gen6 502 camshaft problems
 

I have a rebuilt 98 502, carb engine stock bore, 9.6 cr , brodix race rite oval port heads. The engine runs awesome but getting reversion. The exhaust mixes with the water at the transom and still sucking up water. I changed the plugs twice so far due to salt water fouling. The cam specs are [email protected] is 234/244 the lift is .575 for both and the LSA/ICL IS 114/112 . The cam was recommend by lunati but is not working to good in my boat. I need to change the cam does anyone know a good cam and a part number to install . some input would be greatful.

what exhaust do you have?

i take it u installed the cam "straight up"...car guys do it all the time. it never is what they say it will be. cars guys don't dyno that much either...

a boat is essentially a water brake dyno...1 deg off can result in bad stuff let alone a loss of power. single engine boats are great because i have placed a degree wheel (bigger the better!) and using different props and rpms achieved my goals. this is after dyno work too!

i have built a efi 502 600hp engine using the stock heads. i did custom make the throttle body which netted me nothing at wow but allowed my idle speed to be lower. i think the engine lasted over 500 hours last time i checked.

feel free to email me if ya need some advice.

I had (am probably still having) a similar problem. I bought a Cloyes adjustable timing gear. What did you Degree your cam at? I'm running EMI Thunder with the short risers, I thought that might be my problem but reading this, I'm re-thinking it!

i am not familiar with your exhaust.

every engine is different. even something so precise as a superbike engine. taking a stock bike and slotting the cam gears and adjusting the jetting i have NEVER NEVER ever not made more power!

place a degree wheel on there and you will see fist hand it will not be what they claim. next you will see how little of an adjustment can make a huge difference.

quick and dirty testing can be done with the use of different rocker ratios. on all and just exhaust and just intake. it will provide you invaluable data...and who knows it may net you the result you are looking for.

ps...when looking at plugs people do it incorrectly all the time...it's called a plug chop. cut fuel and ignition at the same time while running steady state WOT. reversion can take place at various places in the engine curve. wot may not be your problem your cruise may be. or even idle; which is most probable.

NOTE!!!: look at what the cam manufacture recommends idle speed to be. most of the time it's WAY HIGH! all of my engines idle below the stock idle spec! one engine i built was over 1500 rpm! even the manufacture could not believe i could idle at 530 rpm clean and as long as i wanted.

and if you must idle high to bandaid; then remove the shift kill from the system to allow you to start the boat in gear.

I have same engines in a Pantera. I used Crane cam #168731 with Ross 10.0 pistons, CMI exhaust, Brodix BB-2 plus heads. Engines are fresh water cooled. No problems with reversion.

The cam was installed straight up, the exhaust is S/M low angle long risers they run thru the transom. I pressure tested the exhaust every thing checked okay. I'm now thinking maybe the big waves are causing this problem. There is not much of an angle on the risers and alot of water exits as the boat rocks I do have rubber flaps on the tips . I'm looking to get a taller set or risers or another exhaust system if anyone knows of something shoot me a call 203 415-4214 Jeff

flaps are for when the engine is not running. so my race boats have never have had them.

get a degree wheel and start there! if you chose not to then you are just guessing.