how much more hp?

[mdb205]

So I have a 289 that came out of my 65. I'm rebuilding it right now. All of the engine internals are new. It still has its original 2 barrel carb, but I will be upgrading in the near future. How much more horsepower would I gain with this cam kit as it sits right now? COMP Cams: High Energy™, 268H: Cam & Kit

[bartl]

Probably a tad between 3,000-4,000 rpm but most likely you'll lose some between idle and 3,000 as well as over 4,000 rpm. You have airflow bottlenecks at the carburetor, intake manifold, exhaust manifolds and exhaust side of the cylinder heads that is going to keep that camshaft from doing much good. An RV or "torque" grind will work much better with a stock engine.

If you're out to improve performance of a stock C-code 289 without spending a lot of money are to home port and port match your cylinder heads, use some non-restrictive exhaust like reproduction HiPo manifolds or tube headers, install an aluminum dual-plane intake like the Weiand Stealth, and a 4V carburetor - the Autolite 4100 is a fine unit. Now, when you add the 268H (after making sure the rest of your valvetrain is up to par), you should get a nice little bump.

[mdb205]

Well I have a set of long tube headers goin on. I'll work on port matching the heads when I get some time. I will also be getting a new intake, probably an Edelbrock, and I'll probably be getting a Holley 4 barrel. So if you add those to the mix...any difference?

[lemonshindig]

Originally Posted by mdb205

Well I have a set of long tube headers goin on. I'll work on port matching the heads when I get some time. I will also be getting a new intake, probably an Edelbrock, and I'll probably be getting a Holley 4 barrel. So if you add those to the mix...any difference?

Yes. You just addressed everything that he cited as a bottleneck...

[09Frank65]

I initially did just what you are talking about doing (except went with XE274H cam). Your heads will become the limiting factor quickly. You will run out of air long before the cam is done.

If you are rebuilding the block now, do yourself a favor and bump up the compression a bit. That'll help things along as well.

Nothing wrong with your plan. You can always replace the heads later!

[sdmustangrider]

I have that exact cam and love it. But you'd want to add more than just a cam. Don't have to go extreme, but a nice aftermarket intake, headers, and some work to your heads would help.