The International Cessna^® 170 Association

Looked up the recommended Champion plugs for the C-145 engine and the REM37BY is it. The C-300 has a recommendation for the REM 40E. It appears that the 37BY has a longer reach, cooler running and some minor differences in the plut itself. I know almost everyone is using the 40E's but why not the 37BY's? There is some indications from folks that the 37BY doesn't lead foul quite as easily.

The projected nose of the REM37BY is more exposed and remains somewhat cleaner of lead fouling than the massive electrodes of the REM40E. But that doesn't mean it's for everybody.

Lead fouling is worsened at long-term low rpm operations and training operations (due to many and varied power setting changes) where elevated (and properly leaned) cruise operations are less common.

In most operations the regular REM40E plugs are better because they undergo smaller temperature excursions and stabilize at their designed heat-range better...AND... 37BY's are also more likely damaged by rough handling and usually don't last as long due to erosion.

Engines that are "oil burners" may benefit from the 37BY's somewhat (similar to the fine-wire applications but at less cost.)

REM37BY on the left, massive electrode on the right (NOT a 40E) for comparison. (This also illustrates the difference in "reach" between short and long-reach plugs. Make certain the plug you select matches the threaded "reach" of your cylinder head.)



The source of the pic is an excellent article by Sacramento Sky Ranch:
http://www.sacskyranch.com/faqsparkplug.htm

Torque value for spark plugs

Teledyne Continental engines 25-30 Ft. Lb (300-360 In. Lb)
Lycoming engines 35 Ft. Lb (420 In. Lb)

Sacramento Sky Ranch is a good aviation partner. Even though they don't know the difference between an aviator and a pilot.

How do you measure the threaded 'reach' of your cylinder heads. Champion only lists one REM37BY for the C-145 engine.

The REM37BY already has the correct 1/2" reach for our C145/O300 engines. (The part number of the plug already addresses engine applicability and thread reach.)

Thanks....just found the Sac. Sky Ranch URL. Lotta good info on plugs there.

It should be noted that in the above pictures of spark plug tips, the one on the right is a "long reach" plug and had certainly better not be installed in a C-145/O-300 engine.