Last Minute Horsepower

Last Minute Horsepower
By Don Terrill (c) -

Ok, you're almost finished with your new engine - all the machine work is done and you're ready to assemble. But, you're starting to worry about power - it won't be enough. Now what?

Well, this is no time to fiddle with cubic inches, compression or new cylinder heads, but there are still things you can do to help power that won't require starting from scratch.

If you've got enough piston-to-valve clearance (measure it, don't assume) and you're not sure about your cam choice, maybe it's time to sell it and try again. For more power focus on picking the right intake duration and then getting as much lift as possible for that duration. Make sure the valve springs (and your maintenance schedule) can handle the increased stress from a more aggressive lobe design.

Rocker Arms
More intake rocker ratio can be a real help - especially if you think the cam is a fuzz short on duration. In addition to the warnings above, make sure the increased rocker ratio won't create clearance problems between the side of the pushrods and cylinder head. A rough estimate for the piston-to-valve clearance lost with a 0.1 increase in rocker ratio is 0.1 x lobe lift @ TDC (a spec listed by most cam companies).

Intake Manifold
Not a ton of power to be found here, but an easy swap. If your manifold was designed 40 years ago (many were), you may want to look at some of the newer offerings. Also, don't get all caught up in having a perfect gasket match - As long as the manifold port is smaller, but not radically smaller, than that of the cylinder head, you'll be fine. Don't believe me? Back to back it on the dyno.

Carb Spacer
Most applications will benefit (max power) from having the tallest carb spacer the hood will allow. Try a 4-hole spacer nicely blended into an open - It doesn't work on all applications, but it works more often than not.

If your carburetor still has a choke tower on it, you're leaving at least 1ohp on the table. Upgrade to a newer high flow model or modify the one you've got - which is not that hard.

Not that cheap anymore, but a simple bolt on. If your headers are the wrong tube diameter, replace them. If you think you've got the right tube diameter, then cut off the collectors and get a set of merge models - they do work. Buy the slip on models if you want to do some tube length testing by adding extensions between the header and collector, or if you want to try different collectors down the road.

Oil Pan
Wet or dry sump, anything you can do to get the oil away from the crankshaft will help free up horsepower. In fact, it's impossible, from a power standpoint, to get the oil pan too big or too deep. And when you're done, don't defeat the whole purpose by adding more oil to the pan.

Want to send off a nasty email about how wrong I am? Well, first read this and then write your own article.