Killogy

So I guess its about time to get rid of my crappy single pattern summit cam and get one of the comp cams that everyone with the Vortecs love so much. But I don't know if I should go with the xe268 or the xe274. I'll have 3.73's very very soon with a 5 speed. I know that pony killer is running very impressive numbers with the 274 but he has some head work done I believe. I'm leaning towards the 274, but what do you guys think. This car is just a weekend/track car. And what about the idle quality of both cams?

F-BIRD'88

Both those cams are actually simular to the one you have now. Idle quality isn't going to be that much different.

I think the XE274H10 has the most potential of the two.


You'll just have to pick one and bolt it in a try it to see
if it actually makes the car faster.
An interesting comparision. Let us know how it works for ya.

How does your car perform now? et ? MPH? 60ft?

More rear gear should help.

Killogy

Well I ran a 14.8@98 with a 2.4 60'. Seems kinda low for my setup I think. Thats also on a one-legger. I don't think that once I put the locker in its gonna cut my times by a second. I'm shooting for mid-low 13's. What do you think is holding me back more, the cam or the performer intake?

F-BIRD'88

Neither really.... Your performance is off.
Something is not right.

Something else is killing the power.
You should be way over 100MPH in the quarter.
Even with bad traction.
you may have a internal mechanical problem.
(valve spring)??? Cam lobe???

you must be just roasting the hides out of the hole.

The Performer RPM will add at least 10net hp but won't improve performance if you're just smoking the tires.

Even if a extreme energy cam is a better cam, it won't be
that much better. the cam u have is no wimp.

a 2.40 60 ft is pretty bad You need some high traction tires to put the power you have now to the ground.
1.70's +/- is within realiity with sticky rear tires even with a stock sustpension.
the MPH is low Fuel delivery problem or restrictive exhaust system are the most likely causes.
Assuming no mechanical problems.

How does it perform with open exhaust?

what is the actual compression ratio of your motor?
Have you done a compression test? inspected the valvetrain lately?
Something if off....

And yes you could gain a full second with a good posi, higher gearing and some slicks. DR's or ET streets
You have to get 'er out of the hole quick to get a good ET. You can run 12.99's at 98mph but have to launch hard.

Killogy

Valve train is fine, as far as lifters, rockers, pushrods, and springs. Could be the exhaust, I had to put flowtech headers on in place of my hookers cause they had all kinds of rust holes. So I have 1.5" primaries going into a 2.5" y-pipe into a 3" catback. I would guess my exhaust isn't helping but i didn't think it would make that huge of a difference. And i have a Vacuum secondary 670 cfm holley street avenger carb. I think its more of an exhaust problem then? I'm glad I posted, I almost wasted $170 on a cam kit thinking that was killing power

F-BIRD'88

Well the 2.5" y pipe is a killer. You need double that.
LOL 2.5" is good enough for one side of the motor, what about the other 4 cylinders...?

Single 3" cat is bad enough. should have 2 3" cats. easy way to tell is uncork it right at the headers and go for a ride.

Most of the available exhaust stuff available ( off the shelf for F-bodys is garbage (including the aftermarket stuff)

An engine with a cam that size (comp cams or any other) needs a good exhaust system.

How good are you at slicing and welding mandrel bent pipe (making your own Y pipe with dual cats)

The vacuum diaphram on the carb may be leaking or the little cork gasket betwween the diaphram and carb body may be pooched. Common problem.

After all this the cam may respond to being advanced
(maximize cylinder pressure) Especially if the true cr is lower than it should be. Lots of variables to look at.
Start with a compression test. Should be 175psi
anything below 160psi is suspect. ( low compression ratio, bad rings-valves, incorrect cam installed C/L.)

scottland

Well i went with a XE268 in my vortec headed motor, and I'm happy with it.

But the only reason i didn't go with the XE274, was that i still have to get through Arizona emissions, and I'm pushing my luck as it is.

As for the difference i noticed compared to the 212/222 degree, .435/.460" cam that came with my motor, the XE268 was a nice kick in the pants.

The motor didn't feel like it lost any low end torque, and it definatly pulls harder from 3,000 on.

As far as drivability, i pull 16" of vacuum @ 750rpm, its very streetable.

But if you don't have to go through emissions where you live, there is no reason i wouldn't go with the XE274.

RB83L69

That Summit cam is one of the oldest "street" cam designs there is. It was already old when I first got into this hobby. It was a great design for its day, didn't have too much trouble giving better results than a "3/4 race" cam or a "Stage 2" cam; but we've learned a thing or 2 since then. It's ALOT different from the XE series, or others with similar design methods from other mfrs; its ramps are slow and lazy so they hold the valves just barely cracked for a long time (to keep them from bouncing of the seat with old stock springs like you used to have to run), and it doesn't hold the valves near full opening for very long. Look at the difference between "advertised" duration and .050" duration; 292 & 224 as compared to the XE268's 268 & 224.

Incidentally, it's exactly the same grind as the Edelbrock RPM cam, and various other generic grinds from just about every other mfr.

If your Vortec heads haven't had their valve guides cut down, the XE274 will probably cause instant catastrophic destruction the first time you hit the key. The XE268 is about as far as you can go with any reasonable risk level, and even that sometimes is too much for an unmdofied set of those heads.

What work has been done to them?

The gta master

what is the XE284 like is that alot better than the 268 or 274?
Whats your opinion?
is anyone running a XE284?
:lala:

rjmcgee

I am running the 274 and it is very tame around town. I went to the track this fall and run a best of 14.05 at 99.7 mph. I was happy with that because it still has stock manifolds and y pipe, stock intermediate pipe, and a lousey Edelbrock 600 carb. It is also a one legged wonder right now and my best 60' was 2.15. I think the combo in the engine is plenty good enough to see 12's, just have to get the last of the restrictions eliminated.

I think that if the heads could handle the lift then you should go with the 274, I know I was suprised with how well behaved this one is when just cruising around.

Killogy

The heads have had the valve guides cut and can handle .525 lift.

The gta master

I ran an edelbrock rpm with a exh lift of .510 on a 305 L69 with stock heads.
How much will the L98 handle ....? is it the retainers that get in the way or the valve guides?

AJ_92RS

I can't say specifically about the Vortec heads with those two cams, but I can tell you this...

Momar (logon name here) had the 268 cam in his 350, and a friend of mine has the 274 in his 350.

Momar heard both of them and told me the 274's idle is quite a bit lumpier than the 268. He was surprised.

It only shows up on paper as 6* more overlap using adv. duration figures, but with the steep flank of the Xtreme cams, it seems to make a big difference.

F-BIRD'88

see this thread

This guy is running right on the 12sec door step with
the same cam. Even changes cams and intake and the car only changed maybe a 10th. if its going to go its going to go. Minor cam changes don't make that much difference. +/-3/10ths at best.

You should be running within 6/10th of him.
Wether your cam is the latest reinvention of the wheel
or has the fastest ramps is irrelevent. If he can run that quick and fast with the same old school cam and low buck ported 305heads on a 305 no less, You should be there too.
I ran 13.0's @104.5 with the same vortec setup as you with a much smaller generic cam 214-224-.442-.465.
My biggest problem was traction.
You have a basic engine or car related problem that a new cam won't cure.
Start with the chassis. Check the front brakes to see if they are dragging.
Mine were (bad flex lines). Check to see if the motor is getting steady supply of fuel at high rpm (pressure guage)

The exhaust sounds like a major restriction. Cut it off and see....
get some sticky tires and a posi..

Killogy

Ok well heres what I'm gonna do. I have a set of Hedman Longtubes on the way. So I'm gonna throw those on and run then with some 36" turndowns if they can fit. Then soon after I'm going to do the cam swap to the xe274 and see how much of a difference it makes. I have all winter to play with the bird and I finally got myself a nice daily driver so down time isn't an issue
And just for fun, think with the cam/exhaust I could hit 12's? :lala:

F-BIRD'88

Not till ya get the 60' times under control.

Killogy

Yeah with drag radials and a locker of course

F-BIRD'88

The XE 284 is just the next bigger cam in that series.

Better, worse depends. It can/will make more top end power and less bottom end than the others. Needs a converter good heads, exhaust intake and rear gearing.
I have it in my 406 but haven't drove it yet.
Canadian Winters and all.....
Low manifold vacuum , rough racey idle power from 3000up much like the Comp 292H magnum.
Not exactly the cam for your TPI...

A good streetmachine /strip, bracket racer hydraulic.

The gta master

let me know what it is like ....
it a better cam than the edelbrock rpm isnt it?:lala:

OMINOUS_87

I like that pick.

274 on a 110 and you will be very happy!

RPM Airgap would be a nice upgrade to at a later time, funds permitting etc...

Get some traction.