To4b80 Turbo questions

It's been 45 years, but I'm pretty sure the D-21 and D-19 used the SAME turbo, which was a Thompson brand which later became a Rajay. I always thought that was interesting, but that D-262 couldn't stand much boost and the bigger size was just what it took to keep boost relatively low.

TO4B80's came with 2 different exhaust housings. The D19,190,200 all used the .69 A/R housing. The 7020 and some combines and industrial (gen sets) used the .58 A/R housing for about 2#'s more boost or the same boost at lower RPM.   The TO4 B90's were used on the 426 engines up to the 8000 series. They used 2 housings as well. Some combines, industrials, used the smaller .8 A/R  but most had the .96 A/R housing.  The smaller A/R housings forced more air to the turbine and spun it faster for more boost. The larger A/R's allowed some gases to escape around the turbine. The A/R # is usually stamped in the exhaust housing inside or on the radius. (some of the later China, perhaps, castings have no stampings)  

Edited by tbran - 01 Feb 2025 at 9:10am

The Turbo I finally found to fit my old 7G was on ALL STATES AG PARTS, contacted Air Research(Garrett) and confirmed would function as a replacement, most of these were Altitude Compensators NOT High boost Super Charging turbos, just meant to clean up Combustion.

Sorry Doc, but swapped many a brand of Turbo on Cummins Detroit and other engines as the OEM Manufacturers disappeared, So long as Volute Housings were produced to the old Specs any physical differences in appearance made no difference.  Biggest issues in swaps were generally Plumbing for Oil Feed and Return, or re-clocking housings.  Boost off the replacements was only limited as to discharge volumes based of Fuel consumption on the engines, generally they ran cleaner than the last units coming off had been.

Edited by DMiller - 26 Feb 2025 at 6:47am

Position differences are manageable if cannot attain a antique that has not been built for thirty years.