212 valve guide question

Bitburger

I recently purchased a 46 212 motor which will need a valve job. Along with the motor came new valves, springs and valve guides.  The valve guides are 6 steel and 6 bronze. The bronze guides are slightly longer than the steel guides.

So two questions: What is the benefit of using bronze guides?  And   Is the longer length of the bronze guides an issue?

Courtesy Man

More than likely the "steel" guides are actually a dark charcoal color cast iron   - bronze guides are a good quality material often used in racing and have better durability. Length may be fine  - I just dont know. I have machined bronze guides for big six engines. Gert

Toddh

Bronze valve guides are generally matched to stainless steel valves and as mentioned are used in high performance applications and last longer than cast iron.  The previous owner may have gone that way intending to use the bronze ones on the exhaust valves. Minor length difference is no issue, just need to make sure the top of the guide is correctly positioned 1 1/16” below the top of the block 

Bitburger

the bronze guides are 1/4" longer than the cast guides. The exhaust valves that came in the package of parts may well be stainless. If they are not stainless can the "standard valves", polished steel I guess, be used with the bronze guides? 

would the bronze guides not come machined correctly to be at 1 1/16"  below the top of the block when installed?

Geoff

No, the guides are straight sided, so you have to insert to the correct height below the deck of 1-1/16".   Check the longer ones, they may have a recess in them which must go toward the top, to allow carbon build up and expansion.

Bitburger

Attached are 4 pics.  if by recessed you mean one end of the bronze guide is longer than the other than by 3/16" +- as marked in the last pic by the blue tape. Is that the end that should go toward the top?

The Exhaust valves are marked Eaton and appear to be stainless and show no shelf life corrosion. The intake valves do show some minor shelf life corrosion.

And I understand that all 12 guides are to be set at 1 1/16" below the top of the block.

Toddh

Bitburger -do you have the 42-47 Mechanical Procedure Manual?  Installing valves and guides is covered quite well in the ‘Engine’ section.  

Essentially you need to knock out the old guides.  They sometimes shatter so make sure to plug the oil drain holes in the valve chamber so no crap falls into the lower block area. You then install the new guides from the top, tapping them in until they’re 1 1/16” below the top of the block.  Hudson had a tool (Kent-Myer?) to set the correct distance but you can use a valve guide drift and a scale and measure from the top of the block to the top of the guide. Then you’ll need to ream the guides to spec to match your valve stem diameters.  From there it’s grinding a proper specification angle on the valve seats and installing the valves, springs and keepers (Don’t forget to remove the oil drain hole plugs before you run it). 

I had new valve seats installed in my ‘34 Terraplane 212 because they were so pitted I couldn’t clean them up. The machine shop I used put in new seats and gave them a 3-angle grind but in a 212, a single angle grind is more than sufficient.  Also finding a shop that had a seat machine able to accommodate an L-head block was problematic but the one I used was able to dig a vintage one out of storage.  

Bitburger

Toddh.  Thanks for the input. I do have a shop manual and have reviewed it. The 212 is currently at a local machine shop to do the valve job as they offered to do it for a very fair price. I already had new valves, new guides and new springs so basically I'm into the machine shop for the labor.

They do intend to gind the seats. I'm not sure what equipment they have for that.

Toddh

To do the seats most use a manual cutter or grindstone or there are machines that can do this too  I personally prefer a manual cutter and I like the ones that Neway make.  The cutter uses an expanding guide shaft that fits in the valve guide snuggly to securely center the tool in the seat.  Once cut, the valve is inserted and with some grinding compound is lapped in to ensure a good seal. The 212 and 254 engines require a single 45 deg angle on the seat and valve.  Some like a 3-angle grind where there’s a small 30 deg and 60 deg angle cut above and below the 45 deg to assist with fuel/air mixture flow on the intakes

Geoff

Check inside the guides.  Later 212 guides had a larger diameter internally for about 1/2", to allow for expansion fo the top of the valve stem, and for carbon build-up.

Toddh

Geoff.  Correct.  There’s a 25/64” (.390) counterbore at the top of the exhaust valve guides

Bitburger

Is that counterbore on the cast guides as well as the bronze guides.?

Toddh

Supposedly just the exhaust valves.  Get your micrometer out 😎

Toddh

Seriously it’s which ever set you decide to use as your exhaust valves.  If it was me, I’d use the bronze guides for the exhaust.  

Bitburger

Ok so looking at the attached pic showing the bronze guide.  Is the counterbore more likely on the long end or the slightly shorter end of the guide?

Geoff

The exhaust guides have the relief in the top.

Toddh

As Geoff says.  

Bitburger

 I'm asking which end is the top?

Toddh

To me, the short outside rebate of the bronze guide is the top as it appears to match the iron intake guide outside rebate dimension. You should check the inside bore to see if it has a 25/64” relief for the top 1/2” or so.  If not, you should ask your machine shop to ream it with this relief as this is important to allow for carbon build-up. 

With regards to the exhaust guide relief 25/64” dimension: I would certainly check the stem diameter of the exhaust valves and see if they match the factory specifications. If the stems are larger, you’ll need to proportion the relief dimension accordingly

Bitburger

Ok thanks for all the info, much appreciated