[Johnny406]

I just put a BOV on my 78 T/A, should I run the reference line under the carb with the pressure gauge or should I run it from the hat with the fuel regulator line?

[RUDOLFSSON]

Intake manifold close to the carb base.

[Johnny406]

Originally Posted by 69GTO

Intake manifold close to the carb base.

Thank You!!

[Tom Vaught]

Make the signal line as short as possible and and get a large BOV as a large BOV will never hurt you but too small of a BOV will cause issues, (especially with belt driven centrifugal high hp superchargers).

Tom Vaught

[Johnny406]

Here is what I got,

[Tom Vaught]

So what size is the valve, Johnny?

Tom Vaught

[Johnny406]

Originally Posted by Tom Vaught

So what size is the valve, Johnny?

Tom Vaught

Hi Tom, I think the valve is 1.5 inches

[Tom Vaught]

That should be ok for a street/ strip deal. If you race very much you would want a 50mm
plus valve (~ 2.0")

Tom Vaught

[PONTIAC DUDE]

From personal experience I have found that once you start forcing air in the engine around 10/12 lbs of boost or so would be a point I would start looking at a BOV over 1.5".

Johnny, Cost effective. I used 2 - 1.5" valves at 1/4 of the cost and 16lbs of boost. Lots of them going on E-bay cheap. They worked.

[RUDOLFSSON]

The big units from JGS/TIAL/TURBOSMART is the way to go... I'm thinking about upgrading to the 60mm JGS bov. It's priced at 230$ new from JGS (made in USA).... that's hard to beat.

[Johnny406]

This is the cheapie I bought, more as precautionary. My BDT is "supposto" be making 7-5PSI. My S-W gauge has shown 12-14 so I will try a different gauge before I do much more.

http://cgi.ebay.com/ebaymotors/ws/eB...m=380176932887

[71 Ventura II]

Originally Posted by Johnny406

This is the cheapie I bought, more as precautionary. My BDT is "supposto" be making 7-5PSI. My S-W gauge has shown 12-14 so I will try a different gauge before I do much more.

http://cgi.ebay.com/ebaymotors/ws/eB...m=380176932887

It might be from the under sized pulley on the power adder, you say turbo I say belt driven centrifical supercharger, causing it to be over driven. Yours has the smallest pulley on it I've ever seen. At what RPM is it reading 12-14 lbs? Near the shift point? Cause if it's pushing that much at idle geesh it's gonna get crazy with rpm. JD

P.S. Turbo's run off exhaust pressure/flow not with a belt. Just stating the facts... LOL

[Johnny406]

Originally Posted by 71 Ventura II

It might be from the under sized pulley on the power adder, you say turbo I say belt driven centrifical supercharger, causing it to be over driven. Yours has the smallest pulley on it I've ever seen. At what RPM is it reading 12-14 lbs? Near the shift point? Cause if it's pushing that much at idle geesh it's gonna get crazy with rpm. JD

P.S. Turbo's run off exhaust pressure/flow not with a belt. Just stating the facts... LOL

Thomas Knight, the builder, calls it a BDT so that's good enough to me but...LOL. This turbo/centrifical started life as a exh driven turbo.

It's about 6-7 at idle and quickly jumps up to 12 by 1100 and levels to 14 at 3500 according to this gauge that is a bit beat up so I want to verify it with another. I think I will order a Summit 2802 for it when I get paid. At 8.3:1 compression with the XE274 and "potential" 12+ psi might be a stretch.

It uses Gates 5M pitch belts usually seen on scooters or industrial equipment. I need to re-count the drive gear, it is either 82 or 88 teeth and the driven gear is 23 teeth.

[71 Ventura II]

Originally Posted by Johnny406

Thomas Knight, the builder, calls it a BDT so that's good enough to me but...LOL. This turbo/centrifical started life as a exh driven turbo.

It's about 6-7 at idle and quickly jumps up to 12 by 1100 and levels to 14 at 3500 according to this gauge that is a bit beat up so I want to verify it with another. I think I will order a Summit 2802 for it when I get paid. At 8.3:1 compression with the XE274 and "potential" 12+ psi might be a stretch.

It uses Gates 5M pitch belts usually seen on scooters or industrial equipment. I need to re-count the drive gear, it is either 82 or 88 teeth and the driven gear is 23 teeth.

Is 12-14 lbs safe? I've seen a ton of guys at the track running 8-10 Max boost on V8's I'm just not familiar enough with this type of power. With the higher boost, if the belt stays on I'd say you would need C16 fuel to make it happy. Let us know what you find out! This is an interesting thread. JD

[71 Ventura II]

Well that confirms the need for extreme caution! I just checked the boost chart over on P-Dudes website, if you have a static compression of 8.5-1 when the boost hits 12-14 lbs the dynamic compression is between 15.4-1 to 16.6-1!!! It's higher than I was expecting for sure. JD
Here's the boost chart: http://www.angelfire.com/fl4/pontiac...owerboost.html

[Johnny406]

Originally Posted by 71 Ventura II

Is 12-14 lbs safe? I've seen a ton of guys at the track running 8-10 Max boost on V8's I'm just not familiar enough with this type of power. With the higher boost, if the belt stays on I'd say you would need C16 fuel to make it happy. Let us know what you find out! This is an interesting thread. JD

According to Thomas Knight, my setup should be making 5-7 psi, that is why I want to verify the gauge. If it is more than that, I will slow it down with a bigger pulley and the BOV as the safety. It will be a little while before I take this to the track...I like my crank in the block...

[johnta1]

I will slow it down with a bigger pulley and the BOV as the safety.

Shouldn't that be 'wastegate' instead of BOV?

Wastegate would regulate the boost.

[RUDOLFSSON]

Not on a centrifugal supercharger and that's what he's running.

[tininjun67]

I don't want to be a kill joy here, so take this for what it's worth, especially me never having seen this unit before:

I sincerely doubt that you're building that kind of boost with that set-up. I think you'll shred the belt immediately. It looks like the driven pulley is directly attached to the compressor wheel shaft, which is probably why the small belt is able to spin it. If there was a "gearbox" attached to it, higher impeller speeds and more boost would be achieved. I think the current impeller speed will max about 20k rpm or so (rough math here).

Making 7lbs of boost at idle does not sound right at all. Typically you need the throttle blades open to make boost. (meaning spinning the engine some)

I'd swap the gauge and check again. Might want to get a vac/boost combo.

I also think the bracket set-up would not be happy at all if you were making 12lbs of boost.

hope my rambling hasn't pi$$ed anyone off.

[Johnny406]

Originally Posted by tininjun67

I don't want to be a kill joy here, so take this for what it's worth, especially me never having seen this unit before:

I sincerely doubt that you're building that kind of boost with that set-up. I think you'll shred the belt immediately. It looks like the driven pulley is directly attached to the compressor wheel shaft, which is probably why the small belt is able to spin it. If there was a "gearbox" attached to it, higher impeller speeds and more boost would be achieved. I think the current impeller speed will max about 20k rpm or so (rough math here).

Making 7lbs of boost at idle does not sound right at all. Typically you need the throttle blades open to make boost. (meaning spinning the engine some)

I'd swap the gauge and check again. Might want to get a vac/boost combo.

I also think the bracket set-up would not be happy at all if you were making 12lbs of boost.

hope my rambling hasn't pi$$ed anyone off.

I spent a couple of hours on it last night beefing it up. I'll take some more pics this afternoon. Believe it or not, it is quite stiff since I was able to triangulate it. The belt is a heavy duty Bates 5-M pitch and is made to the cogs that are turning it. I suspect the gauge is crap and have a new one to try. I may pick up yet another so I can measure boost at the hat and below the carb. This project brings function over appearance to a new (for me) level.