Aluminium Edmunds head 8 cyl

pmlmbigpondcom

G'day All
I have purchased an Edmunds 8 cyl head for our Railton Mid 30's splashie
A couple of the plug threads are a bit scrappy and I am contemplating boring the plug holes out to 18mm dia.
Does anyone know how much material is around the existing plug holes ?

Thanks

Phil
Australia

bob ward

According to the cross sections in the 52 Mechanical Procedure Manual you have more than enough material to go from a 14mm thread to 18mm.  

Alternatively its a straightforward procedure to have the damaged holes welded and rethreaded to stock size.

Park_W

There are also thread inserts available (drill, thread and install), so you can keep your 14mm plugs.

Uncle Josh

Trade name is 'Heli Coil'.  They come several in a kit with the proper tap.  Basically a diamond cross-section spring with an insertion tang.  They work great and are easy to install.  Available at parts houses and small engine shops

.https://www.youtube.com/watch?v=RFYa6sjhh_E   Demo here.

lostmind

NAPA carries the Helicoil kits under their brand. Easy to use. I would try them before you try to go bigger.

It's always and option to go to 18mm if they don't work.

I never had a problem using them. I've done several with the head on the engine.

Ol racer

FYI

Since the head is off I would have a Shop weld and re-tap. However, I agree that Heli coil's work very good. The newest Helicoil Kits have a Tap that enlarges & Taps the hole without needing to drill larger.

Frankvintagefullflowcom

Helicoil is certainly the cheapest and easiest method but some are concerned with the poor heat conductivity of the stainless wire inserts, especially in an Aluminum head. The stainless acts as as an insulator between the plug and head, sometimes making plug heat-range adjustments necessary.
I've been using tooling and products from the Lock and Stitch company of Turlock, Ca and am duly impressed with their products. They have hard anodized Aluminum inserts for Al head plug hole repairs that exhibit identical heat transfer and thermal expansion/contraction properties to that of the head. Of course, they claim a superior repair to the "stainless wire" inserts offered by others.

http://www.locknstitch.com/sparkpluginserts.htm

lostmind

Thanks Frank , never knew of that.

TwinH

I'm a fan of the Lock and Stitch products too but my Clifford aluminum head came to me with steel inserts installed (Lock and Stitch doesn't recommend steel inserts in aluminum heads) I've never had a problem with the Clifford and like the bulletproof steel on steel connection. Makes me wonder if all the Clifford heads are done this way. Anybody know?

Frankvintagefullflowcom

I claim no personal experience with the spark plug repair products but they look like a potentially great method. I've been using some of their crack repair inserts and pins on a 212 rebuild I'm doing. The special thread form is very interesting and, if it performs as claimed, it should turn this block into a thing of beauty.
I have used the usual Helicoil repairs and have not had a problem, either, but I thought the L&S was worth throwing in the mix.
Frankj

50C8DAN

I had the steel Lock and Stitch fix done to the Hudson aluminum head on my Commodore 8 before I reassembled the engine.  I have been running this head now for 8 years without an issue.  The issue with thermal problems between the head and insert is way overblown.

Frankvintagefullflowcom

I'm not so easily duped as to think that there isn't a whole lot of marketing that goes into their presentations, but the points they make have merit. I don't doubt that you have had good results but it begs the question, why did you use the steel inserts instead of the Aluminum ones in an Aluminum head?
I have several Al heads that need attention in that area so I could use more info from the voices of experience.
F

ivanz62

We've used Helicoil inserts successfully for years on many aluminum parts with no problem.  They are a good solution.  Welding is a last resort because the inherent heat in welding anneals the aluminum--makes it soft.  the chart can be heat treated again to harden, but now we have a loot of cost.  and for the record, Clifford  heads were not Helicoiled but were shipped with a tube of Alumaseal to seal up porosity in the castings.

TwinH

Porosity aside on the Clifford piece, the combination of a short thread engagement, countless ham fisted plug changes,and even just a piece of hard carbon on the plug is enough to seriously degrade the aluminum head spark plug threads over time. I have no idea of the vintage or history on my head but can say that the steel inserts are problem free and also provides a bulletproof surface for the spark plug crush gasket to seal to also. If Clifford didn't install the inserts during manufacture then clearly somebody thought there was no sense repairing one or two holes if the inserts would correct and eliminate any future problems. And so far they have.

50C8DAN

My preference is steel.  It does not gall and unless you are not paying attention there is little chance of doing cross threading damage.  Over time there is little chance of corrosion in the threads as well.  In addition they are a flat out stronger thread!

My reference to steel is for the inserts not the head.  Steel inserts in an aluminum head seem to work fine and are superior to aluminum for the reasons I noted above.

Geoff

The option is either alloy or cast iron, not "steel".  I go for the cast iron option every time,  even though most modern cars are alloy blocks and heads.  Alloy does give much better heat transfer, and are usually higher compression, but I can't think of any other advantage.  The disadvantages of alloy are the likelihood of galvanic action between the head bolts and the alloy, stripping of the plug threads,  corrosion of the internal water passages, and likelihood of warping.  My Dad had a 1936 Graham Crusader with an alloy head, and ti was virtually welded tot he studs.  We never did get it off, but threw the whole engine away and replaced  it with a Dodge unit. 

TwinH

But they sure are pretty...




Check out the soon to be 29? Rolls Royce head.

pmlmbigpondcom

G'day All and thanks for the comments
However, going back to my original question - does anyone actually know whether there is room to enlarge the plug holes in this particular type of head ?

Thanks in anticipation

Phil
Australia

Geoff

Phil, if the plug recess is the same shape as a cast iron head then you will have to enlarge the seat area by milling about 4mm  to take the gasket, and then re-tap the hole to 18mm.  It is doable, but personally I  think you would be far better to go the heli-coil way.  Your decision!

Geoff 

TwinH

I would expect that the spark plug well would be solid (no water jacket) across its full width. That Edmunds is an exceedingly rare piece so I understand your concern. Can you see any of the interior construction with a mirror down in the water neck area?

bob ward

........................ However, going back to my original question - does anyone actually know whether there is room to enlarge the plug holes in this particular type of head ?

.....................

I thought the first response in this thread pretty well covered that. 

pmlmbigpondcom

G'day Bob
I wasn't thinking that the 52 Mechanical Procedure manual would address an aftermarket Aluminium head possibly from some years earlier.

I gather from your comments that it does in fact cover my specific head and application

Thanks

Phil