[cutlas]

I CC'd the heads and piston tops last night. These pistons really suck. The 670s came out at 75cc and the pistons at tdc came out at 26cc. using a compression calculator this works out to 8.6 to 1.
Lets pick a new cam for this engine. I am not partial to any one brand but I do like a lopy idle.
This is my combination.
67 Firebird.
th350 and will mach the torque converter to cam.
8.5" 3.08 posi. will be changing to 3.42
Hooker 1 5/8 headers
Performer intake.
sucky 8 eyebrow pistons.
8.6 to 1 compression
any ideas?

[OINK 1]

Welcome to the PY forums !!
Run the XE-274. You might want to port the combustion chambers.
The 670 heads are closed chamber and don't like running on todays gas !!
If you call me I'll walk you through the procedure.
1-303-776-0877
I also offer the Comp cams, LOWEST PRICES out there !
Take a look at my web site:
http://www.pontiacengines.net
Click on cams.

Thanks,
Pontiac Gregg

[Steve C.]

"We've had dyno charts sent here and they clearly show a sharp drop in power right around 4800-4900rpms.


And it has also been shown that on some XE flat tappet cam installiations a drop in power has been caused by not enough seat pressure to control the valve action as it returns to the seat. And yet the cam gets the blame.

Example from a previous topic:

".....it's my understanding his XE284 started to nose over at about 5500 rpm after his springs dropped to about 100 lbs seat pressure, then after a change to new set of differant springs with additonal pressure it then pulled to 5800-5900 rpm."

[roadrage david]

Like my 190 mph drop out of a c-130 turd from witch ""we"" showed the 6000 rpm shifts on foto and video( pictures from this video http://www.youtube.com/watch?v=NFaA51l1HmE ) .But acording to cliff this is seat of the pands proof and that thussend count . acording to him only dyno nr ore time slips count. obviusly my one and two gear upshifts where i shift iven befor the car engine nose over at 6000 rpm are fals!!!!! so is the video and the auto meter guages and my engine builder CVMS (who only build te engine for fastest pontiac engine to date) . and because my lack of ecsperience as a engine builder it is not posible for me to judge acording to Cliff and hase no merrit. i am under the imprssion that as long as a car keeps acselerating and gaining speed while rpm climes peak hp hasend been reatchst yet( hensh the frase nose over when you do) ......If i could not make max hp at 190 mph at 6000 rpm then i would not have been able to beat a Aston Martin vantage as that car is limited at 189 mph .
Now watchs cliff makes his statemend totaly disreguarding my post and that of Steve C. because hes wrong as well...........

[TinjunTribe]

Originally Posted by roadrage david

i am under the imprssion that as long as a car keeps acselerating and gaining speed while rpm climes peak hp hasend been reatchst yet( hensh the frase nose over when you do) ......If i could not make max hp at 190 mph at 6000 rpm then i would not have been able to beat a Aston Martin vantage as that car is limited at 189 mph .
Now watchs cliff makes his statemend totaly disreguarding my post and that of Steve C. because hes wrong as well...........

Rage, you obviously have the disposable income to build a beautiful car. You are so passionate about this debate.......why don't you just man up and spend the money on a day at a chassis dyno for a few pulls?

Then you could put it to rest.....please. I'm not calling you a liar, but the evidence on paper would prove it (better than pictures of your tach).

[Steve C.]

David- Cliff has previously acknowledged potential issues with lack of spring pressure and is quite aware of its ramifications. Below is one example when someone made this statement;
"A friend of mine put a 455/6X combo together with that cam, RPM and an 850DP. With 4 tubes it made 480hp at 5200rpm and about 520ft lbs at 4200rpm."

"Decent numbers, but any particular reason it quit at 5200rpm's? My much smaller cam made peak power in a near identical combination at 5600rpm's....hmm, makes me wonder once again about what Steve mentions about valve bounce......Cliff"

Stated: "...why don't you just man up and spend the money on a day at a chassis dyno for a few pulls?"

Posting copies of the dyno sheet would be better.

[chiphead]

Back on Topic...

What would be a better cam than XE274 for max performance out of a 8.6:1 400 with 3.08s?

[Cliff R]

Steve, we've covered this ground many times. I thought for years that the "short seat timing events" were to blame for not making the power with those cams. Nothing to do with it. The cams have excellent lobes profiles (for flat lobes), if you look at them on paper, and in theory. The problem is the seating velocity and opening velocity, which can and will cause problems in actual use. They seat the valves hard enough to cause valve bounce, and open them quick enough to actually "toss" the lifters off the lobes. This causes instability in the valvetrain, and shows up at high rpms as a sharp drop in power, as we have seen many, many times. Folks just don't pay any attention to it, or dismiss it for other possible causes, like fuel delivery for example.

We have not been able to discuss this topic like adults, as there are always a few who have chosen these parts, get all attched to them, and "territorial" when you start talking bad about them.

What I suggest that Dave would do, instead of trying to convey to the readers that Cliff isn't a "professional" engine builder, and someone else who advocates these cams is, why don't you visit your local track and get a couple of timeslips for us? The information that you will obtain from your experience, I promise you, will be priceless. Your car isn't going to run anywhere nearly as quick as your dyno numbers suggest, but that's just a guess on my part, based on decades of building engines and setting up cars to effectively use the power they produce.....FWIW....Cliff

[Danimal]

I'm running the 274 with a 10:1 400 with E-heads, 1:5 HS rockers, stiff springs, Performer RPM intake, and Dougs 1 7/8 headers with 2-1/2 on out. TH400 with 2600 stall and 3:23s

While it'll rev to 6,500 easy, and lope pretty noticeably at idle, I can't help but feel there's power left on the table with the cam. I've not done a bunch of cross validation on different combos, but I truly expected more.

Admittedly, a tune would likely help (it's still got the break-in tune) so we'll see.

Peeling tires out of Dairy Queen is all I've been able to do so far, but I'll drag it next weekend and get some timeslips.

That said, with stock heads, I'd go with XE268, but I'd strongly suggest consulting a few different Pontiac builders, in addition to posting here, to get their thoughts as well.

My biggest regret is not going roller when I built the engine, so choose carefully my friend.

Cheers!

[TinInjun]

This XE debate is like having to watch the same episode of "The Courtship of Eddie's Father" over and over again. Enough already!

[chiphead]

If somebody would list a HFT cam that would work better than the XE274 in a 9x:1 400, I'll buy it myself and do the testing in my car. Seriously!

I've got a 9.4 400 with a XE274 now. I have 5 years of runtime and I know how it runs now, it'll run low 13s high 12s and the motor is healthy.

List a cam already! Sheesh! Enough!

[old66tiger]

I never measured performance in any engine with how fast a car will top out. Top speed is primarily driven by factors surrounding the engine like gearing, wheel and tire size, transmission selection, etc. I have ridden in a 10.8 car that was very impressive on clicking off 1320 feet but was all done at 135 mph. Take that same motor and put some 3.23 gears behind, OD tranny and tall tires and theoretically, the car should hit 175 mph.

My experience has been and will always be driveability and over all response to the driving conditions for what the car was intended. I respect that David's car can cruise 130 mph and that he feels comfortable with pinning it that hard on public roadways. I personally had my GTO up to 120 on the freeway and with non-modern suspension and other drivers on the road, that was as far as I wanted to go and backed off quickly. Besides, I enjoy cheap insurance courtesy of no speeding tickets in the past 24 years. To me, the car has to have exceptional acceleration, respond well to throttle position and idle with a steady rhythmic lope - if any lope at all.

I had the Xe274 in my 455 and I simply wasn't impressed, period! I lived with the cam for approximately 3 years and if i had my choice, I would look other places for a cam. I had the tri-power on the motor for a bit and then switched over to a highly modified Q-jet and iron intake. The idle quality was marginal and it always had a irratic shake unless I was idling at 1100 rpms. I swapped out distributors, induction systems, wires, plugs, etc, etc, etc. never cleaned up the idle. The periodic shake was always there no matter what I did unless I sped up the idle. For this issue alone, it was enough to pull the motor and swap it for something different. keep in mind, I lived with this cam...not just an acquaintance.

The best that I got this engine to do with 1000 miles on the motor was 326 RWHP and 439 RWTQ. Given some more time and unlimited pulls, maybe there was some more left in it, but the maximum production nosed over before 5K indicating that spinning it harder would not make any more power beyond that point. Let's put it this way, it was OK and for the average guy that wants something to sound tough and isn't looking for the ultimate in high performance, it would be OK. Cruising down the road, it was fine and accelerated OK, but just lacked the punch that I thought it should have. I drove my buddies 68 bird with a nearly identical motor except for the 2802 cam and it felt and drove much more responsive. The idle quality was much better and just was much more drive able.

Back to the 400...I had the 60916 cam in my 389 and it was a good cam. Made really decent mid range power and idled very nice. I know a few guys running this cam in their 400's and it seems as if it is a good compromise between better than stock and not too radical to kill the power of the motor. I would start your search on the boards with a 60916 and see where it takes you.

Good luck.

[screamingchief]

Originally Posted by chiphead

If somebody would list a HFT cam that would work better than the XE274 in a 9x:1 400, I'll buy it myself and do the testing in my car. Seriously!

I've got a 9.4 400 with a XE274 now. I have 5 years of runtime and I know how it runs now, it'll run low 13s high 12s and the motor is healthy.

List a cam already! Sheesh! Enough!

I could probably come up with something to do the job.

You'll hafta order it from the cam vendor though,I'm not running a business or anything.

Any special considerations or restrictions we would need to know of on such?

Like are the heads clearanced for 1.65 rockers,and what sorta max lift are they good for,those sorta things.

And are we talking something that's similar in specs to make the "cam comparo" a reasonably fair fight???

What about idle quality,any concerns there or such?

I would likely use Bullet's lobes,they have pretty good flat/hydraulic lobe coverage.

Give us a little more info and I'll take a shot @ it for you.



Bret P.

[Cliff R]

Oldtiger66, thanks for the detailed post and experience. I've had dozens of others convey nearly the EXACT same experience to me about that cam in the 455 engine. (And yes, this is well worth covering again, there are new members here who need to hear it.).

The common denominators were power production, no more than about 400hp at the flywheel and all DONE by about 4900-5000rpm's. They also complained of "ticking" at idle and "irratic" idle. This comes from the valves bouncing slightly as them drop hard on the seats IMHO.

One very good customer of mine set up his GTO based on ours, 10" Continental Converter, 3.55 gears, Mickey Thompson ET Streets, mildly ported iron heads, just under 10 to 1 compression, etc. Instead of using a RAIV or Crower 60919 cam, he used an XE cam instead (to this day I don't know why?). Anyhow, his car runs high 12's around 105 mph, instead of low 12's at 110-112mph. It is a very well thought out set-up, with perfect traction, 1.70 60' times, 3700lbs race weight, etc. The power just isn't there, and he says it's DONE by about 4800rpm's.

We had two other customers build 455's with ported iron heads and the XE274 camshaft, both of them dyno's their engines, and they quit at 4800-4900rpm's. How many examples to we need to see before someone realizes that there is a problem with these cams?

What throws a monkey wrench into this, is unconfirmed reports from folks who don't have any documented vehicle performance, and one or two here and there that don't have these same problems. There is enough evidence at this point, for our shop to completely avoid these cams. Others still use them and rant and rave about how well they work, and I'm happy for you.

The readers here need to know that there are potential problems with them, nothing more than that, and that everyone who uses them does NOT have a positive experience with them.

Steve Coombes mentions above about a Comp XE284 cam knocking down a set of valvesprings and requiring new springs to bring the power level(s) back up to par. It just so happens that the springs they "killed" were the Crower 68405's, which are excellent springs. We ran a set for over 1000 documented dragstrip runs and 10,000 street miles on top of the Crower 60919 cam. When I switched to a hydraulic roller, we had a new set waiting and ready. We tested the old springs, and they were right on the money for seat and open pressure, so threw a .030" shim under them and kept them in service.....FWIW.....Cliff

[roadrage david]

Originally Posted by Cliff R

What I suggest that Dave would do, instead of trying to convey to the readers that Cliff isn't a "professional" engine builder, and someone else who advocates these cams is, why don't you visit your local track and get a couple of timeslips for us? The information that you will obtain from your experience, I promise you, will be priceless. Your car isn't going to run anywhere nearly as quick as your dyno numbers suggest, but that's just a guess on my part, based on decades of building engines and setting up cars to effectively use the power they produce.....FWIW....Cliff

Cliff To awnser you first sirguestion about me conveying to the readers that you are not a profesional engine builder i never stated that, you asume that , but to go deeper into that . Indeed i belive your not!! in a way that your a profesional engine builder doing it for a living. you might have been in the past not so today . Your bisenis is carbs umogst others.

And to awnser your second question. havend i told you as others did that i do NOT have a Drag race car, but a Endurance ROADRACE car. so yes i wl be slower in the 1/4 then a pro set up drag race car, because its a totaly difernd build car. appels to donuts here.

Your decades of engine building from the past, is in direct contray with some builders of today including mine. So that hase no merrit at least to me.
Hensh the rezen there are so manny difrend parts and combo,s to choose from and so manny diferend ways to aprotch engines building . yours is not gospel to everyone .

P-Dude thusend seem to have a problem nor thuse CVMS,with reving up a XE cam and get more rpm/hp nrs then you seem to get. At the same time P-Dude realy likes Hydralic roller cams, while CVMS thusend like them as mutch and likes sollid roller cams as his first chooice... thuse this meen CVMS is right and ore P-dude. they both aproch engine building diferend in diferned ways .
thise prooves that one ""might"" be beter and ore feel more conferteble in a diferend aprotch/field then the other and visa versa.
And thats your problem!!!!!!! you belive that when you find some buddys that found a simulair problem in ther aprotchs to engine building that yours got to be the one and only way. while there are others that proove you wrong...... then you totaly disreguard these people and there findings ore there way.........

[Cliff R]

Give it a rest, PLEASE. I have no motivation or intentions to degrade anyone or anyone elses parts. We are in business here, have been for a long time, and yes, we build engines. It just so happens that we take most of these engines to the dyno, and follow their progress thru track testing once installed in the vehicles. Aside from Mr. Jim Hand, I don't know of anyone who has tested more parts for the Pontiac "street" engine than I have, back to back, on the dyno and at the track.

I'm not trying to be as good as or better than any of the other engine "builders". I'm not much of a follower here, I'd rather be leading instead. I simply want the very BEST for my customers based on the amount of money they can spend on the parts currently available to us, and to reach the goal(s) for their projects.

As for my engine building abilities, there isn't anyone, anyplace more meticulous than myself. Even with that said, there are PLENTY of others who are just as good, and just as motivated to build the very best engine for their customers. I demand perfection, clearances MUST be right on the money, and use only the best parts available to us. If you don't pay very close attention to every single detail, you don't stay in that line of work very long.

For some reason, you continue to suggest that I am some how substandard in comparison to others, yet the ones that you compare me to do not dyno and/or drag race their engines (some don't even own a car that is Pontiac powered and street/strip capable), at least not nearly as many of them as I do. I don't think they buy dyno time either to test parts, or do back to back track testing, at least not nearly as many times or as often as I have here.

But it is not my style to talk about others in any context. Reality check Mr Roadrage, we are highly motivated to build the best products in this industry, whether it be an engine, transmission, carburetor, etc. Since you have absolutely ZERO experience in any of these areas, and must purchase your parts already finished, and then do not take the time to get accurate test results from them, your comments just don't hold any water with me at any level.

Don't try to play down vehicle performance just because you don't have any dragstrip runs on your car. It's got good tires on it, and you have dragstrips at your disposal, put a couple of runs on it, even if you can't launch hard, your 130mph trap speeds will shut me up and show everyone that you are making 600hp at 6000rpm's, or whatever you claim it does?

My prediction, is that you will not run well at the track. I also suspect you've already made a run or two with your car, and the results were less than desirable, but that just a guess, and I could be all out to lunch with that comment......FWIW....Cliff

[71 T/A]

Roadrage David, please check your spelling before you post. It's sometimes a challenge just trying to figure out what you're saying because your spelling is that bad.

Cliff, there are a couple of people locally running the XE274 cam and with combinations like you described above, are running 12.20s-12.40s. They had their motors built right by a guy, Charlie Kabbaby of Warpath Performance, who has been building Pontiacs for 30 years. Not saying those cams are great because I chose SD Performance's Stump Puller HR cam, but just saying.

[1966goat]

I'm not blaming anyone here, but I think we really need to pull from bickering within posts. I, for one, like to read what Cliff has to say whether or not I follow his advice. It's always good to read other views.

No need to attack anyone. Cliff in his first post gave a suggestion to the OP to directly answer his question. He didn't say anything more until he was trolled.

[Steve C.]

"The readers here need to know that there are potential problems with them, nothing more than that, and that everyone who uses them does NOT have a positive experience with them."

I have no bones to pick against a piticular XE flat tappet cam, but like Cliff suggested there could be a new individual who wanders onto this site seeking information. My intention is only to point out that in some instances the seemingly poor results with these XE cams can come from inadequate spring pressure used to control the valvetrain and not the specific cam itself. My example of the XE284 used here was only one of many similar situations that have been documented. And you can read numerious similar senerios on other non Pontiac websites, magazine tech material prestented, etc. regarding the same thing. That and I have corrasponded with some top individuals around the country that report the same regarding inadequate spring pressure.

Sorry if my rants get old but there are two sides to a coin.

[Cliff R]

Steve, your comments are well warranted here, and spring pressure is a factor at play. From what I've seen, those who use relatively "heavy" components above those cams have the worst results with them.

I know of one very successful 455 engine build using an XE274 camshaft. With mildly ported iron heads it made nearly 480hp and over 550tq. The numbers were backed up by track runs into the high 11's at 3800lbs. This particular engine is using stamped steel rockers, stock retainers/keeps, and very good valvesprings. They also used thick wall pushrods at .116" vs .080".

Those differences alone seem to account for something, as most of the other examples we've been associated with make quite a bit less power and are pretty much DONE at 4800-4900rpm's......Cliff