How does an engine make a car unstreetable?

[Cannoball888]

I'll be shopping for a new engine next year for my '65. I want max horsepower and so I'm even considering a blown stroker. But is there a limit as to how much horsepower I can have before the car isn't streetable? What makes a car unstreetable, is it traction problems?

 

[302 coupe]

if you have an engine that makes 600hp, but you can only use 400 of it, why not just build a 400hp engine. How much power do you need for street driving?

 

[1320stang]

Well, I know a guy in Georgia that can build you a twin turbo'd SBF that'll put out around 2500HP. But it'll get crappy milage, requires constant maintenance, you'll have to upgrade chassis, suspension, fuel system, drivetrain, etc. The engine and turbos will probably set you back about $60k.

Streetable varies from person to person. To me, 4 mpg is unstreetable, especially when you have to run higher octane gas or AV gas, heck 14 mpg is unstreetable for me. My dad used to have a 4x4 Pinto that sat on 40" Ground Hawgs on a stretched early bronco chassis. It was a station wagon that had been converted to a Ranchero type bed, hence the name Pinchero. It was some toy someone built and my dad was the 3rd owner, he used it as a parade vehicle, it was street legal, but only had a top speed of about 60mph because of the mud bog gearing and when you got it up to 60 mph, the dam thing was all over the road because of the ballon type tires and ruts in the pavement. It was hella fun to drive as I could scratch all 4 tires in 4 of the available 6 gears (3-speed manual & 2-speed transfer case).

 

[CarFreakGT]

As a GENERAL (please note that I said GENERAL) rule of thumb, increased HP = increased maintenance/decreased reliability and repairs that cost more $. It's a matter of tolerance for each individual as to what is a proper balance between working on it and actually getting to go out and enjoy it.

Good luck on your decision!

 

[1320stang]

That's a great statement CFGT!

 

[Cannoball888]

Thanks for the replies guys. So, aside from mpg, cost, and maintainance, is there a general horsepower limit which if exceeded a car wil have traction and driveability problems?

 

[Max Power]

It's not really a traction issue, the gas pedal is not an on/off switch. Driveability is a BIG factor. Higher performance engines usually have lower vacuum, poor mileage, and make their power in the upper bands of the rpm range.

If you build an engine with an emphasis on torque rather than horsepower, you can avoid a lot of driveability problems, within reason.

 

[iskwezm]

I know plenty of guys with 600-900 HP cars that are streetable, meaning able to drive in traffic and cruises. Now I wouldnt take it across county, due to wear and tear, but they would probably do fine.

Im not saying mine is a fully built combo, but its a blown stroker, the only thing thats makes mine unstreetable to me is it liked to run warm.Im taking care of the cam issue, which was a mistake from the beginning, after that it should be just as tame, and probably hit over 600 on the dyno.

 

[CarFreakGT]

Thanks for the replies guys. So, aside from mpg, cost, and maintainance, is there a general horsepower limit which if exceeded a car wil have traction and driveability problems?

There is no way to give a 'hard & fast' number to use as a limit for streetable HP, or torque, for that matter. Driveability is contributed to by your induction system, power curve, etc. There are too many factors to try to set an arbitrary limit for your engine. Remember, it's only one component of the car. You could have a 150-HP turd, or a 400+-HP race car, and they could both handle and/or drive like s**t.

With regards to traction, keep in mind that you're talking about a 41-y.o car. The handling and driving characteristics of these cars weren't spectacular off the showroom floor, much less after four decades of wear and tear. Whatever you decide to do for your engine combo, make sure that your suspension, brakes, and other components complement them. You don't want to try to stop a 500-HP beast w/ crappy drum brakes. And no matter what your HP numbers are, you won't be able to use that power if you can't hold the ground at take-off, around turns, or when you try to stop. It's not just a 'total package' issue, it is a SAFETY issue. This is why you will see so many people preaching to 'have a solid foundation under your car.'

I apologize, cannonball, as I'm not familiar w/ the set-up on your car (suspension, brakes, etc.). You may have already addressed those safety issues. If you haven't, I would consider looking at those things first before you get too far into the engine. If you don't, you won't be able to use your power on the road or the track anyway.

This is all IMHO, but I hope it helps anyway. Best of luck, and have fun!

 

[chepsk8]

In the Cobra arena, this also is a constant debate. So many build big motors, but can only use a small amount of it. I always reccommend going conservative, you can always upgrade later.

My Cobra is running a basically staock 5.0, not the fastest Cobra on the street, but a well-balanced and very racy car on the track, where It really shines!

The real bottom line is what are you building the car for? Street, drags, road course, or just having the biggest driver in the golf bag?

 

[70vert]

"Streetable" = driving in traffic with no safety issues?

We need to define what "streetable" means - I always thought it was, very simply, "can you drive this thing in traffic and not have it stall, get away from you with unpredictable bursts of power, have enough vacuum to run power brakes if need be, not overheat in stop and go traffic, etc." A manual trans just exacerbates any rough running condition, and flywheel plays a big part too.

To my limited knowledge, of course engine choice, intake and carb, cam, flywheel choice, trans choice, rear gear choice, as well as clutch type if used with a manual, fan type, and accessories on the engine, all these make a difference. And this is just to define STRICTLY if it can be used in stop and go traffic with no issues. Not even talking about reliability or "daily driver" questions yet.

I can tell you this so far - taking a 35 year old 100k 302-2v that only has rebuilt heads and putting on an AL flywheel, 5-speed OD tranny, and opening up the restrictive exhaust to a 2.5" Magnaflow kit and keeping 2.79 original gears will yield you . . . a car that sometimes takes double-clutching to start up (AL flywheel), runs a little rough and burbles on decel (too much exhaust, not enough intake), and either wants to GO or stop. (AL flywheel and big exhaust play a big part here) My car is happiest at WOT starting at about 15mph. And boy does it sound great at WOT when it starts to rev. I am probably gonna kill that little 302.

I probably have the 150-hp turd, as polished as it can be.

I'm in the "solid foundation" camp - did brakes, tranny, subframes, suspension first (look at .sig) and I will do the rear end before the engine goes in. 408 stroker that will be as "streetable" as possible in the 400-500hp range with a 9 compression or so so that if I go crazy and supercharge it, I can.

 

[CarFreakGT]

In the Cobra arena, this also is a constant debate. So many build big motors, but can only use a small amount of it. I always reccommend going conservative, you can always upgrade later. My Cobra is running a basically staock 5.0, not the fastest Cobra on the street, but a well-balanced and very racy car on the track, where It really shines!

Sorry, I'm OT w/ this question , but your comment got me thinking, chepsk8. It seems that I read recently in a search that this is why the 289 Cobra was regarded as better for (road) racing than the 427. Is that the general perception among those w/ Cobras?

(Sorry, cannonball. I'll stay on-topic now. )

 

[Cannoball888]

We need to define what "streetable" means - I always thought it was, very simply, "can you drive this thing in traffic and not have it stall, get away from you with unpredictable bursts of power, have enough vacuum to run power brakes if need be, not overheat in stop and go traffic, etc." A manual trans just exacerbates any rough running condition, and flywheel plays a big part too.

I'm in the "solid foundation" camp - did brakes, tranny, subframes, suspension first (look at .sig) and I will do the rear end before the engine goes in. 408 stroker that will be as "streetable" as possible in the 400-500hp range with a 9 compression or so so that if I go crazy and supercharge it, I can.

My definition of "streetable is similar to yours. I also have been thinking of getting a 408 stroker for next year and have even been playing with the idea of blowing it, but that may be too much for a street car, hence my original question.

 

[10secgoal]

It's easier with a bigger motor to be streetable. 500 hp is easier from a 408 with nice heads and cam. Rather than a real 302 with a nsty cam and huge heads, revving it to 8k. But bigger motors use more gas. I thik MPG does have a small role. But I do think 15 mpg is OK. If you want blown, a 302 will do nicley. You can make a 302 useless on the street. It takes about 7psi with good heads.

 

[allcarfan]

1320...who in GA can build that engine? Just curious.

As everyone else has said...streetable is a relative term. Has anyone seen the video of the 1000+rwhp saleen on the street? every time the guy touches the gas it loses traction...ie...not streetable IMO. My 90 GT made 624.7 rwhp...it was not even remotely fun on the street. If you are building a race car, build a race car to run on the track. If you are building a street car, build a street car. It is a lot easier to run a street car at the track than a track car on the street. If you dont intend on racing the car at all.....why build a 4-5-600hp engine? You would never use it.

On top of everything....the engine doesnt necessarily make the car streetable or not streetable. Id rather make 350hp at the wheels and be able to launch in a straight line and use every ounce of HP and run in the 12s than build a 500hp motor, worry about something breaking, upgrade everything, spin like a mad man...and....run 12s (hey, that kind of reminds me of the supra guys)

 

[BullittStangV8]

I think im going the other way then allot of you guys are. To me, I'm building my car to be as fast as I can afford, but still be street legal. I KNOW its going to be a pain to crawl in over a 8 point cage into racing seats, and to snap into a 5 point harness all the time, but to me, its worth it to have a street legal drag set up car. The motor will idle just fine, but it will have a "lumpy" cam, and it wont have power breaks/steering/AC. So unstreetable would be a fully gutted out racecar. I'm personally OK with the car being "brutal" or "raw". Infact, I like that aspect of it. To me, it embrasses what musclecars era was all about.

 

[chepsk8]

Back to the question posed before, the 289 Cobras actually ran faster lap times that the 427's! That's why they never got the same results or glory of the 289's. Had to do with better corner speeds, speed of entry, and all that great road racing stuff!

 

[thehueypilot]

You could look at it another way.....driving around in the family sadan you can do a lot of stupid things and get away with it because the car is more forgiving. Throw a lot of HP to it and drive stupid and it could kill you or someone else. Case in point I drove my 68 Mustang to work last year and on the way home it started to rain. I was on the interstate and someone was going super slow so I nailed it to go around and with the higher HP and locker rear end the I almost lost control without even thinking about it. It is a lot less forgiving.

 

[86bluecobra]

The answer for me is quite simple. If the engine over heats in stop and go traffic it is no longer streetable. If the engine does not produce enough vaccuum to supply Power assisted brakes it is starting to become unstreetable. If it is so loud you are getting fines it is unstreetable.

 

[CarFreakGT]

Personally, I'm OK w/ all of your opinions--AS LONG AS THE CAR IS SAFE for you and for everyone else on the road. That's why I love these old cars. There are SO many different ideas that people have w/ them. But, hey, if your car gets away from you when you feather the gas, then you d**n well better have some self-control. Be bold, have fun, but be responsible, too.

Good point about the forgiveness factor, huey.

Thanks for the reply to my OT question, chepsk8. I thought I had read that recently. Good for perspective.