There are not any books out there, but you may find some useful articles in the magazine index.
http://index.mrmag.com/tm.exe?opt=S&cmdtext=gp7&MAG=ANY&output=3&sort=3
If you are looking for the best match to prototype, you would be better off with a P2K model.
drewsdaddy wrote:I recently purchased a Hallmark GP-7 painted for Southern. I feel that I got it pretty cheap, but it needs alot of TLC. I'm pretty sure it needs remotoring and I would like to super detail it, i.e. upgrade lights, paint, etc. Could someone recommend a book about working on brass engines that would address my "to do list" in detail?
What's the end result you want out of this engine? If you want it as a runner, I'd suggest adding the brass shell onto a decent drive and frame, such as Athearn, Life Like or Atlas. Older brass diesels run notoriously badly, and replacing the entire drive is usually the fastest, cheapest, and easiest solution (keep the original drive and frame, just in case you ever want to sell the model).
If you want to restore the entire engine, you'll have to contact NWSL and start asking about options on gear towers, motors and couplings. An interim solution would be to replace the trucks with Athearn trucks, and replacing the stock motor with a can type motor with NWSL flywheels and couplings.
Ray Breyer
Modeling the NKP's Peoria Division, circa 1943
Brass maker KUMATA (KMT) used sh***y motors and drives (1 amp motor combined with high gearing. Hallmark was just one of the importers. Satisfactory Conversion of these is a problem.
Cost - when replacing motor and gears, vs. 'Fit' - when substituting another chassis.
Brass diesels had floors, and commercial (plastic) engines have cast metal chassis'. Hobbytown of Boston (new owner) might make a conversion for you. His 'drives' start at $75. or you can accumulate GP-7 drives 2nd hand, starting with Athearn, 'til you find a reasonable fit. I would look for 20 yr old old Atlas/Kato GP-7's on EBay or swap meets. Drives that changed the Industry.
I WENT the expensive route on my ALCO DL-600's, remotoring and buying needed chassis mounted tower gears. Some $250 was spent correcting running problems plus the cost of the original plus custom paint job. A year ago BLI came out with a beautiful RSD-15 (same unit) for $225.
FRANKLY a new P2K GP-9, or Atlas GP-7 painted in your roadname will run better and look as good and probably cost you only $65. THEN I'd consider removing the works from the Hallmark and running it as a Dummy.