Build Thread Turbo 250 Mod Log 2.0


Well-known member
Hey folks.

Got a turbo 250 project here. Some of you will recognize this motor. I started building it with Jake Good, JGTurbo, about 20 years ago. It was fired up NA and broke in for about 2000 miles, before I swapped in a V8 to sell the car and stowed this 250 and all the turbo related parts in a barn for over a decade. Here's where it sits as of today:

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This project was started when I was younger, poorer, less experienced. Life happens, and necessitated selling the car it was originally in, but I kept the motor.

Fast forward to January 2024 and I'm about to start in on a squarebody Chevy 5.3 LS turbo project. But one night I was down at the barn - and got to looking at the engine over a couple of beers, thinking about how it never really saw it's potential. It just never sat right with me the way it ended.

So - I'm gonna finish it, figure out how much power it makes and give as much info and my own lessons learned as I can back to the community.

So that's the plan. This is not a precious restoration kind of project. I'm just going to document it for the community and for my own sake of just closing the chapter and learning something. Follow if it interests you.

I just want to say up front here - for any especially younger person that has just bought a 60/70's Ford with an inline 6 and thinks that turbo-ing it is a good or unique idea and thus somehow landed here reading this thread of me doing exactly that: probably just don't do it.

These Ford small sixes are NOT a good performance platform. Just get it running and enjoy it for what it is.

These motors with typical bolt ons - headers, 2V carb, DUI timing - will make about 100 WHP on a good day. Often more like 80 WHP. See Dyno 6A in that link for a realistic sense of what you'll get with a log head motor with cam and all the bolt ons. Which is fine. It is what it is. Leave it alone. Even with the new head and intake and EFI they only make 150whp.

You'll see some folks saying that "a hopped up six can surprise a V8" or some variation on this quote, and I think it's a little misleading. That could have been true until about the early 90's (when Corvettes still made 185hp) but it's just not anymore. I wish someone had given it to me straight when I was a 20 year old kid.

To make power with these motors, you have to use forced induction. Research this. Don't trust anything except dyno sheets or ET/MPH through the traps. Take with many grains of salt speculation on a cars weight or power. It's great to love your car, but that's not math.

To boost one of these is not complicated, but it is expensive and it is delicate in the tune - the chambers are shrouded and prone to detonation and hot spots. They're unforgiving. A single episode of overboost or lean AFRs can destroy an engine in less than a second. And it's a lot of down time with your car - this isn't a weekend or even month long project. Most ford small six turbo projects on this forum start well intentioned but end up years long. Just double check yourself - is that what you're prepared for?

I say all of this because I think one of the worst things that can happen to a young person just getting into cars (Ford inline 6 cars from the 60's can still be bought as runners for sub $5k, so they're attractive to younger/shallower pockets) is making modifications that take the car off the street for long periods of time.

It does not make sense to turbo one of these unless you control your afr's against boost, and timing against boost, and detonation at all times. A Holley Super Sniper complete system is currently the only off the shelf way to do that (with a 2.5 bar MAP), with timing control (dizzy, coil, box) for a little over $2k all in, in May of 2024. Add in a progressive water/meth kit (also kind of a necessity IMHO) for a little more tuning window, and you're at $2500.

So just do the quick math - you don't yet have a car, an engine, a turbo, intercooler or a fuel system and you're already at $2500 just for the EFI, spark and water/meth. Motor with machine work and forged pistons is going to be $4k minimum. Turbo kit - varies a lot. Let's say $1k for turbo and intercooler, wastegate and BOV for cheap Chinese stuff (which I have no problem using). Fuel system - at least $500.

This is already $8k to make 180 to 400 finnicky WHP and take your car off the road for months. And I'm talking about the absolute cheapest side of things. We still haven't talked transmission, rear end, wheels/tires or suspension and brakes. All of which you... need.

Sure, if you've built a bunch of other hot rods, have the pockets, the experience and the context for approaching something like this - that's different. But being informed is really important, especially for young folks with a first old car. I wasn't back then. I am more so now. So I'm going to try to share as much info as I can in this thread. If you're still reading - here we go.
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For some reason I thought a white engine was cool back then.

Had put a squirt of marvel mystery/ATF in the cylinders once a year and turned it over by hand, so the insides all looked real clean.

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Gave it a wrap with some 2" eBay titanium wrap. Having some water to dip it in helps cut down on fibers and wrap tighter as you go. Using 1" would have been easier on these bends.

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Needed a rig to put this in for testing, and found a 1963 Falcon hardtop roller that fit the bill for these reasons:

- Previous Modern Drivelines T5 crossmember and cable clutch setup.
- Came with a WC T5 and a no name short shifter (this'll be an extra) and driveline.
- 1 1/8" front swaybar
- Four piston front disc brakes
- 8" rear
- Floor pans replaced
- Clean title, whatever that's worth.

$2300 bucks.

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Oh, also, the car had a new gas tank in it. First thing I did was modify it to drop in an in tank pump. You got a few options on these. I like the AN fittings and design of the FiTech better than the Tanks Inc one and it's about the same price or maybe cheaper? Either works if it hangs the pump in the fuel. This one is the 340lph version, flows a bit more than the 255, which probably would have been just fine.

Washed it out several times with water and Dawn, and let it sit for two days airing out. No odor left.
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These do have a small cavity, wouldn't exactly call it a baffle or anything, centered on the bottom of the tank. I aimed for dropping the anti-slosh sock that the FiTech pump kit comes with right at the bottom of that cavity.
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I wish I had more complete records, but here's what I remember/sourced from the OG build thread:

I remember telling the cam tech at Comp that we'd be done by 5500 rpm (piston speed on the 250 gets up there with the longer stroke IIRC), and that we'd like to build boost starting at 1500. These specs are real similar to the Isky Triple12 cam that a lot of LS turbo guys like, looking at it now.

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From the OG thread:
- Forged 250 rods
- .030 Forged pistons (old TRW's I think, but they were new in box off eBay, back in 2007)
- SpeedPro rings
- Custom grind from Comp
- Custom machined log head (flow chart coming soon)
- Fabricated intake and exhaust manifolds
- Crower single springs
- 1.80" intake, 1.5" exhaust stainless valves
- Garrett T3/T4 Hybrid
Got the trunk area laid out out. All these pics make me realize how dusty it got working under a magnolia tree for two days when we had some sun.

Using an AEM V3 meth kit cause' I like the controller. Fuel line is PTFE, which I like the connections on a little better than regular AN. Using two bulk head connectors to pass through, 10 micron Summit filter under the car.

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Decided to bring most wiring and what not through the passenger side. Fuel pressure regulator is tucked up behind the shock tower brace there.

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I needed a place to put the basic mechanical gauges, as well as a boost gauge and the Sniper handheld, so made this little console. I didn't document it but it's just made from 19mm baltic birch scrap I had, and 5mm baltic, which I steam bent. It's all easy/cheap. I also put in one of those Amazon Apple CarPlay touchscreens ($80) to control a little marine amp. The whole thing is self contained, so just disconnect positive/negative feeds and the gauge signals if I want to take it out. I think it turned out just about right for this rig.

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On this rig I have a lot of stuff being triggered with the ignition +, so I used a two sided bus bar, with one side being direct to battery, and the other being all my relays and on triggers, coming from the C post on the key.

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You can't see it but I ran 1/0 cable under the car up to that ground post.

I also am trying out this little relay/fuse block. So far has saved a lot of connections, and I like the form factor.IMG_0057 Large.png

This wiring will all be cleaned up and bundled. Just laying it in.
What I like about the AEM kit:

Boost safe that will interface directly with the Holley ECU (ie. if it runs out of fluid, it'll cut timing and/or drop redline or whatever).

I like the sequential ramp too. So you can run more injector than you need, and just set up the upper boost point on the controller higher than your actual boost PSI to really fine tune it, if that makes sense.

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Not sure where I'm going to put the controller so it's Velcro'd to the heater core to keep it out of the way for a minute.
I love boost projects. So much cheap street fun! šŸ˜
Fuel system - at least $500.
Maybe I don't understand the goals of the project. Why are you installing (and spending) for a 900+hp system? Please list your goals for this engine or vehicle, so we may follow the choices you are making as you goā€¦ and have fun! :cool:
Thanks Wesman07 and Soldmy66.

PSIG - 340lph is maybe overkill, but not as much as one would think. I'm going to run 58.5 base and while I'm not starting there, my goal is all the systems on this engine have headroom for up to 20 PSI of boost. If you look at the flow chart of the Walbro 255, flow at 12v at 80psi (58.5+20 boost referenced) it's down to 40-45GPH or 175ish LPH at that pressure. If this motor makes 375whp - let's say 430 fwhp - at 20psi, there's actually not a ton of margin there with the 255. That calculator estimates needing 181lph at 20psi for 430 hp. Considering the difference in cost of a 340lph (it was $10 more) to have a pump more efficient at those pressures, I chose to just do that. It is kinda wild how much more pump EFI and boost will eat up compared to a carbed motor.

That said, that's a great point made by PSIG - if someone is reading this for their own project, definitely calculate what you need for any given part based on a goal, and then factor in whatever safety margin you want/can afford on top of that. If I could run 43lbs base pressure in the Sniper that would have made a 255 go further.

In terms of cost - I just find that by the time you buy a pump, regulator, filter, hose and fittings, $500 for any EFI fuel system is just kinda reality these days? I'd love to hear cheaper/better ways. Though I don't like inline pumps, so I suppose someone could save some dough if they're willing to put one on the frame rail.

edit: to answer you in terms of goals, I don't have a numeral power goal per se but if I can sneak up on 18 - 20psi without breaking anything, I think it'll be a good proof of concept and just personally satisfying see this project through having come back to it with more experience. So my goal is just to build the systems to support that PSI/probable power level, and see what she does. And shoot yeah! have fun doing it.