gbauer's 250 engine build thread - Team Camaro Tech
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post #1 of 158 (permalink) Old Aug 10th, 14, 07:14 PM Thread Starter
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gbauer's 250 engine build thread

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.

Sold:
1968 Base hardtop 250 with a P̶G̶ built 2004r
Offy intake
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust
Mild cam
Custom interior
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post #2 of 158 (permalink) Old Aug 10th, 14, 07:29 PM
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Re: gbauer's 250 engine build thread

I will be following along.


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post #3 of 158 (permalink) Old Aug 10th, 14, 07:39 PM
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Re: gbauer's 250 engine build thread

Hit it with Nitrous

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post #4 of 158 (permalink) Old Aug 10th, 14, 08:26 PM Thread Starter
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Re: gbauer's 250 engine build thread

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Originally Posted by Vega$69 View Post
Hit it with Nitrous
Think a 400 shot is enough?

Sold:
1968 Base hardtop 250 with a P̶G̶ built 2004r
Offy intake
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust
Mild cam
Custom interior
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post #5 of 158 (permalink) Old Aug 10th, 14, 08:26 PM Thread Starter
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Re: gbauer's 250 engine build thread

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I will be following along.
It'll be a slow one...

I'll update as we do stuff.

Sold:
1968 Base hardtop 250 with a P̶G̶ built 2004r
Offy intake
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust
Mild cam
Custom interior
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post #6 of 158 (permalink) Old Aug 10th, 14, 08:41 PM
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Re: gbauer's 250 engine build thread

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

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ
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post #7 of 158 (permalink) Old Aug 10th, 14, 11:27 PM
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Re: gbauer's 250 engine build thread

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.

The important thing here is that you ask me what kind of car I've got. "I've got a BITCHIN' CAMARO"
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'68 350 4 speed
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post #8 of 158 (permalink) Old Aug 10th, 14, 11:45 PM
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Thumbs up Re: gbauer's 250 engine build thread

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.

Good luck on your build.

Chevy 250 turbo EFI
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post #9 of 158 (permalink) Old Aug 11th, 14, 05:22 AM
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Re: gbauer's 250 engine build thread

I say shelf the 250 and drop in a turbocharged Ecotec V6.


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post #10 of 158 (permalink) Old Aug 11th, 14, 06:55 AM Thread Starter
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Re: gbauer's 250 engine build thread

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Originally Posted by 67Rally View Post
I say shelf the 250 and drop in a turbocharged Ecotec V6.
Sure thing if you're buying!

Sold:
1968 Base hardtop 250 with a P̶G̶ built 2004r
Offy intake
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust
Mild cam
Custom interior
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post #11 of 158 (permalink) Old Aug 11th, 14, 06:57 AM Thread Starter
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Re: gbauer's 250 engine build thread

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Originally Posted by mean buzzen half dozen View Post
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.

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...

Sold:
1968 Base hardtop 250 with a P̶G̶ built 2004r
Offy intake
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust
Mild cam
Custom interior
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post #12 of 158 (permalink) Old Aug 11th, 14, 07:44 AM
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Re: gbauer's 250 engine build thread

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.

Lynn
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post #13 of 158 (permalink) Old Aug 11th, 14, 07:48 AM
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Re: gbauer's 250 engine build thread

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Originally Posted by Gbauer View Post
Sure thing if you're buying!
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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post #14 of 158 (permalink) Old Aug 11th, 14, 08:56 AM Thread Starter
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Re: gbauer's 250 engine build thread

Quote:
Originally Posted by bilodeaulynn View Post
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.

Sold:
1968 Base hardtop 250 with a P̶G̶ built 2004r
Offy intake
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust
Mild cam
Custom interior
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post #15 of 158 (permalink) Old Aug 11th, 14, 08:57 AM Thread Starter
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Re: gbauer's 250 engine build thread

Quote:
Originally Posted by 67Rally View Post
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.

Sold:
1968 Base hardtop 250 with a P̶G̶ built 2004r
Offy intake
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust
Mild cam
Custom interior
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