unknown_host

iTrader: (1)

I have narrowed my camshaft selection down to 2, but I found something very surprising. I am looking at the Comp Extreme Energy Hyd. Roller 270 and the LT4 cam, both with 1.6's on a 9.5:1 vortec 350.

What surprised me was that in Desktop Dyno, the XR270 makes a ton more power everywhere than the LT4. I can get a good deal on the LT4 cam, but would rule it out if these results seem "typical".

The LT4 cam dyno'd:

377 hp @ 5500 rpm, 403 ft lbs @ 4000 rpm
265 hp @ 3500 rpm, 398 ft lbs @ 3500 rpm

The XR 270 dyno'd:
411 hp @ 5500 rpm, 447 ft lbs @ 4000 rpm
296 hp @ 3500 rpm, 444 ft lbs @ 3500 rpm

Does it seem realistic that the Extreme Energy cam could potentially make 35 horsepower and 45 ft lbs of torque across the board more than the LT4 cam?

Gsoleski

This is interesting. i'm trying to decide between the hotcam or the XR 276 and not sure which to go with yet

Orr89RocZ

iTrader: (20)

Really depends on the setup. Desktop dyno isnt the best sim. You sure it used lt4 hotcam not regular lt4 cam?

I dont see a 30 hp gain there. It should be closer to 10 due to more agressive lobes but most of that power should be area under curve across powerband not so much peak. Cams are close in size. Bigger differences may be seen on higher flowing heads but not on a factory vortec port.

Case in point, if you have seen hotcam dyno numbers on stock lt1 motors, seems like 320-330 whp is common. Comps 503 which is basically the 276hr but on 112 lsa typically makes 330-340 whp. Its a good 10-15 hp more. Would not expect a 270 to do that much better.

conlinj

iTrader: (3)

did you look at the XFI280? I like it in my current setup

unknown_host

iTrader: (1)

I am carb, not efi and the big difference would be that the LSA on the Comp cam is 110 whereas the LT4 cam is 112.

Here is the LT4 Hot Cam:


Here is the XR270:


If the difference is 10 horsepower, I think I can save $150 finding a used LT4 cam. If the difference really is 30 horsepower and 45 ft lbs, I would be crazy not to go XR270.

unknown_host

iTrader: (1)

The XR276 is much bigger than the LT4 hot cam fyi. My same combination with the XR276 made 419 @ 5500 and 440 @ 4000 with the XR276, gave up about 20 ft lbs down low according to desktop dyno.

Orr89RocZ

iTrader: (20)

Flat tappet 268 deg grinds are very popular with vortecs out there in the sbc carb world. Thats about 220-227 deg at .050 depending on the lobes. I wouldnt hesitate to run that setup if you are carbed. I dont like the 112 lsa for carbs. I'd go 108-110 max with that low duration. Good dual plane would run very strong

You can also find the comp 503/276 used on lt1 based forums like camaroz28 and ls1tech

unknown_host

iTrader: (1)

I ran the flat tappet XE274 in my last Vortec 350 and went 12.2 @ 111.85. That is actually sort of what I am copying

Last time around, I had a lobe on my XE274 go flat, and talking to other people it seems like just about everyone has had an XE flat tappet go flat, so this go around I would like to stay roller.

I basically found a great deal on a brand new LT4 hot cam for $130, just trying to decide if it is worth waiting and buying an XE270.

Orr89RocZ

iTrader: (20)

Hot cam should run 111 mph in that setup.

Z28 MeTaL HeAd

I know this is an OLD thread now, but I wanted to bring up some things related to these cams with my own personal experience. No bullshit Desktop dyno and 1/4 mile calculator garbage.


I had a completely stock 1995 LT1 long-block. I installed it into my 1984 Camaro along with the matching T56.

I installed the Comp Cams XR270 camshaft and did a carb conversion on my car. With a holley 650DP and a stock HEI distributor in the back, I made 347RWHP and 341RWTQ with an otherwise stock LT1 long block. CAM ONLY.

I never even took off the stock heads!

-Comp Cams 977 valve springs
-Comp Cams 10* titanium locks and retainers
-Comp Cams chromoloy stock length push-rods
-Comp Cams Pro-Mag 1.6 Roller TIP rockers
-HEI distributor
-Holley 650 double pumper

My AFR's were PEGGED rich @ 10.0's on my AEM UEGO wideband gauge when i went to the track. I made about 10 passes that night on street tires.

13.2 @ 111MPH is what I ran, untuned, rich as all F!!! With 2.2 60' foots.


At my local F-body dyno day, there was 3 or 4 different LT1 cars there. I made more RWHP and more RWTQ then ALL of them, including one of which was a 383 stroker build with a CC503 cam and stock heads. I think his car was horribly tuned and pieced together poorly, but either way I made more Jam then he did.

The other LT1's there ALL had LT4 hot cam kits. All over them made 325-330rwhp range and maybe 335rwtq.

I know if I had dialed in the AFR's i would've picked up another ~2mph in the 1/4 and probably another 15-20rwhp, so to the OP...the XR270 is leeps and bounds better in every conceivable way in comparison to the LT4 hot cam.

Here's my Dyno video:

Here's one of MANY videos I have from the night at the track where I was going LOW 13's and 110+ MPH: