[Cliff R]

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

[Steve C.]

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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[Steve C.]

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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[Skip Fix]

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.

[Steve C.]

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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[hurryinhoosier62]

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.

[Steve C.]

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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[Cliff R]

"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

[tpssonic]

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.

[Blued and Painted]

Originally Posted by Steve C.

catalog states a certain cam with a 110 lobe separation and you want it in a 112 LS, they will do it.

Is the exhaust center normally moved?

[Steve C.]

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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[71 T/A]

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.

[Skip Fix]

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.

[66 Gas Tires Oil]

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

[Cliff R]

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

[1969GTO]

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

[i82much]

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?

[Skip Fix]

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.

[i82much]

Originally Posted by Skip Fix

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

[Steve C.]

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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