I just replaced factory rectangle port heads witc iron eagle dart and they both have stainless valves. Im running a 468 with a b&m 250 blower @ aprox 5-6 lbs boost. I rarely run it hard for long distance. What probs do stainless have?
The Stainless valves can't handle the heat as well as inconnel valves. If they get too hot, they could tulip.
the next time your at an airport and your walking to your jet, note the rotating turbine blades on the engines. these are called "hot rotating parts". if you look at a turbine engine you will quickly understand why it is called "suck and blow"!
air is brought in, fuel is pushed in, it is compressed, and ignition takes place, and thrust is then accomplished, thereby making airplane/boat fly. basics here, ie. turbine 101.
when you look into engine, you see the frontal blades, those and all the other "hot rotating" parts are made of ICONEL 718. usually with a fairly high if not obscene high ROCKWELL HARDNESS!
the base material of iconel is NICKEL!
the next meteorite you happen to see or find, its base material is NICKEL!
nickel is HEAT RESISTANT thereby thats why you find meteorites on occasion, because they have survived the insane heat of rentry thru earths atmosphere.
iconel is very heat resistant, but it is a TOTAL ***** KITTY TO MACHINE as you get into the higher ROCKWELL HARDNESS SCALE.
if you are turning/milling/drilling/threading iconel, you are in for some very high cost tooling because standard tooling (inserts/drills/mills) coated or uncoated will NOT handle repeated tool paths without changing tooling very frequently. in other words you may already have 25 ops on part completed, and if machinist doesnt keep his eyeballs peeled for tool wear it is very easy to scrap part(called a "crash") when insert goes south due to increased wear due to material and its rockwell hardness.
there is a material, to machine iconel available from sandvick(fairlawn,new jersey) called "WHISKERS". this is a man made substance and time doesnt allow me to go into its structure or mfg. process. just suffice it to say its expensive as HELL. but if your doing iconel all day and want to be competitive making parts, bets are on you WILL BE USING it or you will be sucking hind tit, as far as quoting parts, in the jet turbine arena, which is very cutthroat as far as cost per part made, and time spent on part.
so ...............do ya think ya still want stainless valves? apple/apple comparison look up heat resistance of stainless vs. iconel valve. your answer will be obvious. also stainless is about as difficult to machine as butter in comparison to iconel. ie. higher tooling costs for iconel, thereby end user will pay more for iconel valve vs. stainless valve.
as another interesting note.........ICBM missile nosecones are made from ICONEL 718, due to heat factor of rentry into earths atmosphere. ask me how i know all this ?
hope that helps.
Just another note...TUBI headers use iconel tubing on the inner part of their header..ours are over 8 years old with no internal leaks..tough stuff
i spent my entire past life involved in aerospace tooling/machining until 1997. when i say past life i was counting(inventory-summers) carbide inserts/drills/mills/endmills/taps when i was 12 years old for garrett corp here in phx and L.A.
if you want longevity.............buy iconel.
now what do air cooled porsche motors use, where heat is UBER CRITICAL due to no radiator cooling engine?????????
remember on a bug or a porschen...........250degrees F or more and you are MELTING IT DOWN and a little machine shop is happening making lots of lil chips as oil breaks down and parts start to fail.
the only way to make an aircooled 911 engine last is using 17qts of oil for heat transfer, hauling ass(air movement by heads/and thru oil coolers(plural), and iconel valves.
ask me how i know about this??? i used to werk fur der porschen fabrik.
so all mercruiser engines have inconel valves? Idont think so, at what point do you need inconel? 450.00 is a good chunk to most people. What did people do before inconel?
Spend the money, I thought I could get away with a season on regualr stainless valves, I had 2 fail this summer, one did not do much damage and flew out the exhaust, the second one was not so nice, cracked cylinder wall and hole in piston...
I will have Inconel next season I am 440 N/A HP no blowers...
Again, spend the money, 450 for valves is cheaper then engine rebuild....
85 Cigarette Mistress
86 Baja 320 Force R.I.P.
valves are cheap. iconel valves are cheaper than the above.
an average top end job doing valve guides,intake/exhaust and all associated crap on a 6 cylinder aircooled porschen engine is about $8K-$10K at $88 a labor hour. at porschen fabrik they get here $120 an hour labor at north scottsdale porschen.
theres a comparison.
the man made substance from sandvick that is used to machine large quanities and items out of iconel is called "whiskers". that is due to its structural format/composition under a electron microscope. ie. thats what it looks like. very very very SPENDY aka grab yer arse spendy for JUST a standard geometry insert aka CNMG-432 aka 4-sided rectangle with (8) cutting edges when flipped over.
DOC(depth of cut) SPEED and FEED is what is the mitigating factor on longevity of tooling edges of any geometry when machining aerospace nickel alloys.
light speeds and feeds and DOC will allow "whiskers" to last longer. deep cuts,heavy speeds/feeds and your cutting edge is gone toot sweet and you have HIGH POSSIBILITY OF A CRASH wiping out tooling and/or part.
now if you have some moron button pusher werking your iconel part with 25 other previous ops and setups, and you add cost of material,tooling,labor,machine time, and the moron button pusher crashes the tooling................you now have a piece of very very expensive yard art JUNK! after about 10-15 hot rotating turbine parts and turning them into JUNK.....you will be out of the machine shop biz faster than you can spit.
crashing a part is exactly equal to crashing a boat/plane/car/or blowing an engine. its a VERY BAD EXPENSIVE DAY!
Last edited by gottahaveone; 12-05-2009 at 08:28 PM.
Alum Metal Fab
Custom Marine Sales
Dave's Custom Boats
Diamond Performance Parts
Double R Performance
Elton Porter Insurance
Fastboats Marine Group
GGB Exhaust Technologies
Grand Sports Center
Ilmor High Performance Marine
Lake Cumberland Marine
Lake Havasu Boat Show
Marine Technology Inc
McLeod Design Group
Performance Boat Center
Performance Marine Trading
Potter Performance Engines
Ron Sporl Performance
Speed and Custom Marine
Total Dollar Insurance
Teague Custom Marine
Wake Zone Marine Insurance
Young Performance Marine