Race Engine Forum UK

Hello All,

This is my first post though I have been using this forum as a reference source for some years. My car is an '81 Fiat Spider. The 2 liter 132 engine with fuel injection was modified by Legend Industries with a low pressure turbo system when new. The car is used only on the street.

For most the 16 years I've owned the car exhaust leaks have been a problem. I eventually cured the chronic leakage at the turbo/exhaust manifold by discarding the use of the multi-layer stainless steel gaskets used in the original installation and going gasketless at that joint.

The second sealing problem is at the head/manifold joint. The car originally had a gasket with stainless seal rings around the port holes which may have been the original Fiat gasket. When it failed, I could not obtain a direct replacement. Eventually I went with the no-name perforated metal gasket that is widely sold in the U.S. It holds for a few months to a year, but, despite regular attention to the tightness of the exhaust stud nuts, and resurfacing of the manifold face, it develops a leak and eventually burns through.

I'm now getting ready to install a rebuilt head with a freshly resurfaced exhaust flange and am wondering whether I could simply eliminate this problem gasket as well. Would a gasketless joint at the head/exhaust manifold joint work with two flat freshly milled surfaces? Another alternative would be to have a custom copper or multilayer stainless gasket made but that's expensive and my experience with the later on the turbo flanges is not encouraging. Is there another option for sealing the exhaust manifold at the head of an 8v twin cam engine that would stand up to the added temperature of a turbo?

Richard Ridge
Rockville, Maryland USA

if the clamp load from the fixings is good a gasket with fire rings should suffice and I have them here.

G

Are you sure its the gaskets that are failing, and not the fasteners loosening or manifolds buckling?

Chris,

The Legend turbo manifold used on the Spider is nodular cast iron and has a thick flange. All fasteners on the exhaust system and turbo are prone to loosening and get checked regularly. There is clearly some movement between the outer gasket surface and the manifold flange but I believe it is due the expansion and contraction of the cast manifold itself along the length of the head. The manifold never seems to fit on the studs in quite the same way twice and often required minor easing of the stud holes to refit.

The turbo is supported on the block by two brackets, one to the unused alternator studs at the front and another to the motor mount bracket. There is probably less stress on the manifold from exhaust system movement than the stock non-turbo layout in the Spider 2000. I don't think gross movement is an issue.

Richard

Hi Richard, Do you have a flex coupler in the exhaust pipe before the first mount point of the exhaust pipe to the body? The manifold/turbo can't support the weight or vibration generated by a poorly installed exhaust. I like to mount the exhaust pipe in at least three points with the first mount just after the flex coupler.

Tim

Tim,

The Legend setup uses a long stainless steel down pipe with four bends but no flex joint. The side to side movement of the exhaust system, which includes catalyst, resonator and rear muffler is controlled by a strap from the cat to the transmission case and additional hangers on the cat and resonator. The strain of twists and fore/aft movement from engine motion is taken by a cast exhaust elbow on the back of the turbo which is supported by a heavy bracket mounted on the side of the block.

Richard

You don't need a flexy on a RWD setup. What you need is a gasket with fire-ring. Unless the turbo unit is running too lean or with ignition timing to retarded off-boost in which case the EGT will be so high it won't matter what ex gasket you use.

Let us try and keep this simple guys. If the fire-ring gasket can work on a GpA Integrale I am sure it can work for you Richard!....


GC

Guy

The simple solution would be to de-turbo as most Legend owners concluded long ago. Be that as it may, my head rebuilder had the fire ring gasket in stock and that's what I'm going with.

The Jag E-type used flex pipes in its exhaust system. Not maintenance free but doubtless they've improved in fifty years.

Richard

RichardRidge wrote: The simple solution would be to de-turbo as most Legend owners concluded long ago.

You seem to be describing a pattern failure with your turbo conversion. Yet you don't appear to concede that a change might be required. I too like to keep things simple. My experience with installing flex couplers has solved some long standing and expensive problems.

Guy Croft wrote:You don't need a flexy on a RWD setup.

I try my best to never say never. I this case I respectfully have to disagree that flexy couplers and RWD don't mix. Throw in having a 4 cyl. engine and the inability to keep things buttoned up would make it my first choice after installing all the required gaskets.

RichardRidge wrote:exhaust system, which includes catalyst, resonator and rear muffler

I would offer that with a turbo and just a cat you could probably be quiet enough to be within the legal limit for noise under normal driving conditions. At full song it could be questionable.

Tim