308 with extra HP!!!

How does a 308 with 300 hp go ? and then if you make it 400 hp how does it go ? Does it just break the back wheels loose or do they put the power down ? If you have a 400 hp 308 have you changed the rear wheel size (width ) ? How does the chassis handle the extra power ? I would think the brakes need an upgrade ?

 

I have no direct Ferrari experience with your question. But I have a lot of it with other cars. Since cars are cars and engines are engines they will all react more or less the same.

If a car has a 250 HP engine and you increase it to 300, there will normally be no "problems" associated with the increase and, on a 3000lb car, it will make a noticeable increase in performance without particularly straining anything else. Assuming everthing is in good condition, it won't have any problems at all.

Going to 400 HP means you are going to break something if the rest of the drivetrain is not modified. The tires are usually the weakest point, followed by the clutch and that's a good thing. But what happens is that people than figure they'll install wider tires and a stronger clutch and NOW, instead of a clutch slipping/tires spinning they have gears/driveshafts breaking. Sure, you can "tread lightly" as you apply power but then what's the point?

Now, as far as performance. If a standard 3x8 with say, 250 FLYWHEEL HP, can do a 1/4 mile in say 14.5 seconds, increasing the power by 50 HP to 300 will give the car the ability to do the 1/4 in 13.6 seconds which is not bad at all though not very impressive by current high-performance standards. Note that only a few (and you could count without using all the fingers of one hand) of the famous muscle cars could do that in stock form, even with drag slicks.

Adding 150 HP, to 400, will allow the car to POTENTIALLY do the 1/4 in 12.3 seconds. That IS quite impressive even by current standards. But you could not "get the power down" with the standard clutch and without much wider tires. But with the better clutch and much wider tires the odds are when you did that 1/4 mile launch you would leave drivetrain parts scattered at the start line.

A good figure for adding power without generally having to worry about changing a bunch of other drivetrain parts is 33 percent. So if you have a 250HP 3x8 - again that's flywheel, not rear wheel HP, you can be pretty confident that increasing up to 325 FLYWHEEL HP would be workable. This would produce a potential 1/4 time of 13.1. it's faster than the majority of quick stock autos but no you won't be spanking any Z06s (or even 355s) but you won't be breaking anything either.

 

Thanks for the answer . The reason I asked was I saw the dyno chart from I think it was m ke's supercharged QV . It showed well over 400hp if I recall correctly . The Forza/ Scott supercharged motor has also been highlighted recently and I just wondered how they went . Now these are both supercharged so the torque is up substancially . Which must help the acceleration ??
Regards the gearbox internals I have read on this forum they are good for 600 + hp ???

 

For any Mondial guys reading this, my 3.2 has about 320 flywheel hp with the Weber conversion. Much like the t, 300hp or a little better is a good match for the rest of the components and bulletproof reliable. You can catch rubber in first 3 gears at least, 0-60 times in the low 6 - high 5's depending, with a good power band beginning about 4K, which is enough for safe fun. It is the right balance.

 

We have seen a couple very streetable Carobu engineering built engines come around. Good torque and good bhp within usable rpm ranges. The heads on these engines were not really touched other than port matching and made over 270 (274 to be exact) at the flywheel which was achieved with 10:1 compression and about 275 advertised dur cams. Getting a streetable 300bhp out of one of these things is a big task, but once Mark finds a head to play with I am sure he can do it! Would be worthy of a Forza article for sure

 

I can only imagine that 300 hp would be a blast. My car doesn't have that much power but she is pretty amazing to me and has been extremely robust even though I drive 'er like I stole 'er ... 600+ hrs on my new motor and gearbox now and I've been running Hoosiers at the track ... my car is also a GTS/hairdresser model with all the body flex that doesn't seem to effect grip at my level of driving ... I dunno ... I might be driving like a hairdresser though. Some guys rave about the handling of the B and I just don't get how anyone can draw such conclusions with the stock suspension setup, so if these guys tell you the chassis can't handle it, I'd talk to guys that actually have that much power (mke for one).

Brakes ... I run the race Porterfield pads and when I have to brake down to 50 mph from say 145 mph they do need a few seconds to cool down. One of these days I'll get some more of my track videos on youtube. If you're just playing on the street I'd expect the stock brakes to work for 'ya.

cheers

 

Mark had 500 plus in his blown QV, he said it handled fine and had good traction, though he was running wider rubber. These arent like American Muscle cars that hesitate when you kick them and then explode with power and massive torque steer making you fight for all your life to wrestle them into their lane while the tires smoke all over the road. The 308 plants almost all its weight to the rears on hard acceleration and it would take massive power before they would just sit there and go up in smoke. I'm sure Mark had more than enough power to smoke the tires, but I'm sure it grabbed and flew right away, and didn't take Herculean effort to keep it steered the direction he wanted to go. The 308 doesn't have any torque steer!

As for brakes, the 308 had really good brakes in the 70's compared to other cars at the time. But by today's standards they are mediocre at best. Anything that would improve its stopping ability would be a plus. Extra power wont effect the brakes, the car isn't going to have any higher top speed, its just that it will get there much quicker. The extra braking power helps when you accelerate faster than your mind, and find yourself in a jam where you need to avoid something immediately. Like a car pulling out in front of you.

 

I'm sure it's been discussed in great lengths ... my 308 will lock it's front tires under braking on the first hit no problem ... it's the 5th, 6th ... blah blah, during laps. If you can lock up the tires in a straight line, you don't need more brake unless you're doing it repeateadly/putting heat in.

wrong .. right?

 

That's exactly it !! To get 300 streetable HP out of a 3.0L 2V is quite an undertaking and then how reliable is it . So this was the reason for my original question . Is it worth persuing more HP or does it just spoil the balance . Russ has intemated that 320 HP in his Mondial is about right ? Yes I know " there's never enough HP " but at what point does the chassis/suspension start to wind up and you spoil the whole plot ???

 

I don't think I've seen a single thread from a guy with a supercharged/turbocharged 308 saying "it was too much for the car/balance". One guy I spoke to with a twin turbo 308 conversion told me "she's too much" ... tracked it and beat up on turbo P cars easily .... so a naturally aspirated 300 hp will be nothing for the chassis IMO ... if you're wondering to yourself if the investment is worth it? For me it's more time than $$$ and I learn from it all ... if I was just writing checks it'd be different.

 

By now I have a few months driving experience after converting my '82 Mondial QV by mounting a supercharger. Power is around 300HP.

Has this made the car better? Yes! In a Mondial, the change from 235 to 300HP is going from "good" to "yihaaaaa!".

I have not observed any weak spots in this power range. There is off course some tyre smoke in 1-2-3rd gear, but hey - I like the idea that the tyres act as torque limiters and protect the transmission.

The only upcoming change is a brake upgrade. The stock ones tend to run hot annoyingly fast on track days.

300HP?
- Go for it!

 

With a 300 rwhp (so 350/360 crank) bolwer motor the difference is night and day...the car is SOOOO much better to drive in every way.

With 420-450rwhp blower motor (so 550 ish? crank hp)...that is a lot of torque. The car feels like it's got a big block in it...I was actually shifting around 2500 most of the time because there simply was no need to go any higher. 1st gear was useless but 2nd was good. The chassis still felt fine and the thing goes like a frikin rocket but wheel spin was a problem, particularly on cold or wet roads.

So somewhere between 350 crank hp and 550 crank hp blower motors (so high torque) you kind of cross the line and I had planned to add a traction control system. With a naturally aspirated engine the result would be different as the torque would be lower....I'm gussing 500 hp would be no problem fro a naturally aspirated high reving engine like a 3.0 or 3.6

 

The answer to the question about whether the drivetrain can handle 400hp or not is not a yes or no answer. It depends on the manner of driving, specifically, how hard, and how often, the car is going to be launched at WOT. If you do a bunch of drop clutch burn outs then many transaxles will eventually break with just the stock hp/tq. If you're a little more civilized with the clutch then you should be able to put quite a bit more hp/tq through it without damage. Style matters here.

The 308 transaxle is pretty robust and should be able to handle 400hp fairly reliably provided it's not abused with a bunch of WOT drop clutch starts.

There's no way to get anywhere near 400hp out of the 308 motor without forced induction of some kind.

If you do have 400hp and you're really getting on it then yes, the standard 308 brakes could use an upgrade. You'll start to get a soft pedal after a few laps if you're using all of those 400hp.

As to getting the hp/tq to the ground, the LSD in my 308 has a very light breakaway setting - perhaps it's just worn, or worn out! 400hp/tq will require a much higher break away setting.

 

All true. If the wheels lock, you have enough brake, you need more rubber. But can you do it repeatedly? Overheat the brakes and you have nothing. Bigger brakes are just better at repeat braking.

 

mk e you have different rear rims and what size tyres ? I think your car is a GTS which is encouraging . As it seems to have handled 500 + Hp without to much issue ( twist / flex )?
So this is where I'm at ! I am busy building my std motor ( slightly tweeked ) and hope to get somewhere between 250 and 270 crank HP . My car will always have the most value in it's original state with the original drysump 2V carb motor . But I want it to have a bit more poke !! Early on I realised getting reasonable NA HP out of a 2V motor was going to be expensive , not much torque and possible unreliable !
So my idea is to have a complete separate high output motor ! But what Hp gives the best balance ? Carubo's stealth 3,5 QV motor look's interesting with 300 Hp and a nice flat torque curve . Then there is Russ's 320 Hp 3.2 QV carb . Finally , Nick's very extensive 3.5 2V motor at 350 Hp . From what I understand none of these are going to push the chassis to hard . So 400 Hp is not outrageous !!
I have a couple of options available to me . Having bought a burnt 360 motor . I have the crank , pistons/liners and possibly the heads . So could build a 3.2 motor with the 3.0 71mm ( stroke ) crank and the 85mm bore . Then try and see whether the 360 heads could be fitted ??
The next option is to see whether the 360 crank can be used ?? The 360's block deck has a couple of extra mm added to it so I'm not sure if this could be made to work ??
Finally I could just try and adapt a complete 360 motor onto a 308 box ( which was my original idea )
Should be able to get 380 + Hp out of that !!! which by the sounds of things will not be to much for the chassis .
Thanks for all the reply's

 

It's very hard for me to believe that a drivetrain designed for around 200 RWHP can handle anything close to some of RWHP figures that are being posted here. Sure, you can "baby" a Prius into handling 700HP if you wanted to go to the effort but you don't REALLY have a 700HP car if you can't use the power without worrying about breaking parts.

So if you can't dump the clutch and blast away or if you can't downshift at any point and WOT it, then having all that HP is essentially "artificial." I'm not saying that you should do dragstrip launches at every light but if you CAN"T do them occasionally without worrying about breakage or the clutch just slips, it's a total waste of money. Balance is the key.

OTOH, I readily admit that I don't know jack about the actual "design limit" of the 3x8 drivetrain. I suppose it is possible that the drivetrain is robust enough to handle a lot more HP and maybe the clutch is very mild to provide an easy pedal since there isn't actually much power available as delivered. Has anybody just increased power until something broke? Of course that sort of info is readily available for old US cars because there are so many of them. But I would think that even though there aren't that many 3x8s in the real scheme of things, there are at least a few race/track cars around, there might be some good data unless most folks essentially track them stock.

Also...I'm assuming that the HP figures being quoted are actual HP as determined by a dyno or some sort of measurement (1/4 mile traps speed, etc), and not just "It feels really fast so it must be at least 400 HP!" That seems a pretty common statement by just making the exhaust louder!

 

I agree with you entirely re the gearbox . I think the limiting factor is traction . For sure the clutch will need an upgrade . But as soon as the rear wheel break loose you are taking the load off the gearbox components . So as long as you are not running some gumball drag slick the box should be ok !!! That's why I'm keen to know what size tyres mk e is running .

 

In my Koenig 308 with 400 bhp, they upgraded the Clutch, Turbo pistongs, Brakes, Longer 5:th gear. The rest of the engine and drivetrain is orginal. In my old 308 qv euro I could feel the front very light in speeds over 200 Km/H. But the wider Koeing kitt and wheels makes it stable and very nice to handle in speeds 250 km/h and over.

BR // Mr_Sweden

 

Some figurs for you with my Koenig 308.

0-100 Km/h 5,1 seconds
Top speed, I have only tried 270 km/h

// MrSweden

 

MrSweden what size rear tyre and rims do you run ? Any idea on what kind of torque your motor makes ?

 

And is that max power 400 BHP at the rear wheels or at the flywheel (which would be around 330 HP at the rear wheels - still WAAAY more than stock.)

Also, how do you drive the car? Are you aggressive or easy on it? As I noted earlier, you could have 700 HP but if you never apply it in high-torque load situations, then there isn't really much stress on anything. But since you posted a 0-62 time, I guess you do drive it aggressively on occasion!

 

I’m running 285s on the back….and trying to figure out how to go bigger. My wheels are 10.5” so they will easily handle 305 or maybe bigger tires if I can fit them under the fenders.

 

I can assure you that I no one ever accused me of being gentle on my car…I ended up installing a tilton 7.25” triple disc carbon-carbon clutch to stand up to my drop the clutch habit. The trans seemed pretty bullet proof at 550 crank hp and I hope it won’t be more than another year until I find out how it handles 800crank hp

 

Well that's pretty darned impressive - obviously the Ferrari drivetrain is considerably overbuilt for the stock engine output.

 

As you know, the Ferrari 308 transaxle/engine unit was used in rally racing under the most gruelling of circumstances, and it was raced at Le Mans and other venues. I don't think there is much we can throw at it that is going to be much worse than that.