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it's time to build the little 250.

my neighbor is a medical equipment technition. he's also a car man among car guys. i've never met an artist with better abilities than him.

his baby is a 1966 datsun z that has a full ferarri 250 kit car body, hand built suspension that rivals supercars, hand built interior, a 370z motor mated to a 6-speed manual, custom exhaust, etc, etc. it's really too much to list here without pics but suffice to say there's kit cars and there's his kit car.

in his last iteration he had a inline engine, i think a datsun, in the car that he converted to efi with a custom kit he created. he's no longer using it.

so i popped in his garage friday to discuss world issues and petrol since he's a brit. i showed him a couple of my latest changes to my 68 and tossed him the keys. we went for a half-hour drive and i suppose he deemed my car worthy because he brought up his efi kit. he knows i want to build the 6 and that i just won first at camaro nationals for mild modified.

we started talking about the build. turns out my car's been on his mind a bit.

he's suggesting the following to start:

install his efi system with a custom, hand-made polished aluminum intake, tubular header by clifford, dual exhaust, and see how it goes. then follow it with pulling the head, lump ports, oversized valves, roller rockers, and a cam. build it with a future turbo in mind.

for the intake we're going to weld bungs for the injectors close to the head so each injector squirts next to the cylinder instead of upstream so we don't have to deal with heating it. use smaller runners for higher torque and velocity. combine then to a 3 inch throttle body and pull cool air from up front by cutting a hole through the radiator support near the headlight. toss in two o2 sensors for proper tuning.

this set up should make it easier to add a turbo or supercharger in the future.

keep the powerglide, swap out the diff gears and add an eaton posi, possibly make a new driveshaft for weight, and go from there.

we're thinking we'll make it a mix of old and new using the original drive train but highly modified.

does anyone have better suggestions? going for a highly unique build just because, well, we can.
 

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Hit it with Nitrous:D
 

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Discussion Starter #5

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This will be interesting. And unique, everyone else goes straight to an eight.(see what I did there?)
 

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If you want a spare cylinder head to mod, I've got a good one that came off a 250. It is a bare head, already cleaned and has been magged/checked by my head guy: no cracks. This is an early non-smog one without the A.I.R. holes. PM me if you're interested and I will check the casting numbers.

I suggest you invest in Leo Santucci's book if you do not already have it.
 

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I would not run the PG.
A 200R4 will bolt right in IIRC. TH350 will also.

Anytime you can get better gear ratio for a 6, do it. A PG trans just makes the inline 6 slow.

With todays gas prices, it would be wise to use an OD trans.:beers:

Good luck on your build.
 

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I would not run the PG.
A 200R4 will bolt right in IIRC. TH350 will also.

Anytime you can get better gear ratio for a 6, do it. A PG trans just makes the inline 6 slow.

With todays gas prices, it would be wise to use an OD trans.:beers:

Good luck on your build.
I'm not worried about mileage. It's a toy, not a daily driver.

Besides I think it'll be cool to keep the born-with engine block and tranny for this one. Everybody is so quick to swap out major components that there's just not any of these old 6'ers and PG's left in Camaros.

Sometimes cool isn't the most practical...
 

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I only state the following because you asked.
My daily driver is an inline six with a turbo. It has over 300k miles on it. Not a Chevy (OK its a Bimmer, a 1983 745i factory turbo) but the concepts are the same. I had Paul Burke make my pistons and he ground the camshaft. I am running an aftermarket hybrid turbo and exhaust manifold set up. The factory turbo set up did not build any boost below 1800 rpm, and even then it was only 1 or 2 psi until after 2000 rpm. The new set up starts coming on at an astonishingly low 1200 rpm, in other words, just off idle. Paul says it is the camshaft more than any other mod that creates the low boost threshold.

Doing a turbo correctly will require lower compression and a special camshaft. So,,,


1. Personally, I would not go to the trouble of this build without starting out with the lower compression and correct camshaft, even if that means having custom pistons made. Have the head done before ordering pistons. Also have the block decked before ordering pistons, taking off the least amount possible while still getting a clean surface. Shoot for 8.0 to 1 compression, but a quench of about .035. The tight quench will ward off detonation. Be warned that if you use this set up without a turbo, it will be slow, very slow.

2. Find a cam grinder who specializes in turbo grinds. Don't get the wildest one he makes. In fact, my camshaft is the mildest one Paul offers. Follow the cam grinder's rec EXACTLY when setting up the camshaft. If he says 2 degrees advanced, make it exactly 2 degrees advanced.

3. "O" ring the block. You don't need too much sticking out above the deck, just .004 or so. This will keep the head gasket in place under boost. If you don't "O" ring the block, use one of the new head gaskets with an "O" ring built in. However, don't do both. My personal opinion (and others disagree) is that the "O" ring in the block is superior, because it bites a little better.

4. By going turbo from the start, you will eliminate buying and then discarding the 6 into 2 header. Some guys will recommend small twin turbos. This is just my personal opinion, but I prefer the simplicity of a properly sized single.

Just my 02 cents.
 

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Sure thing if you're buying! :D
You can pick up a complete low mileage dropout 4.3l V6 (265 cu in) for $7-800. Then add the turbo down the road when you're ready. That way you don't have to worry about blowing up the 250. Of course there are a lot more costs involved in the conversion!
 

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Discussion Starter #14
I only state the following because you asked.
My daily driver is an inline six with a turbo. It has over 300k miles on it. Not a Chevy (OK its a Bimmer, a 1983 745i factory turbo) but the concepts are the same. I had Paul Burke make my pistons and he ground the camshaft. I am running an aftermarket hybrid turbo and exhaust manifold set up. The factory turbo set up did not build any boost below 1800 rpm, and even then it was only 1 or 2 psi until after 2000 rpm. The new set up starts coming on at an astonishingly low 1200 rpm, in other words, just off idle. Paul says it is the camshaft more than any other mod that creates the low boost threshold.

Doing a turbo correctly will require lower compression and a special camshaft. So,,,


1. Personally, I would not go to the trouble of this build without starting out with the lower compression and correct camshaft, even if that means having custom pistons made. Have the head done before ordering pistons. Also have the block decked before ordering pistons, taking off the least amount possible while still getting a clean surface. Shoot for 8.0 to 1 compression, but a quench of about .035. The tight quench will ward off detonation. Be warned that if you use this set up without a turbo, it will be slow, very slow.

2. Find a cam grinder who specializes in turbo grinds. Don't get the wildest one he makes. In fact, my camshaft is the mildest one Paul offers. Follow the cam grinder's rec EXACTLY when setting up the camshaft. If he says 2 degrees advanced, make it exactly 2 degrees advanced.

3. "O" ring the block. You don't need too much sticking out above the deck, just .004 or so. This will keep the head gasket in place under boost. If you don't "O" ring the block, use one of the new head gaskets with an "O" ring built in. However, don't do both. My personal opinion (and others disagree) is that the "O" ring in the block is superior, because it bites a little better.

4. By going turbo from the start, you will eliminate buying and then discarding the 6 into 2 header. Some guys will recommend small twin turbos. This is just my personal opinion, but I prefer the simplicity of a properly sized single.

Just my 02 cents.
Thanks for that.

I'm not planning on touching the head or block until I'm ready for the turbo. Not even doing a cam just yet. For now it's just the intake, exhaust and EFI.

For the exhaust header: with the price of those things used I can buy a new one, use it until it's time to upgrade, pull it, used the flange as a template, fab up a turbo manifold and sell the old one. I'd only be out $50 or so.

The alternative is to do the headwork, etc, and slap on a supercharger instead. The way I'm envisioning the intake for the EFI system we'd be able to put the supercharger on the passenger's side, run the piping through an intercooler and connect to the existing piping on the driver's side. It would make for a nice and easy installation at that point. In fact that might be the better way to do this for weight distribution (I like to turn...). It would put a relatively equal amount of weight on both sides of the engine. I'd have to relocate the battery to the trunk but that's no big deal. Besides there's a TON of room on the passenger's side and not so much on the driver's with the steering box, intake system, power steering pump, alternator and exhaust header. GM liked to put most of the 250 right in front of the driver...

actually thinking this through more that's probably the way to do this.
 

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Discussion Starter #15
You can pick up a complete low mileage dropout 4.3l V6 (265 cu in) for $7-800. Then add the turbo down the road when you're ready. That way you don't have to worry about blowing up the 250. Of course there are a lot more costs involved in the conversion!
Blowing up the 250 might be more fun, though. :p
 

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The PG, with a 1.76 1st gear is a slug off the line unless you are launching at 5500 rpm. The TH200-4R is a much better tranny gear ratio wise (2.74 1st gear) AND it's a bolt in dimensionaly. With the OD gear you can go with a shorter rear gear ratio like a 3.73/3.90/4.10. This will allow you to launch hard and still be able to drive the highway.

Also, if your friend has a 66 Datsun Roadster then it's a Fairlady as the Z didn't take it's place until the 1970 MY...
 

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Discussion Starter #18
I have a bid in for a set of shorty tubular headers. Also found aluminum intake flanges for the intake. Dirt cheap for the flanges.


...nobody else bid on those darn headers, OK? :p

If I don't get the shorties I'll buy long tube headers and we'll do some cuttin' and weldin' to make them work. I've been talking with my buddy who has the Fauxarri (as I like to tease him about. Truth be told I'd rather have his than the real deal, though. His is faster, more reliable, and better built).

Also traded PM's with a fellow gentleman here about a head. I'm going to talk with my buddy before jumping on it. Mine is so gunked up that it might be better just to get the refurbished one kookykrispy has and go from there. I just have to watch cost-creep. I know I'm due for a new radiator as well and I'm sure this project will bring that due date sooner...

Headers first, flanges second, throttle body third, whatever bits I need to make the EFI work fourth, then it's time to get out the wrenches, saw and tig...

It'll be after labor day before we can start to build it. Maybe a weekend or two of work at the most.
 

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Discussion Starter #19
Also, if your friend has a 66 Datsun Roadster then it's a Fairlady as the Z didn't take it's place until the 1970 MY...
I don't know what year the Datsun is. When I asked him what year the car was he said '66. Must've been referencing the half on top...

actually looking that up that doesn't make sense either.

Oh well. It's a nice car. Looks identical to this:



Interior looks like this but the steering wheel is on the proper side:

 

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Discussion Starter #20
Just in case this thread shows up in someone's search:

I found Leo Santucci's Chevrolet Inline Six-Cylinder Power Manual on Scribd.

...and I know what I'll be reading for the next two or three days when not working...
 
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