Intercoolers
 

I was thinking about installing inter-coolers on my boats blower motors, and I have a few questions.

1. Since you loose some boost going through the inter-cooler than I assume you want to put a smaller top pulley to compensate?

2. Since you are running much cooler air to the engine, even thought you have compensated for the loss of boost with a smaller pulley so the actual boost recognized by the engine is the same just at a cooler temp, and my carbs are boost referenced... do I need to rejet or not?

Just for some info on the boat engines they are 502cu with 7.8:1 compression with B&M 250 blowers running 6psi at 5100rpm, topped by dual Nickerson boost referenced carbs at 900cfm each. Crane roller valve train and dry headers. Dynoed without inter-coolers and 675hp a piece.

Sorry for the long post but I sure would love some help.

Thanks!!!

If the carbs are already running pretty rich from being "boost referenced" you probably won't have to rejet. The drop in pressure under the intercooler isn't from restriction as much as it is from the air being condensed. The intercooler helps to keep detonation down because the incoming mixture is cooler. Hence... you can run more boost without detonation. Keep in mind that if the engine was running 6 lbs boost before... and now you "read" 5 lbs of boost...after the intercooler... the same amount of fuel and air is going into the cylinders, it's just denser. So you can raise the boost ... get more power... and not see detonation. My advise... after the intercoolers are installed... Do one run on the engine with new plugs. Remove the plugs and look down the porcelain insulator and see what the mixture is. If it has some soot down near the bottom of the insulator... the mixture is ok... if it is bone white... it's too lean. Also.... if you do several runs... pull a plug and look for little shiny metallic balls on the plug... that means your piston is melting! I'm assuming that the engine will be in the boat as you add the intercoolers... If you are taking the engine out... do the runs on a dyno.