Comp Cams
 

Anyone know the operating range of a XE-274 cam in a 455 engine ? Thanks.

1,800-6,000 Think thats what your asking..lift 0.488 int./0.491 exh. With a stock 1.5 rocker…On a 110. Basically little under Ram IV range. Probably 3.75 stroke 400 but I’d guess in a 455 more like 5000-5500.

I ran a XE274 in a 400 with 8.8 compression, dished pistons, mild ported 670 heads. Installed 2* advanced. Ran best shifted at 5600 RPM, best time was 13.0 at 104 MPH NA. It ran OK, decent street manners, 10-12" of vacuum. Wanted a lot of timing. It's a lot less seat timing than a RAIV, and less than a RAIII. I think it would be too small in a 455 over 9:1 compression.

Right on the dyno DONE by 4800rpm's. 455, 7K3 heads, mildly ported with a single plane intake and 850 DP carb.

Not my engine by I witnessed the dyno pulls on it. Can't remember the exact numbers, not really very impressive, something in the neighborhood of 412hp from what I can remember.

13.0 @ 104mph would indicate your 670 headed 455 was making a little over 400hp assuming around 3600-3800 race weight.......

5800 in our 455 with 62 heads, ran 12.2s in our 69 GP
6000 in our 400 with 16 heads, ran 11.8s in our 73 Ventura

Here is one test in a 455 with the XE274 hyd cam:

https://www.motortrend.com/how-to/cc...-for-pontiacs/

You can Google up quite a few builds with the Comp XE274 Hydraulic flat tappet cam. The results will vary all over the map depending on the cylinder heads in use, induction, etc.
That and the engine dyno and/or operator used for the testing.


.

"The 455 mule was assembled with the 7K3 heads using Corteco gaskets and stock Pontiac head bolts. With the original pistons 0.015 inch in the hole, the 96cc combustion chambers, and the 0.036-inch compressed thickness of the head gasket, compression was right around 9.2:1. The Comp Cams XE274H hydraulic cam remained from our last Pontiac dyno session.

With this combo, we averaged our best runs to obtain a peak power figure of 390 hp at 4,700 rpm and 494 lb-ft at 3,500. Note that the engine was grunting out 450 lb-ft at the start of the pull at 2,500 rpm."

This is directly from the article in the link and very close to the same specs as the engine I mentioned above that made 412hp. I do remember the 455 I saw on the dyno made more peak torque however. Early pulls were 499ft lbs and after some timing and fuel curve changes it made closer to 530ft lbs right around 3400rpms if memory serves me correctly.

Either way that's a pretty "weak" iron headed 455 build, IMHO. I built a 455 with #46 heads on it from a 350, no ported anyplace or even a port match and made 440hp and 530tq with a Crower 60919 (RAIV clone) cam in it......FWIW....

Steve,
Thanks. I like the stock head built. Nice torque curve. In a 3800 lb w driver vehicle should run in the high 12's @ about 106 MPH and @ 70 MPH turn just under 2500 RPM (2.96:1 with 28" tire) on the highway.

Stan

https://forums.maxperformanceinc.com...1&d=1485836170

A XE274 dyno sheet from so years ago here on PY.

Stan