f4you

My Feedback: (7)

Could use just a bit more space inside the cowling of my F4U (Iron Bay). Those little plugs would do the trick space-wise, but the CH ignition site doesn't recommend their use, and I respect that--but I wonder what the problem(s) could be with them?
I have the 10 mm plugs installed, but could use a bit more room along the sides (D&B 3.7 twin).
Was hoping someone would know of these little critters and could fill me in.

Flypaper 2

Very close distance between the ceramic and the side of the case. Very little fouling will short them out.

tkg

My Feedback: (1)

They work fine, but it costs $100 to make the conversion. They last 20-75 flts and cost $15ea.
They were designed to run in cool running 4c alcohol fuel engines, when you run them in a large gasser they are at the upper end of their temp range, just a bit lean and another $30 for spark plugs

dirtybird

My Feedback: (5)

I have been using one in a G-45 since last summer. maybe 40-50 flights. Still works fine. I tend to run my engines on the rich side.

barryb-RCU

I've got 150 flights on a Brison 6.4 twin with
the 1/4" plugs. The only problem I've had has been that the caps eventually wear out the plug from vibration to the point that they come loose.
I've had to replace my plugs every 50 flights or
so due to the hex bolt shaped part of the plug wearing out.

Otherwise no problems whatsoever. Rich runs, lean (more like ideal) runs, long ones and short ones. Extended hovering, extended idling, and high speed passes haven't caused me any problems.

Antique

My Feedback: (4)

TK is talking about the Rimfire brand plugs, the BEST made..We have found the the Rimfires outlast the NGK brand by a factor of 4 to 1. Last time I looked the NGKs go for about $28.00 EACH..One of my customers gets 100 HOURS on the NGK and 500 hours on a Rimfire..He flies everyday and has about 130 hours already this year, 6 weeks...He documents all flights, I have seen his log....
His engine is a .52 OS four cycle...

gofast1

How much extra room do you actually get with an opposed twin when you go from 10mm to 1/4 32 spark plugs?

CK1

My Feedback: (60)

It may vary somewhat depending on the engine and what brand ignition you are using but on my 3w70 twin I was able to reduce the width from plug cap to plug cap by 1" .I used rcexcl 1/4-32 ignition and 10 mm to 1/4-32 adapters. I have used 1/4-32 plugs in several engines over the years with great success. If the engine is tuned properly you shouldn't have to worry about fouling the small plugs..

ec121

My Feedback: (2)

For even more room read up on the glow/gas conversion and do away with the ignition. I am going to try it on a gas converted Supertigre 3200.

dirtybird

My Feedback: (5)

Many,many years ago all we had was gasoline engines and 1/4x32 plugs.
They cost $1.00.
They were made by Champion. If you ran into their rep at a contest he would give you one.
Later they came out with an improved model. It cost $1.25

kochj

sweet....I would by 10 at 1.25 from you.... Where do I send the money???

dirtybird

My Feedback: (5)

Unfortunately Champion quit making them a while back.

earlwb

I do not see any problems with using the 1/4x32 spark plugs. Some brands may last longer than others though. I have been using them on the small gas engines 17cc and under in displacement. The plugs are holding up really well. But I take a look at them from time to time and replace them when they get all cruddy and coated with combustion byproducts like carbon or other stuff. I do not know how long they might hold up in larger engines though. So spark plug life in the bigger engines is a unknown for me.

MTK

About 1 inch

RJConnet

This may not have a lot to do with the OP's original question but I am curious. It seems to me way back in the dim dark recesses of my mind that Champion used to make two sizes of spark plugs. Back in about 1948 I had both an Ohlsson 23 and a 60. The plug in the 60 might have been like 5/16 or so. Am I remembering correctly? It seems like this would be the ideal size for some of these smaller gas engines that are getting so popular these days. In other words, something in between the 1/4-32 and the 10mm. Oh well, just thinking........RJ

dirtybird

My Feedback: (5)

Yep they also made a larger size called a V3.. I think it was 3/8 dia. I had a replica Super Cyclone that used it. The MFG had rethreaded a CM-6 to fit it

earlwb

The Champion VG1 was a large glow plug with 5/16x24 thread size, if I remember correctly.
Champion used to make a V2 spark plug which was a large one, with 5/16x24 thread size.
The little Champion V3 spark plug was a 1/4x32 thread size.
AC also used to make little 1/4x32 thread size spark plugs too.

zflyer2

I was in the idea they were made for 10 cc 2cycle gasoline engines back in the 40s before alky nitro fuel and glow plugs. Guess my 75 yr olod brain is confused!!!

earlwb

Actually they used to make some amazingly small gasoline engines before WWII too. They used to make sparkies in .19, .23 and .29 sizes way back then. Plus there was the cute little .12 engine that was made by Irwin Ohlsson in 1934 too. I think that the 3/8x24 size plugs were the smallest made for a long time though. The .60 and larger engines tended to use larger spark plugs and some model engines used regular small size automobile spark plugs that looked huge in comparison to the engine. If I remember correctly the 1/4x32 spark plugs didn't get made until after WWII. Now then some people who made their own engines made their own spark plugs too. Some of those people made some amazingly tiny spark plugs too.

ge3740

i have a D& B engine, one of the first, have been running ngk plugs with no trouble, direct connect to the plug, and they are still in the engine today, but i have just changed the, also i have 2 D A 100L the same plug no trouble, 2-- 3W engines no troubles

dirtybird

My Feedback: (5)

The 1/4x32 was made before WW2. It was used in the Atom and the Arden. That is why we ended up with the 1/4x32 glow plug. Ray Arden modified it to hold a coil. It was also used in the Super Cyclone twin ignition head.

The Atom was .09 and Arden made a .09 and a.19. The small Olsens,the Bantom,Phantom P30 and Torpedoes used them