Horsepower Upgrades

there are a couple of offenhauser ( offy ) heads available right now.

this one.



and this one.


i have some big valve 'L' jacket heads with a stock manifold on the waukesha. the top one looks like it would add a little juice.

kenny, that is true on a cast head. you should install valve seats, but that is not the same as porting the heads.

a holman moody cam would be nice............

comp made one for me about 4 years ago for a 351c , but that motor never was assembled.

If your Correct Craft's engine is getting tired and you'd like to step up the performance, it's not difficult or costly when doing a rebuild.

The main and least expensive areas of improvement are in the camshaft and pistons. Those items should always be replaced when doing a rebuild anyway. A higher lift marine cam is available thru several providers including SpeedPro and Crane and the cost with going with the upgrade is negligible. These are reverse rotation cams as well. An average increase of 20-30 horsepower can be expected with the right cam.

Marine engines in these boats are generally produced to run off regular fuel and thus have relatively low compression. Many owners fuel their boats with premium regardless. If that's your case or you don't mind using premium exclusively, then going with a compression increase will result in noticable power as well. This is obtained by a carefull match of piston to cylinder head which will result in a maximum compression ratio that doesn't need more than 92-93 octane fuel. Flat top or other higher compression pistons cost no more that the dished lower comp styles. Some early model marine engines from Holman Moody were based off high performance automotive engines and came with compression ratios similar to cars of the day, 9.5-10.5:1, which required premium fuel. Most all other marine engines were and are based off industrial and truck formats and lower compression has been the norm. An increase of 10-20 horsepower is not uncommon.

Depending on one's budget, cylinder head upgrades can be rewarding, by either having heads ported and polished (which can be expensive) or going with different heads altogther. The heads found on 351 (240-260 hp engines) from +/- '77 or so on, came with essentially 302 Ford heads with the smallest available valves, compared to those before and later GT-40 engines/heads. The heads and camshaft are the main ingredients for that original GT-40 increase to 285hp. Good, rebuilt early model 351 heads are available for +/-$500. High performance cast iron heads, such as GT-40 pieces are available thru several sources but expect to pay upwards of $800 for a set. Aluminum heads will be $900-1100 for a new set, but used ones of all types are out there.

In summation, if you're doing a rebuild, for maybe $200 more you can pick up 40-60 hp, and for about $1000 more, you can gain as much 80 or so hp. This could translate in to even more pulling power and 5+ mph depending on the boat model.