The 347 Stroker is an upgraded 302/289 Ford engine. A 347 Stroker comes in crate kit form, in a part kit form so you need to do some machining, or you can make one form scratch yourself.
If you decide to make one yourself, you need to get hold of a 289 or 302 engine block and machine the 4.000 standard bore all the way up to 4.185 bore, which is what you find in most aftermarket blocks.
Before you start to buy and machine and kit up, ask yourself what horsepower do you want to reach, and at what RPM?
This is followed by the all famous, how much will it cost you question that is actually “how much are you willing to spend” question. This can be answered simply, if you want to get over 600hp you need over $2K. If you have up to $2K, expect to reach around the 400hp range. As you can see, the more you spend the more power you get.
If you don’t buy a 347 Stroker crate engine, and want all the fun of building one yourself, the let’s take a look at how to convert the 302 or 289 block into a 347.
The budget approach is getting hold of an old block, just make sure it’s in good condition and only requires basic machine work. Otherwise you will need to buy a stock block or an aftermarket block and still do some machining.
You will need to clean the block, bore and hone the cylinders and pre-assemble the short block and notch bottoms of cylinders for rod clearance. After this you will check the deck heights, square up the deck of the block to make sure that the piston heights are the same in all cylinders. After this, check the block or align hone the block.
Now let’s move onto cylinder heads, which usually come with the core. You will need to machine these heads and this includes first of all cleaning and checking the head for deformities and cracks. Then perform a 3 angle or better valve job and install new guides too. Make sure you resurface the heads and then assemble them on the block.
For a 347 upgrade you will need to buy springs that match the cam you buy, and that is lift type specific. Also get new retainers and stock type valves. You can get these in sets and the Stainless steel ones are the best.
Don’t forget to pocket port the heads, and set them up with OEM rockers and hydraulic cam springs with new retainers.
Now let’s look at the aftermarket heads, which there are plenty of. Cast iron heads are great for a lot of heavy duty and performance work, but the aluminum one, while lighter, require more maintenance. They and also demand you invest in a head bolt and or stud kit. These use a hardened washer that prevents damage to the head when torqueing.
Apart from the heads you need to buy an aftermarket valve train too, and its best to buy a full set ready to install, that if purchased assembled come with the studs and guide plates. With all this, you must buy new hardened push rods to run with the guide plates as well as a new set or rocker arms.
Take heed that the cast iron heads are significantly cheaper than the aluminum ones, and if you are not into racing, then cast iron is the better head for you. If you do opt for aluminum, don’t buy cheap, they can explode if the casting or forging is not high quality. (The same goes for cast iron too).
347 Stroker Kit
Do not buy a cheap kit, they are made of shit and will ruin your engine faster than you can drive it. Always buy a kit from a known brand, and there are many known brands offering different levels of kits at different prices. A good starter kit is the RPM kit that comes with 4340 steel rods, and this is the metal alloy you want. Do not buy a kit with 5140 steel, this is cheap material and will not give you lasting performance.