I have a holset HT60 on a 408" iron block LS. It has the large turbine housing on it. 28 or 26 cm. Its hard to read the casting. I wanted to try a smaller housing and finally found a donor turbo with the 22 cm housing. I pulled the turbo off and was going to swap housings and ran into a problem. The profile of the exhaust wheel on the large housing turbo is different than the small housing turbo wheel. You could possibly put I larger housing on, but you can't go smaller. The small housing hits the turbine wheel blades before it seats against the center section of the turbo.

I have read that is was as easy as swapping the housings, but it apparently not. I figured I would share this here since there doesn't seem to be much info out there.

Now I'm debating on using the whole core turbo. It has some radial end play on the shaft. I haven't measured it, I am guessing about .015-.020.

Lynn

 

the turbine housings need to the for the same turbine wheel in order to swap them

 

I'm a newb when it comes to that stuff. I guess its a good thing I was going this way and not the other way, because it would have not had the interference problem.

Lynn

 

How did it run for you? I had one I was going to run on a 351 but never finished the project.

 

I ran the 26-28 cm housing on a stock long block iron 6.0 with 1 side of the turbine housing blocked off. It was a little slow to build boost without 1 side blocked off. It ran real good. I didn't make it to the track with the 6.0. I busted a piston trying to get the carb right. I built a 408" stroker out of the block and kept 1 side of the housing blocked. It ran 8.49 @ 83 in the 1/8 in a 5300# 4x4 truck on 8 psi.

 

Your dropping the housing size down to .8x AR by blocking off half of the scroll. It will build up a TON of back pressure with that sized engine at RPM. Likely the reason you busted a piston. You shouldn't block off the whole port on the other housing without a way of opening it at higher RPM. Using nitrous to spool the turbo initially is the cheapest and best route IMO.

 

Im not sure of the exact cause of the busted piston. I was doing a DIY blow through and it was going from 10.0 afr to low 13's as RPM went up. I figured I trapped extra fuel between the rings and lit it off after it leaned out. It lifted the top of the piston off.

 

Usually means your ring gaps were too tight if it lifted the piston top off.

 

It was a stock long block and I was only running 8psi of boost. From what I understand, people are doing way more than that with stock long blocks. Anything is possible though. Back from when I played with nitrous, I remember hearing too fat of a mixture would cause similar issues.