Sherman M4A2 Detroit Injectors

[Andrew Rowe]

You are right in the fact that more diesel requires more air. There are the standard old liners that had a couple of rows of small holes all the around the liner and then for the bigger injectors there are liners with large e-elongated holes. You can view what type of liner you have by removing one of the little side covers on the side of the engine, and that will indicate whether the engine will appear to have been built matched to the injectors. There are quite a few different configurations that can interchange on these motors , from injectors to liners to different heads, 4 valve to the old "low block" 2 valve head. To get the power with bigger injectors the 4 valve head is needed. Cheers Andrew

[Tony Smith]

And don't forget, too, Malcolm, that despite the presence of the Exhaust Valves in the head, the 6-71 is still a 2 stroke engine and the liners (specifically the port shapes and heights) control the timing of the Intake Cycle and cylinder scavenging, in much the same way as a camshaft controls valve timing.

Over the many years of the GM/Detroit Diesel engines, a wide variety of liners were developed to give different operating parameters, just as many 4 stoke engines had a range of camshafts for differing applications. The 6-71 has been used in Trucks, Earthmoving Plant, Locomotives, Boats, Gensets, Waterpumps (and even Tanks!). Each application had a unique need for power, torque and rpm range. The port shape in the liner is modified to optimise engine output to application.

[Malcolm Towrie]

Originally Posted by Tony Smith

And don't forget, too, Malcolm, that despite the presence of the Exhaust Valves in the head, the 6-71 is still a 2 stroke engine and the liners (specifically the port shapes and heights) control the timing of the Intake Cycle and cylinder scavenging, in much the same way as a camshaft controls valve timing.

Over the many years of the GM/Detroit Diesel engines, a wide variety of liners were developed to give different operating parameters, just as many 4 stoke engines had a range of camshafts for differing applications. The 6-71 has been used in Trucks, Earthmoving Plant, Locomotives, Boats, Gensets, Waterpumps (and even Tanks!). Each application had a unique need for power, torque and rpm range. The port shape in the liner is modified to optimise engine output to application.

Ah, yes, good point, Tony. So I should have said above that it’s effectively the ignition timing the varying injectors types can change.

Talking of 2-strokes, we have these two tanks and a bunch of military vehicles with Detroit 6V53’s, also 2-strokes. I knew they should all idle around 500 rpm, but it always sounded to me like they were idling way too fast. My light bulb moment was when I remembered that they were firing twice as fast at 500 rpm as the old rumbly 4 stroke gas engines I was used to!
Great old engines. We’ll never see the likes again.
Malcolm

[Malcolm Towrie]

Originally Posted by Andrew Rowe

You are right in the fact that more diesel requires more air. There are the standard old liners that had a couple of rows of small holes all the around the liner and then for the bigger injectors there are liners with large e-elongated holes. You can view what type of liner you have by removing one of the little side covers on the side of the engine, and that will indicate whether the engine will appear to have been built matched to the injectors. There are quite a few different configurations that can interchange on these motors , from injectors to liners to different heads, 4 valve to the old "low block" 2 valve head. To get the power with bigger injectors the 4 valve head is needed. Cheers Andrew

We’ve got the liners with large holes. We had those airbox covers off to check out the pistons, ring, and bores. Pretty handy!

This tank has 4-valve heads on the original 2-valve blocks. Strangely enough, the other tank with the larger N95 injectors still has the original 2-valve heads.
Malcolm