[Stan Weiss]

Originally Posted by Cliff R

"This is what I was thinking. Wanted some honest opinions like this. My present setup is very strong up to about 4500. Flattening out a bit above that."

The 068 is a very good cam choice for a 400 build with moderate compression, but smallish on a 455 build. I've built a LOT of 455's here, one time I put a 744 cam in one with high ratio rockers and it was a "turd" for the most part. Don't get me wrong it did OK, but nothing going on much past 4500rpm's.

So I wouldn't expect it to pull much further in the RPM range with an 068 cam. Even with the much larger 041 camshaft we saw peak HP at 5100rpm's on a 455 build with Edelbrock aluminum round port heads. With that said a larger intake isn't going to bring much to the table either, but for sure you'll see a little more upper mid-range power with higher ratio rocker arms.......IMHO......

Since then the 455/744 build (did that one in the late 1980's) the smallest cam I'd even considered for a 455 build would be 230 @ .050 and at least 280 degrees @ .006". Attached is a dyno chart from a Super Duty 455 around 8.8 to 1 compression and the cam used in it. Dead smooth idle making 16" vacuum with only 12 degrees initial timing. I put these things up here for folks contemplating camshaft choices so it may help beyond what the OP is looking for. I've had so many troubled 455's brought here to custom tune, and complaints from folks who've put them in service and not happy, that I feel it's important to realize that a HUGE engine does well with cams this big especially if you've spend money on the heads for improved air flow.

I'll also add here since the topic is intake manifolds that the brief testing I did with the Edelbrock Performer intake very quickly told me that the big 455 sees it as a restriction on higher HP builds (past about 425-430hp). I was unable to even test it effectively on my last 455 at the 500hp mark because the engine simply hated it. Installing it with no other changes induced a stumble/hesitation/big that would NOT tune out. I also had pronounced "surging" in the mid-range when it did get past the stumble. Putting the iron intake back in place instantly cured the issues so when we carried a pile of intakes to the track for back to back testing the Performer wasn't in it.........Cliff

Cliff,
Do you have an explanation for the crazy Air Fuel Ratios on that dyno sheet? This graph show it verses the Air Fuel Ratios from the 2 dyno pulls on the combo sheet that you general post.

Stan