[ry57pont]

Originally Posted by Mr. P-Body

I recommend XE274H when compression is below 9.5:1 (iron) and 10.2:1 (aluminum) for a street-driven car "with attitude". I do NOT recommend it for "racing".

Jim

just curious why its not recommded for "racing" just trying to pick your brains about cam selection. - Ryan

[Region Warrior]

Just noticed i posted 114.93 mph. Was 113.93

[PONTIAC LARRY]

Originally Posted by ry57pont

is that statement true with stroked 400's?- Ryan

Yes, a 4.25" stroked 400 = same issues a 455 with 4.21" stroke

More suited to 389-412 ci Pontiacs with a 3.75" stock stroke

[Cliff R]

"The low-11 and mid-10 second cars discussed do not have XE274H. They ALL have XE cams, but they're solid rollers. They use the same "fast ramp" technology as the other XE grinds,"

The roller lobe removes the limitations imposed by the lifter diameter. Those XE solid roller, as with most of Comp's roller grinds, XFI, etc, are automatically going to be "fast ramp". Roller cams can be ground with very fast lobe lift rates, and all manufacturer's take advantage of this, from what I've seen.

The Comp flat XE lobes use some of the fastest opening/closing rates in the industry for flat style cams, but they have been critisized by some engine builders for taking the technology just a bit too far. I am one of those engine builders, as we tested a custom ground Comp cam and experienced problems with it at high rpm's. At that time, I was only trying to replace my old Crower 60919 cam with a "modern" lobe profile flat solid cam. I chose XTQ lobes, which are supposed to be even better than XE lobes. We also chose the cam 10 degrees bigger and .060" more lift than the Crower cam.

Anyhow, the engine LOST 10hp/22ft lbs and there was no getting it back. The power also ended abruptly at 5200rpm's, when the Crower cam made peak power to 5600rpm's and was just leveling off.

I beleive that we were seeing some valve train instability issues with the XTQ lobes, even though we had PLENTY of valve spring on the engine. There is no other reason that I can think of why the power just stopped at 5200rpms. I swapped in a custom ground HR cam, and the power cam right back....Cliff

[ry57pont]

cliff, do 60919's make power past 6K? my xe274 quickly leveled off at 5200. but that is about where i go through the traps at.

[Cliff R]

Peak HP in my last engine was right at 5600rpm's, but it wasn't falling off, just leveling off.

When we tested the larger 240/248/112 Comp XTQ lobed cam, power ENDED sharply at exactly 5200rpm's. This fact alone should have folks scratching their heads, arses, and just about everything else....IF you buy into all the "propoganda" cam companies throw at us about their "modern" lobe profiles.

How do you go from a 40 year old designed 231/240/113 cam to a "modern" 240/248/112 cam, with .060" MORE lift, and LOOSE power at every rpm???

I put .030" shims under the valvesprings, it changed NOTHING.

I didn't hone in on the problem at that time, just figured the seat to seat timing wasn't enough to sustain the big 455 engine as well as the old "lazy" 60919 lobes.

I was WRONG in that assessment, looking back on it now. I'm convinced we were seeing some instability "issues" with the valvetrain, even though we had very good parts everyplace.

Part of the testing I never talked about was that in one pull we actually made MORE peak HP, over 510 (up from 494). This was done with a T-II intake and 850 Demon carb, but the power still ENDED sharply at exactly 5200rpm's, just like you shut the ignition down. That one pull should have clued me in on the fact that the cam was trying to make more power, but was being held back by an unknown "issue" in the basic combination of parts.

I consulted with several folks on that deal in recent years, and got some good information on the subject. I posted some of it here, and, as expected got "flamed" for even thinking that there could be a problem with those cams....even when there were dyno reports right in front of us showing the same problems we saw during testing, etc.

In any case, I'd avoid those cams in favor of grinds with "soften" opening/closing rates (flat cams).

No need to re-invent the wheel with this sort of thing, there are grinds out there that work without any of the associated "issues" we've seen with those cams.

One or two success stories amongst all the contraversy doesn't cut it for me.

FWIW, we just had a customer send a carb here yesterday to upgrade it for his new cam, as he decided to yank out an XE262 cam from his custom built 455 engine after trying for 2 years to get it to quit pinging on pump gas and make enough power to do a decent burnout in a hard right hand turn leaving Dairy Queen!.......Cliff

[PONTIAC LARRY]

Cliff, in previous threads you used the term "lifter crash" with 5200 XE phenonoma. That makes sense to me that the hydraulics can't take the hammering (like valve float but all inside the lifter) This is still the case why a solid lifter version of the cam is OK right?

[Mr. P-Body]

Ryan,

The smaller XE grinds are STREET cams. When I use the term "race", I mean a serious effort to maximize power in a specific range based on the class, the car and the engine. Most of the classes where XE274H would "fit" are engines with higher compression (stock, super stock, etc.), making the XE grinds not a good choice. I consider the XE284H the "smallest" cam to use for racing, but even then, I recommend solids or solid rollers. Mike's wagon runs so well with XE274H because he has high compression and he feeds it a steady diet of 110. He's also geared specifically for the combination.

If you're trying to make maximum power, these may not be the cams "for you". If you want a good running powerful engine with decent street manners on pump gas, there are none better. Believe, don't believe. Your choice. But Comp sells more of them than all other cams combined, regardless of engine "family". "5000 Frenchmen can't be wrong..."

I promise not to get involved in these discussions in the future. The only reason I'm here now is because another brought my name into it. With hundreds of happy customers and about five unhappy ones (in 10 years of business), we will continue to use our approach.

PAX

Jim

[PONTIAC LARRY]

Gearing is absolutely essential to use a milder gear with an XE274 in a 455, trap rpm up to or right below 5200 I would imagine, so if you want to run mid 11's with one it needs to not exceed 5200 including converter slippage at 115 mph. 110 mph seems to be a common wall probably because of hitting peak rpm before the traps.

[TinInjun]

This dyno sheet is not for the XE274, its the XE284, but it can used as a reference. It is in a 455 with 3800 stall converter.

[Cliff R]

"Cliff, in previous threads you used the term "lifter crash" with 5200 XE phenonoma."

The term "lifter crash" came from a very well known Buick engine builder, who ran into troubles with XE cams in Buick engines back when they were first introduced. They were unable to get those engines to rev past, or at least make power past apprx 5200rpm's. They also experienced some valve train breakage issues as well in several engines.

I was told by a cam designer that the quick closing/opening ramps can cause valve train instability issues at high rpm's.

Whatever the reason(s), makes no sense to me whatsoever to mess around with any technology, or parts that may have issues associated with them. My personal comments are all based on this simple FACT.

Even more important than that, that particular line of cams doesn't bring anything to the table in the way of total power production over older cams, or cams from other manufacturer's that don't have any trouble(s) with their lobe profiles.

Two very basic reasons I stay away from those parts.

This entire topic really doesn't have any more than that to it. A few folks like those parts, some love them, some avoid them, I'm part of the last group, for the reasons we have mentioned........Cliff

[aktattoo]

Originally Posted by shoebox1.1

i read a lot of not so good things about this cam for a 400-455 pontiac. im curious to see who here really likes theirs and whats the fastest it can go? (in a street type setup)

Shoebox did you get the response you were looking for? LOL
So what was the fastest we saw here in a street setup, 11.5ish?

[Region Warrior]

Guys, you have to realize you can only get so much power in a certain rpm range.
Other then roller cams, theres nothing new or magical invented since the 60's.
Just revised over and over again try'n to find something that Pontiac engineers possibly missed.
Here argue'n comps modern raiv vs Pontiacs raiv. 41 yrs later, and still nearly the same results.
The hard truth is, if you want more power, your gon'a have to turn more rpm.

[Brent Flynn]

Originally Posted by Region Warrior

Guys, you have to realize you can only get so much power in a certain rpm range.
Other then roller cams, theres nothing new or magical invented since the 60's.
Just revised over and over again try'n to find something that Pontiac engineers possibly missed.
Here argue'n comps modern raiv vs Pontiacs raiv. 41 yrs later, and still nearly the same results.
The hard truth is, if you want more power, your gon'a have to turn more rpm.

I dont agree with this statement wholeheartedly.... HYdraulic roller cams(the right one, of course) can make more power and torque at or less than 6000rpms... if i had the money, i'd try a set up like that. On the other hand, this XE cam sounds like a doorstop to me....my cams are 100% streetable and will run deep into the 11's all day with a decent set of heads, iron intake and qjet... im already at 11.57/114.05(ran 114.95 with taller tires) and im shifting at 5300rpm. When i gear back to 3.73, i will go 116-117. I dont have any ''trick'' stuff. The closest thing i have on my bird to that is 1.5 Harland Sharps... it would run just the same with stock rockers. Im gonna flog the crap outta this combo... im seein 11.30s before its all over... and i dont have ported heads or intake. Basically, torque is what we're after... thats what gets the car moving... horsepower is for guys that have big heads, bigs gears and big cams/intakes.... just sayin

[shoebox1.1]

Originally Posted by aktattoo

Shoebox did you get the response you were looking for? LOL
So what was the fastest we saw here in a street setup, 11.5ish?

well yes! actually! i love to hear different points of view and get all this information. because im new to pontiacs WHAT I CAN DO is copy this,that, or the other combo and see what i can make of it. my car is heavy (4400lbs) and i have certain goals i want to achieve. for me id love to have the magic HAND combo albeit several hundred more pounds. i think it could crack high 11's. i cant go wrong with a HAND 234/5xx/112 combo
or a PONTIAC LARRY 224/5xx/114 combo or what i want to do-GREG MERRICK/TIM AT UD. 223/231/110 COMBO. i know all these three examples need to be geared appropriately, stalled appropriately and "installed" appropriately. for me its a cost factor with the converter. if i can get the HAND 10 inch ill do his combo. 2802 on the cheap and a lil cash gets the UD!!

[Cliff R]

"I dont agree with this statement wholeheartedly.... HYdraulic roller cams(the right one, of course) can make more power and torque at or less than 6000rpms... if i had the money, i'd try a set up like that."

If cost is a factor here, keep in mind that you can mimic a hydraulic roller cam power curve by using a flat hydraulic cam with a lot of seat to seat timing, then add Rhoad's lifters and high ratio rocker arms.

I've watched Jim Hand and others do this for years, and it does work.

Case in point. When we dyno'd my old engine, with the 304/314/231/240/113 cam, it had Rhoad's lifters and 1.73 ratio rockers. That engine made 494hp on KRE's dyno. We tested the Comp XTQ cam and LOST some power, then went to an XFI hydraulic roller cam, 230/242/112 and made 3 more HP and 4ft lbs torque with NO OTHER CHANGES.

Pretty much shows that you can make great power from flat cams.

The biggest basic difference I see in HR cams to flat hydraulic cams, is that you can actually use shorter seat timing and still make as much as or more power. By doing this, the engine also idles considerably better than it does with the long duration flat cam, more overlap, etc.

The Rhoad's lifters reduce seat timing at low rpm's and have the flat cam idling considerably better, or closer to a comparable HR cam.

What the dyno doesn't show us, is that the engine revs up and thru the rpm range a tad quicker with the roller cam. This shows up on the drag strip where it doesn't on the dyno.

We went from a best run of 11.64 with the Crower 60919 cam, to 11.52 with the 230/242/112 HR cam. Some would say this improvement was hardly worth the near $1000 price tag.

There are other benefits associated with roller cams. You take the chance of "scrubbing" a lobe out of the equation, which is a big problem these days.

Oil and jacket water temperatures are reduced some.

The engine revs faster.

The engine will idle better.

IMHO, when you apply the fast ramp theory to the flat lobes, like the XE cams for example, you just can't get the same amount of air thru the engine by reducing seat to seat timing and taking out overlap, etc, due to the limitations imposed by the lifter diameter......Cliff

[77 TRASHCAN]

When Smokey Yunick wrote his book, "Best Damn Garage in Town" He bragged on Mac McKeller, said he was the only camshaft guy that knew what he was doing....said the others were lost balls in the tall weeds....

Seems to me like his ideas are still Gitt'n er Done...LOL,

[Steve C.]

The Cam Performance page discusses the importance of a quick opening and closing cam.

A slow opening and closing cam, i.e. one with a large area C, will be a poor performer. It will have poor idle quality and poor off idle performance.

Summary
The most important cam design parameters are the four timing events or equivalently the advance, intake and exhaust duration and lobe separation angle.
Once the four timing parameters are established, the cam should be designed for maximum lift
A quick opening and closing cam will provide better low end performance than one that is slower opening.

http://www.tildentechnologies.com/Te...e.html#Summary

[Steve C.]

"It is a rush to go cruising with customers in their cars. When a customer has an aspirated motor at only 8:1 compression, and no power adders, it makes my day when the car runs so good that everyone thinks it is a really big motor with a solid roller cam and tons of compression. Actually, the most recent case from this last Saturday Night is a very successful combination that utilizes a fast ramp flat tappet cam that has a short seat duration, and a middle of the road LSA of 110 with a 104 intake C/L.
Why? Because it only has 8.17:1 compression. The motor runs hard to 6500. I see low compression (especially carbeurated) motors with some huge seat duration cams with stupidly wide LSA's way too often. They are usually in heavy cars with automatic trannys too. People always ask me what is their best choice for LSA. I like narrow LSA's even when compression is not an issue.
The narrower LSA's aid low comp motors. I feel that most of the choices made by consumers are due to ignorance. Many cams are so lazy in reguards to high lift area, that they only RPM because of their wide LSA. I see this in Pro Stockers daily. I also change their opinions and make them smile daily. But, Pro Stockers are the Extreme and they don't get my recommendation of 106 or even 110LSA cams. I usually preach 114 to them when everyone else is 118.
Economy and emissions aside, and since they flatten and broaden torque curves, low compression motors only need wide LSA's when they have really small cams that are also having to RPM. In Drag cars, the 106 LSA's are hardly ever slower than 112 LSA's especially in heavy cars with automatic tranny's. In dirt track cars, sometimes a 108 will be faster than a 106 simply because the track is slick, or the driver is having trouble controlling it and putting it to the track and he is getting out ran on the top end. Incidently, I recomend 108's to dirt trackers regularly. Many of them are my own loyal customers with 106LSA's who call me reporting a problem such as hard to hook up and also running out of steam a little early. A 108LSA fixes them and usually they win the race. My advice to the big cam wide LSA heavy car with small motor and low compression scenario's is: Either narrow the LSA 4+degrees or remove about 15+degrees of seat duration from the motor, and open the valve faster if you don't want a motor to be a slow reving lazy dog (especially one with low compression) with your wide LSA cam.
Bersides, It will be alot funner to drive and have more hit at idle, which is something most ask for."

Above statement from Shaun Tiede .... the "cam designer".

[ry57pont]

i finally figured out how to scan, here are my dyno runs with the xe274