[71hondachopper]

Ok I have a 62 chevy 2/nova I am restoring my question is how do you think a turbo on a 250 straight 6 would run. I have a turbo off of a turbo coupe thunderbird I could use just need to make the exhaust and mounting plate to get it to work. Can this turbo be plumbed to a two barrel carb and get more power from the 250. Oh yea its been bored .030 over new rings a hotter cam and is running a 194 head thats been ported polished and shaved .010 to even out the bottom(was slightly damaged from sliding on a concrete floor). The engine is linked to a turbo 350 with a 2200 stall converter. 4.10 gears in the rear.

[HemmiGremmie]

I know they was turboing the 258 amc's with nice results. Do a search and Im sure youll have luck. HG

p.s. Nice bike!

[71hondachopper]

Did the search and went to turbofast.com entered in my engine specs and it is estimated to put out 300 to 320hp and 325 to 350 pound feet of torque. I think thats pretty good for an engine with 145 stock hp.

Chop

[454C10]

What compression ratio?

What are your cam specs?

What boost are you planning to run?

I would recommend doing a megasquirt II efi conversion first.

[71hondachopper]

the compression ratio is around 8.75 or 9:1. the boost I plan to run is 8 to 9 psi. And the cam is a clifford 280 duration with .544 lift any advice will be appreciated I have also thought about spraying a 50 to 75 shot of nos through the turbo but I think I have to much compression. I have never ran nos so I know nothing about it any thoughts? What is a megasquirt?

[xxllmm4]

Turbo + Nitrous + stock parts = BOOM!!!!

Seriously if your going to do this then you should use all forged parts and it's not going to be cheap on a straight 6. Your going to have to check compressor maps and do some calculations but the turbo off a 4 banger T-bird is probably to small.

Jordon

[71hondachopper]

yeah it was just a thought I know everything needs to be forged but it would be cool to see it work I think I will just stick with the turbo and some major porting to get some good flow. And your also right about the turbo being small it doesnt put out as much boost as I originally thought after some research. heck I may dithch the turbo idea. I was looking around and found a site for Sissel automotive and it looks like they are making some good power with the bore and stroke and a lot of head work but it expensive. yeah I know you have to pay to play. All I really want out of the engine is 200 to 250 hp and I think its possible with some good decisions and planning as of now I probably have about 175 with more of a head shave and more agressive porting and a intake and carb change(twin rochester b's) and some good headers it would put me in the middle of my goal numbers. thanks for all the help I guess I was just getting caried away with the turbo thing and not thinking about the affordability thanks for helping me realize I dont need all this stuff to make the power I want

chop

[454C10]

Originally Posted by 71hondachopper

the compression ratio is around 8.75 or 9:1. the boost I plan to run is 8 to 9 psi. And the cam is a clifford 280 duration with .544 lift any advice will be appreciated I have also thought about spraying a 50 to 75 shot of nos through the turbo but I think I have to much compression. I have never ran nos so I know nothing about it any thoughts? What is a megasquirt?

You could run around 7 or 8 psi of boost with 9:1 cr and that 280 cam. However, you would need to use a very big exhaust turbine due to the large amount of valve overlap from that cam.

When there is lots of overlap, it is very important to keep the exhaust manifold pressure lower than the intake pressure. Reversion is really bad with a turbo engine. So, a free flow turbine need to be used, however this delays the boost until the upper rpms.

Turbo street cams tend to have very wide lobe centers and shorter duration to reduce overlap.

With a small restrictive turbo, a cam with no overlap should be used, along with low compression (7.5:1). A setup like this makes instant boost response and makes huge low rpm torque. Great for a stock converter and a 3.08 gear.

Megasquirt is a DIY efi system that also have ignition timing control, which is the best way for a turbo. However, 280 degree cam is getting kind of big for efi system that works from a manifold pressure signal.

If you want to make a 250cid street turbo engine then it should have around 8:1cr and use a cam with 114 lsa and 260 degrees on the intake and 250 on the exhaust. Use efi with six 450cc low impedance injectors and ignition timing control.

If your engine is making 150hp without boost then it should make 225hp at 7.5 psi, 252hp at 10 psi, 272hp at 12 psi,and 300hp at 15 psi. An ic should be used after 10 psi of boost.

The pressure ratio (boost + 14.7)/14.7 is the hp and torque multiplier that can be used to estimate power increase. So 7.5 psi is good for a 50% increase in torque and hp. 150hp goes to 225hp at 7.5 psi.

You should also do some research on turbo selection. The compressor and turbine selection is critical. You should talk with a turbo shop such as Majestic Turbo in Dallas texas.

[matt167]

only if you want the N20 will you need forged pistions.. otherwise cast/ hypers will be ok.. my 200 I6 runs cast with a turbo.

[SBCfan04]

that same motor is in our family boat thats a 22' starcraft and it sat for 16 years outside..after new cap, rotor,points, coil, carb rebuild. the motor fired and ran like a charm...very tough motor