3-53 injector question

[NH2112]

I have a customer's machine in the shop now and am working off an old list of gigs. One was a coolant leak, I found the radiator & water pump were both leaking so I ordered a pump and sent the radiator out for repair. The radiator shop called me and said there was quite a bit of oil in it, so I pulled the oil cooler and had the local Detroit dealer pressure-test it. It came back good, now the customer wants a compression test done to see if oil is getting in the coolant that way.

Now I don't have very much experience at all with Detroits, but I could have sworn that I've seen "regular" injectors under the valve cover in at least one other. Looking online for a compression tester adapter reinforced that, because the adapters I saw somewhat resembled the portion of a DT466E or T444E injector that's in the head. But when I pulled the valve cover off the Detroit in question, what I saw didn't look anything like what I expected. There are 3 rockers & pushrods per cylinder, 2 for the valves and one for the injector. So I'm guessing they function like a mechanical version of HEUI, with low-pressure fuel from the fuel manifold continuously being pumped to the injectors, and a cam lobe to squirt the fuel. So are these the only type of Detroit injectors, and if so, how do I do a compression test?

[NH2112]

Well after reading up on these things in this cool book I found at home and didn't even know I had, I've decided that my memory is terrible because none of the Detroits have injectors like I thought I remembered. The local DD shop got back to us with a compression test quote today - $667! So that alone seems to tell me it's more than I want to mess with. I guess injector depth and the racks have to be set, etc, and since we don't have any of the tools it's probably not economical to buy the tools and probably never need them again.