outlawinil

I am wanting to rebuild a pair of Mark IV 502's. I am going with a crane hyd roller cam, roller lifters, new pushrods, roller rockers, and new valve springs. The heads will be reworked, cleaned up and polished. With these improvements are the stock factory carb and intake sufficient? If not will a Holley 800 and an Edelbrock Air Gap Intake be a good combo for this setup? I am wanting to ditch the factory mercruiser exhaust while the engines are out but still use my Corsa Q&Q II exhaust. What is a good exhaust for this system without really digging deep into the pocket?

Any opinions are greatly appreciated

blown1500

Hi, outlawinil,
The intake and carb you have chosen are good pieces, but we need to know more about your set up-which cam, what head modifications, compression ratio, rpm you want, hp level you want, ..............
I am not familiar with your exhaust, but the Mercruiser exhaust needs to go if you want to go!!!!!!!

bobby daniels

GIL OR STAINLESS MARINE EXHAUST ARE GOOD LOOK QUICK YOU MAY BE ABLE TO FIND A GOOD USED PAIR USED !!

formula31

I second the Gils but on twins the center bolts and plugs will be a bear to get at unless your engines are seperated by a lot more than 33". If I had to buy again for my twins, I would use something else so I dont have to pull an engine to change plugs ir get a manifold off. If your small and have lots of room under them then ignore this.

Pure Energy

Unless someone has a really good reason to change, your Merc exhaust is fine. I have heard the HP gains on the dyno, but when I switched from Merc to Imco on a procharged motor, I noticed no change, even sounded the same. Everyone is so quick to jump and change their exhaust thinking it is going to make a big difference, I disagree.

If I am wrong please explain.

Back4More

A Holley 850 on top of a Dart single-plane would be my guess...

Payton

Ken, I would think it would depend on your cam, Procharged or not. The more overlap you have the longer the runners you should have. There is a great article in the newest Family and Performance Boating.