Cams for 455 engine builds.
 

In recent years we have been getting a LOT of complaints from folks who have build 455 Pontiac (and Oldsmobile) engines using relatively "small" cams on 110 or tighter LSA angles. Also getting a good many complaints from those who built BBC engines as well, although they aren't nearly as effected by this issue having a larger bore and shorter stroke at nearly the same CID, but it still applies to those engines as well.

Most don't go public with their troubles, so I'll put it up here for them.

The 455 is a HUGE engine. Avoid small cams right to start with in them, and for sure stay away from little cams on tight LSA's.

Even 455's with relatively "low" compression still need a lot of seat timing to perform well, as the basic laws of physics doesn't change with these things.

A tiny cam that's completely happy in a 350cid build at 8 to 1 compression is a PISS-POOR choice for a 455 build at any compression ratio.

I've helped about a dozen folks out in the last year or so building 455 street engines in the 9.5 to 1 compression ratio range who chose the Comp XE268 or XR276HR cam for their engine builds. All of them were disappointed in the end results, and a few were forced to removed those cams for a better choice.

Had two folks last month who chose the roller version for their 455's and one of them was a very well established engine shop in PA. They installed the XR276HR cam into a 455 engine with 250cfm #96 heads and it worked very poorly on the dyno. They actually "pinged" the engine and hurt the bearings trying to get it to make acceptable power for the combination of parts.

I got involved as we supplied all the parts to the Q-jet they were using and it was getting the blame for all the troubles.

After a long talk with the owner/engine builder he ordered a custom ground HR cam basically the same as the Old Faithful grind but on a 114LSA. The end result was fantastic.

The first dyno runs with the Comp 276 cam maxed at 428hp/516tq, DONE by 4900rpms.

With the new cam and no other changes it made 514hp/559tq, and made MORE power (torque) at every rpm and idled better than the smaller cam on a tighter LSA!

So much for camming your 455 to make MORE power earlier in the rpm range and not worrying so much about top end power. The wrong cam or cam designed to pull power down in the rpm range simply doesn't accomplish this.

You can have your cake and eat it too with these engines. With the right cam your engine will manage pump fuel without any issues, and make over 500ft lbs torque clear across the loaded rpm range. The second cam had the big 455 producing 519ft lbs at 5000rpms, and still 500ft lbs at 5300rpm's! The first cam only made 441tq at 5000rpms and was pretty much DONE making HP by then anyhow.

A conversation I had a few days ago with a customer who built an Olds 455 with 10 to 1 compression and 224/230/110 cam with short seat timing prompted me to go ahead and put this post up. He's having issues, and the carb we built for him is getting some of the blame. It idles "quirky" (common issue with these engines and small-tight LSA cams), and really isn't making nearly the power him and the engine builder had expected.

I figured as much good information that's out there these days we need to avoid making mistakes when it comes to this topic. I hope a few of the Olds enthusiasts wonder over here and see this.........Cliff

Just for conversation only, not a recommendation here in response to the Cliff, or his opinions and/or results.

Related, below are comments made by Harold Brookshire years ago regarding UltraDyne lobes. Note his comments on opening and seating velocity and about 'sewing-machine' sound we hear so often regarding Comp Hydraulic flat tappet cams.


"Although I have done only a few Buick cams, I have done an awful lot of Pontiacs and Oldsmobiles. Jim Butler, famed Pontiac engine builder, was my largest buyer of camshafts at UltraDyne, doing over $65,000 a year. He thought they worked very well, until the Recession of 2000 left us with an inability to keep him supplied.
As was said, I do all my cam designs as unsymmetrical cam designs. Although I design my hydraulics just like I do my roller profiles, The information I will give applies just to my hydraulic flat profiles.
Using Harvey Crane's Hydraulic Intensity formula, ALL my .842" tappet designs have an Hydraulic Intensity of 53.88 degrees.
This is the duration at .050" subtracted from the duration at .004", where the SAE has decided that hydraulic durations begin and end.
This Hydraulic Intensity of 53.88 is considered to be very aggressive, yet the cams do not have that 'sewing-machine' sound to them.
The opening side of the cam has a 45.26 degree equivalent Hydraulic Intensity, and the closing side is 62.50 degrees Hydraulic Intensity. The SEATING velocity of the valve is only 37% as fast as the OPENING velocity. This seating velocity is only slightly faster than GM uses on all their engines. At UltraDyne, I have had many hydraulic, as well as solids, go over 100,000 miles on the street. I keep the edge of the tappet about .018" away from the point of contact between the cam and tappet.
That 'sewing-machine' sound is caused by the valves hitting the valve seats too fast. The original High Energy cams, which I designed, produced that sound. I was shutting the valve at .0007"/*, only .0002"/* faster than GM. After hearing about the noise, a little thought made me realize the .0002"/* was only 40% faster than GM.
You do not have to shut the valve faster to keep the charge from getting out.
You have to design the cam so the charge, or inertia ram, is still filling the cylinder when you shut the valve.
Every cam I design, hydraulic, hydraulic roller, solid, solid roller, is designed using the same theory I have used for the past 29 years, and they all make excellent bottom-end torque for their duration."

Now with these comments from Harold in mind. At one time I thought the Lunati Voodoo lobes were the same as UltraDyne lobes, since then I have read from conversations on PY that they are not. Apparently Harold while at Lunati revised lobe designs and developed the Voodoo line.

To further that here is quote I recently found from Harold the cam engineer himself just as his line of voodoo cams came onto the market about 7 or so years ago:

"The Lunati Voodoo cams are not old Ultradyne cams, although as designer of both there are certain similarities. Both are unsymmetrical, with aggressive opening sides and gentle seating ramps (to control seating noise). The specs on the Voodoo's are set by Lunati's former sales manager as far as lift and duration. The shape of the curve is the way I design, the names Ultradyne and Voodoo aren't interchangeable."

Paul Carter had good contact with Harold before he died recently. I asked Paul on the subject. His reply to me...

"Steve, the Voodoo lobes have the same closing velocity as stock GM. They are quiet. Harold split the duration on them as 57.5% on the opening side, and 42.5% on the closing side. Or there about. They open fast, and close slow."


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And if interested here is another source for information that relates:

Cams and Engine Performance

http://www.tildentechnologies.com/Ca...rformance.html



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Jim Butler used to sell a boat load of UD cams. 280/288 and 288/296 HFT were big sellers and still work good! I have the 296/304 in my pump gas 455 int he 78 TA now.

Harold was also a big proponent of matching the intake/exhaust duration split to the head flow.

To further Skip's comment of matching the intake/exhaust duration split to the head flow.

Years ago I asked Harold at Ultradyne when he was posting here on PY about the subject of a single pattern vs. a dual pattern cam. Here was his reply:

There are two different items at work here.
1.---On most cylinder heads, whenever I have around a 75% exhaust-to-intake ratio, I use an 8 degree bigger exhaust cam. If the ratio is under 70%, I use 12 degrees, and around 80%, only 4. Whenver the ratio gets around 85%, single pattern cams seem to work as good as anything. Rarely do reverse-pattern (intake bigger than exhaust) cams work.
The two times they do, blown alcohol and turbo-charged, are both for putting heat into the engine or the exhaust.
2.---At the same time, it depends upon what you want the engine to do. Single pattern cams have better bottom-end, dual pattern cams have better top-end. At low RPM, the longer power stroke of a single pattern cam puts more torque into the crank. At high RPM, the most important thing is getting exhaust gas out of the engine. You can't get more charge in if old exhaust gas is still in the chamber. This is why the torque curve makes a sudden down-turn at peak horsepower. The exhaust cam has suddenly become inefficient about getting the old exhaust out, and some gas is retained and trapped, and the intake cannot fill completely because of this extra exhaust gas hanging around.
So, for the best overall power curve, on the average you want a dual-pattern cam, and around 8 to 10 degrees more exhaust. However, if a lot of bottom-end is your goal, or you have heads with a high exhaust/intake ratio, a single-pattern cam will work better.
Was this confusing enough? This is based on 30 years(1972-2002) of cam design and application.
UDHarold

( side note: There have been interesting conversations, and opinions, here with skip and others regarding reverse pattern cams. Remember the above was Harold's opinion )


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Good info, gentlemen, but you know the "keyboard experts" are going to tell you that "my buddy, this magazine I read, etc. (ad nausem) said this" instead of reading and LEARNING from REAL world professionals.

Personaly I'm not a cam expert, I just provide good solid proven information for conversation around the coffee table from many who are experts. Like Cliff has and does. Take it or leave it :)

And in my opinion look at catalogs for interest and ideas, when the time comes it's easy to call a cam designer and discuss it with them. If necessary purchase a custom cam suited for your needs... not just a catalog number !

For those interested and are not aware the Old UltraDyne lobes are available today at Bullet Racing. Excellent cams and good people to deal with. They do custom cams, any intake lobe, any exhaust lobe and any desired lobe separation... be it 110 or a 112 LS.

On my 505 I removed my first Crower solid roller cam and replaced it with a custom UltraDyne MSP solid roller from Bullet, it had 3 degrees less intake duation and a bit more valve lift, and with the same 110 LS. I picked up about 20 hp on the dyno.... thanks Bullet !

http://bulletcams.com/

For Voodoo lobes go to Lunati. They can do custom cams as well. Note if the Lunati catalog states a certain cam with a 110 lobe separation and you want it in a 112 LS, they will do it. You can order it custom direct from Lunati and I suspect even thru some place like Summit. If ordered thru Summit or others the cam will probably be shipped directly from the manufacture to you.

The voodoo cams listed in the 'Pontiac' section are limited. However if you look at the Small Block Chevy section you will find additional lobes there. The answer, you call Lunati and they will grind a custom cam based on those Chevy lobes on a Pontiac size billet core using the lobes desired. As you see it listed in the sbc section, or maybe with a different exhaust lobe with less duration if desired, or with a 112 lobe separation. Bingo there is your custom Pontiac cam.

Same applies for Comp Cams.

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"Jim Butler used to sell a boat load of UD cams. 280/288 and 288/296 HFT were big sellers and still work good! I have the 296/304 in my pump gas 455 int he 78 TA now."

Those cams were, and still are very good choices for these engines, and note how much seat timing they have compared to the "short seat timing" cams we've seen used in these engines that don't make the grade.

Also keep in mind when selecting a cam, that a stock replacement cam for a 350 SBC with 8.5 to 1 compression that works very well sports 274 degrees seat timing. Another very good choice for a 350cid build is the generic "RV" grind shown here:

http://www.northernautoparts.com/part/ml-mtc1

That cam works fantastic in 350cid engine builds to about 9.5 to 1 compression and is sold by just about everyone in this industry who markets "performance" cams for SBC engines. It's a near duplicate of the Summit 2800 cam which also works quite well in 350 and 400 cid engines with low compression.

http://www.summitracing.com/parts/sum-k2800

So why would anyone, educated or not about this topic put a 262 or 268XE grind in a 455 build at 9.5 or higher to 1 compression? Talk about to much cylinder pressure too early in the rpm range, which is one of the reasons many of the 455 builds that are using those cams work so poorly. The cams are too small, close the intake too early, and WAY too good at cylinder filling early in the engines RPM range......Cliff

Funny, when I purchased my engine (461 stroker, 300+ E-heads, approx. 10.0:1 compression with reported 1000 miles on it) it had the XR276HR cam in it. Chassis dyno from the previous owner showed approximately 340 hp at 4800 rpm on the chassis dyno with about 410 ft. lbs. of torque (this was with an Edelbrock Performer intake). I didn't run it that way as I wanted to have it 0-decked and to check out the bearings, bores, etc. When the bearings were pulled, they showed accelerated wear, but the rest of the engine looked beautiful. I can't help but think the original cam choice with the resultant deto may have attributed to bearing wear. I replaced the XR276HR cam with the OF on a 114 LSA and an Edelbrock Performer RPM intake and it now idles cleanly and fume-free, cruises beautifully (with better fuel mileage than some of my newer cars thanks to the 2004r trans- even using an Edelbrock 800 cfm 1413 carb) and accelerates seamlessly and brutally. Cold engine? Pump the accelerator twice, turn the key and drive away-no blipping the throttle and waiting it to warm up. Hot engine shut off? Twist the key and drive away. The engine has been the farthest thing from fussy.

Is the exhaust center normally moved?

Blued and painted, not sure on the question or answer.

There are various on line calculators available to help with timing events. Wallace Racing is a good one.
http://www.wallaceracing.com/Calculators.htm

The Kelly site deals with DCR ratio but note his calculator is handy for timing events as well.
http://cochise.uia.net/pkelley2/DynamicCR.html

Remember I'm an enthusiast, not a engine builder or machanic. I've dealt with experts on my cam selections over the last 20+ years, many of them custom cams for my various engine combinations. As an example Chris Mays at Comp Cams (so has Pontiac Dude), Harold Brookshire at both UltraDyne and Lunati and John Partridge at Bullet Racing.

That said, I'll mirror Cliff's thoughts.... in my opinion many Pontiac people often under cam their engines !

(and as a side note, by chance if any feel I'm sitting safely behind my computer screen and bad mouthing Cliff's opinions or his accomplishments, while "googling" up tons of great information from a variety of reputable sources, then you are sadly mistaken. Cliff is a friend and I listen to his opinions. Enough said ! )


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It would be interesting to compare the Stump Puller and OF cams with iron vs. aluminum heads to see which cam works better with which head.

My RAIV 400 motor I raced in the NMCA Top Stock classed had 5 different cams in it. Different sizes , degreed to different IC same cam, different LSA, HFT, solid FT, mainly Ultradynes.

Finally stopped with a Comp Magnum 242/236 @ 0.050 reverse split that picked that particular motor combination up 0.2 seconds and 2-3 mph.

Cliff do you recommend a Summit 2802/lifters kit for a 455 with 9.5:1, #48 heads, Ross deep dish pistons, 4 speed with 3.31 gears 66 GTO street driven? I need to order a cam for the builder next week. using the 4 barrel but have a tri power all built and on the bench to get installed after engine is run a while.

Jim

I have NEVER used the 2802 cam in a 455 at any compression ratio, so I'd really be guessing as to how well it would work or not? My gut says it would be fine for what you are doing, and I've read good reviews from others that have went that route, as well as the very similar Crower 60243 grind.

My personal favorite in 455's at 9.5 to 1 is a custom ground HR cam with 230/242/112 specs. It's big shorter in seat timing than Dave' Stumpuller, and smaller .361" lobes, but we've made great power with that cam in 455 HO/Super Duty builds with closer to 9 to 1 compression, as well as excellent results with ported iron head builds with 46, 96, 4x and 6x heads on them.

I have used the Crower 60919 cam in 455's down as low as 9.3 to 1 compression, and with Rhoad's lifters and 1.5 rockers they work very well, but that "package" is still best suited for closer to 10 to 1 compression and high ratio rockers like the Harland Sharp 1.65's or Crane 1.73 Ford units.......Cliff

just listing in...[I have a stump puller in my 400-462]

I see some fairly wide lobe separation angles in the street-type cams being recommended. Does this change as the .050 and/or seat numbers increase? Something like the 290b6 has made for quite a few fast Pontiacs but I believe that cam is on a 106?

I had good luck with a 288/296 on a 108 in a street 455, think Lee Atkinson also had a similar one in his first 455 in the first gen Bird he had until he went SFT.

You would almost think a solid would want a wider lobe sep since that seems to help the engine hang on at higher RPM vs. concentrating the power in a smaller rpm band.

Also curious whether increasing the bore has any effect on how you cam a car? Most of the discussion seems to revolve around stroke/LSA relationships. Where the heck is Screamingchief? He could do a doctoral dissertation in this thread ;)

You can see here where Harold at UltraDyne used narrow lobe separations on Pontiac:

http://web.archive.org/web/200301162..._camshafts.htm

Both Chris Mays at Comp and John Partridge at Bullet have recommended, and I've used cams with a 108 LS on a 4.210" stroke.

Lee used a 108 LS with his UltraDyne 231 degree hyd flat tappet cam, then changed to a solid flat tappet with 247 degrees and the same 108 LS. His car picked up. And if memory serves me right street driveability wasn't much different.

Jim Butler used to tout the UltraDyne 243/251 solid flat tappet cam with a 110 LS as potential for 1.2 BHP/CID at 9.5 compression. 455 = 540 hp.

X2
Where the heck is Screamingchief ? He could do a doctoral dissertation in this thread.


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lots of good info cliff, thanks for educating us all. however i do have a question regarding these "bigger" cams you recommend for 455+ engines, i always see you mention the heads are ported to benefit from these cams in your examples, does the same logic apply to NON-ported head engines?

reason i ask is because i posted a similar thread recently asking about what HR cam is best for 100% street engine with stock 6x heads, majority of the replies i got said to use the stump puller or old faithfull size cams... yet, SD & butler both said to NOT use those cams or anything that big because the heads dont flow enough to benefit from them & will require longer valves set up on a taller installled height. & ironically butler & comp both suggest that xr276 comp cam for a stock head 9-9.5 462 (stroked 400) engine... both said a lower compression engine doesnt need the bleed off of a wider lsa cam.

just trying to understand the reasoning why one would want such a big cam with stock heads, low(er) compression & lower stall speed (~2500) or does this "big cam" logic only apply to guys with ported heads & 3000+ stall speed? my understanding is you want to match the cam to the rest of the cars specs, in otherwords dont overcam it just because it may make more max hp on a dyno if the rest of the car wont benefit from or perform well on a bigger cam.

NHRA stocker guys run some BIG duration cams stock lift(by rule) in non ported head motors. One RAIV stocker I knew used a 274@ 0.050 cam!

I'm never too far away,just not feeling especially long winded today.

Plus I dont have much to add here except that any talk of seat timing should also make some mention of where said seat timing is being rated at.

I say that as Harold B. was a big fan of shorter seat timing for all applications,just look closely at the progression of his lobes thru the years and that's obvious to see as they got shorter and shorter in seat timing as they evolved (ie: the VooDoo lobes are shorter than the UD lobes).

And if you look at the UD hydraulic lobes you need to note that he rated those @ .0045" vs. most everyone else rating their lobes @ .006",and when you look at the UD lobes @ .006" they drop a few ° of seat timing making them look shorter in seat timing than most folks see as SOP.

Me,I dont necessarily think that short seat timing and tight LSA's are the problem,that is if one knows to account for that detail and choose the given cam accordingly (ie: they need to choose a cam that's a bit bigger than one would normally use with lazy lobes on a wider LSA),but that does'nt always happen in the real world,so yeah folks often have problems as it confuses the cam selection process for many less informed buyers.

It's the same deal with solid cams,that old "add 10° to compare to a hydraulic" axiom is'nt always true,often it'll take 20° (or more) to find a comparable solid cam to any given hydraulic cam,especially when other factors are thrown in like specific lobe choice,LSA and ICL differences and such.

Fact of the matter is cam selection just is'nt as simple as we would like it to be.

I do agree that I'm not a huge fan of "fast" lobes myself,I say that as I've mostly stuck with the old Crower stuff as SOP,so I got no stake in this debate one way or the other,but I do feel there is always some merit to any given approach if the practical application of said tactics are based in sound reasoning.

FWIW

Bret P.

A fwiw.... statements by Paul Carter here on PY....

I have two friends with 455's in their cars, that drag race them. Both are iron heads, and both run pump gas.

One 455 is a budget build with ported iron heads[6X-4, 249/209 CFM], has 9.9:1 compression, runs a Harold cam ground on a 108° LSA, and ran 10.90's in hot Phoenix air, on pump gas.

The other is a 455 with mildly ported d-port heads[#16's, 228 CFM]. It is 9.4:1 compression with dished pistons, has a solid flat tappet Harold cam ground on a 110° LSA, and runs 11.50's on pump gas in hot Phoenix air.

455's can run fast with tighter LSA's, with the right lobes, and person designing those lobes.


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Yep,generally ground on tighter LSA's as SOP to somewhat mitigate the additional duration they use.

It's all a game of give & take.

Stack the deck too much one way or the other,and yeah the whole deal can get away from a person.

IMO those fast lobes were largely meant to address the age old problem of folks "overcamming" their engines,allowing them to THINK they were getting cams that were bigger than they really were,and that's the cruxt of their problem,as nowadays people seem to be a bit more educated than they were in the past.

But you know what they say,a little education is a dangerous thing,LOL

Bret P.

I just like a "3/4 race cam" myself:)

As Screamingchief eluded to... my old UltraDyne catalog on hand shows two separate sections for hyd flat tappet cams, one based on .0045 duration for the seat timing and the other based on .006 duration for the seat timing.

I'm not suggesting these two as examples are apples-to-apples, but here goes:

Rated at .0045" with 280 degrees, 223 degrees at .050", 132 degrees at .200" and .3088" lobe lift.
Rated at.006" with 280 degrees, 229 degrees at .050", 139 degrees at .200" and .3200" lobe lift

As typical both the sold flat tappet cams and solid roller cams were rated at .020". That's why comparing a hyd cam to a solid cam can be difficult. Screamingchief has pointed out on numerous occasions how to do so with the timing events.

And related to lobe separation many cam experts have stated similar, but here is what Lee Atkinson stated regarding the subject:

FWIW, I have not used "LSA" as a factor in cam design in years. I get the opening and closing events where they need to be, and LSA is just a by-product. When you use exhaust lobes that are more than 10 degrees bigger than the exhaust, the old LSA "rules" no longer apply.

The Link I posted previously here to Tilden Technologies goes into some details regarding this.


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Well thank you, it's only been on the track a few times with the 505 and only to confirm it's a legitimate 10-second street car. I'm sure there is more in it with converter changes, gearing, tuning, tire pressure changes, good weather, etc., etc.

But I have no intentions to try for a faster time nor do I care. And it's not a light car set up for the track. It's a 10:1 pump gas car to cruse around in only and to enjoy. And with a 'small' cam !

And 'no answers', again just conversation for interest. As stated previously... take it or leave it.

And at a light 3360 lb race weight like yours ....my ET / MPH computed is 10.02 seconds and MPH of 134.87 MPH.

And if your comment was not directed at me personly, my sincere apologies to you. But I felt it was since you posted right after me. Sorry for any confusion.


Have a good day :)

"i always see you mention the heads are ported to benefit from these cams in your examples, does the same logic apply to NON-ported head engines?"

We've built several of these engines without touching the heads anyplace and the same logic still applies. A big cam still makes big power even with stone stock heads.

We built a 455 with untouched #46 heads from a 350 engine and it was only down 15hp from an identical engine with 230cfm ported heads.

We also built a 455 with a pretty "hefty" cam in it with the smaller chamber #46 small valve heads, unported, and it' pushed a 1981 Firebird to 11.90's at 112mph on it first outing it the heat of August at Norwalk.

For sure you will see some additional benefits from correct head porting with larger cams, but these engine can still run pretty well without porting the heads at all. Just take a look at the Pure Stock and Stock Eliminator cars.

"reason i ask is because i posted a similar thread recently asking about what HR cam is best for 100% street engine with stock 6x heads, majority of the replies i got said to use the stump puller or old faithfull size cams... yet, SD & butler both said to NOT use those cams or anything that big because the heads dont flow enough to benefit from them & will require longer valves set up on a taller installled height. & ironically butler & comp both suggest that xr276 comp cam for a stock head 9-9.5 462 (stroked 400) engine... both said a lower compression engine doesnt need the bleed off of a wider lsa cam."

I've had several of those engines brought in here for us to tune using that cam, it's a complete TURD in a 455 build at 9.5 compression with ported or unported heads. One of the engines brought here was a 455 Super Duty using that cam, with the compression raised to 9.5 to 1. It was a complete DOG, and very octane sensitive as well. Hated "normal" timing and fuel curves, and really wasn't trying to make any power no matter what we did for tuning.

I would also mention here that I never once said or even tried to indicate that you can't run well with a "tight" LSA cam in one of these engines. I'm telling folks in this thread that "tiny" short seat timing cams on "tight" LSA's work poorly, and you are leaving a LOT of power on the table choosing them for these engines......Cliff

My buddy read in a magazine about someone who sim'd this cam on a computer dyno. He said it would run awesome.

;)

No, for real. This is a cool thread, even tho I don't play in the big cube sandbox. Lots of good stuff.

Voodoo guy here. I'm a fan so far.

Steve, Harold told me those two different HFT sections are different families of lobes slightly different. Kind of like the different families or rollers he had.

I picked up for cheap an old Late Model asphalt car with a 350 SBC with an UD NF series solid FT lobe that is a pretty strong little motor-pretty wild sounding with the 180 degree headers too. Those are a different family than their regular solid FT lobes.

Thanks Skip. That's why I stated probably not apples-to apples. And you know me well enough that my comments are just conversation and I presume some might find them of interest. I'm retired and have nothing better to do :)


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Easiest way to see the difference in the UD lobes @ .0045" & .006" is to look at the listings for the UD lobes in the Lunati lobe catalog,as they got a set of those UD master lobes when Harold went to work for them,and in the Lunati lobe catalog you'll see that Lunati lists those UD lobes with the .006" rated duration per their SOP.

Cam is the tried & true 288-296 UD hydraulic:

UD lobes H5/H15

UD seat duration @ .0045" = 288°/296°

Lunati lobes UH5/UH15

Lunati duration @ .006" = 282°/290°

That's a 6° difference in seat timing,and that's often enough to be considered one "step" change in terms of cam "size".

Which often can be enough to throw off the results of a fellas cam choice if said choice were "on the edge" in the first place.

Also gotta watch for this on flat solid/hyd-solid roller lobes too,many are rated @ .015" and not .020",especially the milder comp lobes.

As far as "stock" heads are concerned,the first issue anyone will run into is lift related,not duration related,as stock heads with OE valve lengths often max out right at/around .525" lift or so when using OE valvetrain hardware (and remember you need to leave .050"/.060" for "safe" retainer 2 guide/seal clearance),that's likely why those recommendations from SD & Butler,so yeah it's not the duration of those stump puller or Old Faithful cam @ all,it's the lift they run that would be the problem with "stock" heads.

FWIW

Bret P.

See that's why Bret is missed around here. And I failed to mention many Comp solid cams are rated at 015" tappet lift. I was only talking about Ultradyne solid lobes.

Thanks Bret.

post #2 is a good read on LSA with some additional info. as well.

http://forums.maxperformanceinc.com/...ed+compression

Cliff. At what point would you want to start tightening up the LSA on a 455 past 112? At a glance it seems theres a general correlation between LSA and .050 duration on the older cam grinds.

This is also why I have no interest in picking my own cams out anymore. So much power, driveability, money, time etc can be gained or lost in the details. Thanks for posting this

We've built several of these engines without touching the heads anyplace and the same logic still applies. A big cam still makes big power even with stone stock heads.

We built a 455 with untouched #46 heads from a 350 engine and it was only down 15hp from an identical engine with 230cfm ported heads.

Cliff, do u happen to remember the details of these engines? I'm currently port matching a pair of '73 #46 heads. I'm upgrading the valves to 2.11/1.77 ferrea ss valves. I love hearing about stock heads, particularly the small valves.
Thanks

We used 1973 #46 heads, Crower 60919 cam, no porting anyplace, not even a gasket match. We did open them up for the bigger valves.

The engine made 440hp/530tq on the dyno, compared to the 455 I did a few years earlier that was identical except it used 230cfm 6X heads. It made 455.4hp/540tq.....Cliff

"Cliff. At what point would you want to start tightening up the LSA on a 455 past 112? At a glance it seems theres a general correlation between LSA and .050 duration on the older cam grinds."

At about 250 @ .050" it may help to start pulling the lobes in some, as you are raising the peak HP point past the capabilities of the shortblock and in many cases the head flow.

All of the 260 @ .050" (and larger) cams we've used in 455 have been on a 110LSA, but they have all been high compression "race" engines......Cliff

Ok just read this entire thread. My brain hurts now! You guys have way too much knowledge! ;)

Seriously, great thread. I plan to eventually change me tight little cam (xe274) on my 469 with ported, 255cfm #46 heads. So I will follow this and other conversations, on and off the forums, to learn.

Thanks for sharing!

Look at the numbers we got on the dyno with the Old Faithful Clone HR cam on a 114LSA compared to the XR276HR cam in a very similar engine.

The bigger cam idled better, and made more power at every rpm, nearly 90 MORE HP, and over 500ft lbs torque clear across the loaded rpm range.

With the bigger cam on a wider LSA peak HP moved up almost 1000rpms compared to power ending abruptly at 4900rpm's with the smaller HR cam.

Before someone says "I never plan on revving my 455 that high, it's just a "street" engine", keep in mind that at 5000rpms we could still shift the engine with the bigger cam in it and make good track runs, and enjoy nearly 519ft lbs torque @ 5000rpms vs 441ft lbs the smaller cam was making.

I do this all the time with my own engine, shift at 5000rpms for all track runs, and it only slows down about half a tenth or so compared to shifting it clear up at 5800rpms. Basically the car runs good using the broad/flat torque curve, and there is no need to "grind" up the engine with a much higher shift point.

I also use that deal to my advantage at the track. If I'm not getting the guy covered I'll "buzz" the engine a little harder and push him out on the top side, never giving him a chance to back out of it and get the win light.

Short shifting not only saves the engine some, but it also helps me slow the car down to stay roll bar legal, as flat out it will run almost into the 10's in good air, and really low 11's in the "heat".

https://www.youtube.com/watch?v=6zVdoLR-VzM


.....Cliff

"Look at the numbers we got on the dyno with the Old Faithful Clone HR cam on a 114LSA compared to the XR276HR cam in a very similar engine."

Cliff, do you have the dyno sheets for the pulls? I don't see them.

Thanks,

Tony

Yes, I have the dyno sheets, but haven't had the time to figure out how to scan them into the computer and post them.....Cliff

Snap a picture with your smartphone {assuming you have one}. Download the photobucket app. Upload your pics to photobucket. Use the IMG code to copy and paste here.

thats how I get it done

http://i1177.photobucket.com/albums/...ps7tfqbsju.jpg[/URL] :)

dont need photobucket for basic smaller pics, just use the pic upload tool here.

Dogs rule!

It's a pic of an Old Dog (Cliff and B&P) who prefers the old milk bones vs. the new Organic dog snacks

I'll get the pics of the dyno sheets and put them up later this week, most likely on Friday....Cliff

I can't say that I've done the test back to back on the same engine the same day, but I've had enough of these combo's on the dyno that I feel I can answer that question to some degree. The "old faithful" cam was designed primarily for our ported aluminum heads and came about after testing a number of lobe configurations including running a single pattern 236/236 using the intake lobe we use on the OF cam on both the intake and exhaust which was down about 15hp over the current 236/245 we use. The idea behind the "stump puller" was a cam designed to work well with our ported cast iron heads, cast iron intake and RA/HO exhaust manifolds. I've run both cams in many iron headed as well as aluminum headed combo's.

With the cast iron headed engines the power difference with everything else being the same is 10hp or less with similar torque peak numbers. The power curve is produced at a lower rpm with the SP cam and the vac. at idle is about 3-5" higher with the SP. Now if you were running a Torker II and headers there might (I doubt it would be much) be a bit more of a spread but I haven't had an iron headed engine on the dyno with a Torker II for a lot of years now as the demand for more hp while maintaining a stock appearance only seems to be getting stronger. When it comes to ported aluminum heads, the difference in power is 30-50hp more with the OF cam depending on which intake is used.

I always like to look at the entire drivetrain combo and application before making a cam recommendation as more hp on the dyno doesn't necessarily mean a quicker car.

Hope this info helps