testors mccoy running poorly video

chevyiron420 Sun Nov 19, 2017 5:20 pm

I know it sounds like if I would lean it a little more it would clean up, but it just slows down. Its like the needle has no sweet spot.

Mark Boesen Sun Nov 19, 2017 11:41 pm

the needles were not the best, it might be fun to slap a fine thread needle from a older postage stamp backplate on it. i might have a non blued (black oxide) cylinder, i'll look when i get back from thanksgiving. i know for sure i got a few NOS piston/cylinders from the later series Testors engines.

Oldenginerod Mon Nov 20, 2017 3:21 am

Phil. One observation from the video which confirms a needle problem. Every time you touch the needle to adjust it, before you've begun to turn it, the engine dies a little. That tells me that the thread on the needle is loose causing either an air leak, sidways movement in the needle tip altering the fuel flow or probably a combination of both. If you haven't already tried, slip a little fuel hose over the needle to seal the threads & see if that helps.

Rod.

roddie Mon Nov 20, 2017 8:13 am

Hey Phil, I pressed-out the NVA's of both; a Wen-Mac .049 case that Bob had sent me.. and an old broken Cox .049 "horseshoe" backplate that I had in my parts-box. They're very close in size.

testors mccoy running poorly video Wen-ma10

The Wen-Mac NVA's OD measures .1135". The thru-hole in the venturi measures .113". The "Cox" NVA's OD at the splines measures .119". Ideally; a 3mm drill (.1181") would be the size to use for a press-fit. You could alternately use a #31 drill (.120") and some JB-Weld.

If you don't have any Cox NVA's laying around.. I'd be glad to send you the one I just pressed-out.. along with a needle and spring.

chevyiron420 Tue Nov 21, 2017 4:31 pm

I wanted to make three test runs with this nos needle on 10%-15%-20% fuel today, but mother nature wouldnt have it. Here is a short clip with the new needle on 10% fuel before I got rained out.
Phil

Oldenginerod Wed Nov 22, 2017 6:17 am

chevyiron420 wrote:I wanted to make three test runs with this nos needle on 10%-15%-20% fuel today, but mother nature wouldnt have it. Here is a short clip with the new needle on 10% fuel before I got rained out.
Phil

Well that sounds far happier. Thumbs Up

A little more nitro & she'd be running sweet as a button. Needle must have been the problem as suggested.

chevyiron420 Wed Nov 22, 2017 5:25 pm

I finished up making the three runs First is the 10%, then 15%, then 20%.

66 Malibu Wed Nov 22, 2017 6:52 pm

Looks like the design limitation factor hit a proverbial brick wall in that there was scarcely 200 rpm variation between 10%, 15%,and 20% Nitro fuel used .....
Great work and informative vid !!!!
Thanks for sharing ..........
Steve.................

batjac Thu Nov 23, 2017 1:10 am

Phil, if you remember, a couple of years ago I had a Wen-Mac engine that had a broken needle valve, so I pressed out the Wen-Mac NVA and pressed in a Cox product engine NVA. I was getting around 14.6K on it with a 5x3 and 35%. So what you're getting is about the same. I think these engines like to run at about that RPM, and no matter what NVA, they have a very narrow adjustment band.

The Narrow Minded Mark