[BruceWilkie]

Originally Posted by KEN CROCIE

Turbo Vacuum control : For standard dist. I used the 68 Firebird dual outlet control.believe it was a delco 1115411.Also 1115367 By digging deep in the parts book ,I found a dual port HEI control used on some Caddys about 1980-81.delco P/N 1973595

THANK YOU!!! I think that helps me a bunch. I used to have easy access to a bunch of old Motors Parts and Labor books...a gold mine for finding part numbers. But the old man that had them passed on and his family threw them away before they sold his shop!

I often found myself being the go to guy for hard to find or oddball parts...even when I was in the Air Force. Seems I have a knack for finding them one way or another.

Think I know someone not far from me who just may have one of those(more maybe?) cannisters now that I have some numbers...

Thanks again. I'll let you know what I turn up.

[CROCIE JR]

If you find a extra 2 port 68 vac. control, let me or Ken Crocie (Dad) know. This will help our latest project. Pure simplicity.

[CROCIE JR]

Not sure if I understood a previous post. Instaling a BOV will keep the turbo speed in check, not increase it. If air is moving the turbo is doing "work." With no BOV the turbo can overspeed when airflow stops, like throttle shut. Put your hand over a running shop vac inlet and listen to the motor speed up. Correct me if I'm wrong here.

[meanone]

Originally Posted by CROCIE JR

Not sure if I understood a previous post. Instaling a BOV will keep the turbo speed in check, not increase it. If air is moving the turbo is doing "work." With no BOV the turbo can overspeed when airflow stops, like throttle shut. Put your hand over a running shop vac inlet and listen to the motor speed up. Correct me if I'm wrong here.

The wastegate is used to control turbo speed, not the bov. A portion of the exhaust mass and pressure is bypassed around the turbine so that only enough mass and pressure enters the turbine to spin the turbo to a speed wich produces a desired boost level. If a wastegate wasn't used, and 100% of the exhaust mass was allowed to enter the turbine, the turbo would overspin and there would be no control over the boost level.
If there wasn't a bov in the system the turbo could be damaged when the throttle closes. When the throttle closes the air stacks up and pressure is sent back toward the compressor wheel. The wheel could be stopped and started again very rapidly by this, and could damage the wheel or even break the shaft. The turbo does not speed up when the throttle is closed and there is no bov installed. The reason that the the turbo could possibly speed up when the bov is opened is because of pressure on each side of the turbo. Pressure and mass is driving the turbine wheel wich is driving the compressor wheel. The compressor wheel is pushing air into the engine when the throttle blade is open. When you shut the throttle blade and the bov opens there is no more pressure in the charge pipe, but there could be some pressure in the turbine side. Think of it as a tug-a-war. Two guys are pulling on the rope and one guy lets go letting the other guy go flying. If everything is sized correctly and a w/g is used the turbo shouldn't overspeed when the bov opens because as the throttle closes exhaust mass decreases putting little pressure on the turbine wheel. This is how I understand it. I hope this helps. Ronnie

[CROCIE JR]

My BOV post was a throttle shut scenario, just after WOT.

[Joe37]

Moving forward with the project, I tore into the engine for a quick check. Turns out water had gotten to the cylinders when the car was being wet sanded during its paint job. The block and pistons were damaged, heads ok. The block is .030" over now with a TRW forged piston. I suspect it will have to .060" to clean up, it might at .040" but unlikely. We will need new pistons and are wondering if we should lower the compression. Summit sells Icon forged pistons that are dished +14 cc, the TRW / Sealed Power are a +6cc piston. Will that make much difference? Remember, this is a restoration project, 6-8 psi boost only and no racing. I know Ross makes great pistons but may be out of the budget, we are still in the planning / recovery mode.

It also has the exhaust crossovers in the head filled. I believe this should come out to help cold starts and atomize the fuel better, but being a turbo engine, will it matter?

One more thing, the engine has a solid harmonic balancer install. When I say solid, I mean solid, no moving parts! I can not see any point in this, who was selling them back in the late '90s when this engine was built and why?

Joe

[Craig Hendrickson]

Originally Posted by Joe37

Moving forward with the project, I tore into the engine for a quick check. Turns out water had gotten to the cylinders when the car was being wet sanded during its paint job. The block and pistons were damaged, heads ok. The block is .030" over now with a TRW forged piston. I suspect it will have to .060" to clean up, it might at .040" but unlikely. We will need new pistons and are wondering if we should lower the compression. Summit sells Icon forged pistons that are dished +14 cc, the TRW / Sealed Power are a +6cc piston. Will that make much difference? Remember, this is a restoration project, 6-8 psi boost only and no racing. I know Ross makes great pistons but may be out of the budget, we are still in the planning / recovery mode.

The W72 engine has a CR of 8.1:1, so that will be fine with the TurboForce. I used TRW flat tops in my 1976 Firebird T-F Revival with a 73 400 engine.

It also has the exhaust crossovers in the head filled. I believe this should come out to help cold starts and atomize the fuel better, but being a turbo engine, will it matter?

If not too much trouble, remove the exhaust crossover fill.

One more thing, the engine has a solid harmonic balancer install. When I say solid, I mean solid, no moving parts! I can not see any point in this, who was selling them back in the late '90s when this engine was built and why?

I never saw one much less used one. As your dad, Jim says, "throw it as far as you can!" LOL

[Tom Vaught]

Originally Posted by meanone

The wastegate is used to control turbo speed, not the bov. A portion of the exhaust mass and pressure is bypassed around the turbine so that only enough mass and pressure enters the turbine to spin the turbo to a speed wich produces a desired boost level. If a wastegate wasn't used, and 100% of the exhaust mass was allowed to enter the turbine, the turbo would overspin and there would be no control over the boost level.
If there wasn't a bov in the system the turbo could be damaged when the throttle closes. When the throttle closes the air stacks up and pressure is sent back toward the compressor wheel. The wheel could be stopped and started again very rapidly by this, and could damage the wheel or even break the shaft. The turbo does not speed up when the throttle is closed and there is no bov installed. The reason that the the turbo could possibly speed up when the bov is opened is because of pressure on each side of the turbo. Pressure and mass is driving the turbine wheel wich is driving the compressor wheel. The compressor wheel is pushing air into the engine when the throttle blade is open. When you shut the throttle blade and the bov opens there is no more pressure in the charge pipe, but there could be some pressure in the turbine side. Think of it as a tug-a-war. Two guys are pulling on the rope and one guy lets go letting the other guy go flying. If everything is sized correctly and a w/g is used the turbo shouldn't overspeed when the bov opens because as the throttle closes exhaust mass decreases putting little pressure on the turbine wheel. This is how I understand it. I hope this helps. Ronnie

When the throttle slams shut, I agree with Ronnie, that the interrupted flow sends the compressor into massive surge without a CBV (compressor BY-PASS valve), a BOV (Blow-off valve), or a CRV (Compressor Recirculation Valve). CRVs are used on EFI systems with Mass Air Meters.

You can also (as Ken C jr mentioned) set up your system to where you can run a oversized Turbo and keep it out of surge by having the BOV open (adding mass flow to the system but wasting it) until the engine goes into WOT and then BOV closes and the turbo supplies the larger air flow to the engine.

Tom Vaught

[meanone]

Originally Posted by Tom Vaught

When the throttle slams shut, I agree with Ronnie, that the interrupted flow sends the compressor into massive surge without a CBV (compressor BY-PASS valve), a BOV (Blow-off valve), or a CRV (Compressor Recirculation Valve). CRVs are used on EFI systems with Mass Air Meters.

You can also (as Ken C jr mentioned) set up your system to where you can run a oversized Turbo and keep it out of surge by having the BOV open (adding mass flow to the system but wasting it) until the engine goes into WOT and then BOV closes and the turbo supplies the larger air flow to the engine.

Tom Vaught

I 100% agree with you Tom. My buddie had his car set up like that.It was a stickshift and he wanted to keep the turbo speed up to prevent lag between shifts. I was trying to help Ken Jr. understand what happens to the turbo when the throttle closes, and why the bov is used. He was stating that the turbo would overspeed from shutting the throttle without a bov, and used the hand over a shop vac as an example. That would make the engine the shop vac and the turbo it's motor in his example. Ronnie