i figured out how to eliminate the vst and the pulley fuel pump all together(1996). it took me alot of trial and error but it 100% trouble free and alot less than $1000.
check here for a pic you can see i have a block off plate where pump used to be
http://www.classicglastron.com/phpbb...=169&start=110
im running 2 electric pumps, high and low pressure, 2 fuel regulators and a return line. if you get the new style cool fuel assembly you get the high pressure pump and regulator, so all you do is replace mech pump with low pressure electric pump, run the return line from fuel rail back to tank, and change out your in line to fuel rail hose to one that fits the fuel cooler. i have the whole project in that classic glastron site listed above, just check the last few pages.
65 at 4000 rpms.... still breaking in motor....with small 23" prop!
good luck
jay

What kind of pressure do these vst tanks build above idle? Also if someone has links or pics to all the vst mods would be helpfull

Floatindirty, I don't think it should have any pressure if everything is working properly. When the engine is running, the VST tank should be vented to relieve the pressure that builds up after driving and shutting the engine off.
When I was having this problem my pressure would increase up to about 10lb's of pressure, therefore the mechanical pump could not pump gas into the VST and it would run empty. Then the electric pump had no gas to pump to the injectors. I scanned the picture of my VST repair section of my manual, and can email it to you so you can post it.

I'm interested in what you did and am also considering removing the VST. After I complete the project this spring, I'll have pictures, a line drawing of the new system, and a complete list of parts that I used. If everything works and it solves all the VST problems, I'll let everyone know. It has to be a better setup than the Merc VST system. A couple of questions. Why did you use two fuel pumps? It doesn't make sense to me. Did you use the existing Merc relay to control the fuel pump? In other words, did you tap into existing electrical wires to the VST fuel pump to run the new pump? I'm thinking that connecting to the ignition key switch (on) side might be better because, in case of vapor lock, you could let the pump run and circulate fuel back to the fuel tank to wash out any air. It might be a good idea, if doing this, to install an oil pressure fuel pump stop switch.

Old post, but the stock system has a lift pump to the VST tank then a high pressure (in VST) to the injectors. I have replaced all of my fuel supply to 1 pump, filter, FPR and have not had any issues since. I installed a Y to supply fuel to the whipple injectors. What jay did was replace the lift pump with a low pressure electric pump, but it doesn't look like he had the VST tank, so really don't need the low pressure pump. The return to the fuel tank is what most likely fixed the problem.
Oh, I used the stock fuel relay to trigger a big relay to supply power to the Areomotive pump

Which Aeromotive pump did you use?

Thanks

A1000

I know this is a old post ,I have read also to install check valve in water line to hold water up in block.So i also need to know if i have old style vst 1993 can i change spring in vst ? its seems like there is some differant lines inside of new and old style vst tanks .

Not heard about a check Valve in the water line before for a 502, and no reason it should need one. The VST spring change was in a transition year (96 or 97) where they changed the top housing, so if yours is a stock 1993 then it should be installed correctly and would not need to be changed.

More importantly,,,,do you have the mechanical pump mopunted at the sea pump???