My Ideas on Building a 302
Yeah I know what you are thinking, "....another guy that thinks he knows something about building Ford 5.0 motors." Well I admit I am no expert, but I have been doing this 302 stuff for 10 years now, and I have seen a lot of other people trying the same thing. The common goal with most 'street' 5.0 guys is reliable power, doing only what's necessary. There's never any point in performing mods to your 5.0/302 engine if they won't make it more powerful, or reliable. I believe in keeping it as simple as possible, I don't believe in too may 'custom' or very expensive parts. What I like most is seeing a very stock or mild combination car that beats high dollar bolt-on parts cars.
I will start with a late model fuel injected 5.0 motor. I will go into modifications of every part of the engine and my opinion in these matters. Keep in mind there are any number of ways you could accomplish the same goals, these are just my opinions, and how I would do (and do do) things.
My goal here is to build an 11 second street car. Eleven seconds is what I believe to be the outer limit of 'street'. If it cost you $4000 to go 11's, it will cost you another $4000 to go tens because the stock drivetrain won't hold up (not for long anyway)
Any motor needs efficient flow to make good power. For a mild car, the stock components are excellent (with exception to the air silencer and filter). Many people are running or have run high 12's with the stock intake tract. On supercharged cars, several people I know of have run 11's (I'm one of them) and even high tens with stock intake, throttle body and mass air meter. On my car that made 402 rwhp with a 6 psi blower, I only gained ~40 hp by going to 8 psi and a Cobra intake, 65mm throttle body and 73mm mass air meter (with 30# injectors). I don't consider 40 hp a good gain for the money I spent. I still wonder if the whole 40hp came from the additional 2 psi of boost! If you are running a supercharged car, an easy way to pick up 10hp and 10 lb ft of torque is by replacing the tiny K&N that comes with most kits with a decent sized one (7" long or so).
For naturally aspirated combination, more than one guy has run into the 12's or even 11's with the stock stuff. If your goal is bang for the buck, leave the high priced intakes and stuff for the other guys. Some items that are effective are a bored factory mass air meter. These can generally be bored out to 61mm for about $20 to $30. This lets a bit more air into the motor, and causes it to run a 'bit' leaner. This will make more power. Also an effective mod for a 'street' car is a phenolic spacer. If you have ever driven your car through traffic for a while, and then put you hand on the upper intake, you know it can get very hot. Heat kills power, so a phenolic spacer will help out here. At the track they are not that critical, as most people allow sufficient time for cooling between runs, but on the street, you can't pull over for 1/2 hour before you race the Camaro in the next lane. If you run a phenolic spacer (with the egr hole blocked off), you can safely than bypass the coolant line at your throttle body as well. Some people say this is bad for drive-ability in colder weather, well maybe, in the winter time then I would just re-attach the throttle body coolant lines. To fight heat even more in your intake, you could polish the upper intake. This only do if you have a phenolic spacer and bypassed TB coolant lines. A polished intake will reflect under-hood heat and help keep it cooler. Also this mod I would also only do if you can do it yourself, the performance gain is very, very minor and I would not pay to have it done.
How fast do you want to go? To beat most anything built, you need a good 12 second car. This is what I will concentrate on. If you want to go faster, and keep it streetable (so it drives nice) you will need to consider nitrous or forced induction. Like I said earlier, I really don't believe in changing the stock intake upto about 450 or 500 hp from a force fed car.
There is a lot of BS floating around out there about what heads to buy. Honestly I think that any after market head will do a good job. The choice comes down to price and reliability. I remember a while back a couple guys were debating who had better heads. One guy said his Edelbrocks were better than the TFS heads the other guy had because his car went faster. Oh how many times I hear this, and how many times I want to be sick. IT DOESN'T MATTER! Unless the two guys had IDENTICAL motors, and cars, and suspension mods and both the cars had the same mileage on an identically built short block, that came from the factory, built on the same assembly line, on the same day, any bench racing is pointless.
I have seen a guy with well thought out combo, and well set up car running 111mph in the quarter with nothing more than a 'Dremel' clean up of the stock heads. That's faster than both the guys that were arguing the E'bock vs. TFS thing (but that's not to say stock heads are better). Also I just want to say that the only advantage to aluminum heads over steel heads is the weight. Also maybe for the really serious guys, aluminum is easier to weld in case you want some very serious port work. For power and durability, I would dare say a steel head is better.
My opinion is that if you have a stock 50,000 mile 5.0, and you bolt on a set of heads (I don't care what kind), you will not gain any performance, unless you go through the trouble of prepping your short block. Aluminum heads are said to drop between 1/2 and 1 full point of your effective compression because they draw more heat out of your combustion chamber (the one place you actually want some heat). This is especially important if you live and race at higher alltitudes (2000 feet and up). Up where the air is thinner and has less O2 content, you need all the compression you can get (for stock apps). Aluminum heads at these altittudes on a stock motor can actually hurt performance... believe me, I have seen it. Just to convince you, I will give you two examples.
On one Ford shoot out I attended back in 1990, two guys from out of town came to race in Calgary. The effective alltitude here is often 4000 - 6000 feet. I had my stock motored Stang with 3.55 gears, underdrive pulleys and free flowing exhaust. The two guys both had nearly identical combos. Aluminum heads, GT 40 intakes, and B303 cams. One guy had 4.10 gears, the other guy had 3.73's. They both had slicks, while I was on Mcreary 'street' tires. Anyway, both these guys ran low 14's at 97-98 mph. The cars were standard fare, one was an LX the other a GT. Being in such 'shitty' air made all the difference, but my LX hatch ran a email@example.com mph.
What am I trying to say about heads??? Same as the intake, stock heads can put you into the 12's naturally aspirated, and 11's blown. Ported stock heads (with bigger valves) can put you into the low 11's or even tens! I would only upgrade the heads if you bump your compression to 10:1 and rebuild your shortblock, or you are going to run a blower. These days its almost the same money to buy an aftermarket head as it is to have the stock ones ported and have larger valves installed.
While on the subject of heads, I have a little tip for you guys when assembling your motors. When you bolt down the heads, get some 'aircraft' quality washers (hardened steel washers), and put them under the bolts. Oil the bolts and waskers well. You can actually feel the difference in your torque wrench when you bolt them down. The motion will be smoother and much less jerky at the higher torque levels. I am convinced that this gives a much better and more accurate torque reading and holds the heads down better.
Ahhh, the short block. Leave the stock one alone! If you need a rebuild, then do it right. Try not to undercut the crank if it's in good shape, just have it polished, this will open your clearances up a bit, but that's ok (upto about .003"). .0022" is ideal for rods and mains. Buy new bolts, and don't bother with a high volume oil pump unless the rod/main clearances are closer to .003". Even this loose, you could get away with the stock pump and thicker oil (20w50). A high volume oil pump is not necessary in most cases, and will rob you of 7hp! Install a windage tray, these do work and are probably worth 5 or more hp at 5500 or 6000 rpm. Make sure you clearance the windage tray for the oil dip stick (on FMS trays anyway, the dip stick hits the tray, and wont always go down into the pan...a major PITA!).
If you get your rods done, go to a ARP rod bolt. As for pistons, don't change them unless the old ones are badly damaged and the piston to wall clearances are to high. Going to a 306 will not make more power, and you probably get a heavier piston in return. The one exception is if you have factory cast pistons and want BOOST or a lot of nitrous. In this case I would get after market forged items .... There is absolutely nothing wrong with the stock replacement TRW forged pistons. Anyway, if the stock pistons are in good shape, just get a good hone job done on the bores and aim for a piston to wall clearance of about .005". Some people may say this is to high, but I disagree and prefer it loser, I have never experienced any piston chatter, even up to .006" p/w. I always run Total Seal rings in my motors. Some people claim that there is more drag with these rings, but I feel that a 6000 rpm motor, this 'extra' drag will not be significant. Also for a 'street' motor that sees a lot of driving, the Total Seals rings will maintain a level of performance longer than conventional rings. On my blown Coupe, after 2 years of track, street and dyno abuse, my leak down was less than 5% across the board. The gapless rings will also give you extra power through better cylinder seal which should really show up on forced induction or nitrous applications.
Cam selection is always fun, and I will say that for our performance goals, the stock cam is adequate. There are a several racers running blowers or turbos with a stock cam, and are running in the tens. I would recommend a set of 1.7 roller rockers, but beware the stock valve springs (have them checked or replaced, they don't cost that much). Another excellent cam is the FMS E303. This cam is not too big and works great naturally aspirated or with forced induction. Again I would not bother changing the stock cam unless you are rebuilding the motor anyway, or want a 'meaner' sounding idle. I see no point in buying the $270 custom grind cam for an 11 second street car.
What I Would Do To Run 12's
Assuming sea level conditions, and a standard tranny I would do the following to the car:
•1 5/8" long tube headers (these are most likely too big, but will give you headroom if you go with a blower or NOS)
•2.5" Hi Flo H pipe (with long tube headers, most shops can build an H pipe with only 1 minor bend. Cheaper this way)
•Bored stock mass air meter (61mm) with K&N filter
•Ported stock heads with 1.94/1.6 valves and 1.7 rockers.
•Stock bottom end with windage tray
•190 or 255 lph fuel pump
•Adjustable fuel pressure regulator
I had a combination like this on two separate occasions. Both cars ran ~13.2 @ 103 mph (12.6 @ 107 mph NHRA corrected for Calgary's 'bad' air). The only difference between the 2 cars and the combo above was that they had 3.55 gears. If you want faster than this naturally aspirated, a good rebuild may help (depending on the condition of your motor). Also a bump to about 10:1 compression, and maybe 4.10 gears. If your motor is in good shape, and you still want to go faster, I would recommend the next step.....forced induction.
It is now apparent that a well designed turbo kit (INCON makes a great and all inclusive 'street' kit) will put a completely stock motored Mustang into the low 12's with very few other changes. In fact with 10 psi boost, and other wise stock motor (but had gears, and hi flow exhaust), several cars have run 11's! Turbos work so well because they can make full boost as low as 2500 rpm, giving the car true big block torque. A centrifugal blower (Paxton, Vortech, Powedyne) builds boost with rpm, so on the bottom end (at 3000 rpm or so) there will be very little boost (2 psi maybe), where as the turbo maybe able to generate the full 10 psi by this point.
What I Would Do to Run 11's
The 11 second zone is a scary place, only the most expensive and exotic production cars are 11 second capable. These cars include Lamborghini's, Mclaren's, Ferrari's, some exotic Porsch's and Vector's. This is also the area that can break your piggy bank.
Why are the 11's expensive??? This is where parts will start to break. If your stock T5 is still alive (you shift it nice and don't miss shifts) it will almost surely break once you're making this much power. Also the stock axles will let go if your car hooks HARD. Your posi is probably already screaming 'stop'. If you race at the track you will need a 6 point roll bar, a blow proof bellhousing, c-clip eliminators etc. That is why I consider the 11 second zone the limit for a 'true' fairly low budget street Mustang. You will have a lot of fun, but now you must be careful how you drive it. If you want to run 10's, you are almost 100% going to need at least a transmission and a good rear end (believe it or not, some people have run tens on stock trannies!).
All of the 12 second stuff plus a 150 hp 'wet' nitrous kit WILL put a good hooking car into the 11's. Also any of the blowers on the market will do the same thing. Make sure it makes about 8 psi.
So to run 11's you need:
•Blower, nitrous or turbo
•At this stage you will need to upgrade your ignition (I like MSD)
•If you want mid to low 11's, you will need 30# injectors and a matching air meter (75mm or bigger).
If you have come this far, you will need very little else to run 10's. Some of the other thing you will need:
•65 - 75 mm throttle body
•Extrude honed/heavily ported stock intake with a box upper or aftermarket intake
•More Boost. A very well built car can probably dip into th 10's with as little as 10 psi, although 14 or so may be required
•Upgraded fuel system . You will need an external pump and bigger fuel lines. You may also need bigger fuel rails and 36 or 42 pound injectors
•Replacement parts for all the broken drivetrain pieces
Upto the tens, you will most likely get away with the stock block. I believe and from what I have seen, that the block goes before the rods and the stock crank. If you are making enough power to break blocks, its time for some serious money, but that was not the point of our 'budget' Mustang. Anybody can go really fast with a big enough bank account, but going fast on a budget is what I like the most.