- This topic has 29 replies, 11 voices, and was last updated 14 years, 9 months ago by
.
-
Posts
-
There was an article in the digest Dec 2003 about using regular 1/4-32 plugs in a Cox TD 020 with reported success. I’ve tried this using the essentials of the article but without the success. Has any one else tried this, and with what success, details? Ben Cleveland are you out there?
Glenn, I guess you mean to drill and tap a burnt out head to take a plug.
It never seems to work quite as well on any of the Cox stuff, bit I reckon if you played around with various heat range plugs and varied the depth the plug goes in and out with different thickness shims you might get a better result.
I have never needed to play about, as I have a few heads for 02, 049/051, and 09s, but of course one day, you never know do you?
There is a guy here in OZ making and selling on eBay 049/051 heads that screw in that you add a plug. He claims they work well.
He also makes them for Wenmac. I did buy one of these as I only have two good Wenmac heads, so one day I may get the chance to try it.>a guy here in OZ making and selling on eBay 049/051 heads that screw in that you add a plug.
Bruce Duncan, in Vancouver, is manufacturing “Firefly” clones of the Cox #1702 high compression head for all Cox .049/.051’s. Similar performance to standard Cox heads, good at 30% but life is shortened at more than 40% nitro. US$ 4.95 each + shipping – good price! a.b.duncan@shaw.ca
Doug Galbreath makes great heads for Cox 049/051 as well as the AME/Norvel series of engines. They take the excellent Nelson plug which is nearly bullet-proof.
Do a web search on Google for his website.
Nelsons go for around $3.75US. A bargain!!!!
I have never found a deal that works as well as a standard Cox plug. In fact, I used to cut down the TD.15 plugs for use in the ST .15 as well as the Rossi. It was rare that I never had an rpm increase with that combination.
If you want to experiment, the important part of the entire deal is that the plug is not drilled all the way thru into the chamber. The plug should be bottom tapped with the element basically flush with the chamber. This maintains the chamber shape. Note that this is the same thing that is done with the Nelson plugs. It seems that thru tapping disrupts the chamber and makes the engine run 1000+ rpm slower.
I could see this being a big problem with the .020 plug as it is quite small.
Now, something I just thought of…Maybe there is a way that a clamp could be made that would adapt .010 plugs to the .020…Hmmmm…..
We really could use someone to make the original trumpet shaped .020 plugs for those of us that run .020’s….
John
Thanks for the replies, I’ve tried all you suggested including not drilling thru and bottom tapping still without great success. In addition I emailed Mr. Duncan, the guy in Canada making 049 heads, about 020 heads, maybe, but not in the near future. If any of you have not tried one of the Galbreath/Nelson heads, you should. My experience has been that it ADDS about a thousand RPM to even the best TDs. Even better than the globees Must have something to do with the element. There is nothing in the nostalgia rules that forbids using that head on a reed valve or a Medallion, only the Killer Bees have a specified head. Might even bring a sure start to life, are you listening Rocco?
One of the best ways to aquire these is to go to collectos. At recent Meca collecto here in AZ. I bought glow plugs for .010/.049/.09/.15. Several of each new in pack for $2.00 each. My friend beat me to the .020’s. As most of you know Cox is history. People who took it over dumped all prodution so no more TD’s/ PeeWee’s etc. Even Norvell stoped production of their decent engines. In my years of buying/ selling you need to keep looking for what you want. Even trading amoung other hobby folks can unvail many iyems. Kind of fun to. Good luck,Dan.
A NIB 020 TD on ebay has hit $100.00! Plugs for same may be soon to follow unless the “Firefly” folks come up with some, or someone starts making a decent 020 we can all use. One thought may be when push comes to shove is to run the ones we have on Davis Diesel heads.
Hi Glenn
How many spare crankshafts have you got? Dieselizing, bad move.
Ployd
If someone can put in the wire and the seal, I may be able to get the machine work for a 020 glow head done at reasonable cost. What we really need is the GloBee type head. The GB patent for a helical flat coil has run out, so that is the way to go. Glass seal.
@Pelaero wrote:
Hi Glenn
How many spare crankshafts have you got? Dieselizing, bad move.
Ployd
Spot on Ployd. I did the diesel thing on a TD 049, 30 years ago, never over compressed it, and it knocked the crank pin off.
In those days I puchased a replacement crank for very little, so that didn’t matter, but it did teach me a good lesson.On a TD, if you will heat treat the crankshaft, you will keep the pin from breaking off. Soak it at 500 F for a while, and then slowly let it cool. Will turn blue. And will not break. At least with high nitro gas. Don’t know about diesel stress.
As a glow engine the cranks are just fine with or without heat treatment but the stresses that a diesel imposses (about 1.5 times increase in compression ratio) is beyond the design limitations of a standard crank pin; it needs to be of a larger diameter which means a new rod and piston. Not worth the effort.
Ployd
Sorry, but you are incorrect. The TD .049/051 crank pins are subject to breaking wihout heat treating to eliminate stress. This happens at RPMs over 22,000. I have experienced such personally and George Aldrich told me how to avoid it in the future. If you want to disagree with George, fine, but I have not broken any crank that has been heat treated. This is on glow fuel.
- You must be logged in to reply to this topic.