Let me just get this out of the way, I love Camaro’s. Why a post about the Ford 302? Because my wife does not love Camaro’s! We have recently made a compromise and I can get a 4th gen or newer Camaro as a project! In my quest for a project car and before we made that compromise, I had been looking for a Mustang GT, the Camaro’s rival. I figured it would be a similar experience behind the wheel and would be easier for me to sell when the time comes. With that out of the way, this is what I have discovered about 302 Performance!
So I see these Mustangs’s on Craigslist all the time, most need work, but that is what I’m looking for. I would want to rebuild the motor and re-do the top end for more horsepower and torque. A rebuild kit doesn’t cost too much and is cheap insurance that all the parts on the bottom end are new and reliable. You may be able to even just be able to do a re-ring kit since the 85-92 5.0L Motors came with forged TRW pistons and the blocks were a high concentration of nickel which resists bore wear more than cast iron. With new rings and pistons (if necessary), combustion should not be a problem. Of course you could just do a compression test across all cylinders and find out if the bottom end is any good, if so you’re good to go.
Now on to the top end, this is where your money and effort is really well spent. Most of the gain in power will be found in the cylinder heads, camshaft, and induction system of the engine. For a Ford 302 I would be looking for a tried and true path to very street able performance, something that I could drive everyday but still have fun with at an autocross or driving event.
It seems that this path is quite simple. Bolt on a set of aftermarket heads to get the flow working properly, a street able camshaft, a decent intake, and you’re 80’s mustang is at 300HP or better.
The real budget route and get a set of GT40 heads. These heads have been shown to produce up to 40 HP on a mildly modded 5.0 engine. On a completely stock motor, you can expect around 20HP, give or take. Considering that we will be modding the exhaust and intake, these head may just be the ticket. I’ve been able to locate decent examples between $100 and $300. I’ve seen them go for more, but for used heads I would be leery spending more.
It seems that the next level up would be a set of new heads. Expect to pay upwards of $1300 for a set of new heads to put on that 302. However it appears that a camshaft and intake will be necessary to obtain maximum HP potential of those new high flowing heads. After doing some research and attempting to find a dyno run with new aftermarket heads on an otherwise stock motor, and failing, it appears that aftermarket heads will gain anywhere between 50 and 100 horsepower. With other supporting mods it could be much more.
I was looking at camshafts to help boost power, but it does not appear that they boost power so much. It seems that the cams in these cars adjust where and how the power comes on. I would keep the stock cam in a budget scenario, or upgrade to a more street/strip cam profile. This may raise the redline a little bit and help make power up high in the RPM range. The power is made in the heads!
If you are going to upgrade the heads, you should think about upgrading the intake manifold as well to get better air flow, and more power. If going with the GT40 heads, a cobra intake manifold should do the trick for the intake part. Match that to a good street cam and you should be good to go. If you decide to go with more expensive aftermarket heads for an even bigger increase in power, you may want to invest in a slightly better intake manifold. I’ve seen the trick flow intake manifold online for around $700 and on the Ford forums they seem to be pretty popular.
There is one more thing that you are going to need to upgrade to get the power that you are after. The throttle body! The stock throttle body is a 60mm piece, it is fine for a stock motor but once you start upping the flow characteristics of the heads and intake manifold the stock Throttle Body becomes restrictive and unable to flow enough air to support the higher flow numbers. On a naturally aspirated engine like we are talking about, the largest throttle body that is recommended is a 75mm. For the power numbers that I am describing in this post, a 65mm or 70mm throttle body would be sufficient. They make bigger throttle bodies but they would be overkill in this application. It seems that the 75mm throttle body can be had for less than $200.
So, to wrap this up, it seems that if you could get your hands on a fox body Mustang with a decent bottom end, or even one that just needed a re-ring kit, you could upgrade it to make around 300HP without too much cost. You could build this motor with GT40 Heads, Explorer (Cobra) Intake, and a throttle body and get the stock 220HP motor to around 280HP. If you wanted to spend a little more on the better heads and intake you will be up around the 300 mark if not over it. I see Mustangs on Craigslist all the time that can be had for around $2500, pump another $1000 into it and you have a little monster on your hands. Maybe this should be in the fantasy builds section!?