89FX3

Anybody here running the 280XFI?

It's a fairly new & more aggressive grind than the 268XFI.

I know there's a thread on thirdgen.org from this spring w/ Orr89RocZ posting some good skinny about upgrading your springs to handle the lift at high rpm:

http://www.thirdgen.org/techboard/tp...mp-280xfi.html

Thoughts & experience are welcome.

Especially experience.

GREGGPENN

Do a search on my userid and the word "cam".

I asked about these two a few weeks back. I had one thread on the two.

The consensus was use the 280 -- if you're bothing to upgrade. Most felt the duration on the 268 was just too close to stock (even though lots more lift is present).

I bet you find a couple of users of the 280. You might not find anyone using the 268 version. I considered it though because of the higher compression and lower pulling power (esp in 6th gear on the hwy).

Later conversations with cam sellers brought out feelings that the difference would be small enough to stick with the bigger (280) cam.

I'm still putting together my parts.

gp

89FX3

I did a search and found some, but not a lot, of talk about the 280XFI.

I'm giving serious thought about switching to it in my mostly dd 96CE/LT4 stroker coupe which now has a custom regrind 224/230 .54x/.54x lift w/112 lsa /AFR LT4 Eliminator heads, etc and to me seems like a fairly mild-mannered/ well-behaved cam.

[That last observation probably means I ought to leave well enough alone, but what fun is that?]

My own personal concern is that: the 280XFI may prove to be a little more unruly than I'd like for street purposes; and the 268XFI doesn't provide improvement over my current cam to warrant a change out.

But this thread isn't meant to focus solely on my interests.

I'd just like to hear what current feelings & experience are w/ what seems to be a good but somewhat aggressive choice for the C4 street/strip owner who has a setup to take advantage of its features.

89FX3

Here's a link to a CHP article about the 280XFI vs the 268XFI

http://www.chevyhiperformance.com/te...ick/index.html

Iroc57

I have the 268 in my 454. If you are looking for a cam that you won't even hear that is the grind. As long as it is around 1K it is smooth as silk. It does get a bit sloppy under that though. If you want to hear it go longer. The cam was designed to give good idle and vacuum but still move air when needed. I do recommend that you use the comp cams lifters either way, the short ramp with this grind caused a couple of the lifters to stick so I had to switch to the comp cams lifters. No problems since

I wish that I could give you apples to apples comparison but I figured I would chime in just the same.

1989TransAm

"Here's a link to a CHP article about the 280XFI vs the 268XFI"

Actually it is another cam not the 268XFI. Comp also has a custom 274XFI which would be good for many builds.

NightTrain66

nothing wrong with the XFI lobes but the way the cams are in the Comp catalog (113 LSA, 109 ICL, 117 ECL) will sacrifice alot of power.

Lloyd

89FX3

I focused on the reference to the 280XFI and not XE268H in the first part of the "artichoke" by mistake

Thanks for the info on the 274XFI.

I'll check out.

Bart

89FX3

Lloyd: At which end of the power range will you 'sacrifice alot of power'?

If the lower rpm range-does a normal stroker block help enough to offset that loss??

Is that tradeoff worth the higher rpm benefit for a street ride that doesn't dwell in 6k+ la-la land that often???

Also is there a problem w/ this cam in a mostly street application trying to appear to comply w/ emissions requirements (OBDII)????

If it's gonna kick off codes etc. even w/ a proper tune maybe it isn't that good on the street after all...

If not where's its niche????

Thanks-
Bart

89FX3

Your actual experience w/ the 268XFI is much appreciated.

Although Comp claims a "strong idle" for the 280XFI I get the impression it may not be any lower than 1k ...

I guess "strong idle" as used by Comp may really mean...

"STRONG idle" relative to "NO idle"...

aboatguy

I was running a 280XFI on my stock bottom end AI 190CC build but I went BIGGER for my high compression 355 AI 200 build.

In my opinion the 280XFI had better idle than I expected but I didn't make the power I wanted so I went to a custom cam with a tighter LSA, about the same duration, and a LOT MORE LIFT.

However, with good tuning the drivability around town was great on the 280XFI and just as good on my custom cam.
(*Ed Wright)

If I were doing it over I'd skip the off the shelf and go custom first.


(I have the low mileage 280XFI sitting on the shelf and it may end up in my Impy SS but a custom cam will probably win out there too.)

NightTrain66

emissions will be dictated by the cams overlap. About 55 degrees of advertised duration overlap and about 4 or 5 degrees of overlap @ .050 duration is all you can really handle and pass emissions (CC 503, etc). Anything over this and it is TOUGH to pass emissions "snifgf tests".

The lobes are not opening/closing the valves in relation to what the piston is doing very well and opening the intake valve that late wastes alot of cylinder filling, closing it that late wastes alot of cuylinder pressure on compression stroke (especially on a 350/355).

The exhaust lobe is so far advanced that is is opening the exhaust valve way too soon in relation to built up exhaust pressure and will be closing the valve when exhaust is still left in the cylinder and piston is still pushing up on the exhaust. Pretty much like a big EGR valve. It will just contaminate the mixture of the next intake stroke and take up space that "good" air can now not fill.

The exhaust stroke is the beginning of the intake stroke and if you can't get it out, you can't put more in. This is why larger duration exhaust lobes work well, make more HP and allow the HP #'s to hang on longer after peak HP is made before they start falling.

Intake and exhaust centerlines need to be alot closer together and alot lower to make good power. As long as you can tolerate some overlap (no emissions) and a lil rougher idle, this is a MUCH better way to go. It will build more HP and TQ EVERYWHERE.

If you do not want a lil rougher idle, knock the duration down so the overlap is the same but align the intake and exhaust lobe with the pistons movement first. End up with less duration and a lower LSA but there again, it will make more power EVERYWHERE.

Lloyd

89FX3

...1) according to Lloyd it's a cam with a lot of advertised 'bark' but not so much actual 'bite'; and

2) it may be better to get a 'custom' grind if you've got all those expensive 'custom' parts on your car.

Verdict: maybe this "off-the shelf" cam is going to stay "on-the-shelf" for right now.

Thanks for the info.

Bart

LT4POWR

I'm honestly not a big fan of these cam specs/lobes......or really much else that comp cams is selling these days.

Vic'89

LTPOWR - Can you please provide some details of your setup ? 400+RWHP out a stock bottem end ? I am very interested in the cam you have.

Thanks

Vic

LT4POWR

Almost three year old thread now ...http://forums.corvetteforum.com/show...858&highlight=

The custom cam is an older style comp lobe...low/mid 230s dur, lift around .600, 11x lsa.

Vic'89

Thanks. Have you ever tracked the car since the build ?
MPH ?

Vic

LT4POWR

Not in a long time http://forums.corvetteforum.com/show...415&highlight=
It's really a street/highway toy. I should probably get back to the track one more time before doing my new motor

Sorry about hijacking your thread 89FX3.

89FX3

No problemo; I enjoy hearing what others are running.

JAKE

I put the 280 XFI in the 388 (+.060) LT1 I built for my 96. PCMFORLESS did the PCM tune. No complaints. Never raced or dynoed the engine.

I drove the car from Chicago to TX and averaged 24 MPG (3.07 gear); engine passed TX emissions testing (we don't tail pipe here; only ALDL for OBDIIs). I degreed it in at 109.5 LSA method.

No power brake vacuum problem; Bryan at PCMFORLESS set the idle at 950 and it's idles excellently. Daily driver; cam has no vices. My opinion: Others may bad-mouth it in order to sell you theirs.

In an interview with CompCams which was printed in one of the mags, the CC Tech said it's the best lobe they've ground.

Just my experience.

Jake