I'm building a 400, 0.040 over.
Studded 2 bolt.
Scat crank.
KB flat top hypereutectic pistons.
5.7" rebuilt stock rods with aftermarket bolts, slightly machined for clearance.

I will probably use AFR heads, or something similar, and keep the revs under 6000.

So, being inexperienced, I need a cam that won't give me much trouble and is easy to install - lifters, rod clearance, etc.

Given these constraints, I am looking for as much power, torque, acceleration, go, you know, as possible!

What should I buy?

We really need more info. What kind/weight of vehicle, intended useage, desired idle quality, gearing, torque convertor, etc?

oh, yeah, that makes sense. Thanks for asking.

1968 Camaro.
4 speed.
3.73 gears.

Just enough idle for the stock power disc brakes.

Intended use? Not a daily driver, seasonal only (summer). Premium gas ok.

If you are planning on using AFR heads, make sure you get them with the 74cc combustion chambers so your compression ratio stays down within reason.

With a 0 decked block and a .040" thick head gasket you would be at 10.3:1 with a 74cc chamber.

With 10.4:1 compression and the intended usage you describe I'd suggest a cam with approx 280* advertised duration on a 110* LSA. Get a cam with fairly agressive lobes so you have as much lift as you can get.

Since you describe yourself as a rookie, I'd suggest staying with a hydraulic cam. Something like the Comp Cams XE284 (specs are 284/296* advertised duration, 240/246* duration @ .050, .507/.510" lift, 110* LSA) would work pretty well in your combo. It should have just barely enough vacuum for power brakes and a rough idle.

Thanks for the answers. The 284 looks good. However, I really don't think I will rev this engine over 6000 and the specs on this cam are up to 6500.

What will I lose to run the XE284H only up to 6000 vs. scaling back to the XE274H but getting power quicker (lower RPM)?

Thanks!

I've got the XE274 in my 355 and it runs pretty well. Pulls just enough vacuum... It is fine unless you're constantly riding the brake in which case the pedal gets a bit soft. I would think the 284 would give you a really spongy brake pedal. Also gives a nice choppy idle when you turn it down to 650-700rpm. :D

Just curious. Is there a particular reason why you are going 40 over? You might want to have the block sonic tested for thickness, just to be sure you'll be OK.

It started 30 over and needed a little more than a hone but not so much as for 60 over. If it goes boom I guess I'll just collect the parts and find a new block smile.gif

Rogue theres no problem with a .040 over 400 ,I have ran many of them in dirt track cars,,even some that where .060 over, just remember to get the cam degreed in right,,and make sure your cooling system is in good working order,I liked the 400's for the raw power they produce!!!!\
be sure to check the clearance of the cam and lower rotating assembly,gets close with some cams ,, Frank

Please consider a good old Isky 280 Mega hy-cam, 280/230, 108, .485" lift. (Install at 106.)

It should be POWERFUL in your combination, imho...

And I figure that since it is more max. old-school then new, that it's lobes won't be as hard on the valve-train as an Extreme deigned cam will??

I think it will still operate power brakes??

pdq67

i run the comp 274xe solid ft currently in my sb 400 with afr 195s and it has a broad flat torque range and peaks out about 6000 rpm.

with 3.90 gears i have gotten 18mpg on the way to the track :eek: and it has run in the 12.40s up here in the clouds.

I was in the same boat with my 68 Camaro, 355, 4 spd., 373's. I was web surfing and found SMITHBERGRACING.com. The owner seemed like he knew what he was talking about and was a lot more friendly than a lot of other businesses I called. As it turned out, I bought a set of World Products heads and a solid lifter and cam kit cheaper than Jegs or Summit. I will be starting the installation today. Those AFR heads are pricey and I saved enough to buy even more parts. Oh yeah, this is not an advertisement, just a suggestion for you to investigate.

Originally posted by rogue68:
Thanks for the answers. The 284 looks good. However, I really don't think I will rev this engine over 6000 and the specs on this cam are up to 6500.

What will I lose to run the XE284H only up to 6000 vs. scaling back to the XE274H but getting power quicker (lower RPM)?

Thanks! Those RPM specs for SBCs in the catalogs are generally for a 350. Your 400 will make the cam "act" smaller than it would in a 350, so I doubt it will run to 6500 in a 408" motor.

RPM band is determined by more than just the cam too. If you run the XE284 with a Victor Jr single plane intake it will want to go over 6000 for sure, if you run a Performer RPM dual plane it will probably want to be shifted right around 6000 RPM.

The XE274 is a little too small IMO for your compression ratio. You do not want to push the limits with KB pistons . . . they do not handle detonation well. I broke one with 10.3:1 compression and a 282*/236* cam in my 383 when I had a little detonation.

Also, when someone says their cam "pulled hard" to a certain RPM that does not mean that the engine was making more power running it that high. The only ways to tell where power starts to fall off is on a dyno or by changing shift points at a track.

When I play with DD2k (Dyno simulation software program) it says your engine with a dual plane intake and the XE284 would make 425 HP at 5500, 426 HP @ 6000 RPM and 407 HP @ 6500 RPM. This seems to indicate to me that peak HP is somewhere just under 6000 RPM -- your shift points at the track would probably be right at or just over 6000 RPM.

Awesome info! Thanks to everyone who posted with help for me.

One difference is that my engine is not 0 decked. Unfortunately the pistons are stock 0.025" down. Probably not a good decision, but its too late now.

So my compression with the 74cc is more like 9.7? Eric68, I am not sure how much this changes your estimates.

I really appreciate your guidance and running those numbers for my combo. Much thanks!

No big deal on the deck height. Just measure it before ordering your head gaskets and bolting your heads on.

You can use a thinner head gasket if needed to get your total quench height as close to .040" as you can. Felpro makes a rubberized steel shim gasket that I belive is right about .018" thick -- just about perfect for your situation IMO.