How essential is a blowoff valve on a supercharged engine?

My current setup is a 3.5L Rover V8 with a Sprintex twin screw supercharger.

The supercharger is bolted onto the inlet manifold on top of the engine with twin SU carbs bolted to the end of the supercharger.

I have been advised to fit a popoff/ blowoff valve to the manifold in the event there is an internal backfire and the supercharger might be blown off as there is no where for the gas to go.

Was just wondering if I should get one fitted? If so, what sort of valve should I fit? links or pics much apprechiated.

Lawrence

Yes. A pop-off valve would be a very wise investment. As of now, assuming you don't have one on, if a backfire in the intake manifold occured, the supercharger would most likely be destroyed and in an extreme case, could be separated from the engine.

Any ideas where I can get a blow off valve in the UK? I cant seem to find them anywhere.

What internal diameter to they need to be?

Cheers

Lawrence

depens what kind/manufacturer you want. there's loads of stockists. try www.demon-tweeks.co.uk (http://www.demon-tweeks.co.uk) for a bailey dump valve, they're said to be very good. there's quite a few listed, but here's the bailey ones in particular http://www.demon-tweeks.co.uk/products/search.asp?keyword=blow+off+valve&classCode=ROAD&brandCode=B63&x=18&y=13, worth browsing through to find exactly what you want.

Have a Bailey "dump" valve on my car. It is actually a bypass valve used when the turbo, or blower is upstream of the throttle butterflys and injectors. The center fitting on the valve is plumbed to an intake manifold vacuum source downstream of the throttle. The valve only works off vacuum. IMO, I don't think this part would be appropriate to use to vent the intake manifold in the event of a blower backfire. An installation is shown in my picture Gallery.

It should basically be a "plug" that installs on the supercharger or intake manifold that pops out when pressure exceeds something crazy(like 30+psi). Pressures far exceed that in the event of a backfire. Which is why entire blowers and even intake manifolds have been separated from the block/head due to extreme backfires.