Revving my 250 over 6500rpms!

[Anonymous]

Well, it's insane, i know, but I've done it on a few ocassions where i wanted to see if i could blow it up. i got this engine from a friend who had it in his 70 mustang coupe, and i did a 200 - 250 swap in my 68 mustang coupe. boy did it help tremendously to finally hear even the slightest tire peel outs. i'm not made fun of anymore because i can't peel out in a mustang my stang has a 3-speed auto tranny (C4) with a 2.83 rearend axle ratio. it takes off like it's scared to get a nose bleed, but i've actually had it up to about 115 on a straight stretch in highway in my hometown.

the reason that i'm telling you all this, is because i don't know if anyone hear has had the same luck with an old 250 motor. i'm always reading that someone is having trouble in the mid-range revs and cannot get it to rev high, but I've had this enigne since 1999 and it's been kinda fun driving with it. my car can hang off the line with only small 4-bangers like honda crx, etc, but i think he even had a quicker rearend gear than me, so my torque numbers aren't for nothing. i beat him by 6 car-lengths on the highway at about a 1/3 mile distance. the top end has an issue though...and i just don't want to cut off my lead foot just yet, so here's what i need help with. once i reach speeds of 100mph or more, the car starts to pulseate violently and it sounds like the engine is going to blow itself to hell and back. but i don't understand it because i can rev the engine in excess of 6500rpms in 1st and 2nd gear, but it only goes to about 4500rpms in 3rd before i hit 105mph. i would naturally think that it has something to do with the way each gear in the tranny is set apart from eachother, ratio-wise, but i'm still not sure. i don't know a lot about transmissions, but i do know that my 250 seems to not be able to blow up. it seems bullet-proof, (thanks to ford's 7 main bearing design) i just need to find out what is causing these violent pulsations through the car and how i can stop them from happening, without cutting off my foot just to let you know, my rearend is the small 7.5 inch that came with the 200 and it clunks into action when i have to go from drive to reverse and vice versa, so i know it's a little loose at the U-joint, and it slightly wiggles too. could this be the whole thing? or part of it? those little axles aren't meant to do the speeds that i've driven at

on a different note: my dad and i are talking about cuting off the intake log and fabricating a custom aluminum tube-type manifold to mount three 1bbl's or three 2bbl's. now my other question is: which setup would be better for low-end torque and which for high-end pull and what kind of setup would be recommended for short squirts of speed around town? my car can't seem to get outta its own way when i'm in the city, but it's great in the mid-range like the on-ramp...LOL

any and all help is greatly appreciated.

thanks

 

[CobraSix]

the vibrations probably has nothing to do with your engine and it's revability. It is probably a combination of factors. First, what rating are your tires? WHen is the last time they were balanced? Chances are what you are feeling is vibration in the wheels being transmitted through the drivetrain to the engine. Despite RPMs, you may be approaching the maximum speed of the car based on your engine output. This will change the way the engine feels, regardless of RPMs.

Good luck...glad to hear a 250 is holding up. No experience here with one though.

Slade

 

[rbohm]

8) our little sixes are hardt o kill. they take a bunch of abuse and ask for more, kind of like a marine or navy seal. as for your top end deal, its called aerodynamics. your mustang is a comparative brick at high speeds, so you need alot more power to get to and maintain speeds above 100. as for the, vibration problem, slade is right on. the tires likely need balancing.

 

[Anonymous]

I have run these engines for years and 4500 to 5000 is more realistic for RPM. I doubt that you are reaching 6500 with a stock motor. If you have points they may be bouncing or you are floating the valves. 6500 would be way past the HP and torque peaks aval. with the stock porting and cam and carb. The point bounce I have cured to some extent by using dual springs on the points. Cant rember who's but some MFG's the spring is removeable otheres are rivited and not as easy to modify.

 

[BIGREDRASA]

My guess would be either ignition cutting out, or carb float too low, or insufficient fuel pump output. You need to dump the points and go either Pertronix II or Duraspark. Make sure you have good plugs and wires. See what happens then.

 

[Anonymous]

My Uncle told me a story once about an old Falcon 6 they owned. They were going to take it to the tip but instead they wanted to see if they could blow up the engine. They put some weights on the accelerator pedal till it was right down until the engine was screaming for Mercy.
1,2,3,5,10 minutes latter the engine was still running. I dont know what happended in the end but from memory I think the only way they could destroy the old thing was to drain out all the oil and even that didnt work immediately.

 

[Anonymous]

WOW! posting to an old topic is bringing back memories of my recklessness in my old stang

Anyway, I stated in my first post up there, that I was having serious vibration issues at high speeds. someone told me to upgrade to an electronic ignition, but I'm already using a Crane Fireball II electronic ignition kit, with a very hot coil. My spark plugs are doing well, since last time i pulled them and checked. They have no carbon deposites and are clean looking on the electrodes. I haven't driven the car in about a year now, and it's currently parked in my Granddad's garage. One more drop of moisture and it'll fall apart, literally. Well, just to let you know, my floorpans have holes like Swish cheese, and I don't trust the car to hold up in rainy or snowy weather. It's too loose because of the old ragged suspension.

Well, my father and I are talking more about what we want to do to it, and we are deffinately going to put a more modern suspension underneath it...front and rear. We like the idea of a sleeper 6. It appeals to me, because I've seen so many sleeper V8's it makes me sick, not the mention all the loud mouth open exhaust cars that talk trash when they are revved. I'd like to do a complete Multiport Fuel Injection system on the US 250, with the US 250 head, and see what's possible. I'm an adventurer and I don't doubt that we can achieve 1 HP per cubic inch (250HP) with all the mods we're considering. I appreciate all of the advice about what head to use, and whatnot. It shows that you guys care. But like I said, I am looking for an adventure in this car, and using the very limited US block and head will make it all the more fun and merrier once it has small block performance.

Now, don't go flaming me because I'm dreaming, heck, it's fun to dream. And I believe I can do it too. I believe that most-any engine used today can achieve 1 HP per cube. plus, that's an ideal that seems to be just right for the street. I don't need a monster on the street, thought I admit that I've run the crap out of this car a few times, I still want a driver that will be at least semi-comfortable going to work in. I'm a young hot-head still, but I really have this ambition to go for it. Wish me the best, please. And thank you to all of the Ford Vets out there.

I also appreciate everyone's opinions and info on my other posts regarding MPFI on the US 250. I still like the SDS, but I've yet to research the Megasquirt. I'll do that now.

Thanks,
Biff

 

[mugsy]

Well....

Energy is one half times the mass times the square of the velocity. In plain English that means the energy to move your car at 100 mph is 4 TIMES as much at 50 mph. Remember, "life ain't linear". Then add wind resistance, short cam duration, possible fuel starvation (that's where the energy comes from in the first place) and you are well on your way to your answer.

As for your "shake" look at the suspension ball joints and loose steering linkage. And lastly the tires might be the source.

tanx,
Mugsy

 

[Anonymous]

AH! I forgot to mention. My steering has a lot of wiggle, so I won't be going that fast anymore anyway. I can drive down the street and when i apply the brakes, the car will pull to one side and my sterring system is so worn out that i have to forcefully pull (jerk) the wheel in the opposite direct to keep from running off the road or into someone. this car is dangerous. If you're in the Nashville, Tn area, watch out for a beater LT Green with tons of bondo and primer, 68 Mustang coupe

J/K, I haven't driven the car in a long time, but I deffinately will not until all of these issues are fixed correctly.

Thanks for the advice.

 

[jarb]

Im all for fun and even dieing for what i love to do the most, either driving fast ,fishing or ....well we all know the 3rd one, but dude fix your u joints and rear end ,pole vaulting would definately not be one of my choices. but just for kicks you could disconnect just 1 of your front brakes teah when at speed JAM the stop pedal and see how many 360's you can do thats reall the only true test of a mans testosterone concentration ..
HA HA hhave fun just be safe as possible about it we would all miss you

 

[BIGREDRASA]

Go for it!
One word of advice, make sure you can stop before you go fast, and I think you already know it. If you want to be safe, suspension and brakes must both be good. Many "brake" pulling problems are actually suspension probs.

 

[ludwig]

I have a vibration problem that cuts in at about 50 mph and disappears at about 60. When I decelerate (take foot off) it re-appears at somewhere in there and then goes away at 45 or more. Wheel problems or out of balance driveline? The engine is smooth all the way up when not in gear?

 

[Anonymous]

Ludwig:

Yeah, my problem is similar if not just like your's. I can rev my engine in upwards of 6500rpms or more sometimes and it never vibrates the same way that i described as when i was actually driving fast. the problem seems to be just exactly what these folks are saying. my suspension is COMPLETELY SHOT! i mean, it must have a complete rebuld of all control arms, ball joints and we're seriously going to put a modern type of aftermarket mustang suspension underneath it. I really love my car, but I value my life even more, so if i were to get into a situation where the older, worn out suspension failed on me, then I would be up the creek without a paddle. it would most-likely kill me or anyone else nearby if i was being reckless using the car like that in it's current condition. I said that I've spead to high speeds a few times, but I've learned my lesson from reading about the young man who was hit head-on by a sleepy driver while in his mustang. That young man was killed instantly, read about him on www.fordsixparts.com. It's very sad that he had to leave us so quickly and without warning, but I'm like the guy on the website said, "I feel lesser burdened because he didn't suffer." But he's still gone, and the spirit of his death seemed to reach out a grab me by the throat when i first read the story. Yes, I still want to go fast, but I believe I'll save it for the track from now on. You'll be fortunate to learn from his destiny too.

Just be careful in these old cars. They are not up to parr with todays safety standards, and could get you hurt or killed very quickly.

Another time, I was racing my co-worker in the rain (I was 18 and a dumbass then) and i did a complete 360 in the length of 100 yards with an oncoming car who swirved at the last instant and BARELY missed me. I was scared, but I drove home, and then freaked out about it. I was in shock. It just didn't affect me until I told good ole mom and dad. They told me even before that day, that i should exercise caution while in my car. Dad said it was dangerous to drive, and I didn't listen. I might not have been here to tell you if that man would've kept going straight. He was aimed directly at my door, when I slid around and i would have been nailed in the door, and killed. I want to take a moment to thank the Lord for his protection, and I pray for all of the hot-heads here to DRIVE WITH CARE AND BE CURTIOUS TO OTHER DRIVERS. Let them pass you, and NOT vice-versa. I used to get nervous when people would ride my tail, and it made me want to speed up and leave them in the dust, but when i tried they stayed right behind me anyway. Please don't speed up to leave them, just go the speed limit and don't keep looking in the rear view mirror at them. It'll just make you more upset and you'll be inclined to do what I did.

I'm way off topic, but I felt it was needed to say something helpful to the community about safe driving habits. And YES, make them HABITS. Practice them ALWAYS. Remember, you're life cannot be replaced, you're car can.

Sincerely,
Biff

 

[ludwig]

Believe me, most of my dumb@ss driving moves are behind me at the start of my second half century. Plus, my suspension, brakes and tires are all new. The only problem is this stupid vibration at 50 or so (not me, the car).

 

[Anonymous]

but just for kicks you could disconnect just 1 of your front brakes teah when at speed JAM the stop pedal and see how many 360's you can do thats reall the only true test of a mans testosterone concentration ..

do it in the rain...better results!!

 

[Anonymous]

LOL

 

[Anonymous]

anyone know what the RPMs would be for the 250 in first gear at around 60 mph??? cause yea...i did that...and it sounded like i could go even faster in first....but just cause it doesnt sound too high doesnt mean that its not...it was fun though...but will only do that if i have purpose to speed...