In most cases a 305 exhaust manifold will fit on a 350 motor engine and a 302 exhaust manifold will fit on a 351 motor engine.
There are some cases where they may not fit but even if this is a problem you encounter, you can still have the manifold or the motor engine modified to make them fit properly.
This can take some time and money so it’s a good idea to find out if the specific exhaust manifold you have will fit on your engine or if it will require some extra effort.
Let’s Find Out If 305 Exhaust Manifold Fits A 350 Or 302 Exhaust Manifold Fit A 351
When it comes to swapping engine parts it’s usually possible between vehicles of the same make, even if they are different models. Both the 305 and the 350 are common motors found in Chevrolet vehicles and can swap many of the same parts, including exhaust manifolds. It comes down to the year and make/model of the vehicle.
Certain Chevrolet vehicles have different connections, bolt patterns, bolt sizes, and adapters that are available to make the parts compatible.
When trying to determine if the exhaust manifold will work on the opposite engine, it’s important to inspect the motor and the manifold to determine if they are compatible or will need modifications to work properly.
The same is true for a 302 and a 351 motor. These are motors commonly found in Ford vehicles. The same logic applies to these components.
Many Ford parts and components are compatible but it comes down to the specific year and parts. The only way you can tell if the exhaust manifold can be swapped is to look at the manifold and the motor for the specific vehicle you have.
While this may require some research, it will allow you to have a good understanding of the work and time that will be required to make the swap work.
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Will A 305 Exhaust Manifold Fit A 350?
A 305 exhaust manifold will not directly fit a 350, but there are some adjustments that can be made to allow it to fit.
If you have replaced your 305 with a 350 or happen to have an extra 305 exhaust manifold on hand and need to add it to your 350, it may be worth swapping them.
Certain engines may also have different bolt patterns or different-sized exhaust ports.
For the most part, the parts for 305 and 350 motors are interchangeable, but there are different factors that come into play to make this true.
However, the exhaust’s Y pipe from the 305 may not fit the 350. If this is a problem, you can have them drilled out so they can fit properly or have the holes drilled at a different angle so the Y pipe will fit properly.
High octane is recommended for those who switch to a 305 exhaust manifold in a 350 motor. You can increase the compression ratio of your engine by using a higher octane gas.
The timing of the ignition or forced air induction on your car will be more advanced with fuel with more octane.
Gas with a higher octane rating is recommended for turbochargers and superchargers. Gasoline with a premium rating performs better in these engines. A car’s octane rating will be listed when you purchase it.
Octane ratings should always be followed. You will not see any difference in your car if you purchase gas with a higher octane rating unless you have made modifications that can help your car benefit from higher octane.
Using lower octane ratings than what your car’s manufacturer recommends may harm the engine. You will not be able to meet the fuel efficiency estimated if you use lower-octane fuel.
Low-octane fuel damages your engine and emissions control system if you continue to use it for a long time. Your car won’t suffer any harm or benefit if you use a gas that has a higher octane than it needs.
Swapping the manifold will also result in a higher compression ratio.
Thermal efficiency will be higher in engines with a higher compression ratio.
The combustion process generates more heat, so the engine is able to convert more of it into horsepower. Heat is converted into horsepower and fuel efficiency through thermal efficiencies.
Will A 302 Exhaust Manifold Fit A 351?
Most 302 exhaust manifolds will fit a 351, but it depends on the year. Some vehicles have the same mounting locations for the pipes, which means they should slide in without any additional drilling or adjustments. In other years where the mounting locations are not the same.
Older engines have different bolt patterns and the manifold may not bolt on directly. Depending on the year, the combustion chamber size can vary, but overall 302 heads will not provide any performance boost.
Since the 351W uses larger head bolts, you will need to drill out all the holes. If this is the case, you can find adapters for some manifolds that make it possible to attach them or you can have new mounts attached to make it fit.
Another option is to install headers instead of an exhaust manifold. There are some clear advantages to adding the 302 manifold instead of headers to your exhaust system.
They are better than headers and retain a stock appearance while improving over log manifolds. As ram-air manifolds are rare, they are more affordable than factory-made copies. Once installed, they require only cosmetic maintenance due to thick flanges and lots of iron.
Even though the manifold may take some adjusting if it does not connect directly to the motor, it’s still likely to be more durable and last longer than the headers.
While different manifolds can be added to different engines from the same manufacturer they don’t always match up perfectly. A 305 manifold can be used on a 350 and a 302 can be used on a 351, but there are some exceptions.
If they don’t match up, they can likely be altered or modified to fit. The year of the motor and manifold is a big factor that determines if the manifold can attach naturally or will require modification.
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302 to 351 exhaust manifold options | Ford Muscle Cars Tech Forum (fordmuscleforums.com)