data plate gone, got these numbers stamped into front right side, (it's an inline engine) 4A157403(and a star) then under that it's RC(star)4057N. if it helps it's in and old Taylor Y-40-W forklift.
Welcome the HEF MonkeyWrench302. :drinkup I don't know if you can post pics of the engine as a probationary member, but my first guess, a 4-71, 4 cylinder 71 series.
Id be willing to bet its probably a 4-53 or variant of the 53 series displacements
That would be my guess, but have posted the S/N over to a Yahoo Group I'm on someone there will probable know everything down to the year it was built! Still waiting on the Yahoo site but found a link to a list: http://www.scribd.com/doc/77959821/Detroit-Diesel-Engine-Serial-Numbers#scribd According to this one it looks to be a 1969 4-71 Guessing that is a pretty large fork truck!
Just watched the owner use a huge Taylor forklift at a local junkyard today when I needed fuel lines for a F550 custom fuel tank project. The 8ft long forks were 6" thick. It had a 4-53 Detroit in it. I would like to see a picture of both the forklift and the engine.
Well reply from Detroit Diesel group confirms my research: That's a 4-71 built in 1969. "A" indicates a 71 series "D" indicates a 53 series "F" indicates a 92 series
An easy visual ID for the 53 and 71 series is the valve cover fasteners. The 53 series has the screws on the valve cover edges. The 71 series have the large hand knobs on top the valve covers fastening thru the cover.
And the 71s had the crankcase covers that can be removed when overhauling if the oil pan cannot me dropped.
It has been too many years since I dealt with this on a daily basis, but here is what I remember. There are 8 configurations for Detroits; 4 right hand and 4 left hand rotations. R means right hand. A, B, C, & D refer to which side the cam shaft is on and where the starter and oil cooler are located. Think of a bus. The engine sits sideways so the starter must be on the side facing the rear of the bus or it would be miserable to swap. 4 means 4 cylinder, 5 should be a 53 series and 7 tells what configuration for the cam and starter. N means it is an N (new) series engine and has 4 valves per cylinder as opposed to the old style with 2. N's were designed with the internal water jacket at a higher level to increase cooling. Hope this helps and that I did not suffer from old-timers and get something wrong.
Many of the old Greyhound buses with the cross mount engine were left hand rotation. A bridge contractor I worked for years ago replaced the engine on a cofer dam pump with a newly rebuilt V6-71 that came out of a bus. You sure can not get the pump to prime when the engine is running backwards. We had quite a laugh over that one. Don't remember what all they did, but the dealer did reverse the rotation in a days work or less.
Everything else sounds right except this one. At least on the V71's I have worked on the newer blocks have the small air box covers and I believe they are call "Water Below Port" style. So the "N"'s would have a lower water jacket not higher. This is not to be confused with "High Block" and "Low Block" engines that if I'm recalling refers to the style of head gasket system used. The "Low Block" would be the older/original design that used a one piece gasket just like used on most car engines, the "High Block" engines use the individual seals.