Are any of the aftermarket valve mfgr's making the .003" first oversize valve stem beyond the OEM 351C, 351M, and 400 standard stem Dia .3415-.3420" ?

I have found a couple (SBI & Elgin) that offer new .015" oversize stem valves - and some also come with oversize head diameters (that's like severe damage or the engine is on a final rebuild ! !). I find those extreme oversizes in excess overkill, with a lot of unnecessary work in boring & reaming that should not be required to refinish a mild first time service wear limit of .0055" clearance that is mostly exhibiting at the ends of a typical "hour glass" guide & stem friction wear.

If I could find those "first over" valves, it would be a simple afternoon chore to pilot a single reamer on the seats with a double-sided NEWAY cone (maybe pilot the other end off the spring landing),run the reamer through and park it with a nut to hold as a pilot so that the NEWAY can clean up the seats upon the reamer/pilot. 3, 6, 9, 12, could be five re-build lifetimes before you ever reached .015", and you could skip a step if necessary without ever removing a guide.

Any "first over's" out there...?

 

Ford is the only one who made .003 oversize valves that I know of
I have a few of the old 390 ones for nostalgia and show and tell
Search Ebay for NOS .003 oversize Ford valves and look for 351C ones
Those C and M motors were hard on guides and you might be able to find some
good luck

 

I think that most line rebuilders use .015 oversize stems simply because they will fix just about any guide. Same with why they nearly always bore to .040. Even the most worn of bores will generally clean up at .040.

For what its worth I just did a Cummins 6.7 diesel head for a customer and it had valves and guides that were .010 oversize. Of course it needed a few valves and I couldn't find those anyplace. I ended up putting in 3 guides and using std stem valves.

 

If a guide is worn bad any reaming or honing could end in disaster. A guide could end up loosing its alignment with the seat and rocker arm.

 

That's why you grind the seat last. It won't move any significant amount if it is done right.

 

Why then do you suppose Ford had .003 reamers in the special tools?
I have a few in my box

 

I may have found 6-8 of the old ford .003" on ebay, but not sure of some of the ford part number scripts :
I definately know # DOAZ-6507-B is a 1970 Full size FORD intake valve .003" O/S (with 4 grooves in picture) as one selling vendor stated "351 cleveland" also.
6507 is an "intake valve" part number, and "B" appears to be a "second revision" or the first oversize stem designation @ .003". (An "-A" at the end of this part number is usually the "STD" valve stem dia.)

Now D4TZ and D47Z were also found with -6507-B part numbers, and with a picture of the box that also stated .003" O/S.
D4 = 1974; T = truck; 7 = Courier (1971-82); -6507 = intake valve; -B = .003" O/S; but I don't know how to identify engine type eg: 302, 351 windsor, 351C/400, or one of the FE big blocks from these part numbers.

Some venders get "Cleveland" identified correctly, but do not realize the huge difference between 2-barrel and 4 barrel heads & valves for example.

How do I identify the engine type ?

 

I don't take chances, this is what the seat and guide machine is for. If a guide is worn so bad it needs a .003 over valve good luck, you will need it.

 

The last time I had heads rebuilt, I had the valve guides replaced. Is that no longer an option?

 

i do about 8 motors a month, when the guide is worn. we machine and install liners in them all keeping the stems standard
https://goodson.com/blogs/goodson-ga...e-guide-liners

 

That is the best option
Bronze wall is what the machine shops do to hotrods

 

The drawing above are the existing measured clearances that I was considering reaming for .003" O/S valves on a 351M. The clearances were measured in the elongated oval portion of the bores, and have much tighter clearances across the narrow oval and center section of the guide. Both my 1973 CHILTON's Manual and a '79 Haynes book give the same stem to guide standard clearance range of .001" to .0027" Intake, and .0015" to .0032" Exhaust - with a Service Limit at .005"-.0055" for both intake and exhaust. The valves that are shown RED would be the clearances with a new set of Standard valves installed without any reaming or honing. Most of the old valves that were removed have as much as .0015" wear in addition to the guides shown in the drawing. I used a micrometer and expanding ball gauge in these measurements. A .3430" boring reamer will just start to enter the lower seat end of the exhaust guides, and will only fit all the way through one of the intake guides at this time.

The guides are basically still within the standard range, and about half-way to the OEM service limit. So, I'm going to re-consider using a full set of brand-new Standard valves to put the truck back into service. If the engine lasts another 20 years, then I'll save the $ to do a full re-build & balance like my '70 Cleveland/FMX F250 build.

So now, what do you guys think about slightly reaming out the bottle-neck center section of the guides - perhaps .0005 - .001" more - so that the middle clearance "straighten's/opens up" along with the wider bell-mouthed clearances at either ends of the guide bores ? It would likely make for a looser valve, but may have less "focused wear" at the middle of the stem, and may last longer in friction bearing along a longer contact surface area. However, It would surely suck more oil through the guides, and could create a chronic coking issue.

 

That is a go for the first shot on a steel head (knurling the guide)
Ask a machinist about knurling the guide in an aluminum head
They have guide inserts and should be okay for the first time around
Just know that knurled guides do not last long
That is why Ford made reamers and .003 valves in the first place, To make the repair last a while

 

OOHHH how true, manic, alloy heads replace the guide, warm the head, freeze the guide, use the correct tools .correct parts, do it right or don't do it,

 

I've got a seat and guide machine and a valve guide hone. Honing the guide to .003 over would be easy and not change the centerline any significant amount. I just did this on a set of heads going from worn.312 to new 8mm valves. Seats were easy to clean up.