Crane Cams is BACK!!!

[Joe C.]

Re: Crane Cams is BACK!!!

[quote=Gene Manno (8571);476244]

........BTW if anyone does have a custom Duntov ground by Crane for a 283 I recommend increasing the LSA to 114 from 110 deg. and setting the inlet POML at 110 deg. ATDC. The OE LSA is 110 with an inlet POML of 108.5. ......

I was under the impression that widen the lobe separation angle will reduce the cylinder pressure. This may be good for idle but will reduce mid range torque. During mid range does not exhaust opening help pull in intake charge? Keeping in mind most performance set up's have more rear end gear. What do you say?

Widening the LSA by itself has a negligible effect on reducing cylinder pressure, unless it results in a later closing of the intake valve. For example, if you begin with a cam ground at 110 LSA, and installed at 110 degrees (0 degrees advanced,110/110/110, or "straight up)), take that same cam and widen the LSA to 114, and install that cam at 110/114/118, or 4 degrees advanced, then the cylinder pressure will not change to any great extent, unless you consider the effect of the now retarded exhaust valve timing.

In Duke's example, the slight advance of the ICL will increase cylinder pressure ever so slightly, and so will provide a hairline less detonation resistance. The wider LSA will decrease overlap, thereby increasing idle vacuum and boosting low/midrange torque.

In general, wider LSA's are better suited to smaller displacement engines, while narrower LSA's are better tolerated by larger engines, all other things being equal...................

[Duke W.]

Re: Crane Cams is BACK!!!

To expand on what Joe said, LSA is a general indication of overlap. The lower the LSA for a given duration the less overlap and vice versa.

My research has consistently yielded that high overlap HURTS the entire performance curve with OE manifolds and even the modest exhaust backpressure of most OE Corvette exhaust systems. High overlap in conjunction with properly designed headers in and OPEN exhaust can considerably improve engine performance.

For example, a well massaged SHP/FI engine can achieve a peak of a little over 90 percent VE in the upper mid rev range with OE manifolds and exhaust. These configurations can make pretty good racing engines with nothing more than a good racing exhaust system as above because VE jumps to about 105 percent making the engine a whole different animal, but you can't run headers and open exhaust on the road.

Even the OE SHP cams have too much overlap and most aftermarket cams have WAAAAAAY too much. Without headers and open exhaust, high overlap causes considerable dilution of the fresh charge with exhaust gas which reduced VE and slows flame propagation speed. That's why high overlap causes a rough idle, kills low end torque, and needs lots of spark advance at idle and low load.

Various Web discussions about "cylinder pressure" are mostly gobbledygook. The point the inlet valve closes has the greatest single effect on the torque curve. Closing the inlet valve later shifts the torque curve up the rev scale by creating more reversion at lower revs and greater inertia filling at high revs. This decreases the octane requirement since there is less tendency to detonate at low revs due to less VE, which means less cylinder pressure near the point of ignition.

If you look at the valve timing on modern Corvette engines you will find that they have less overlap and later closing inlet valves than vintage cams, and I use the same philosophy for my own designs.

The "McCagh Special" cam is a design I did for Mike McCagh. It appeared to provide equal if not better torque curve than my "Special 300 Horsepower" cam design, so I am pursuing the McCagh Special for furture base engine restoration projects. You will be hearing more about these two custom designs later this year in the Corvette Restorer.

Duke

[Duke W.]

Re: Crane Cams is BACK!!!

Duke, would the LT-1 cam be a better cam if it had more lift, say around 525???

As a general rule, higher lift is good, but valve train dynamics is critical, especially in a pushrod engine, and higher lift will almost always reduce valve train limiting speed, even with gorilla valvesprings that put the whole valvetrain in jeopardy.

Chevrolet had a very good handle on valvetrain dynamics by the mid-sixties, and it shows in their lobe designs, which I have thoroughly analyzed. With proper attention to valve train details like spring height, OE hydraulic lifter cams will rev to 6500+ and mechanical lifter cams will rev to 7000+. Higher lift on the same duration might increase peak torque and power slightly, but will limit revs to lower values. The extended rev range of OE cams means that average power through the gears is higher because their is little drop off in peak power in the last 500-1000 revs, especially with "massaged" heads.

Duke

[Dick W.]

Re: Crane Cams is BACK!!!

The "McCagh Special" cam is a design I did for Mike McCagh. It appeared to provide equal if not better torque curve than my "Special 300 Horsepower" cam design, so I am pursuing the McCagh Special for furture base engine restoration projects. You will be hearing more about these two custom designs later this year in the Corvette Restorer.

Duke

Knowing Doc McQuack, it will probably be in a 400" engine with a correctly numbered and dated 283 block.

[Clem Z.]

Re: Crane Cams is BACK!!!

To expand on what Joe said, LSA is a general indication of overlap. The lower the LSA for a given duration the less overlap and vice versa.

My research has consistently yielded that high overlap HURTS the entire performance curve with OE manifolds and even the modest exhaust backpressure of most OE Corvette exhaust systems. High overlap in conjunction with properly designed headers in and OPEN exhaust can considerably improve engine performance.

For example, a well massaged SHP/FI engine can achieve a peak of a little over 90 percent VE in the upper mid rev range with OE manifolds and exhaust. These configurations can make pretty good racing engines with nothing more than a good racing exhaust system as above because VE jumps to about 105 percent making the engine a whole different animal, but you can't run headers and open exhaust on the road.

Even the OE SHP cams have too much overlap and most aftermarket cams have WAAAAAAY too much. Without headers and open exhaust, high overlap causes considerable dilution of the fresh charge with exhaust gas which reduced VE and slows flame propagation speed. That's why high overlap causes a rough idle, kills low end torque, and needs lots of spark advance at idle and low load.

Various Web discussions about "cylinder pressure" are mostly gobbledygook. The point the inlet valve closes has the greatest single effect on the torque curve. Closing the inlet valve later shifts the torque curve up the rev scale by creating more reversion at lower revs and greater inertia filling at high revs. This decreases the octane requirement since there is less tendency to detonate at low revs due to less VE, which means less cylinder pressure near the point of ignition.

If you look at the valve timing on modern Corvette engines you will find that they have less overlap and later closing inlet valves than vintage cams, and I use the same philosophy for my own designs.

The "McCagh Special" cam is a design I did for Mike McCagh. It appeared to provide equal if not better torque curve than my "Special 300 Horsepower" cam design, so I am pursuing the McCagh Special for furture base engine restoration projects. You will be hearing more about these two custom designs later this year in the Corvette Restorer.

Duke

these cams were used so chevy would come out on top in racing were they allowed open exhaust but required a "stock" camshaft like SCCA back in the day.

[Duke W.]

Re: Crane Cams is BACK!!!

[quote=Gene Manno (8571);476244]

........BTW if anyone does have a custom Duntov ground by Crane for a 283 I recommend increasing the LSA to 114 from 110 deg. and setting the inlet POML at 110 deg. ATDC. The OE LSA is 110 with an inlet POML of 108.5. ......

I was under the impression that widen the lobe separation angle will reduce the cylinder pressure. This may be good for idle but will reduce mid range torque. During mid range does not exhaust opening help pull in intake charge? Keeping in mind most performance set up's have more rear end gear. What do you say?

Peak torque is basically a function of displacement and compression ratio. The peak torque ratings for vintage 327s range from 344 to 360 pound feet, a very narrow range, yet rated SAE gross horsepower ranged from a low of 250 to 375.

On a Dynojet chassis dyno any vintage OE configured 327 in good operating condition should achieve 270-280 lb-ft equivalent SAE corrected peak engine torque, yet peak power will range from less than 200 to close to 300 SAE corrected RWHP.

Look at a nearby reply about overlap. SHP camshafts combine increasing overlap with a later closing inlet valve and it's the latter that has the greatest effect shifting the torque curve up the scale, which yields higher top end power at high revs at the expense of low end torque.

Simulations and actual test results indicate that low to modest overlap with relatively a late closing inlet valve in conjuction with "head massaging" and relative high compression are the key to detonation free high torque bandwidth, which is what you need in a road engine.

My conclusion is that high overlap hurts low end torque more than a late closing inlet valve, so low overlap and a late closing inlet valve is the way to go, and being as how no aftermarket cams follow this philosophy I design my own using OE lobes and all OE valvetrain components to maintain the excellent durability of the OE valvetrain.

Now that Crane is back NCRS members can take advantage of my research and install my custom cam designs because Crane is the only vendor I ever found that has master patterns for the OE lobes and is willing to grind them to order, one at a time.

Duke

[Joe C.]

Re: Crane Cams is BACK!!!

Knowing Doc McQuack, it will probably be in a 400" engine with a correctly numbered and dated 283 block.

Do it run on alcohol?

[Joe C.]

Re: Crane Cams is BACK!!!

If you look at the valve timing on modern Corvette engines you will find that they have less overlap and later closing inlet valves than vintage cams, and I use the same philosophy for my own designs.
Duke

Did you mean to say "earlier" rather than later.

[Duke W.]

Re: Crane Cams is BACK!!!

Did you mean to say "earlier" rather than later.

Nope. Typical inlet POML of modern Corvette engine cams is later than 110 ATDC with LSAs in the 115-120 degree range.

Duke

[Duke W.]

Re: Crane Cams is BACK!!!

Knowing Doc McQuack, it will probably be in a 400" engine with a correctly numbered and dated 283 block.

It was definitely a conspiracy that successfully fooled all the judges.

Duke

[Duke W.]

Re: Crane Cams is BACK!!!

these cams were used so chevy would come out on top in racing were they allowed open exhaust but required a "stock" camshaft like SCCA back in the day.

That's what I've always said. The 30-30 cam was designed when SCCA engines had to be essentially "stock", so they went way overboard on overlap.

When they got around to designing the LT-1 configuration, SCCA had loosened the rules allowing aftermarket cams, so they cut back on the overlap by combining the 30-30 lobe on the exhaust side and the shoter L-72 lobe on the inlet side at a 116 deg. LSA, which cut overlap back to about what the Duntov cam was, but the longer stroke mitigated the bad effects.

This results in a rather early opening inlet valve, which can hurt low end torque. I tried a cam in EA that substitued the L-72 lobe on the exhaust side, too, with LSAs in the 114-1181 deg. range, which both closed the inlet valve earlier and opened it later. There was some improvement in low end torque, but not dramatic - not enough the warrant the cost of a custom grind.

I then tried a Duntov exhaust lobe with a 30-30 inlet lobe. That one was worth grinding, but the LSA was so wide there wasn't enough material on the blank.

Bottom line is that opening the exhaust valve early doesn't have too bad and effect.

Duke

[Joe C.]

Re: Crane Cams is BACK!!!

Quote:
Originally Posted by Duke Williams (22045)
If you look at the valve timing on modern Corvette engines you will find that they have less overlap and later closing inlet valves than vintage cams, and I use the same philosophy for my own designs.
Duke

Quote:
Originally Posted by Joe Ciaravino (32899)
Did you mean to say "earlier" rather than later.

Nope. Typical inlet POMLof modern Corvette engine cams is later than 110 ATDC with LSAs in the 115-120 degree range.

Duke

3849346 (30-30 cam):
254/254; 114LSA; 110/114/118 (installed 4 degrees advanced)
IVC: [110ATDC + (254/2)] -180 = 57 ABDC

12571251 (LS7 cam):
211/230; 121LSA; 116/121/126 (with 5 degrees advance)
IVC: [116ATDC + (211/2)] -180 = 41.5 ABDC

[Joe C.]

Re: Crane Cams is BACK!!!

To expand on what Joe said, LSA is a general indication of overlap. The lower the LSA for a given duration the less overlap and vice versa.

My research has consistently yielded that high overlap HURTS the entire performance curve with OE manifolds and even the modest exhaust backpressure of most OE Corvette exhaust systems. High overlap in conjunction with properly designed headers in and OPEN exhaust can considerably improve engine performance.

For example, a well massaged SHP/FI engine can achieve a peak of a little over 90 percent VE in the upper mid rev range with OE manifolds and exhaust. These configurations can make pretty good racing engines with nothing more than a good racing exhaust system as above because VE jumps to about 105 percent making the engine a whole different animal, but you can't run headers and open exhaust on the road.

Even the OE SHP cams have too much overlap and most aftermarket cams have WAAAAAAY too much. Without headers and open exhaust, high overlap causes considerable dilution of the fresh charge with exhaust gas which reduced VE and slows flame propagation speed. That's why high overlap causes a rough idle, kills low end torque, and needs lots of spark advance at idle and low load.

Various Web discussions about "cylinder pressure" are mostly gobbledygook. The point the inlet valve closes has the greatest single effect on the torque curve. Closing the inlet valve later shifts the torque curve up the rev scale by creating more reversion at lower revs and greater inertia filling at high revs. This decreases the octane requirement since there is less tendency to detonate at low revs due to less VE, which means less cylinder pressure near the point of ignition.

If you look at the valve timing on modern Corvette engines you will find that they have less overlap and later closing inlet valves than vintage cams, and I use the same philosophy for my own designs.

The "McCagh Special" cam is a design I did for Mike McCagh. It appeared to provide equal if not better torque curve than my "Special 300 Horsepower" cam design, so I am pursuing the McCagh Special for furture base engine restoration projects. You will be hearing more about these two custom designs later this year in the Corvette Restorer.

Duke

This same philosophy cannot be carried over to vintage engines.

Modern roller cams get more "area under the curve" despite the fact that they use shorter durations by using higher lobe lifts, and then multiplying this already higher lift (than the vintage flat tappet cams) by using high ratio rocker arms: typically 1.6 and 1.7........to 1.8 with the LS7!

The reason this is possible, is because the efficiencies of modern heads provide a supplemental ram effect, which in itself enables VE's greater than 100 per cent in normally aspirated engines. Stock LS7 intake ports reportedly flow 360 cfm @ 0.600 valve lift!!!! Consequently, pressure wave scavenging created by higher overlap becomes less important. This provides the best of both worlds: excellent low/midrange torque and prodigious horsepower.

Not so in a vintage cast iron head found in a Gen I smallblock. The most skillfully race ported "461" head will flow no more than about 260 cfm @ 0.600 valve lift on the inlet side. It is possible to get another 10-20 cfm by relocating the pushrods and further widening the port at its "choke point", but that is all! Because the intake port is not as efficient, there is little to no ram effect, thus the pressure wave scavenging created by large overlap cams, is the only way to obtain higher VE's in a normally aspirated engine.

[Joe C.]

Re: Crane Cams is BACK!!!

As a general rule, higher lift is good, but valve train dynamics is critical, especially in a pushrod engine, and higher lift will almost always reduce valve train limiting speed, even with gorilla valvesprings that put the whole valvetrain in jeopardy.

Chevrolet had a very good handle on valvetrain dynamics by the mid-sixties, and it shows in their lobe designs, which I have thoroughly analyzed. With proper attention to valve train details like spring height, OE hydraulic lifter cams will rev to 6500+ and mechanical lifter cams will rev to 7000+. Higher lift on the same duration might increase peak torque and power slightly, but will limit revs to lower values. The extended rev range of OE cams means that average power through the gears is higher because their is little drop off in peak power in the last 500-1000 revs, especially with "massaged" heads.

Duke

Until the advent of beehive valve springs I would have agreed with you. Modern springs, such as those used with the LS series engines are an excellent choice for vintage engines. They will allow somewhat higher lift and somewhat faster ramp rates while providing valvetrain control impossible to achieve with old fashioned springs. They are lighter in weight, do not require inner springs, and do not require dampers.

The LS1 spring provides 114 pounds on the seat, a 313 lb/in rate, and 255 pounds over the nose at .450 lift. Compare this to the much heavier 068 spring with damper which delivers 80 pounds on the seat, a 267 lb/in rate, and 200 pounds over the nose at 0.450 lift. The old "Z28" spring (142) has 110 pounds on the seat, a 358 lb/in rate, and 271 pounds over the nose at 0.450 lift.

[Duke W.]

Re: Crane Cams is BACK!!!

There you go again Joe, using "advance" and "retard" in vague, nonsensical hot rod lingo. Engineers don't deal with such foolishness.

You should note that I speak in terms of valve opening and closing points and "phasing", and the inlet lobe is most important because of the effect of its phasing on the position of the torque curve on the rev scale.

Most vintage OE cams have an inlet POML in the range of 108-110 deg. ATDC, and I used this range as a benchmark. If a cam has an inlet POML later than 110 I call that "late phased", and vice versa.

Note that many high overlap aftermarket cams try to make up the lost low end torque by phasing the inlet valve early - about 106 deg. ATDC inlet POML, but then the thing drops dead at 6000 revs, where an OE cam of similar duration and less overlap will keep making power another 500 to 1000 revs higher, in addition to making better low end torque. It's like trying to jam a square peg in a round hole.

The LS7 cam is an excellent example of modern valve timing that is matched to the flow characteristics of the engine with a very road worthy torque bandwidth spec - modest duration, late phased inlet valve, and a wide LSA for low overlap. The exhaust duration is longer with a very early phased exhaust event because GM purposely made the exhaust valve and port restrictive in order to achieve the largest inlet valve/port possible, but this can be compensated with an early opening exhaust valve, which is what you get with 230 deg. .050" duration and a POML of 127 deg. BTDC. That's VERY early phasing compared to a vintage OE or aftermarket cam.

I follow the same basic philosophy with my designs to replace the OE 300 HP cam, however, there's a twist. As machined by Flint the E/I ratio is about 0.65 (same as the LS7), which, as is the case with the LS7, responds well to longer exhaust than inlet duration to yield an early opening exhaust valve.

However, massaging OE big port heads yields an E/I ratio in the range of 0.75-0.80. With such a free flowing exhaust (compared to the inlet) a late phased exhaust event with shorter exhaust than inlet duration is the key to broad torque bandwidth.

Another way to look at lobe phasing is to look at the "split overlap" point, which is where the point of equal valve opening occurs relative to TDC. On most vintage engines it is before TDC. On the McCagh Special cam it's 7.7 deg. after TDC. EA will tell you the point within a few degrees, but EA's cam models assume symmetrical lobes. Most OE lobes are asymmentrical with a slower closing than opening below .050" lift so the actual split overlap point is several degrees later than what EA reports. The 7.7 deg. is based on the lift data from the GM drawing for the lobes with the inlet POML at 116 deg. ATDC and the exhaust POML at 108 deg. BTDC.

My first design forced an early split overlap point due to 20 degrees more inlet than exhaust duration. Though it made L-79 top end power with 300 HP low end torque, it did not meet my peak power and revs expectation. After the dyno numbers were in I set up an isentropic flow analysis on Excel covering the beginning of the exhaust stroke to the end of the inlet stroke, which includes the overlap period. I used lift right off the GM drawings so (for an isentropic analysis) I believe it is accurate.

What it told me is that at high revs the early closing inlet valve builds up high pressure as the piston approaches TDC, which increases pumping work and dilutes the incoming fresh charge - a double downside whammy. The analysis showed that my cam design has double the pumping power loss of the L-79 cam, which has a much later closing exhaust valve. The algorithms in EA are apparently are not sophistiated enough to pick this up, which is probably why the actual engines did not meet EA's prediction

So for the next design I shortened both durations with only 8 more degrees at .050" on the inlet side and phased everything late so the exhaust valve hung open much longer than before while maintaining the same effective overlap.

The test engine has a torque curve nearly as flat as Nebraska. In addition, it made EA's predicted top end power with more low end torque than predicted. I was happy with the performance and the owner had a ball scaring the sh...t out of the PV judge!

In the case of the LS7 cam it has a late phased inlet event and early phased exhaust event (relative to vintage OE cams). These combine to yield a very wide LSA and low overlap. The valve timing is very well matched to the head flow and is the reason why the LS7 provides torque bandwith that is unobtainable in a vintage engine with conventional vintage engine valve timing.

Valve timing has to take into account the relative flow of the the two ports and the torque bandwidth specification. Simplifying this to typical hot rod terms like LSA, advance, and retard looses site of the complex physics that is going on inside IC engines, and is the reason why most aftermarket cam designs are poor choices for broad torque bandwidth road engines.

The sacred cow "LSA" is not a design parameter, but most hot rod types think it contains some kind of magic. I design by indepently optimizing the inlet and exhaust phasing to get the broadest torque bandwidth once I have selected durations that take into account the E/I ratio. LSA is just a simple number that falls out out of the final design valve events, but I could care less what it is, as long as, in the case for my 300 HP replacement designs, that the effective overlap (that EA tells you) is maintained at about 0.9 sq-in-deg, because maintaining that value is critical to maintaining the 300 HP engine's idle characteristic - butter smooth 500 in neutral with about 18" Hg manifold vacuum

If you only understand valve timing through the myopic lens of hot rod magazines and aftermarket cam catalogs, you will never understand the big picture.

Duke