Inconel valves a necessity?

[curtis73]

I have some street Vortec heads with Manley stainless valves. I've read that you need Inconel valves in at least the exhaust side. Should I go to the expense of buying new valves and another valve job, or will the stainless ones work fine?

[blowngas]

a lot is gona hinge on how hard the motor is gona have to work, where the timing is set, how lean do you run it-----I've seen a big single engine scarab tulip some street stainless valves pretty quick------don't know how much $$ you have in the rest of the motor, or application, but if there is a doubt, consult a good marine engine builder and give him all the info you can

[GofastRacer]

Plain Manley stainless or "Severe Duty"???, blown, unblown??.. Unless your'e pushing max effort out of the motor, Severe Duty is plenty adequate!..

[curtis73]

Not blown. This is basically a copy of a Mercruiser 300-hp 350 that I'm building myself
I'm not sure which Manleys they are so I'll assume stock replacement style. I have two sets of Vortec heads; the stock marine set I just got with the longblock, and a street set that have been mildly pocket ported and have the Manley valves. I could swap the inconels over from the marine heads to the street heads, but who knows if the valve guides will be right. I'll also have to have 8 valves redone which isn't cheap and it also means a complete teardown and reassembly.
Since I'm running a cam with .488 and .495 lift I need the extra lift capability I've already engineered into the street heads. Its just frustrating to have to do a complete teardown and rebuild of both heads just to swap 8 valves. I know its not that bad, I'm just concerned about making more money and work than I need at this point.

[BrendellaJet]

Just run it the way it is. If you trash a few valves you can just rebuild the motor!

[steelcomp]

In your HP range and application even a good "street" stainless valve will work. The Manleys are fine.

[WannabeRacing]

I have never seen the need for inconel valves unless you are running forced induction, fair amounts of nitrous or the tune-up of the engine is way off.
You would really need to have a viscious N/A engine and running it HARD to need inconel valves.

[fkboatman]

i went through what you are concerned about, my sbc motor was built by local builder knew up front intensions of use of motor, motor turned 6700 rpms in 19 ft open bow campion with bravo one drive with 1.50 ratio and land and sea extension box, first thought was spring and valves floating and hitting pistons, went to heavier springs no such luck, smacked pistons again, had motor ripped down check deck height with pistons in motor all good...... i was using iron eagle heads, so we opened guides as far as possiple still did it again......... found valve stems swelling and bindind in guides, went to inconels no problen turn motor all day seven grand. so think twice of your choices

[shockwaveharry]

Teague on Tech sez:
Answer: Yes, you do need Inconel exhaust valves if reliability is important to you.
The Manley Extreme Duty valve is made with exotic XH-430 Inconel material. Inconel valves are usually only used for exhaust. Generally speaking, the Inconel valve is about twice the cost of Manley's Severe Duty series valves. The constant load and high rpm on marine engines creates excessive and prolonged exhaust heat which is detrimental to inferior valve materials. If you do not install Inconel valves and drop the head off one of the less expensive alternatives, the damage that will be caused will be tens of times greater than the difference in the valve costs
IMHO, especially necessary if you have a cam with excessive overlap. Water reversion will very quickly kill lesser valves.

[DEL51]

The Inconel valves are cheap compared to replacement of junk stainless. New Heads, sell the old ones with the inconel ex and it will be easier.

[TIMINATOR]

I prefer Ferrea, since a Manley issue a few years ago. Manley was kind enough to replace the VALVE that was defective and came apart. The other $3800 was "not there problem and considered consequential damage". Ya pays yer money and takes yer choice. TIMINATOR

[Infomaniac]

Yep I always do a "ballistic" overhaul to marine heads. Ferrea inconel exhaust and competition plus intake valves. new guides retainers springs locks seals etc. Nothing but the original castings remain.
After 120 hours the springs are dead and 200 hours a valve can pop a head off for no apparent reason. More hours than this and it can beat a seat loose also.
I explain that metal fatigue is not predictable and cannot be measured. Just change all the valves with good ones or change a piston, sleeve a cyl and/or replace a busted head later on.

[fkboatman]

just put the inconel valves in it and be done, i did a lot of research after my motor ate the first set of severe duty by manley, i can send you the reciepts to show you what it cost to fix mine and it may influence you to just put them in

[GoCiggie31]

STEPUP-its cheap insurance:idea:
Info from Manleys web page
RACE SERIES
- Stainless Steel ( XH-426 Exhaust and NK-842 Intake )
- Chrome Stems and Hard Tips
- Swirl Polished and Fully Machined
- Race Master ( Straight Stem ) and Race Flo Shapes Available
- Recommended Exhaust Valves for Alcohol Engines
SEVERE DUTY¨ SERIES
- Superior Stainless for High Temperature Gasoline Engines
- Exhaust Material XH-428 with Double the Ultimate Tensile Strength ( at 1500û F ) over the competition
- Intake Material NK-844 with 1000 Times Better Fatigue Strength than competitorsÕ offerings
EXTREME DUTY SERIES
- Top Fuel, Funny Car and Marine Engine Exhaust Valves
- More Hot Hardness and High Temperature Strength than any Competitive Offerings
- Exotic XH-4-0 Inconel Material
- XH-4-2 XtremeAlloy