Milwaukee Midget

[Dr Goggles]

anyone have an equivalence on the ISO measurement the "poofteenth"?........

[Captthundarr]

I still have a verity of measuring devices...1st wife was a blonde and last 2 redheads. not to mention feeler gages and micrometers. sorry guys long day remodeling a bath..

[Milwaukee Midget]

I still have a verity of measuring devices...1st wife was a blonde and last 2 redheads. not to mention feeler gages and micrometers. sorry guys long day remodeling a bath..

So Frank, your second or third wife never swept the floor?   

For clarity - we're shooting for .0010 -.0012 inch = .025 -.030 mm = ~2/5 of 1% of the gap between Alfred E. Neuman's remaining front teeth.

[Freud]

I still have a verity of measuring devices...1st wife was a blonde and last 2 redheads. not to mention feeler gages and micrometers.

I think the spell checker missed some punctuation and spelling errors.

"not to mention feel'er gagas and....."

FREUD

[Tman]

Now we are measuring British stuff in RCH's and BCH's!?

[Peter Jack]

Sure can tell the season's ended! 

Pete

[Jack Gifford]

Why "shooting for .0010" - .0012"? That's tighter than I'd "shoot for" on a street engine. Competition engines with their potentially extreme temperature ranges and other stresses call for more generous clearances.

As for stem seals- be careful that they don't do too good a job (as the initial Perfect Circle teflon ones did back in the sixties, giving PC seals a bad name). You're actually better off without seals if you can get away with it, but that depends on a number of factors- volume of oil striking the guide/stem juncture, intake tract pressure (or vacuum), engine's sensitivity to octane reduction from oil contamination, etc. If oil cooling of springs isn't required, study the path the lube oil takes in the rocker chamber- and attempt to divert most of it away from the valve stems, along with restricting the flow volume to the minimum needed.

As for narrow seat widths limiting heat rejection- don't blame it on "three angle" seats. You're free to set seat width at whatever you feel is appropriate, with any "style" of seat configuration (with the exception of full-radius seats, which is seldom preferred on intakes anyway).

[fordboy628]

Midget,

Small diameter (.240" - .700" internal diameters) dial bore gages should arrive at ranch today, if USPS tracking can be trusted.   Will chart existing clearances of each valve/guide by cylinder # and post to build diary for a record of pre-existing condition(s).

TOP 6 REASONS RACING VALVES "STICK" IN GUIDES:         (In my opinion.......)    (Sorry Dave, I couldn't come up with 10....)

6   Valve/guide not properly cleaned for assembly.
5   Valve/guide contaminated with foreign matter while being assembled.   (ie: lapping grit, glass beads, sandblasting sand, etc.)
4   Valve stem & valve guide used not made from "compatable" materials.
3   Valve seals working too well.   (Too "tight" to valve stem.)
2   Lack of or lack of sufficient/proper assembly lube.
1   Insufficient valve to guide clearance for racing conditions.

This is trickey because various valve stem/valve guide combinations REQUIRE differing clearance values just based on the materials/application.  My 40+ years of experience building street and racing engines is as follows.   Full race engines typically REQUIRE more clearance than street or street performance engines regardless of the valve stem/valve guide combination.   This is understandable given the more severe operating conditions of full race engines.   The amount of clearance required also varies with the valve stem diameter, ie: a .375" diameter valve stem/guide needs more clearance than a .279" diameter valve/guide.   Guides with internal "knurling" or other oil channels can be fitted tighter than guide/stem combos without this extra oiling.   And of course, the effectiveness of the valve seal has an impact on the clearance required.   For instance: .279" (9/32"-7mm) phosphor bronze/manganese bronze/naval bronze guides (no knurling) with stainless steel valve stems & rubber 'top hat' stem seals can be fitted @ .0006"/.0010" clearance, typically with NO problems.   BUT, a similar setup with silicon aluminum bronze guides, (which are harder & more wear resistant giving longer valve seat life) fitted with stainless steel valves MUST have more clearance, .0010"/.0018", or the valves will stick in the guides.   That has been my experience with those materials.

Are there other combos of materials out there?   I'm sure that there are.   Of what is available, how much is suitable for full out racing?   I don't know and I don't want to spend a lot of time effort and money experimenting.   So I tend to go with what I know will work.

At the core I am basically a simpleton.   If what I do doesn't work........    I change the setup/specs for something that will work.........

The key issue on Midget's jewel is:  At least one valve/guide combo didn't like each other.   Perhaps, like an older married couple, they just needed more room.........................
 
Fordboy

[Milwaukee Midget]

Hi, Jack -

Yeah, the deal in the writing on the subject, which is Vizard's book on the A series, says to keep them a tad tight to dissipate heat.  That said, the book is 20+ years old, and valve guide materials have changed, so again, as my friend who backs the 4 and 1 Chicago Bears points out, "Does paying attention to all the "little details" matter?   I dunno, but I think you should ask the guy who finishes second." 

And of course, they do - I've got the evidence in Fordboy's garage.

I DO have the teflon seals, a product forced upon me for vertical clearance issues.  They are physically shorter than the umbrella caps that are standard issue on the BMC, and the valve spring retainers won't hit them as they did the rubber umbrellas.  Actually a combination of better valve control combined with the shorter seal is what is required to work with the lift I'm running on this engine. 

Running without seals is an option I won't look at on the intakes.  The valves are vertical, and even with the oil restricted to the rocker shaft and head, there is still considerable puddling around the base of the valve guide, and detonation leads to broken parts that are more expensive than valve seals and guides.

So it's a balancing act, and by golly, we're going to figure it out.  We're on the path.

I suspect Grummy might be working on similar issues on the S.O.S. Holden, but he has the advantage of the commonalities of essentially a SBC design parameter.  I'm working with an antique that has more in common with a Buick straight 8 than a modern engine.  I’m not complaining, but if the rules permitted foreign engines, a strong argument could be made to include it in a vintage category.

Have I ever mentioned that I'm having a blast doing this?
 

 

[manta22]

MM;

How about running a reamer through your Teflon valve seals to open them up a bit so a little more oil can get past them?

Regards, Neil  Tucson, AZ

[Milwaukee Midget]

MM;

How about running a reamer through your Teflon valve seals to open them up a bit so a little more oil can get past them?

Regards, Neil  Tucson, AZ

Looking at all options - it shouldn't take much.

Logged and noted.

Thanks, Neil!

Chris

[Frankie7799]

Another excellent build that I can now check off the list  Chris,what a amazing journey this has been to witness. IM sorry to read about your latest setback but as you have with the past setbacks, you shall overcome this and be ready for Speedweek 2013 ( which Im hoping will be my first SW to attend as a spectator ) I need to go back through and read more in depth the technical stuff that FB has put in. Again, a great read and I look foward to following along as you move towards SW '13.

[fordboy628]

Valve Stem sizes & Clearance in Longman Head, Post Mortem.

Midget,

Sorry for the various delays.  At long last, INFORMATION........

Chart of dimensions after checking sizes of all parts with micrometer & dial bore gages.  Same micrometer used to check valve sizes & set dial bore gages:

Cyl #/Type   Valve #   Valve Stem dia.   Clearance
      1 Ex        1          .2790/.2793      .0015/.0010
      1 In        2          .2793/.2796        unknown
      2 In        3          .2794/.2798      .0020/.0004
      2 Ex        4          .2788/.2792      .0017/.0012
      3 Ex        5          .2790/.2792      .0020/.0014
      3 In        6          .2793/.2796      .0015/.0010
      4 In        7          .2793/.2795      .0020/.0004
      4 Ex        8          .2790/.2793      .0018/.0010

The guides, as opposed to being 'straight' & cylindrical in shape, are 'bellmouthed' at both the top and bottom of the guide.  I suspect that this is a result of a worn guide hone/worn trueing sleeve or poor guide honing technique/operator error.   Depending on how the clearance was measured, this probably contributed to a erroneous conclusion about the actual clearance.

As far as repairs are concerned:

1)  The intake guide hole is not cracked and measures out at .4695" dia.  about .0005" oversize.   A .4710"/.4720" OD guide, fitted @ .0015" press fit, will fix that problem.   If it remains concentric to the old guide C/L and the seat C/L you might get lucky be able to lap-in the new valve to the seat.   Worst case scenario is grinding in the seat to align with the new guide.   No big deal.   Hopefully the new valve will be thick enough to equalize the the valve/chamber depth, and keep the cc's equal.

2)  The 'tight' guides can be honed further to increase the clearance, but there isn't much that can be done about the 'bellmouthing' that is beyond the intended clearance.   I don't think that it will affect performance adversely, although seat life will be reduced somewhat.

edit:  Running without valve seals is not an option here.  Verticality is not the only issue.  The valves and springs are half 'submerged' in oil at speed.   Given the vacuum in the inlet tract(s) (siamesed ports, don't forget) without seals, oil 'rains' down the guide into the cylinder.  I can't think of a faster way to decrease power or court detonation than by 'injecting' oil into the cylinder.................

If it was mine, I would open the clearance on the tight guides, lap in (or grind if req'd) the valves & seats, cut the spring pockets for the hardened spring cups, reassemble the head and reinstall it to the short block.   Run in would depend on cam/tappet condition, etc.

Bottom line is that it should not have happened, BUT, it could have been MUCH, MUCH worse....................
 
Fordboy
P.S.  Having a 'blast', is not usually a good experience during a dyno session.......................... F/B

[Dean Los Angeles]

So all things considered, it could have been much worse, but wasn't.

The repairs won't take that long, so when is the next dyno session!

[Milwaukee Midget]

So all things considered, it could have been much worse, but wasn't.

The repairs won't take that long, so when is the next dyno session!

My old pal, Dumb Luck.

I want this engine done, dynoed, and in the chassis no later than Christmas.  I’m looking into engine dyno facilities rather than a chassis dyno.  We popped a tire – actually an inner tube – last time.  What I’m finding out is that the chassis dynos are great for some quick tweaks, but on cars as small and light as the Midget, it’s actually kind of hard on the chassis, especially at the revs I need to test this engine. 

If I isolate the engine and concentrate on getting it right, I’ll be removing some variables from the equation.


Frankie, you must have insomnia, but thanks for taking the time.

And Fordboy, thanks again for the detail work.  I'll see you Saturday - we'll discuss it over a bottle of beer and a bucket of paint.