Inliners International Forums General Discussion Blown and Injected Turbo 250 Results

Does anyone or does anyone know of somebody who runs a turbo 250 regularly on the street or the strip? I know a lot of people who run a turbo 292 (like santucci who runs low 10s with a hybrid head) but haven't seen anyone besides tom's slapped-together turbo 250 dyno. I'd just be interested to see what types of horsepower/tq a higher boost (10+psi) 250 with all the upgrades (4 barrel, built bottom end, turbo valvetrain, lumps, upgraded ignition, etc...) would make.

Please don't take this as an insult to what the 250 can do. The fact that a simple 5psi blow-though could make 350bhp and somewhere around 300hp at the wheels is awesome. That's comparable to a 350ci (280hp) or 400ci (340hp) size engine from back then even though they made quite a bit more torque.

EDIT: that makes me think of a question... hypothetically, if you had a 250 making 350hp/320ft-lbs and a 350 making 280hp/390ft-lbs, which would make an identical car run the quarter faster?

You may be looking at this somewhat wrong. The advantage of a turbo engine is pure tq at a lower rpm and a broader rpm range of tq. To get high hp #'s a engine needs to hold torq to a higher rpm ( above 5250 rpm) then high hp #'s will be produced.

A street turbo 250 can be built simular to my 250 turbo project and expect to see with intercooler, 4 bbl, timing controls ect 400+ ft lbs torq from around 3k rpm - 5500 rpm @ around 10 psi.

Mine did make more hp than you can see in vids, I did not show all the vids.
The intercooler can ad 10 % more power, so in my case 35 more ft lbs tq would have been seen.

In answer to the second question the turbo 250 I did would pose a big challenge to a 300 HP 350 from a 70 camaro as they came back in the day as Z-28's. More tq over a larger rpm range.

Snowman,

Torque is what moves the (weight) car, it can be measured, HP is just a calculation of torque x engine speed.

If your torque is in the lower RPM range (max. boost) then you need to gear the car higher to use the torque made at that point of time.

A turbo has a flat torque curve and allows the engine to flow more air and makes it think it has a larger intake port therefore turning more RPM.

Harry

thanks for the responses guys

damn... that supercharged 250 must've been amazing... And the syclone beating the 406 made me chuckle...

btw tom, do you happen to have those videos of the turbo 250 on the dyno so that you could upload them to youtube? I really do love seeing more of your work and videos of your elky (I JUST WISH SOMEONE COULD HOLD THE CAMERA ON THE GAUGES...).

Not a problem,
the Paxton combo was fun to drive & it really moved better @ top end power 3000 RPM & up.

When I ran 12.1 compression & 3 DCOE webers, that combo had much better low end grunt.

The 406 was 166 CI bigger than my 4.3, so dont listen to that old saying, "There's no replacement for displacemenrt"
Obviously that's just talking normally aspirated.

MBHD

Haha that's what my dad always says and that's why he think he's going to beat me when we drag. His Buick 400 is going to be some stiff competition but I think if I finally get my plan all together, I'll be passing the finish line first.

Forgot what does his Buick run in the 1/4?

MBHD

I should have some results for everyone in a couple months.
254ci,lump port head, intercooler, holley 4150 390cfm double pumper blow through carb, etc,...
Starting with 6psi and most likely going with E85 fuel.

Check my signature for a link to the build thread on 67-72.com

Well his car is in pieces right now and he's having his engine built but we should get it back in a month or two. He's running it through a Turbo 400 (which we already had rebuilt and have at the house). But a stock 1969 GS 400 runs low 15s. I expect with the cam, tires, tranny, posi, carb, etc. that he'll run 13s. That should be doable with my engine and tranny setup.

Just checked your thread and I CANNOT WAIT TO SEE WHAT THIS ENGINE PUTS OUT. This is damn-near the EXACT setup I wanted to see.

Thanks. My goal is to have it done by the end of May. I'll be sure to post videos for all to see!

Just make sure he's not stroking the 400 into a 455+ CI.

Very easy thing to do,like Pontiacs & Olds, (Pontiac 326),350,400 455's all look the same dimensions on the outside & can easily be stroked & not look any different on the outside,not saying your dad is doing that ,but,, just sayin.

MBHD

Nice build. I have checked it out on the C10 forum. I have a turbo 250 also. I want to know how you are controlling such a low boost psi?

Most factory stock GM turbo actuators will only get between 4-6 PSi controlled by the wastegate spring.

Some have threaded wastegate actuator rods which will allow you to change the boost ,anywheres from 2-4 psi up to 8-10 PSi , give or take a few psi.
The tighter/shorter you make the threaded rod the more boost,but if you go too tight,,the wastegate valve will only open so far, (meaning less)& will give you poor boost control.

So if if kyull67 is only controlling boost around this low PSI, then that is why it is low. Using only the wastegate spring pressure. No electronic boost controllers.

I use this one on my Syclone http://www.aemelectronics.com/tru-boost-boost-controller-gauge-757

& it makes the turbo spool up faster because it will only open the wastegate @ the last possible second. Works great!

Hope that makes sense.

Also, IIRC, my Syclones factory wastegate actuator opens @ 6 PSI,why it goes to 14.7 psi stock, is because it has an electronic solenoid that is controlled by the factory ECU.

MBHD