushrod cup hole tends to also give more consistent readings. With the lobe at max lift, rotate or adjust the dial indicator dial so that it’s reading zero. Now rotate the engine backwards (CCW looking from the front) so the lifter falls back down ~0.060”. Then rotate the engine forward until the lifter rise is at 0.050” before the top of the lobe. The reasoning for going back to a point more than 0.050” from lift peak and then coming back to the 0.050” mark is to insure that any slack in the timing chain is compensated for by loading the chain in the direction that the engine normally turns. At this point, take a reading from the degree wheel as the number of degrees from TDC. In this instance, we’ll use 49° ATDC for the example.

Now rotate the engine in a forward direction (CW looking from the front) so that the lifter crests at full lift and continue rotating so that the lifter is now at 0.050” down on the other side of the lobe. At this point take another degree wheel reading as degrees from TDC. In this instance, we’ll use 157° ATDC for the example. Taking the sum of the 49 and 157 values and then dividing by two, the resulting value is 103. This would be the number of degrees that the intake lobe centerline is from TDC. Now looking at the cam spec card, look for the number of degrees that the camshaft is ground on. For this example, the card says the camshaft is ground on 108° lobe centers. With the measured intake lobe value being less than 108° and subsequently closer to TDC, then 108 minus 103 would have this camshaft being 5° advanced. Some cam cards will include the manufacturers recommended intake lobe centerline installation value which can be compared to your measured value. Our card has the recommended installation being at 104° degrees intake lobe centerline which has the camshaft as measured having one more additional degree of advance. Had the intake lobe centerline value been a number greater than the advertised lobe centerline value, then the camshaft would be that number of degrees retarded. If the measured intake lobe centerline equals the advertised ‘as ground’ lobe centerline value, then the camshaft is installed straight up (no advance, no retard).

Click on picture for larger image.

Because of manufacturing variances, we are now going to go an extra step and check the exhaust lobe to get some real numbers on the camshaft and how it has been ground. This is being performed to both verify the checking procedure and also insure that the camshaft is ground as advertised at least for this particular cylinder. So with that in mind, move the dial indicator to the #1 exhaust lifter. Rotate the engine in a forward manner until maximum lobe lift is obtained on the dial indicator and then zero out the indicator dial. Rotate the engine backwards so that lifter falls back down approximately 0.060” and then forward so that the lifter is sitting at 0.050” before max lobe lift. Take a degree wheel reading as degrees from TDC. In this instance a 160° BTDC value is indicated on the degree wheel. Now rotate the engine forward (CW looking from the front) so that the lifter crests to max lift and continue forward until the lifter is sitting 0.050” down on the other side of the lobe. The reading on the degree wheel at this point is 64° BTDC. Taking the sum of 160 and 64 and dividing by two gets a value of 112° for the exhaust lobe centerline. Because we are now dealing with the exhaust lobe, any value greater than the advertised lobe centerline will also indicate degrees of advance. In this case, 112 minus 108 equals 4° of cam advance based on the advertised ‘as ground’ lobe centerline value on the spec card.

As determined by the individual lobe measurements, the intake is installed at 5° of advance and the exhaust lobe measurement says 4° of advance. Which is correct? To determine this, the two sets of degree wheel measurements must be combined. Add together the measured 112° exhaust lobe centerline and the measured 103° intake lobe centerline values obtained earlier and divide by two. 107½° is the revised or actual ‘as ground’ lobe centerline value rather than the 108° that is listed on the cam card. Revisiting the intake and/or exhaust lobe centerline values and recalculating using the actual ‘as ground’ lobe centerline, the camshaft is actually 4½° advanced instead of the 5° value that was determined earlier by only doing the intake lobe measurement.

SAME DRILL, DIFFERENT CYLINDER.

Because the #1 and #6 cylinders on most V8 engines share the same TDC on the degree wheel, the #6 cylinder will now be used to reaffirm both the checking procedure and any variances in the camshaft itself. (The Buick V8 Nail Head engines are a known exception to the cylinders 1 & 6 sharing the same TDC.)  Because the #6 cylinder is being used for the double check, the degree wheel can remain as it was for the #1 cylinder check. Any other cylinder can be used for the recheck as long as exact TDC for that cylinder is found and the degree wheel is adjusted accordingly.

In this case, the dial indicator is simply moved to the #6 intake lifter and the same procedure as used for the #1 intake lobe is performed once again. In this instance, the intake lobe centerline measures to be 104°. The dial indicator is then moved to the #6 exhaust lifter and that ends up being installed at 113° lobe centerline. Adding the 104 and 113 values together and dividing by two gives us a 108½° ‘as ground’ lobe centerline for cylinder #6. Taking the 104 value and subtracting from the 108½ value leaves the intake on this cylinder being installed at 4½° of advance. The check for the #1 cylinder also had the actual amount of advance right at 4½° so in this instance, both are identical. In the event there was a difference, then averaging the values would give the advance value to be used for this particular engine.

With the numbers obtained from the #6 cam lobes check, the variability within the cam lobes between cylinders 1 & 6 can now be observed. The 108½° value on cylinder #6 is compared to the 107½° degree value that was obtained on the #1 cylinder and there is a 1° difference. That is your lobe centerline manufacturing variance for these two cylinders. This is assuming your cam checking methodology is both consistent and accurate. While 1° of variance would be my own upper limit of variability, there are those cam manufacturers that are comfortable with 2° or more of variability. In summary, the more accurately the cam lobes are ground, the more potential power an engine will make once that camshaft is installed at its optimum position. If so inclined, the camshaft lobes for all eight cylinders can be checked for a better feel for how the camshaft is ground. In this particular instance, the camshaft that was just checked will be left where it is and ran.

The scary part of all this is if you only check the lobe or lobes on the #1 cylinder, the variability within the camshaft is basically unknown. That variability can be an engine performance issue all by itself once the engine is in the vehicle and being operated. The caveat to checking a large number of cams from the different manufacturers gives the installer a good feel for which cam grinders do a consistently better job in keeping variances to a minimum; or said differently, which cam companies to stay clear of.

HOW MUCH ADVANCE OR RETARD?:

As a general rule, most camshaft installations prefer a given amount of advance when being installed. Examining the spec card will give the manufacturers recommended installation specs but if not given those values, then 4° of advance covers most installations. Why advance the camshaft rather than simply install the camshaft straight up? Because a timing chain has a given amount of elasticity, the camshaft retards as the rpm increases so this initial amount of cam advance helps to compensate for this. Also, as a timing chain wears it stretches and as a result, the camshaft is also being retarded over time. All out race engines will break many of these rules in that the camshaft is simply being installed for the best power numbers in a given rpm range. Long term wear or stretch in this instance is not being compensated for.

Here is a word of caution regarding moving the camshaft phasing around. As the camshaft is advanced or retarded, the intake and exhaust valve relationship to the piston at TDC is changed. Depending upon the engine and the piston design, the potential is there for a valve to contact the piston resulting in a catastrophic failure if valve to piston clearances are not being checked. As the camshaft is being advanced, the intake valve becomes closer to the piston; as the camshaft is being retarded, the exhaust valve becomes closer to the piston.

A general rule of thumb for flat tappet camshafts is for each 4° the camshaft is moved, the valve to piston clearance is altered roughly 0.025”. If the camshaft is advanced 4°, the intake valve becomes ~0.025” closer to the piston; if the camshaft is retarded 4°, the exhaust valve becomes ~0.025” closer to the piston.

MAKING ADJUSTMENTS:

While the first part of degreeing in the camshaft is simply checking to see where it is initially installed, the second phase of the operation is actually moving the camshaft so its relationship to TDC is altered. If the camshaft has been found to be off enough to necessitate a change, then the camshaft phasing in relation to TDC will need to be moved. On some engines, one degree of change may be critical while on others it may take four degrees to be significant. Changing the camshaft phasing on some engines can be performed at the camshaft gear by lieu of using an offset key or offset bushings. Where the crankshaft gear has multiple key slots, then the appropriate slot can be used to move the camshaft a given number of degrees in one direction or the other. Where the crankshaft gear has only a single slot, then an offset key can be used at the crankshaft with the direction of the offset that’s built into the key determining either advance or retard. Another option where the crank gear only has one key slot is broaching an additional slot at a new position in the gear to also move the camshaft in the desired direction and amount. Likewise, a new key way slot can be broached into the cam gear or a new dowel pin hole placed at the appropriate spot on the gear.

To advance a camshaft, then either the cam gear is turned more clockwise (looking at the front of the engine) or the crank gear is turned more counter clockwise in relation to the opposite gear not moving at all. To retard a camshaft it’s the opposite scenario where the cam gear is turned counter clock wise or the crank gear is moved clockwise. Advancing the camshaft simply has the cam timing events occurring sooner while retarding the camshaft has those same events occurring later.

While part II of this article ended up being more complicated than I envisioned, I trust it is laid out in such a manner that the cam degreeing in process has been simplified. Part III will go into the specifics of the Rollmaster timing set for the Ford Y-Block and the nuances in moving that particular crank sprocket to achieve the desired results. Until next issue, happy Y motoring. Ted Eaton.

This article was originally published in The Y-Block Magazine, May-Jun 2015, Issue #128.

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.

There have been too many instances recorded where Ford Y engines have been assembled with the cam and crank gear timing marks aligned with each other rather than counting the pins between the marks. Even some very reputable shops have been blindsided by this. Unfortunately many of these incorrectly installed timing sets were not discovered until the engine was installed in the vehicle. In these cases, the engine simply spins over quite easily without any compression and obviously doesn’t fire up. Once the problem is isolated to ‘cam timing’ (which usually takes awhile), it’s an ordeal to either fix this in the vehicle or actually pull the engine back out and return the engine to the shop that did the work.

While it is an embarrassment for anyone that does this, it’s easily prevented by knowing one basic cam design nuance. For most V8 engines and with the #1 piston sitting at or close to TDC, either the #1 or #6 cylinder intake and exhaust tappets will be caught at the overlap cycle.  (An exception to this rule would be the Nailhead Buick V8’s which would be cylinders #1 and #4 being at TDC simultaneously.)  This is where both lifters on the same cylinder are in the process of moving but will be approximately level with each other when the timing set is correctly installed. The exhaust tappet will be going down (almost closed) while the intake tappet will be moving up (just opening); both will be approximately the same distance off of the heel of the camshaft. This also applies to the Ford Y with the following additional detail. With the timing set installed with the twelve pins between marks on the oil filter side of the engine and the #1 piston at or close to TDC, it will be the #1 cylinder intake and exhaust tappets being close to level with each other although both are in the process of moving. This is simply a good double check for anyone installing a camshaft in a Y engine without going to the trouble of actually degreeing it in. For those of you that are going to that next level and degreeing in the camshaft, this lets you know that the cam is in the right neighborhood before actually getting some real numbers on where it’s really residing.

While the Rollmaster roller timing set for the Ford Y-Block family of engines comes in a variety of flavors, they all share a crankshaft gear that has nine different key slots in which to install on the crankshaft. Only one of those key slots and a corresponding outer tooth is marked though. There are eight other key slots on the crank gear that are unmarked and this can become a mind teaser when the camshaft needs to be either advanced or retarded beyond that zero marked position. To simplify moving the crankshaft gear to another position, here are some illustrations to facilitate advancing or retarding the camshaft a given number of degrees.

Click on pictures for larger images.

Until next issue, happy Y motoring. Ted Eaton.

This article was originally published in The Y-Block Magazine, Jul-Aug 2015, Issue #129

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. One intake manifold feature that comes to the forefront on the aftermarket four barrel dual plane intakes is a slot in the divider located directly under the secondary side of the carburetor. These slots came into prominence in the late Sixties with the popularity and use of the Holley three barrel carburetors and that slot was simply required to allow the secondary throttle blade on those carbs to open without interference at the intake manifold. Although the three barrel carbs have been pretty much extinct for several decades, the practice of the intake manifolds being slotted by the manufacturers has remained. When the Blue Thunder intake for the Y engines was introduced, it too had that slot located at the rear of the divider under the secondary portion of the carb. I’ll hence forth refer to that slot as the ‘three barrel’ slot simply due to it working for that purpose.

For the Ford Y-Block engines, the two aftermarket intakes currently available are the Blue Thunder (BT) and the Mummert. In breaking with conventional practice, the Mummert aluminum intake manifold was introduced without that ‘three barrel’ slot in place. The BT intake being introduced a few years earlier has the slot. So that begs the question, exactly what effect does that slot have on the engines power curve if any?

Click on pictures for larger images.

To test the effect of the ‘three barrel’ slot on overall engine performance, four 1” tall four hole carb spacers are obtained and appropriately modified so they can be dyno tested. While one 4 hole spacer is left stock, another is modified with a slot across the secondary throttle bores. The other two spacers are machined so that they are dual ovals closely matching the dual oval configuration used in the plenums of both the Blue Thunder and Mummert intakes. Again, one of the dual oval spacers has the slot added so it’s across the secondary throttle bores while the other does not. To add another nuance to the tests, the slotted spacers are tested both right side up and upside down just to see if this provides an additional difference to the power curve. This makes for six different test variants which includes the four different spacers and then the two slotted spacers being run with slots down as well as slots up.

 

Click on pictures for larger images.

The dyno mule is the well tested +060 over 312 with a set of mildly ported G heads. The intake manifold being used for this test is the Mummert aluminum intake which is being used in lieu of the Blue Thunder intake simply due to the lack of a slot in the plenum divider. The carb is the 750 vacuum secondary Holley which has proven to be a solid performer on this engine in past tests. The camshaft is a Seventies era Crower Monarch grind with 238° duration at 0.050” on both the intakes and exhausts and ground on 110° lobe centers. The cam is installed with 2° of advance (108° intake lobe centerline). The net valve lift is 0.459” lift using the Harland Sharp 1.6:1 roller tipped rockers with the valve lash set at 0.019”.

The following chart shows the various dyno results. The *Score is calculated by adding the average torque and horsepower values together, multiplying by 1000 and dividing by the cubic inch (322).

Spacer > 4 holeNo slot 4 holeSlot up 4 holeSlot down Dual OvalNo slot Dual OvalSlot up Dual OvalSlot down
TQ –Peak 340 341 342 338 338 338
HP – Peak 298 303 302 302 302 302
TQ – Avg2500-5500 rpms 324 324 322 323 320 320
HP – Avg2500-5500 rpms 245 246 245 245 244 243
*Score2500-5500 rpms 1769 1772 1763 1766 1752 1751
TQ – Avg2500-3500 rpms 329 324 319 326 316 315
HP – Avg2500-3500 rpms 189 186 183 187 181 181
*Score2500-3500 rpms 1608 1582 1559 1593 1544 1538

In this case, the charts don’t tell the whole story so this is where a series of graphs come into play. The following two graphs show the HP and TQ results for the four hole spacers. There is a pronounced dip in the torque curve when the slots are incorporated into the spacers versus the dyno runs that are made without the 3 barrel slot in place.

Click on pictures for larger images.

The next pair of graphs shows the results of testing with the dual oval spacers with and without the three barrel slots. Again, that mid-range dip in the torque curve becomes more pronounced with the slots in place versus without.

Click on pictures for larger images.

This next pair of graphs simply compares the four hole carb spacer without a slot to the dual oval carb spacer also without a slot. Low end torque is enhanced with the four hole spacer while the top end horsepower is better with the dual oval spacer. No surprise there. This reaffirms the practice of putting the oval slots in the ECZ-B iron intakes for an increase in top end power.

Click on pictures for larger images.

What is obvious on the graphs comparing ‘slot’ versus ‘no slot’ performance is how the addition of a slot does make for a more pronounced dip in the mid range torque values. Based on past experience, that dip or mid-range drop in the torque numbers does look like it can be reduced by simply making the carb spacer taller. For this particular test, the carb spacer height was simply kept at one inch but past testing has shown that the two inch high carburetor spacers are a better choice for optimum horsepower and torque numbers on most Y engine combinations when using either the Blue Thunder or Mummert intake manifolds. There are instances where even more than two inches of spacer works so keep an open mind.

The addition of plenum slots do tend to help the overall performance scores and top end horsepower numbers when used on a 4 hole spacer design. When using ovals under the carbs rather than four individual holes, the same slots prove to be a detriment to the overall score values while top end horsepower values do continue to be higher. The low end performance is reduced with both spacer designs with the slots when compared to the same ‘no slot’ spacers. In summary, not having a slot in the plenum divider does enhance the low end torque values so it simply ends up being a case of exactly what kind of driving is being performed as to whether the intake plenum having a three barrel slot or not is going to be the best for a particular engine combination.

585 HP with 3″ of dual slotted carb spacers on Blue Thunder intake manifold.  Click on picture for larger image.

Until next time, happy Y motoring. Ted Eaton.

This article was previously published in The Y-Block Magazine, Jan-Feb 2014, Issue #120, Vol. 20, No. 6