I have read for years that Buick motors were picky about cam lobe profiles. Jim Bell at Kenne Bell really harped on this, and his stuff was all old school and long outdated by the '90s. TA, TorqueTech, Poston and others constantly tested and provided better grinds, eliminating the ineffective lobes and hype, as mainstream cam companies like Crane, Comp etc. kept making intense/extreme lobes an issue. Buicks continued to reject this "technology". TA explained the problem as a hydraulic lifter "crash" problem with fast-acting lobes above a certain rpm. Coincidentally, Steve Dulcich, a MoPar guy who writes for MoPar Muscle and editors Engine Masters magazines, ran into this same phenomenon trying to make 600hp in a 446" Chrysler with streetable vacuum and 6500rpm max rpm with a hyd. flat tappet cam. He, too, ran into instability at a certain (6000, IIRC) rpm with even the "Pro-Magnum" Comp special anti-pump-up lifters when using Extreme Hi-Lift (.904" lifter-specific) lobes (they were 275*@.006", 231*@.050", 149*@.200",.560" lift w/1.6 rockers). The MoPar and Buick share short, shaft mounted rockers, and the short rocker is said to contribute to the inability of the lifter to "keep-up". Some people on this forum are using the Extreme Energy and VooDoo (Lunati) lobes and having them custom ground, with or without problems on shaft rockers, I guess. My question is: If you are running the Edelbrock head with Chevy rockers, does this "lifter crash" theory/fact still apply??? I want to run some moderately aggressive small lobes (.842" lobes, of course) in my 464, which is going in a heavy car with O/D and a 4.10 rear (2.73 effective in O/D). It has P/S and power brakes, so I need good vacuum, these aggressive lobes give the most power per vacuum/drivability, IF THEY CAN BE CONTROLLED. Will the valvegear change to Chevy rockers be enough (the pushrods will be very long!) to make this work??? RB
Cliff Ruggles reports the same symptoms on Pontiacs with these "Xtreme cams".. I will email him, and let him tell the story. Pontiacs, of course, have stud rockers.. JW
Thanks, Jim. This is why I ask these questions, because I don't know enough to gamble on this selection. I am researching with you guys' help so I'm not making a mistake on this critical part. I like the TA cams the BEST of all the shelf cams, and am keeping a few of them (or custom variants) in reserve...
We have been following the Comp XE cams for some time, and even installed and tested one several years ago. My own test was a Pontiac 400 cid engine, about 10 to 1 SCR, 240cfm heads. We chose the Comp XE268 camshaft, which sports 224/230/110 specs and 268/274 degrees of off seat duration. Prior to this, we had been using either the Crower 60916 (221/229/112) or the Crower 60243 (228/235/112) in these engines. Either one of the Crower cams will tear your head off to at least 5500rpm's, both have a LOT off off seat duration, they exhibit a choppy idle, strong mid-range, broad power curve, etc, complimented by a strong top end charge to well past 5000rpm's. Right on the dyno we made 417hp/453tq (5500rpms peak), and 424hp/465tq (5800rpm peak) using those cams in a 400 cid engine, 10 to 1 SCR, unported heads. Not ever being completely content with anything, I chose the XE268 cam mentioned above to see how it would do in a well prepared 400 engine. The opportunity to dyno the engine never presented itself, so we just installed the engine in the car and did some street testing. Immediately, I noticed that the engine had no "lope" at idle whatsoever, somewhat "noisey" valvetrain. After break-in we did some street testing, and the engine was a TURD. Yes, one more time, TURD. It pulled OK off idle, and decent in the mid-range, but all DONE by 4800rpm's if not a tad sooner. I ran the timing/fuel curves all over the place, ran better before I touched anything. The initial results were so poor, I never even attempted track runs with that car to see how much power it really wasn't making. Jump ahead about 4 years. In my own 455, after having my engine and car in HPP and Popular Hot Rodding's Engine Masters addition, we decided to do a cam change. The engine (very basic 455) had made 494hp on the dyno and pushed my car to 11.64 @ 116mph at the track. The cam we were using was a Crower 60919 (304/314/113), basically a copy of the "old" Pontiac RAIV cam. Yes, an old design with tons off off seat duration, and slow/lazy lobe profiles. The cam chose to replace it was from Comp, custom XTQ lobes (very aggressive), 240/248/112. It sported less advertised duration, but .060" more lift than the old RAIV copy. We figured it had to make more power, right? WRONG, we lost 10hp and 22 ft lbs torque, peak number, and a LOT of average power. The engine went "dead" right at 5200rpm's. I tuned and tuned, even changed intakes and carbs, MSD billet distributor with locked out timing, etc, it made more power on the very first pull, every single thing I did just made things worse. The cam came out, and a custom hydraulic roller cam was installed, 230/242/112, with .361" lobes. It made 514hp and 587tq, and improved by cars performance at the track from 11.64 to 11.52, almost exactly what the power difference should have. OK folks, I'll add a couple of more examples, then tell you what I'm pretty sure is going on here. 455, 232cfm heads, XE274 camshaft, 414hp/487tq, DONE at 4900rpm's. Another 455, 230cfm heads, XE274 camshaft, 412hp, 457tq, DONE at 4900rpm's. Yet another 455, XE284 camshaft, head flow unknown, 400hp/499tq, DONE at 5000rpm's. (Yes, the bigger cam made LESS power). I could list another dozen or so examples, but by now we should be able to see a "trend" here. For the past 5 years or so, we have avoided the XE or any other "fast ramp"/short seat timing/more area under the curve flat cam like the plague. All the while I'm thinking that the short seat timing is not allowing enough air to flow thru the engine to make up what the long duration lobes can do. Not so, the problem is actually caused by the ultra fast seating velocity of the lobes. This causes valve bounce and instability in the valvetrain ("lifter crash"), which not only limits upper rpm power production, but kills off power in the upper mid-range as well. Jim Weise and I have spoken on this topic on several occassions. My conversations with him prompted me to contact a cam design expert, who fully explained what is going on here. All the while I'm thinking the lobes are just too "small", when they are actually really good lobes, as far as technology goes, but just don't work very well in actual use. Anyhow, I've taken considerable critisism for releasing this sort of information. There is always someone here and there that runs pretty good with this stuff, like most anything else. There are always a few that get "territorial" about parts that they use, whether they work all that well or not, anyhow. I try to stick to facts, and the facts are, that I keep seeing folks running near identical combinations of parts as I do, but using these sort of cams instead, and coming up WAY short of the power we are making, and the track numbers we are running. As a disclaimer, I've seen a few exceptions. Most recently, a customer of mine used the XE274 cam in a 455 for pure stock, and he must run the stamped steel rockers. He installed really light retainers, and pretty strong springs, along with stiff thick-wall pushrods, with perfect valve train geometry. His engine made up near 480hp, and his car runs much better than any other set-up I've seen using that particular cam. He may be onto something there, not sure? In any case, I apologize for the long post, although I left out about 20 pages of specifics, etc, just wanted to let the Buick folks know that quite a few Pontiac engines have not responded well to this sort of cam technology.....Cliff
WOW! :eek2: Thank you to JIM and CLIFF for the information on these "breakthrough" designs that don't always work! Every dyno test I have seen on mostly MoPar (but many Ford/Chevy ones,too) engines has shown noticeable increases with "fast-acting" cams. Comp, Lunati, Ultradyne, Engle, Hughes Engines (Bullet Cams?) and even MoPar Performance offer .904"-lifter-specific profiles that are even FASTER rate-of-lift than the GM-type profiles. These motors have heavy 3/8 stem valves, shaft rockers and other design features dating back to the mid/late '50s, so it is odd that they respond and it is documented that the Buicks and Pontiacs DON'T! So much for "technology", I think a proven, STABLE design will be in MY future! Thanks a million for the knowlege, guys, that's why this forum is so great!!! RB :TU:
This sound just like the problems Weekender has been having with his Comp cam. Noisey valves and it will not pull over 5000. Runs better with an old Postons cam that is much smaller.
What is the limiting factor in using a fast-ramp cam.....is it the valve springs, or valvetrain weight in general? One could achieve the same result of an 'extreme-profile cam' by using a std profile cam with some higher-ratio rocker arms.....duration would be nearly the same, but opening/closing rates. max lift, and 'area under the curve' would be significantly increased. Being a Nailhead guy, I'm curious if the extra ratio of the roller rockers I'm using will have any detrimental side effects...
This is where I think that Harold Brookshire (Ultradyne/Bullet/Lunati/Custom Camshaft) separates himself from the rest of the cam designers. While his mid-lift rates do produce fairly quick valve action, his non-symmetrical lobe designs provide slower valve seating velocities that are (according to him) only 10% faster than the stock old-tech GM numbers.
Very good discussion.I wonder if oiling has anything to do with the results.Altough not for a racing application,I have used two XE cams in two sbc's and was very pleased with the performance.I don't know how the Pontiac oil system works but I know that in the sbc and bbc they are very reliable.I know of others that have run those cams but they are all chevies too. The way that I understand the fast ramp lure is to be as close to needing a roller set up but save the money while using flat tappets.That's asking for a lot.I only decided to try them after some friends installed them with good results(no testing but hot street cars and trucks). I'll have to say though,that after giving a hard look at my sbb and bbb's,I would not consider that type of cam for either.Just my opinion.
Hello, everyone!!! Scott asked me to drop by and talk a little about cams, so here I am. 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 Hydaulic 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 realise 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. I will keep checking in to continue to answer questions. UDHarold
HAROLD! You will not remember me, but I bought some of your last MoPar cams direct back in 2000-1. (NF series tight-lash solid "A" small-block 259/263*@.050, .579/.590", 110*LSA in my 416" stroker installed at 104*)(Roller "B" big block 259/267*@.050, .652/.645", 108*LSA in my 446" wedge installed at 106*) I really appreciate your help and have raved about the good service/product for years. I used the Ford lobes out of paranoia on my 416, since it was a street/pump-gas, longevity thing, and it has been flawless! I want the same dependability and performance advantage out of the .842" lifter-limited Buick. With the desired low speed characteristics, vacuum, etc. I have in mind, an aggressive intake lobe seems beneficial, but the dyno seems to reject this in a Buick (Pontiac as well?). I do not require the 100,000mi. service life, but I don't want to spend weekends swapping springs or pulling cams either. Just hoping to glean some insight on why these do/don't function as well in one make/design of engine over another (even with similar rockers, when they were thought to be a contributing factor). Thanks for the interest, RB
Here's a 350 Buick with a Lunati Voodoo cam:http://www.youtube.com/watch?v=j_TXmApWlQs. Sounds good to me. I think the next cam I get will be a Voodoo cam. No Comp Cam stuff for me.
I was spooked by the recent post about the cam core shortage for BB Buicks, and hastily ordered a compromise stick from Comp.:Comp: I needed one to work with either iron heads and stock rockers OR Edelbrock heads with 1.6 roller rockers (Chevy), so I wanted less than .500 lift with the stock rockers and just over .500" with the rollers. I picked a modified "Thumpr" profile, the 287TH, but WITHOUT the 107*LSA. I went with a 113*LSA, for 16* overlap@.050", which should work well with the available compression, power brakes, etc. and have a good sounding idle. It has 287/305* advertised duration and 235/249*@.050" with .506/.491" lift, a compromise in intensity over the Extreme Energy and the newer "XFI" lobes for .842" tappets. I had it ground this week, and their tech said no problem with a core for the job.ray: While waiting on the semi-custom Comp stick, I scored a new TA-C113 (12* O/L@.050) from Ebay, in case I get too nervous to run this cam in my wagon. I've got to have enough bottom end to pull the O/D and lockup torque converter on the highway without surging/loping (3.91 gears = 2.73 in O/D)... :TU: RB PS: I may put the bigger Comp cam in first and swap to the TA113 later if it's TOO big, I don't think it will be...:Brow:
Generally speaking to be safe and have enuff vacuum for power brakes with the 455's you want 15* or less of overlap @ .050 but you are so close it probaly want matter. Thats a healthy cam you ordered so I hope it works..the Voodoo cam in the 350 Buick Youtube video in posts #12 and 13 is 227I/233E @ .050 with .505/.521 lift on a 110* LC and sounds great..I know someone that has that same spec Voodoo cam in a SBC and it runs like crazy from 2600 to 6100 and has no noise in the valve train.:3gears:
I know the modified "Thumpr" is pushing it, I just liked the lobe "rate" and the split on the durations. It was so easy to just have the LSA changed and roll with it, instead of going through column after column of master lobes! Some of the VooDoo cams were very appealing, but their rate and total lift was a little high, which seems to be controversial with Buicks (Pontiacs?). I had a TorqueTech SP235 (238/248*@.050"/112LSA) in a 9.5:1 455 with a Performer intake and had enough vacuum for my power brakes with 19*overlap@.050", so I figured this one would be safe. The big difference is I had a TH400 with a 3000stall back then in a Regal, now it will be in front of a 200R4 with a 2500stall in an '87 Estate wagon. All this talk of "noise" in the valvetrain is puzzling, even some of the TA cams are rated as having more noise than others, and yet they are not considered "extreme". We will have to see with this Thumpr-hybrid! RB
Looked at some of the TA cams specs and the Voodoo cams do have a little bit more lift at approx the same duration but nothing that would worry me. I've heard and read about many problems with the the Comp Cams Extreme Energy cams though. Their are a some that run the Comp stuff and do well with them but I'm not going to try one in a 455 Buick, however I would try a Voodoo cam.
The first post mentioned the fast ramp not working in Mopars but like you the ones I've seen work well. I believe Mopars have a larger base circle on the cam as well as a larger lifter diameter. The larger base circle is the key I think. Pro Stock blocks are going with huge base circle cams to get better control over the lifter. The lobe base circle is limited by the cam bearing bores.
UDHarold designed the voodoo line for lunati and so they use a much slower valve seating rate than comp's xe and xfi profiles. It's the valve closing quickly on its seat that causes the valvetrain noises with the comp stuff. The voodoos will not have this.
Not sure if this applies to the thread, but.... I have a (small) Straight line (Scott Brown) fast ramp cam 224/236 @ .050 I have had valve clatter since day one (9-10 years ago). We changed the lifters....still sounded noisy. There was no wear on the lifters we replaced, or the cam. I have been driving it ever since with no problems, or change to the noise. Is the noise I am hearing due to the valves closing quickly, even on my size of a cam? James
