I came across a Holset H1C for free from my friend who is moving away. I'm curious about my rebuild options. If I'm not mistaken, it's essentially just an older-style hx-35. I'm not big into rebuilding my own turbos, so I'm wondering, are there any options for companies/people to rebuild this turbo? It doesn't NEED it, it's just for good measure.
Are there options for hybriding it?

Justin here is the turbo god. He is who rebuilds most of our turbos.

Bobs is the place to get best quality turbo rebuild kits, if you want to rebuild it yourself.

They have a weaker thrust bearing than the hx35's. If you plan on using/abusing it, I would get an upgraded thrust for it. It is basically just an hx35 thrust drilled for the h1c mounting screws.

Also you would need to measure the compressor wheels as they came in several different sizes just like the hx35s.

Could always reach out to some other freelancers or vendors to see if they can do rebuilding. I've personally done a few myself, just sent out for VSR balancing, but I know there's a few shops in Cali and the corners States that do them for sure. Could also try turbolab.

Ah, the mighty H1 series...predecessor to the HX but with better compressor housing clamping and a weaker thrust system- the latter of which I can address. The compressor aero is dated and the seal plate also interferes with the drain flange a good bit and makes using a 12AN drain (recommended) nearly impossible.

Unless it was wastegated from the factory it won't have a surge-ported cover which tends to increase the chance of surge and decrease reliability when used in a small a/r turbine housing. There are also no direct-fit compressor upgrades for the H1 turbos...and HX compressors do not fit due to differences in the seal plate thickness which is taken up in the thrust parts and compressor wheel taper on the H1 turbos.

So free was a good price as they're an inexpensive turbo option that are still very capable (especially once serviced with the correct parts) but don't really have the high-boost performance factor and interchangeability of the HX series.


These turbos were mainly all rotor-balanced from the factory...there will be a mark on the shaft, the compressor, and both thrust parts that all need to realign once the turbo is reassembled during a rebuild. If you're replacing any combination of the shaft, compressor, locknut, thrust spacer, and compressor seal collar you'll definitely need to have the torqued rotor group rebalanced before use.