Inliners International Forums General Discussion Blown and Injected Starting turbo build on a 250

Starting a turbo build on a 250 gm and could use some advice from you experienced people in here. Have a cummins turbo and GM tbi from a 93 350. Wondering what experiences you have had out there. Anything will be helpful. Thanks guys!

Well I wouldn't be much help on the fuel delivery side of your project considering I did a blow through setup on my 250 with a holley 2bbl.

As for actually getting the turbo hooked up, you have two options. You can either get a SPA turbo manifold which is a cast manifold with a premade outlet for a t3 or t4 turbo. Here it is on ebay
The second option would be doing what I did and getting a chevy 292 exhaust manifold with a 3 bolt outlet and welding up an uppipe with a flange to mount the turbo on. The 292 manifold has 3 studs and a 2.5" outlet as opposed to a 194/230/250 manifold which has 2 studs and a 2" or 2.25" outlet. Here's a few pictures of mine.




I've been told that the stock rotating assembly can handle up to 350ish hp. After that your stock cast pistons become your weak point. Also, be very conservative with your timing when you are tuning or get a knock protector like J&S safeguard because stock pistons will VERY easily EXPLODE with any amount of detonation (from what I've heard). Now I'm just a 17 year old with a turbo 250 in his daily driver and I drove it around pretty hard for a few days at 15psi with a pretty hefty amount of initial timing and I know I heard some detonation but it survived 12-15 pulls at 15psi with some pretty good initial timing. Also just a sidenote, at 15psi with a completely stock engine besides the carb and turbo, it was a race engine. I did a rolling burnout at 40mph on a 3 speed manual. It was scary fast. Fastest car I've been in hands down.
Since then I've dialed the psi back to 10psi and reduced the timing some and it runs just fine and pulls pretty dedgum hard all on a completely stock block and rotating assembly. All I've done is taken it apart and cleaned it and welded in a return fitting for the oil pan and replaced the head gasket with a high performance one and some other gaskets.

The things to really add power to this type of setup are INTERCOOLER definately, alcohol injection, Turbo MSD ignition box, turbo cam/valvetrain, lump ports, and port/polish heads.

Feel free to ask me questions or message me. My thread on my build is the really long one on this turbo sub-forum and that'll probably be pretty helpful. I just can't give a whole lot advice on the fuel injection though. That's more Tom's (tlowe) domain with his turbo EFI 292 el camino.

Now that looks exactly what I was thinking about. Great! The 292 manifold will fit the 250?

The big truck 3 bolt manifold is a dirrect bolt on for the 230-250. There is new ones for sale on Ebay. They are repops made for ag equipment. Tom

Yes the 292 and 194/230/250 use the same head but the 292 has a taller block. So yes the 292 exhaust manifold would fit the 250. I got mine from Tom (poster above me) but ask around on the forums and somebody might haveone for cheaper than a repro or ebay one.

Sverhoon, that turbo doesn't have a carbon seal, so it isn't a candidate for draw through.

Don't know if that was your plan, but is worth a mention.

Good luck.

That's a good point! Was going to blow through. Thanks for the tip!