valve size - Moparchat

pishta · #1 10-18-2009, 12:58 AM

I understand the LA head uses 3/8 stem valves. Is this the actual OD of the valve stem or is it the size of the guide? I bought some Miloden valves and they spec the stem at .371, and they fit so what is the deal? also is there a way to touch up your own seats with a Sioux or Kwik-way stone with a pneumatic drill, ie. do they sell a stone holder that chucks into a drill? I have seen the guys in the shops do it with an air die grinder looking tool and a valve inserted backwards as an arbor, ghetto or what?

cudabob496 · #2 10-18-2009, 02:37 AM

My small block motor book shows only 3/8 and 11/32 diameter valve stems available. 3/8 would be .375 inch, and 11/32 would be .344 inch. I'd be nervous with .371, unless the guides are machined for that diameter. Just noticed in Summit that .371 valves are for Chevys.

DJM · #3 10-18-2009, 08:16 AM

OEM valve stem size is 3/8. Have no idea where the 11/32 came from or where they were used. Un less it is in some of the engiens from the ninties up era.

cudabob496 · #4 10-18-2009, 09:14 AM

Quote:

Originally Posted by DJM

OEM valve stem size is 3/8. Have no idea where the 11/32 came from or where they were used. Un less it is in some of the engiens from the ninties up era.

Book says long stem valves for W2 and W5 heads could be ordered with 11/32 stem diameters.

aarracer · #5 10-18-2009, 01:16 PM

I would send the milodons back. I have no faith in their products or their support! Usually it is a fitment problem.

DJM · #6 10-18-2009, 01:50 PM

Quote:

Originally Posted by cudabob496

Book says long stem valves for W2 and W5 heads could be ordered with 11/32 stem diameters.

OK - like I said nothing stock then. After market can be about anything the manufacuter wants ream the guide to and use.

John Kunkel · #7 10-18-2009, 04:18 PM

.375" is the nominal dimension of the valve guide, look at any FSM and it'll often show the actual stem size as .371"-.372" for the exhaust and .372"-.373" for the intakes.

cudabob496 · #8 10-18-2009, 10:02 PM

Quote:

Originally Posted by DJM

OK - like I said nothing stock then. After market can be about anything the manufacuter wants ream the guide to and use.

They were sold by Mopar Performance with a MOPAR part number. But I see your point.

340_GTS · #9 10-18-2009, 10:50 PM

If the guide is .375" that's 3/8", and as John said, the valves are always a few thousandths smaller, which are also what would be called 3/8". .001-.003 clearance on intakes, .002-.004 clearance on the exhausts.

11/32" valves are normally only found on racing engines.

70AARCuda · #10 10-19-2009, 02:27 AM

11/32 are a good performance upgrade...does not necessary mean race...

actually using sb chevy 11/32 valve +.100 longer is pretty much the stock length of a small block mopar....lighter valve...cheaper..flow better due to smaller stem in port.

cudabob496 · #11 10-19-2009, 02:41 AM

Quote:

Originally Posted by 70AARCuda

11/32 are a good performance upgrade...does not necessary mean race...

actually using sb chevy 11/32 valve +.100 longer is pretty much the stock length of a small block mopar....lighter valve...cheaper..flow better due to smaller stem in port.

I went to 11/32s, but they are not necked down at the valve like other performance 3/8s, so they are lighter, but I'm not sure if they flow a lot better. I hope they do!

340_GTS · #12 10-19-2009, 06:16 AM

Quote:

Originally Posted by 70AARCuda

11/32 are a good performance upgrade...does not necessary mean race...

O.K. if you want to get into semantics. Maybe I should say "performance" instead of "race". Sheesh.....

pishta · #13 10-19-2009, 05:12 PM

OK so .371 is actual OD of the valves, and they fit with no lateral movement like they were made for it. So I guess a .371 valve fits a .375 valve guide per design. I saw some reams at a shop and I bought a .375 but I also saw .371 and .372 bit I didnt get them because 3/8 is .375. Jeez, these things arent 2X4's why cant they use simple sizing across the board? Thanks

pishta · #14 10-19-2009, 05:14 PM

Now I gotta ask, what size is the actual size of a +.001 oversized valve?

340_GTS · #15 10-19-2009, 06:13 PM

"Nominal" or "Factory" specs are:

EXHAUST:
Valve stem: .371"-.372"
Valve guide: .374"-.375"
Stem to Guide clearance: .002"-.004"
Oversize valves: (.005") .376"-.377" , (.015") .386"-.387" , (.030") .401"-.402"

INTAKE:
Valve stem: .372"-.373"
Valve guide: .374"-.375"
Stem to Guide clearance: .001"-.003"
Oversize valves: (.005") .377"-.378" , (.015") .387"-.388" , (.030") .402"-.403"

The reamers are sold for several reasons. Some engine builders like more, or less, clearance than stock. They can install new guides and ream them to match custom valves. Or use the reamers for their original intent, which was to ream the existing guides oversize for oversize valves. Remember, on a stock '60s Mopar engine the guides were cast into the heads.

aarracer · #16 10-19-2009, 10:31 PM

A good honed finish valve guide to valve clearance will be 0.001 int., and 0.0015 exh.

cudabob496 · #17 10-19-2009, 10:44 PM

Quote:

Originally Posted by 340_GTS

"Nominal" or "Factory" specs are:

EXHAUST:
Valve stem: .371"-.372"
Valve guide: .374"-.375"
Stem to Guide clearance: .002"-.004"
Oversize valves: (.005") .376"-.377" , (.015") .386"-.387" , (.030") .401"-.402"

INTAKE:
Valve stem: .372"-.373"
Valve guide: .374"-.375"
Stem to Guide clearance: .001"-.003"
Oversize valves: (.005") .377"-.378" , (.015") .387"-.388" , (.030") .402"-.403"

The reamers are sold for several reasons. Some engine builders like more, or less, clearance than stock. They can install new guides and ream them to match custom valves. Or use the reamers for their original intent, which was to ream the existing guides oversize for oversize valves. Remember, on a stock '60s Mopar engine the guides were cast into the heads.

Something doesn't make sense to me, but I may be a little slow here. Mopar valve stems are advertised at 3/8, or .375 inches. So why would a factory spec be .371 to .373? Doesn't make sense! Certainly we can make a valve at .375, if we can put a man on the moon in 1969!

340_GTS · #18 10-19-2009, 11:05 PM

3/8" is fractional. It is just a general size identifier. Valve stems are made in all sorts of sizes. You cannot tell someone you want a 3/8" valve and expect it to be exactly .3750" diameter. It is just not the way things work! Almost everything is made this way. For example you'd think a 1/2-13 bolt's threads would measure .5000" right? But a 1/2-13UNC-1A bolt thread can measure anywhere from .4822" to .4985" on the OD. A 1/2-13UNC-2A will measure .4876"-.4985". But they are both common 1/2" bolts.

cudabob496 · #19 10-19-2009, 11:35 PM

Quote:

Originally Posted by 340_GTS

3/8" is fractional. It is just a general size identifier. Valve stems are made in all sorts of sizes. You cannot tell someone you want a 3/8" valve and expect it to be exactly .3750" diameter. It is just not the way things work! Almost everything is made this way. For example you'd think a 1/2-13 bolt's threads would measure .5000" right? But a 1/2-13UNC-1A bolt thread can measure anywhere from .4822" to .4985" on the OD. A 1/2-13UNC-2A will measure .4876"-.4985". But they are both common 1/2" bolts.

Ok, like a 2 x 4 is not really 2 inches by 4 inches! What genius came up with that! Here's the problem, your building an engine, and I go into the Summit catalog, and they sell valves for 318 and 340 engines. And some valves are listed at .371, and some are listed at .372, and some are listed at .375 inches, yet they are all supposed to be for a 340 Mopar engine. How the *&^% is a person supposed to know which one to buy!! Which is the problem that prompted this thread!! Just plain stupid!! Come on industry, get your act together!!

Ray Bell · #20 10-19-2009, 11:35 PM

So the guide is nominally 0.375 (or ⅜"), not the valve stem...

See, it all works out. Right?

cudabob496 · #21 10-19-2009, 11:48 PM

Quote:

Originally Posted by Ray Bell

So the guide is nominally 0.375 (or ⅜"), not the valve stem...

See, it all works out. Right?

Actually, the problem may only get worse, in that there is a necessary clearance required between the guide and valve stem, or you are going to have failure. So if you can order stems with diameters of .371 to .375, you better have a good idea of what kinda guide you are using!! My service manual lists the valve guide bore as .374 to .375 inches. So you could buy some .375 valves from Summit, and they will not fit!!!

340_GTS · #22 10-20-2009, 03:02 AM

Quote:

Originally Posted by cudabob496

Actually, the problem may only get worse, in that there is a necessary clearance required between the guide and valve stem, or you are going to have failure. So if you can order stems with diameters of .371 to .375, you better have a good idea of what kinda guide you are using!! My service manual lists the valve guide bore as .374 to .375 inches. So you could buy some .375 valves from Summit, and they will not fit!!!

And that's when you set up a machine with the correct reamer, and ream the guides to whatever size you need to obtain the clearance desired.

cudabob496 · #23 10-20-2009, 03:36 AM

Quote:

Originally Posted by 340_GTS

And that's when you set up a machine with the correct reamer, and ream the guides to whatever size you need to obtain the clearance desired.

Can't you just order the correct guides to match the valve stems?

340_GTS · #24 10-20-2009, 06:55 AM

Quote:

Originally Posted by cudabob496

Can't you just order the correct guides to match the valve stems?

A) Guides are part of the head casting on older engines. You can do some machining and put new guides in. Or just ream the existing casting oversize for oversize valves.

B) I do not believe that valve guides come in a variety of sizes for small block Mopars. If for some reason you have oversize valves you ream the guides to match.

Why not just get normal guides @ .374-.375, normal intake valves @ .372-.373, and normal exhaust valves @ .371-.372 and not worry about it?

cudabob496 · #25 10-20-2009, 06:58 PM

Per my 1972 Service Manual, valves with oversize stems of.005, .015, and
.030 were available from Mopar to achieve correct stem/guide clearance.

340_GTS · #26 10-20-2009, 07:36 PM

Quote:

Originally Posted by cudabob496

Per my 1972 Service Manual, valves with oversize stems of.005, .015, and
.030 were available from Mopar to achieve correct stem/guide clearance.

Yeah, but you didn't have to look that up. I posted the exact same info at 6:13PM yesterday.

adodgemann · #27 10-20-2009, 09:10 PM

Quote:

Originally Posted by cudabob496

Can't you just order the correct guides to match the valve stems?

When you have new guides pressed in they distort and ya need to ream them to size anyway.

cudabob496 · #28 10-20-2009, 11:21 PM

Quote:

Originally Posted by 340_GTS

Yeah, but you didn't have to look that up. I posted the exact same info at 6:13PM yesterday.

Yes, I see those numbers. I just didn't conclude from your posting that Mopar actually sold oversize valves at the time. Wouldn't think they sell them anymore, but not sure.

pishta · #29 10-21-2009, 05:22 PM

Im new to buying valves so I guess when they sell a valve that says 3/8 stem, you think it would be .3750. When they sell a 3/8 guide, they say its for a 3/8 valve. So if they sold a valve that states for 3/8 guides, we would all be happy. Live and learn. Now if you had a choice of .371 and .372 valves, that would be a toss up. Although I might get some .005 oversized if I can find them, and ream out my existing old X heads guides, that would save 16 valve guides being replaced.

cudabob496 · #30 10-23-2009, 01:37 AM

Before I'd ream, I'd have new guides put in by a head shop.

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