Been wanting to do the $20XX challenge with my dad since 1999 or so, and 2020 will finally be the year. SWMBO and I are moving from Baltimore to Tampa later this year and we'll build a car along with my dad. I've convinced her that buying/building an SN95 Mustang GT would be cheaper than modifying my S197, so she's agreed to a track car and likes the thought of the $2020 challenge. So I've been doing a lot of research on these cars, so once I move down there I can get a cheap one and start with a solid knowledge base. My question is on engines - most people say get the 94-95 5.0, as it's easier and cheaper to upgrade than the 96-98 4.6, which is underpowered and slow. After some digging I found quite a few alarming posts on the interwebs about the stock 5.0 engine block literally splitting in half once you get some higher RPM and 4-500 horsepower, whereas the stock 4.6 block can handle pretty much anything I would ever consider doing to it. I'm not hugely concerned with the 4.6 having a bit less power; the car will be fully gutted and lightweight and it'll have all the cheapo performance parts I can squeeze into the $2020 budget, and either engine would be fast enough for fun. I'm mostly concerned about the reliability of taking either of these engines at 100K miles, building them cheap, and flogging them regularly in autocross, HPDE over at Sebring, and the 2020 challenge. I'd rather not have to deal with a blown engine, and I'm willing to sacrifice some speed for that. My goal isn't to set any new lap records, it's to just have a great time and sound good doing it.
Is there a general consensus on here about the SN95s? Is the sturdier 4.6 worth the extra ~100 pounds and less power? Would the 5.0 be 100% okay with mild mods and close to 300hp, or is it going to explode the first time I hit 7K RPM and set the whole car on fire and leave my wife a widow who would then sell my '12 GT and buy a Prius? Has the interwebs highlighted a potentially disastrous weakness in the 5.0 block, or do I not have to worry at all unless I'm literally turning 7000RPM+ and pushing 500 horsepower? I'm just trying to have the best knowledge base I can, so in 6 months or so when I'm hopefully able to pick one of these up, I'll be able to build it right (cheaply) and make it last through some abuse.
A properly built 300HP small block Ford is a 100k mile motor. I've built 400HP road race 302s that run multiple seasons between rebuilds. I've built around 40 302s and I've never had one split a block. I've never tried to get more than 450 HP out of one however.
APEowner said:
A properly built 300HP small block Ford is a 100k mile motor. I've built 400HP road race 302s that run multiple seasons between rebuilds. I've built around 40 302s and I've never had one split a block. I've never tried to get more than 450 HP out of one however.
Yeah I'm concerned this may be a case of the internet blowing something out of proportion. I read in multiple places that 500hp was the limit on the stock block, and saw pictures of several instances where the block literally split in half. I know I would never get near 500hp, but the weakness in the casting still just kinda concerns me. However, I have also read that the 4.6 is an improvement over the 5.0 in terms of reliability, and those 4.6 engines will just keep going and going. Even if it's harder and/or more expensive to upgrade, if it truly is more reliable then I think it may be a better choice for me. Also everyone talks about how awfully slow the 96-98 GTs are, so they're usually super cheap as well.
You do not need to worry until you pushing all the RPM and big power and do some road racing where you are holding it there for minutes. To get to that point would be more than Challenge budget.
Knurled. said:
You do not need to worry until you pushing all the RPM and big power and do some road racing where you are holding it there for minutes. To get to that point would be more than Challenge budget.
Okay, thanks. Just there being issues with 500 horsepower kinda worried me, but if it'll handle 300 hp no problem then I should be set.
Or go plan C and buy a 96-98 Cobra and have both power and a great block. There's one for sale on the forum for Challenge money.
Javelin said:
Or go plan C and buy a 96-98 Cobra and have both power and a great block. There's one for sale on the forum for Challenge money.
I wish I could! All my pennies right now are tied up in fixing my house so I can sell it and move to Florida. Hell, I'll even be selling a car (1990 Mercedes 300E) for challenge money to help finance this move.
Although I guess another option is to get a 96-98 4.6 and swap the engine with a 4 valve from a junkyard MK VIII, which from what I understand was either the same as the Cobra engine or almost the same.
In reply to infinitenexus :
There is a lot of can't get there from here, since the heads are smaller and the intake manifold kinda sucked in order to fit under the low MN10 hood. There's a reason why Mark VIII engines are so cheap. But it's still a good starting point if you plan on modifying anyway.
infinitenexus said:
Javelin said:
Or go plan C and buy a 96-98 Cobra and have both power and a great block. There's one for sale on the forum for Challenge money.
I wish I could! All my pennies right now are tied up in fixing my house so I can sell it and move to Florida. Hell, I'll even be selling a car (1990 Mercedes 300E) for challenge money to help finance this move.
Although I guess another option is to get a 96-98 4.6 and swap the engine with a 4 valve from a junkyard MK VIII, which from what I understand was either the same as the Cobra engine or almost the same.
So does that mean you can't get two engines? When I was planning my last challenge car, the goal was like yours- start with a challenge car, and then move into road racing with it. But that was with the full thinking that I had a challenge engine and then a real racing engine. So you can deal with whatever compromises you need to make to keep within the challenge budget, and still can make the better race motor...
infinitenexus said:, or is it going to explode the first time I hit 7K RPM
So keep the rev limiter? Then the only way you'll hit that high is to moneyshift it?
They stop making power before then on the stock cam anyway.
alfadriver said:
So does that mean you can't get two engines? When I was planning my last challenge car, the goal was like yours- start with a challenge car, and then move into road racing with it. But that was with the full thinking that I had a challenge engine and then a real racing engine. So you can deal with whatever compromises you need to make to keep within the challenge budget, and still can make the better race motor...
Ideally I would be keeping this simple and using it as a project to learn on. I'm a decent wrencher but I've never swapped motors or rebuilt one before. My plan was to gut an SN95 and bolt on better suspension/brakes and a few performance parts and go wild with the (spray) paint job. If I wind up with enough money left over to pick up a spare engine and build it on the cheap, that's definitely something I'll consider.
I always thought the crank went before the block in the later 5.0s. If you're staying naturally aspirated, it's going to be cheaper to get a few more HP out of a 5.0 than a 4.6 just because cam swaps tend to be cheaper on the 5.0. How much power do you think you'll need on a road course?
dclafleur said:
I always thought the crank went before the block in the later 5.0s. If you're staying naturally aspirated, it's going to be cheaper to get a few more HP out of a 5.0 than a 4.6 just because cam swaps tend to be cheaper on the 5.0. How much power do you think you'll need on a road course?
That is a solid it depends... for sure the cranks do like to crack after extended time over 6000rpm. But the block can still fail before that depending on all sorts of factors. You can easily drop in a stronger crank.
FWIW, A/Sedan racers in the early 70s were cracking Boss 302 blocks at around 500hp. We have much better heads available to us nowadays than the gigantic-port Cleveland heads. The Boss 302 was probably the strongest production 8.2 deck block.
I’d say go with whichever SN95 you can get in the best shape in your price range. The 5.0 is reasonably reliable at non-insane power levels, and the 4.6 can be retrofitted with PI heads from a 99-04 Mustang.
If you want something that you are going to do most of the work on, finding a car that isn’t rusty, and isn’t trashed is going to be a much bigger concern. Presumably, if you get to a point where a reliable 500 HP is a goal, you’ll probably be looking at a T56 or other pricey transmission anyway. Not to mention the cost of a supercharger or turbocharger kit to get you there.
My vote is for the pushrod engine, just because they're so simple.
You're making me want one again.
My power levels won't be too high; the whole thing will be built on the $2020 budget. My main concern is that I do plan on doing some HPDE with this car, so it will be in the upper RPM for extended periods of time. Basic bolt ons on the stock engine would be enough power for me; this car is more about just enjoying being on a track again. But even with just some bolt ons (or a mild cam with the 5.0 since I understand they're cheap) the reliability of the 5.0 might concern me. Ultimately all of this will probably not matter hugely once I start shopping, since I'll just be picking up the best deal I can get. I just want to make sure the 5.0 isn't going to be problematic, due to how I plan on driving it.
Also thank you everyone for your replies, I do really appreciate it.
infinitenexus said:
My power levels won't be too high; the whole thing will be built on the $2020 budget. My main concern is that I do plan on doing some HPDE with this car, so it will be in the upper RPM for extended periods of time. Basic bolt ons on the stock engine would be enough power for me; this car is more about just enjoying being on a track again. But even with just some bolt ons (or a mild cam with the 5.0 since I understand they're cheap) the reliability of the 5.0 might concern me. Ultimately all of this will probably not matter hugely once I start shopping, since I'll just be picking up the best deal I can get. I just want to make sure the 5.0 isn't going to be problematic, due to how I plan on driving it.
An obvious solution is to not run the engine at high revs so much. Even at HPDE events, you can short shift. If it's not about ultimate power, then lowering the peak engine speed will just help.
That would be a good solution definitely. Would shifting 500RPM short really make a big difference in wear and tear? From what I understand both engines run out of steam above 5KRPM anyways.
I broke a 5.0 block at (probably way) less than 500 hp, but it was a 347, and it turns out that the balance wasn't right. It was a year and a half old when it broke, and had done several autocrosses, and 6 track days. The rev limiter was set at 6700, and it spent more time there at autocrosess than on the track. I was able to reuse the crank, rods, pistons, and cam for the Boss block build. The machine shop took 19g off the front and 24g off the back when they checked the balance.
Sonic
UltraDork
6/3/19 3:23 p.m.
In Lemons the 4.6 has proven to be nearly indestructible, where the 5.0 is merely average for longevity.
In reply to Sonic :
I was just reading about that. One guy was saying they had a 4.6 with a broken water pump and they would just run it until it got so hot the pistons seized, then they would dump a few gallons of water directly on the engine to cool it down, and it would start right back up. Pretty ridiculous.
If you want to build a motor, go 5.0, cheap power options abound and able to get good power naturally aspirated with intake, heads, pistons, etc.
Gt motor, a few options. I don't know them too well, but if I recall correctly the best bang for buck is still a blower. If you want more than 280ish HP, blower or big money heads. Also I believe they have hypereutetic pistons that give up at about 450. Stock for stock, will last longer than a 5.0 on or off track though.
Cobra motor, if you want more than 350 HP, a blower or big money is in your future. Still needs rods and pistons above 450HP. Block and crank are reportedly good for 800 though. Trans and rear would need attention above 450 as well. New blower kit is about $5k I've thought about that a lot for mine.
That out of the way, if motor is staying stock, mod motor all day every day for longevity. Saw lemons teams running 4.6 2vs many races and teams running 5.0s changing engines mid weekend as a habit. The 4v should be as reliable, but more power. Biggest problem might be timing chain guide wear.
Based on nothing more than lemons experience... The 4.6 gets my vote as well. PI swap with headers, cold air intake and a decent tune would get you to about 275whp. Strip enough weight out and you have a momentum car.
