vandeano

After reading this thread you guys got me all paranoid. I have a 502 Magnum stock engine rated a 390 hp with a very mild cam 139721 Crane Cam. And I just put brand new factory GM marine heads on them.(188) These are the same type of heads that came with it, just brand new ones.
The only thing I changed on the heads were the springs. My question is are the factory valves good enough. Should I really think about changing them. I have about 50 hrs so far on engine. I was eventually thinking about putting a 177 blower on it.

Monkey Spanker

It does make you want to bounce your head off the table a few times doesn't it?? There are many, many, many marine motors running every day without inconnel valves. Just good ol' stainless valves. There are more factors than what a valve is made of that decide whether they break. Most important of all is not running the motor on the lean side. Most, no, alot of people who build up their motors don't take the time to jet them properly. They guess at the jetting by looking at the plugs and getting close. Jetting fatter until you slow down and leaving the jetting there is better than going back down one size from there to get the little bit of speed back. General Motors ran their new 572 crate motors for 40 hours at full throttle cycling between peak HP and peak TQ for durability testing, and they don't have inconnel valves in them. How much more abuse can you do to a valve other than that????

jmherbert

The wildcard is the water that could hit the valves. The GM 572 is not tested or intended as a wet exhaust motor. That being said, I am not putting inconel in my motor (SBC) The motor that was in it before dropped (shattered) a valve SEAT, not a valve, due to ingestion, not reversion. The valves were stock merc 350 mag valves...

Monkey Spanker

Though I'm not a Metalurgical Engineer, I do weld in Nuclear powerplants almost every day. Been doing it for 20 years since the U.S Navy gave me the education. This includes stainless and exotic stainless alloys (inconnel). Stainless is one of the few metals that you can actually force cool by immersing in, or spraying, with water. I know it has something to do with the lack of carbon in it. When we finish welding a stainless joint, we actually take a spray bottle of water and spray the joint to help pull the pipe/ tube in the direction we need to keep it straight. Exactly why your seat cracked and not the valve. Congrats on not blaming the valve for being the pboblem. Most seem to be blaming the part for breaking, not the conditions that made the part fail.

ratman

spanker,with as many things that can be damaged with an engine when droping a valve, its not a lot of money for inconel ex valves compared to the overall cost of an engine. anyone can have some type of fuel starvation issue at one point in time or another and lean a motor out. reversion and leaks in the ex are also common. why not go that little extra mile for some insurance. non stainless valves in true hi po marine app is kinda like a poker player saying all in. lol

Monkey Spanker

If I had to go all in between a valve going bad or a roller lifter, I'd take the lifter. Paid the price for a lifter twice, valve once.(but it was an intake) Still have the piston, valve head looks like a crashed flying saucer in it. Believe me, I blow money on really stupid stuff every day(ask the wife about the $280 box of jumbo king crab legs). It would not have been a problem for me to cough up a couple hundred to change them. In all honesty I just don't really believe I need them. I'll most likely end up killing the outdrive first. Every time I go to the machine shop I look at really high dollar extreme quality parts, that are now a pile of scrap. Something killed them, but what? Plans for next year are to rebuild the chevelle short block for an 8-71 and swap the heads back on and put back in the boat. If the valves make the year, I'll put inco's in for the blower. First we'll see if the boat likes 80 mph, then?????

Big Block Billy

I am under the impression that all stock 330hp motors had inconel exh valves. Part #1081040 , and is not the same valve used in a car or truck head. Maybe thats why they are $40 ea. BBB

Leathl_WS6

Good stuff here. Is anyone running just the severe duty's. At 500hp level? Seems to be much better option than just stock GM stainless.

How about the cost differance between SD and Inconnel any have any information here?

adk61

iTrader: (5)

if anyone is looking for inconel exhaust valves for chrysler, i have several new sets. call alan @ 905-722-6684

Leathl_WS6

I need some for a BBC do you have any?