Tune Your Own Custom Made Header/Exhaust Manifold continued… If you have a highly modified engine then regular pre-made headers/exhaust manifolds probably won’t cut the mustard Header/Exhaust Manifold Design A camshaft’s duration and lobe centers have a direct effect on overlap and the ideal primary length, diameter and collector type of the header. The last of these changes, the camshafts, have the largest effect on header/exhaust manifold design. You have camshafts with an aggressive profile. You have high-compression, a ported head, different intake manifold and perhaps a different combination of bore and stroke. By this point your motor will be built to the limit or near-limit. If you are serious about your all-motor power, then a custom header/exhaust manifold will be mandatory for your project vehicle. Burns stainless offer a wealth of information on exhaust manifold design. Keep in mind that any exhaust leak also introduces oxygen into the manifold, allowing the fuel delivery to skew since the engine sensors will see the false air.Tune Your Own Custom Made Header/Exhaust Manifold. Some controlled heat with a torch (if possible) and soaking with a good penetrating fluid go a long way in saving you from a major headache. Take special care when removing the old fasteners to not pull the threads out of the cylinder head casting. If the manifold is being replaced, always use a new gasket(s) and fasteners.Īpply antiseize compound to all threads so that they do not freeze in the head. Anything that will increase the exhaust gas temperature will impact the manifold casting’s integrity.
EXHAUST MANIFOLD CRACKED
You may also run into cracked castings, which are tricky since you need to determine if the casting failed due to fatigue or from an engine running problem such as timing or fuel delivery (diesel) or lean mixture (gas engine). If there are multiple broken studs, then I usually replace the exhaust manifold with a new casting since it, too, is near the end of its service life. With luck and patience, the job can often be done in a few hours. But it is better than taking the engine apart. I do not want to mislead you: Even with the tool, this job is no picnic. It is not uncommon to find an engine today with four or five broken fasteners to the cylinder head. They usually resemble a jig and come with the required drill bit. There are many model-specific tools made to allow the fasteners to be drilled out that do not require disassembly. The goal would be to accomplish the repair without removing the cylinder head from the engine block. The load eventually snaps the fastener, requiring it to be drilled out in the cylinder head. The action can also cause manifold castings to twist.
The use of lightweight materials along with the high rate of thermal cycling both in frequency and magnitude produces a transverse load on the exhaust manifold fasteners (side to side). If you plan on doing any exhaust manifold work, buy this tool first. With rare exception, this is met with either a broken cylinder head or other components being pried against. You insert and loosely snug the fastener and then move the tool to the next branch, if need be.īeing unaware of this tool and the need for it has many mechanics using a pry bar – in frustration – to attempt to reinstall the manifold. It is placed between the manifold branches and is expanded with an open-end wrench until the fastener holes are aligned. There are many different styles, but the least expensive spreader resembles a turnbuckle.
There is a simple workaround for this problem, but it requires a special tool called an exhaust manifold spreader. If you have never experienced this before, you will be dumbfounded, since the manifold is not visibly shorter.
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