Camshaft Selection for your New Engine

[Cliff Ruggles]

Had a few extra minutes this morning and wanted to put up some information on currently available camshafts.

The purpose here is not to "bash" any particular company or line of camshafts, just to provide useable and accurate information on the subject based on what is currently happening with this sort of thing in our hobby.

In the past decade or so companies grinding and selling camshafts have came up with quite a few different types of camshafts and pushing this "new" technology pretty hard.

It's pretty much the same thing, you will hear words like "more area under the curve", improved idle quality, more power on top end, improved street manners, etc, etc.

Folks, when the smoke clears and dust settles with this sort of thing there isn't much improvement, if any waiting for you by going to "modern" lobe profiles over what's been available for decades. 

Now I'm talking about flat camshafts here, not roller profiles because when we take the lifter diameter out of this equation there are going to be some really nice benefits waiting for you in the areas these companies are promoting.

A roller camshaft will truly allow for reduced seat timing for improved vacuum production, smoother idle, and improved street manners but still offer excellent cylinder filling abilities at higher rpms.  This means that the end user can sort of have their cake and eat it too.

Trying to do the same thing with a flat cam is not nearly as easy.  Think of this whole situation like you are sitting in front of a large window in your kitchen and the wind outside is blowing pretty strong.  If you lift the window up and down very quickly but never stop the movement how much air will get into the room vs throwing the window open completely, hesitating for a moment, then very quickly slamming it shut while keeping the actual time the window was open for both scenarios EXACTLY the same.

Rest assured the very quick movements to fully open, leaving it there for a moment, then very quickly slamming it shut will allow more air to enter the room for each cycle.  This is how a roller cam works in comparison to a flat camshaft.

What's happened in recent years is that companies making these cams have removed seat timing (actual time the valves are off the seats or "advertised" duration), then picked up the .050" numbers considerably.  With this move they have came up with all sorts of names for the "modern" lobe profiles as well, claiming greatly improved power, better idle quality, blah, blah, blah, you get the idea at this point.

Continued below....

[Cliff Ruggles]

What actually happens with a flat cam is that this super-quick seating velocity has pushed the envelope too far.  Flat camshafts that used to be fine with 80lbs seat pressure and 200lbs over the nose now require a LOT more pressure to keep things in check to prevent problems with harmonics at high rpms and noise with the valve bouncing off the seats, etc, etc.

Super strong springs are NOT favorable to flat lobes and we are seeing a very high lobe failure rate in the past 10 years or so with this sort of thing.  It doesn't help that many lifters are now "off-shore" production, but that is another topic I'll cover on another day.

What I'll say here is that currently we are getting and have been getting a LOT of complaints to the shop from folks who have just built a new "high performance" engine for their pride and joy and are having considerable running issues with it.

The common denominator I'm seeing are these "new" camshaft profiles with "modern" lobe designs.  They also more times than not have much tighter LSA than stock type cams and older designs used to do the same thing.  The tight LSA alone produces more overlap, so idle quality, power right off idle, and power in the normal driving range is negatively effected.  This happens even if they have taken out some actual seat timing to improve vacuum and cylinder pressure.

The camshaft companies seem to be targeting the audience that wants that "aggressive" idle quality or "lope" in the exhaust note.  That's all good but remember here that increasing overlap does a little more than make for a rough idle.  It allows unburned fuel over into the exhaust, and reduces cylinder pressure which both hurt combustion efficiency at idle and low rpm's and also make for "stinky" exhaust.

A couple of other things happen as well.  Tight LSA also narrows up the power curve and pulls peak power DOWN in the rpm range.  Both of these facts increase octane requirements all else being equal.  So for the guy who just chose a compression ratio for his new engine that typically is fine on currently available pump fuel, he quickly finds out that it isn't when the engine is placed in service.

This happens so often I felt needed to mention it here.

Second problem is that with these tight LSA camshafts with greater .050" and .200" numbers is idle quality is greatly reduced and vacuum production at idle low for the CID and compression ratio.  This requires MORE timing from the distributor at idle and greatly increase idle fuel from the carburetor. 

This is how I get involved in the first place as folks put these engines into service and very quickly find out that they idle very poorly with "normal" timing and idle fuel settings.  I'd like to have a nickel right now for every phone call I've received in the past 4 or 5 years where the owner of one of these sort of engines calls up and says that the idle mixture screws have no control, engine refuses to idle much below 1000rpm's or so, and the that the exhaust is so stinky it runs him right out of the garage on start up and stinks up his cloths, his wife's hair (never a good thing), and it's stalling at stoplights/consuming more fuel that it should, etc, etc.

Continued below.....

[Cliff Ruggles]

So basically I just wanted to put up a post this morning for folks who are contemplating their camshaft choice for a new engine build.  Nothing has really changed with this sort of thing as far as a bunch of power waiting for you with a modern cam profile.  That technology is all played out with flat cams and has been for many years.  Since we still can't get past the laws of physics with these things choose the camshaft for your new engine based on CID, true static compression ratio, drivetrain specs and intended use of the vehicle. 

Also look very closely at the camshafts that the factory used for similar engines.  Yes, the engineers really did know what they were doing with these things and designed and used camshafts that worked very well back in the day and still do.

I would for sure avoid any cam on a really tight LSA for most builds, and look very closely at the advertised duration to .050" specs and spring requirements.  Also avoid any lifters that are not USA production. 

Hope this thread helps some.......Cliff

[429bbf]

nice right up cliff thanks .has anyone on here ever used a cam doctor . i have not yet seen a cam that is ground  perfect  some are plum bad . if anyone gets the chance put your new (supposedly perfect cam on one) and you will see how bad some are and its not just one brand.fwiw

[markedmondson]

Thanks Cliff; very insightful.

I posted a link to this on the NCRS forum; the guys there will find it useful.

[jamesF]

GOOD INFO.That was a great read...... That made me  pull the trigger.. I ordered a Stump Puller on a 112 from Dave at SD this afternoon for my 455 to replace my XE type on a 110 LSA..

[Cliff Ruggles]

Thanks guys. 

The Stumpuller cam is excellent for a Pontiac 455 engine build.  I like to see at least 9.5 to 1 compression with it. Idle quality is excellent, relatively smooth with just a hint of attitude. It produces a very strong/broad/flat power curve and works quite well with stock converter/gearing, but really shows it's colors with a very well made aftermarket converter with a little added stall/torque multiplication but still very well coupled in the "normal" driving range.......Cliff

[Cliff Ruggles]

Had a few extra minutes this morning and wanted to put up some dyno sheets here.

It's a great story and on topic about camshafts if you have time for the read. 

The story goes that an engine builder and machine shop owner builds his first Pontiac engine.  He had extensive experience with other engines but never took a Pontiac 400 and installed one of the available "stroker" kits to make it a 455 (actually 467). 

He took on the project and bought the stroker assembly, and topped with an nice set of #96 heads ported to 250cfm on the intake side.  Stock head flow is around 215 or so for those heads.  Anyhow, he computed the static compression ratio and it came in around 9.3 to 1.  So he should be fine on pump gas, IF you believe all the "experts" on the Forums who continue to regurgitate information on that subject.  The engine builder also wanted to upgrade to a hydraulic roller cam with retro-fit lifters.  Comp cams recommended and sent him an XR276HR camshaft.  On paper it really doesn't look too bad for the build, sporting 276/282 @ .006", 224/230 @ .050 duration, .335/.340" lobes (.502/.510" lift) and 110LSA. 

The cams is installed, degree'd at 106ICL and they go to the dyno.  My only contribution to the project is supplying a rebuild kit and tuning parts for the Q-jet they are going to use.  The dyno runs are a bit disappointing and of course everyone is blaming the Q-jet from the dyno operator all the way down to the guy who takes out the trash.  They actually installed their "dyno mule" Holley and cranked up the timing to make acceptable power and blew up the engine on the dyno from detonation.  Yep, pinged it so hard it spun the rod bearing and damaged the crankshaft.

So I get the call from the shop owner and we go over the engine specs and I tell him that the cam is the problem with it and to replace it with a larger cam on a wider LSA.  Of course initially he's a little set-back by my comments not fully understanding that the relatively "small" cam on the tight LSA was simply too good at cylinder filling and making excessive cylinder pressure early in the RPM range.  Yes, tight LSA yanks power down and narrows up the power curve.  This not only hurt power it would not allow the engine to effectively manage pump gas even a little less than 9.5 to 1 compression.  We also talked a little bit about my experiences/track history with long stroke Pontiac engines and tight LSA with early closing intake specs and finding that the wider we go with LSA and bigger the camshaft the better they work when placed in service and the more power we are rewarded with.

So I supplied some cam lobe recommendations, we moved up to a 289/308 @ .006" with 236/245 @ .050" with bigger .381" lobes and wider 114LSA.  I advised to set the ICL at 110 degrees and not advance the cam any further.

The engine was repaired, and the only change done was the cam replacement.  They put it back on the dyno and low and behold it is now fine on pump gas with "optimum" timing/fuel curves, idles better, and cranked out quite a bit more power as shown on the dyno sheets!.......Cliff

[Cliff Ruggles]

Bump.

[David Haskins]

Very informative article Cliff. You have me thinking about my 69 Pontiac 350 rebuild and the cam I chose to use in it.  I was wondering about the god awful smell in the garage every time I fired it up. I have used nothing but 93 octane non-ethanol fuel ever since the motor has been rebuilt (approx 2 yrs ago and 500 miles)with a Holley 600 that I never could get to work properly.  Gonna need to give some serious consideration to re-camming the bird.  Thanks for your wisdom.

[Cliff Ruggles]

Bump

[73ss]

Cliff, I am new to the world of roller cams and would like to ask if you have a favorite in mind for a BBC? This is a gen 6 block with a factory roller. I am putting together a 489, Scat stroker kit with Brodix race rite oval port aluminum heads. Block has been decked and pistons are 10 in the hole. Compression should be right at 10:1, depending on gasket. Edelbrock Q-jet RPM intake topped with of course, a q-jet.

I am very pleased with my old flat tappet 454 set-up. when I put this motor together 15 years ago I fell victim to the magazine hype and installed a Comp extreme energy. I experienced everything you have posted above. What a piece of junk!!!! I called comp for some help and they blamed??? You guessed it, The Q-jet. Based on your forum posts I removed it and installed a Summit 1302.https://www.summitracing.com/parts/sum-1302. This is a 114 LSA cam, the comp was a 110, very similar lift & duration specs between the 2. This is by far the best cam I have ever run in a mild street BBC. Perfect blend of vacuum, idle speed, Very quiet, and would not wash down the cylinders at an idle. This has been a great combo for me over the years but it has gotten boring, and I am starting to lose a lobe. I got 10 yrs out of it but I'm done with the flat tappets. I would like to find a roller that would behave the same way. Any recommendations? Thanks for any help.   

[Cliff Ruggles]

A hydraulic roller cam is chosen in the same manner as a flat tappet.  They compare pretty close except many roller camshafts push the envelope a bit for opening/closing velocity and will require pretty strong springs to keep thing in check.

I use and prefer older lobe profiles with slower ramps and I run less spring on them.  I've taken some criticism for this, but have had zero issues.  When I've strayed over to faster ramps we've seen the engines take "nose dives" on the dyno at higher RPM's.  At first I thought it was simply the heavier parts but have found out that it's the ramp profiles and inability of the springs to keep things from getting "stupid" at high RPM.

Going to a HR camshaft is not any sort of guarantee that you woln't have lifter/lobe issues.  There are a LOT of lifters being sold that will not go the distance and we're seeing quite a few failures.  There are several suppliers, Johnson, Morel, Isky, etc.  The better HR's are quite a bit more expensive than others but superior in quality so avoid any of the cheaper retrofit HR's.

I'd also avoid running a lot of spring pressure and stick with "softer" lober profiles.  The factory is able to get away with using HR set-ups and they will go hundreds of thousands of miles w/o issue and guess what, they don't get stupid with super-quick ramps and don't use a lot of pressure on them either. 

Maybe there is something to be learned from this?

My current HR cam uses Comp Magnum roller lobes, advertised is 289/308, .050" is 236/245, LSA 112.  I decided back in 2009 to run Crower HIPPO solid roller lifters on it because we were seeing so many problems with HR's.  I set the lash at .005" and it's not only been pretty much maintenance free it's the quietest engine that has ever sat between the fenders of the Ventura.

I just checked the lash couple of days ago, haven't even looked at it in at least 3 years and they were right on the money.  I'm not recommending using the "hybrid" set-up, but I would get good HR lifters if you plan on going that route.  Hylift Johnson would be my first choice.

I'd also mention that there is nothing wrong with flat camshafts and no need to worry about loosing a lobe.  With all the problems we've been seeing with this sort of thing I've been sending our cams off to be "coated".  They come back looking like black chrome and will last just about forever.  Ion Bond did the last one for us, excellent work and reasonably priced.  We topped it with genuine Johnson lifters......Cliff

[73ss]

Thank you for the info. I already bought GMPP factory style lifters for it. I figured I should be ok since this is what is used in the 454/502 crate engines. I will avoid radical lobe profiles and too stiff of a spring. Comp does not offer a "standard" cam for this engine. They have the extreme energy & big mutha thumpa line. Howards looks like they have a nice selection, I've contacted straub as well.

This engine was a few miles shy of the 200K mark and the roller lifters were starting to wear a groove in the lobes, but they were not going flat over the nose like a flat tappet set-up would do. From the looks of it, oil changes were few and far between, probably once it hit beater status. Still ran good and was quiet.
Thanks again for the insight.

[Cliff Ruggles]

Comp also grinds just about everything on a "tight" LSA.  This is done more for the "bling" factor than anything else.  Wider LSA isn't going to produce a "choppy" idle, stinky exhaust and reversion at lower RPM's.  The target audience typically prefers that deal compared to a smooth idling engine that is efficient at lower RPM's, clean exhaust and smooth/broad/flat power curve.

I'd add here that I get butt-loads of complaints from folks who went to XE lobes and even more from those who did the 107LSA Thump-ya-mutha stuff.....FWIW......Cliff