Hi,

My car has a B18 with twin SUs and a Simons 4 branch manifold. The manifold is about 14 years old, the car is always garaged and has only covered around 1500 miles since the manifold was fitted.

I'm constantly getting exhaust fumes in the car and noticed recently when I started it that there was exhaust smoke in the engine bay around the manifold. All the mounting nuts are tight but I can't say where exactly the fumes were coming from. Subsequent startups have been less smoky so it hasn't been possible to identify the source.

I'm guessing that the three main culprits are either the manifold gasket, the manifold itself (they aren't very substantial and its possible that its rusted through somewhere or a weld has failed) or the gasket between the manifold and downpipe.

Can anyone suggest a quick way of narrowing down the leak?

Thanks in anticipation,

Aidan
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1967 131, 71 VW Westy

While it is idling, get an assistant to stick his hand over the tail pipe, or stick a potatoe in it, and the leak will become obvious.

You're best bet is to toss away the junk headers and fit a stock twin secondary arrangement on. B20E twin 1.75 into 2.125 gets the job done. Only a good head, twin DCOE's & a BIIIG cam can use a a set of quality 4-1 & then you need a big exhaust behind it of a tuned length.

Don't be tempted by vpd's headers eaither, they are far too big in diametre, wrong length and feature a very crappy collector. They sure look pretty but.....

Build a cheap & simple "smoke generator" (several videos on Youtube show how) & blow smoke up the tail-pipe. If there's a leak, you'll see it. They're also great for finding vacuum leaks, leaky valves, etc.

Thanks for the responses. I'm working on my own at the moment so options are a bit limited. I've tried using hose as stethoscope but no luck - I think that the leak, wherever it is, is too small to hear over the sound of the engine. I like the idea of the leaf blower and will try that next.
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1967 131, 71 VW Westy

A 4 of 5 foot length of 3/4 inch hose can be used as a stethoscope to find a noise - hold one end to your ear and search around with the other end for the sound.

I've used an electric leaf blower duct taped to the tail pipe in combination with the stethoscope. Just not on a 120...
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Art Benstein near Baltimore

It's always darkest before dawn. So if you're going to steal your neighbor's newspaper, that's the time to do it.

What Art said, tho I use the blower off my shop vac taped on. You should be able to feel the leaking air rushing thru any holes. With a little luck, you can even get a whistle

If you restrict the outlet you'll be able to hear where the leaks are. Best to have a helper with a cloth pad and leather glove to put over the end of the exhaust. If you block it with a rag and a stick you can do it yourself but little or no leakage will mean the engine will stop due to backpressure. Keep the revs up with the idle screws not by pulling the choke out.