Inline 250 - T3 Turbo - w/ Video

[theastronaut]

The T5 in our S10 has started making alot of noise in the first three gears. The first three gears have seen alot of abuse though.

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[longbed67]

How's your fuel economy so far with this? I get my block and head back soon and am curious what to expect.

[krazy_texan]

wow that looks like it really wasnt that hard to do. what did you use for engine internals like camshaft and such.

[boucher racing]

Originally Posted by longbed67

How's your fuel economy so far with this?

I actually just got my speedo / odometer back working with the 5 speed. I will a have to calculate it. I have always wondered also.

[boucher racing]

Originally Posted by krazy_texan

wow that looks like it really wasnt that hard to do. what did you use for engine internals like camshaft and such.

I used the stock head that was cleaned up, rebuilt, Z28 valve springs.

Stock polished crank

Lunati cam- reverse duration efficiency design (212/202 adv dur, .465/.458 lift, 114 lsa)

.030 over forged NOS TRW pistons

[tkeduk8r]

I just read through this and i am very impressed... I too talked to Tom Lowe and I recommend anyone thinking of going down the turbo path to talk with him... My question is how/where did you source your GN Turbo from. I would think that they are fairly scarce... Also, so you have any pics of your T5 and your exhaust install on your truck. Love to see how your shifter is placed in your cab and how the pipe(s) are run.... Very cool!!!!
--Mike

[1972RedNeck]

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[Tutt]

super cool build! do you have fuel mileage numbers yet?

[boucher racing]

Alright, I planned a route where I know the exact mileage. My OD is hooked up, but way off. I will post the MPG numbers when I get them. I am very curious to know.

Boucher'
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[yunkyarddog]

never turbod a 6 but did plenty of 4 cyl in my yunger days...........................can you say FLASH BACKS

[boucher racing]

The numbers are in....
Did about a 50 mile cruise, two lane highway mixed with stop and go.

MPG's = 17 all hand calculated with gps to measure distance.

Not too bad for a 46 yr old truck!

Boucher'
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[longbed67]

Very Nice! That is good to hear #'s like that out of a performance setup, it still keeps it affordable to drive!

[6772owner]

That is awesome man!
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[ChrisDollins]

Awesome build! I may just have to stick with the 250 anyhow! Always thought a turbo would be cool. Sounds amazing, and thanks for posting all of the info with links. Amazing little truck!

Chris
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[Tutt]

pretty good mileage! do you run premium or are you able to get away with regular?

[boucher racing]

Originally Posted by Tutt

pretty good mileage! do you run premium or are you able to get away with regular?

I was sure shocked with the results. I bet I could get 20mpg on the highway if I could stay out of boost. Hell, most trucks on the road today get worse than that.

I only run premium fuel. The engine is low compression, but I try to avoid detonation.

I do not really drive it often, but when I do.. its balls out!

[Torqueforce]

Love the truck! Any updates? I have a 250 as well and this thread inspired me to ditch the 8 and attempt to turbo the 6. Have you been able to go WOT yet and what kind of power do you think you're making? Also why the holley 350?

[boucher racing]

Originally Posted by Torqueforce

Love the truck! Any updates? I have a 250 as well and this thread inspired me to ditch the 8 and attempt to turbo the 6. Have you been able to go WOT yet and what kind of power do you think you're making? Also why the holley 350?

Thanks. I have finally got it to a point where I have a hard time touching it. I mean, making more adjustments/modifying. I adjust the boost ever so often, but that is it. I have it opening around 10 psi. It seems just right for the truck. I can still lay ass in it, but it is still very drivable.

I would like to put a blow-off valve on it. When I am in boost and I let off to shift all of that compressed air reverses and makes the turbo impeller flutter. If you listen close to the videos, you can hear it.

I go WOT almost every time I drive it! To me, that is the beauty of a turbo. Your wastegate controls the psi, so WOT is no big deal.

Power?.... I tell people, it feels twice as fast as compared to the stock 250. I would ROUGH estimate between 250-300HP.

Holley 350? A turbo engine does not move more air, it just compresses it. So, the carb should be sized for the engine in NA form.

All the best,

Boucher

http://youtu.be/JiAbg7MdpiU

[Torqueforce]

Looks like I'm going with a holley 350 then, your advice plus researching other blow thru setups show it's a great choice for boosted 6's. Anything above 250hp would make me very happy. I'm ordering up a clifford manifold and possibly an SPA manifold to pair with it, thinking stock heads at low boost (6-8 psi). BOV's are good for the turbo but for some reason I love the sound of compressor surge. You need some WOT footage!!

[norm roll]

compressor surge is hard on the turbo.

[longbed67]

Originally Posted by Torqueforce

Looks like I'm going with a holley 350 then, your advice plus researching other blow thru setups show it's a great choice for boosted 6's. Anything above 250hp would make me very happy. I'm ordering up a clifford manifold and possibly an SPA manifold to pair with it, thinking stock heads at low boost (6-8 psi). BOV's are good for the turbo but for some reason I love the sound of compressor surge. You need some WOT footage!!

x2 compressor surge is a good way to damage equipment (bad idea)....
you can get 250-300hp out of a 250 naturally aspirated 350-400+ range would be a better low boost goal.
Stock heads on the 250 leave a lot to be desired... a few small changes that anyone can do in a home garage can really add some power. After my dealings with SPA and their manifold, I would never use one again! The still require a fair amount of machining to work properly, mine still had casting sand stuck in the corners and you Have to use an On center housing turbo to get it to fit with any of the intakes... and on-center exhaust housing turbos are not as efficient and harder to find the correct sized housings for! And your pretty much limited to a p-trim exhaust wheel then.

Not trying to counter-dict or offend Boucher here but you may want to contact C & S carbs about the sizing.... n/a sized carbs DO NOT correlate to Blow through setups! Blow through is a whole different beast.... Also if this is going to be your first serious turbo build you may want to do some research over at theturboforums.com

Good luck with your build!

[JumboAMONGus]

iam doing research for a turbo on my 235 be basically the same set up .... its a stock rebuilt 235 where did you get you purchase turbo from ?does the j pipe off exhaust manifold get red hot ?

[boucher racing]

Originally Posted by longbed67

x2 compressor surge is a good way to damage equipment (bad idea)....
you can get 250-300hp out of a 250 naturally aspirated 350-400+ range would be a better low boost goal.
Stock heads on the 250 leave a lot to be desired... a few small changes that anyone can do in a home garage can really add some power. After my dealings with SPA and their manifold, I would never use one again!

Not trying to counter-dict or offend Boucher here but you may want to contact C & S carbs about the sizing.... n/a sized carbs DO NOT correlate to Blow through setups! Blow through is a whole different beast.... Also if this is going to be your first serious turbo build you may want to do some research over at theturboforums.com

Good luck with your build!

LongBed, good info on the SPA, I guess there is only one way to find out!

As far as my carb, from a calculation standpoint. You can size your carb for your engine and then multiply it by 1.5. I should have probably used the same carb, just in the 500 cfm model. I found this one for $50 & couldn't pass it up. It does really good at idle and WOT. The only area of struggle is cruise /transitions. I made the mistake of drilling my PVCR's too big from the start. (.078"). My jets in there now are size 57's!

The turbo is a factory takeoff, from a 1987 Grand National, including the wastegate elbow.

Boucher'
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[gofastnut]

VERY cool!! I like the fact that you got it figured out with help from others, not just dropped it off and paid someone to do it.
I gotta say, this seriously makes me re-think ditching my ole 235! Keep us posted!

[tincan1966]

I contacted Tom Lowe, as well. Man that guy is a wealth of information and a nice guy to talk with to boot!.

My build is starting aith a late 70's 292 short block, decked .015" Using a head from a 1967 250 cid with one of Tom's cylinder head kits(1.84/1.6" valves,locks, springs, etc) Also installing a lump kit.(seemed like some easy HP for less than $100)Milled .020"
Pistoms will be .040" over flat tops for a 307 cid with 2 valve reliefs, on 6" rods. Compression should be in the 9.3-9.5:1 range.
Using a 1990 700R4 trans with a Alabama Converter Co.mild stall.
Rear gears are 3.08:1.
Hoping the OEM torque of the 292, with a little mid-range turbo help will make this a smooth combo for a 4000 lb Suburban

Will be updating my build thread soon with pics from the machine shop and the recent body work.