Here's a list of trouble areas and insights I've come upon while doing my engine build and buying a blower.
Doing forged internals:
1. Find a machine shop before you start anything that will work on 4.6 motors, they are hard to find even though these motors have been around for over 10 years.
2. Decide If you want to reuse your old block or buy new. If you use your old there are pluses and minuses. Your old block has already been heat stressed and relieved so you don't have to worry about breaking it in. You also know all of your accesories will mate properly. Unfortunately it will also cost you more to have your old block machined than to buy a new block. If you buy new you don't have to machine it very much unless you are going with oversize pistons. I found that new blocks are always backordered from Ford Racing so be aware if may take you over 6 months to get a new block. I started collecting parts for my build in November and the blocks are still backordered to this day.
3. First of all buy from a reputable dealer, ModularPowerhouse, VT, SHM, MMR, DSS etc. What type of internals are you going with? What is your ultimate goal? Are you going to stay N/A or go power adder? If your staying N/A or Nitrous go with high compression pistons. If you are going supercharger or turbo get some low compression dished pistons. I'd suggest 23cc-28cc dishes but ask the seller of the internals you are buying their suggestions and give them all of the information you have of where you want to be ultimately with the car. What type of crank is it? Most aftermarket internals come with 8 bolt forged Cobra cranks. Most GT's have a 6 bolt crankshaft. This means you will have to buy a new 8 bolt flywheel and it's a good idea to buy a new clutch when you buy a new flywheel. You will also need 2 new flywheel bolts, these are actually a pain to find. It starts to get expensive in a hurry. Make sure you get your internals balanced from the company you are buying them from, this will cost about $200-$300 extra. Get all of the main bearing, rod bearing, and piston ring clearances for your internals from the seller.
4. Get all new gaskets and replace hardware with ARP hardware where you can. Head bolts are torque to yield, get new ones or better yet buy ARP studs. Buy ARP maincap studs as well. Make sure you have all of the gaskets. Here's a list of the ones I remeber, hope I'm not forgetting any. Oil pan gasket, remote oil filter housing gasket, head gaskets, intake manifold gaskets, timing cover gaskets, valve cover gaskets. You will also need a lower seal kit. The Ford Racing head changing kit is pretty useless. It only comes with some new head bolts, head gaskets, and a new oil dipstick tube. It does not contain timing cover gaskets, valve cover gaskets, or intake manifold gaskets. All of which need to be changed when you take off your heads
5. Always replace your water pump and oil pump with new ones when you take a motor apart. I would also suggest a new starter while you are at it if you have longtubes especially. That stupid starter is a pain to get at when you have longtubes and it would really suck to get everything back together and have that fail.
Fuel System:
1. Do I need to change my fuel system to compensate for my new power? If you are going for high horsepower ie. 400+ it is best you look at new injectors and a new fuel pump. Ask a performance shop what they would recommend for your application.
Supercharging:
1. What supercharger should I buy? This is a personal decision but some information might help you decide what is best for you. Is it mainly a street car or track car? For a street car i would suggest a Kenne Bell, Eaton, Saleen, Roush, or any positive displacement blower. They have instant boost for you at anytime. For a track car i would go with a Centrifugal blower because they spool up slower which enables you to get better traction off the line but they go like crazy when you get them up to rpm. Centrifugals generally make more peak horsepower than positive displacement blowers. Examples are Novi, Vortech, Procharger, Powerdyne. Decide what you want before you buy and do a lot of research.
2. If I buy a supercharger will I need anything else? Some places sell fairly complete kits such as Modular Powerhouse with their Mongoose kits and Kenne Bell with their 1.7 kits. Others you will need to change a few things. Injectors, computer tune/chip. You will almost always have to buy a new maf if you are going big power, most kits do not come with them. The Ford Lightning 90mm MAF is popular as well as the SCT 90mm MAF. You need to decide if you are going intercooled as well. This will limit your boost potential.
This is all I can think of for now and I'm getting pretty long winded. Hopefully some of you guys will have other ideas and comments to throw in as well that I might have missed. I haven't touched on heads and cams yet.
Doing forged internals:
1. Find a machine shop before you start anything that will work on 4.6 motors, they are hard to find even though these motors have been around for over 10 years.
2. Decide If you want to reuse your old block or buy new. If you use your old there are pluses and minuses. Your old block has already been heat stressed and relieved so you don't have to worry about breaking it in. You also know all of your accesories will mate properly. Unfortunately it will also cost you more to have your old block machined than to buy a new block. If you buy new you don't have to machine it very much unless you are going with oversize pistons. I found that new blocks are always backordered from Ford Racing so be aware if may take you over 6 months to get a new block. I started collecting parts for my build in November and the blocks are still backordered to this day.
3. First of all buy from a reputable dealer, ModularPowerhouse, VT, SHM, MMR, DSS etc. What type of internals are you going with? What is your ultimate goal? Are you going to stay N/A or go power adder? If your staying N/A or Nitrous go with high compression pistons. If you are going supercharger or turbo get some low compression dished pistons. I'd suggest 23cc-28cc dishes but ask the seller of the internals you are buying their suggestions and give them all of the information you have of where you want to be ultimately with the car. What type of crank is it? Most aftermarket internals come with 8 bolt forged Cobra cranks. Most GT's have a 6 bolt crankshaft. This means you will have to buy a new 8 bolt flywheel and it's a good idea to buy a new clutch when you buy a new flywheel. You will also need 2 new flywheel bolts, these are actually a pain to find. It starts to get expensive in a hurry. Make sure you get your internals balanced from the company you are buying them from, this will cost about $200-$300 extra. Get all of the main bearing, rod bearing, and piston ring clearances for your internals from the seller.
4. Get all new gaskets and replace hardware with ARP hardware where you can. Head bolts are torque to yield, get new ones or better yet buy ARP studs. Buy ARP maincap studs as well. Make sure you have all of the gaskets. Here's a list of the ones I remeber, hope I'm not forgetting any. Oil pan gasket, remote oil filter housing gasket, head gaskets, intake manifold gaskets, timing cover gaskets, valve cover gaskets. You will also need a lower seal kit. The Ford Racing head changing kit is pretty useless. It only comes with some new head bolts, head gaskets, and a new oil dipstick tube. It does not contain timing cover gaskets, valve cover gaskets, or intake manifold gaskets. All of which need to be changed when you take off your heads
5. Always replace your water pump and oil pump with new ones when you take a motor apart. I would also suggest a new starter while you are at it if you have longtubes especially. That stupid starter is a pain to get at when you have longtubes and it would really suck to get everything back together and have that fail.
Fuel System:
1. Do I need to change my fuel system to compensate for my new power? If you are going for high horsepower ie. 400+ it is best you look at new injectors and a new fuel pump. Ask a performance shop what they would recommend for your application.
Supercharging:
1. What supercharger should I buy? This is a personal decision but some information might help you decide what is best for you. Is it mainly a street car or track car? For a street car i would suggest a Kenne Bell, Eaton, Saleen, Roush, or any positive displacement blower. They have instant boost for you at anytime. For a track car i would go with a Centrifugal blower because they spool up slower which enables you to get better traction off the line but they go like crazy when you get them up to rpm. Centrifugals generally make more peak horsepower than positive displacement blowers. Examples are Novi, Vortech, Procharger, Powerdyne. Decide what you want before you buy and do a lot of research.
2. If I buy a supercharger will I need anything else? Some places sell fairly complete kits such as Modular Powerhouse with their Mongoose kits and Kenne Bell with their 1.7 kits. Others you will need to change a few things. Injectors, computer tune/chip. You will almost always have to buy a new maf if you are going big power, most kits do not come with them. The Ford Lightning 90mm MAF is popular as well as the SCT 90mm MAF. You need to decide if you are going intercooled as well. This will limit your boost potential.
This is all I can think of for now and I'm getting pretty long winded. Hopefully some of you guys will have other ideas and comments to throw in as well that I might have missed. I haven't touched on heads and cams yet.