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Old 08-21-2004, 10:36 PM
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top speed improvement?

im am wondering how i could get a better top end speed without loosing the power off the line? car is quick off the line right now and gets up to top speed pretty quick but then the rpm's get up around 4,5000 and go alittle bit higher and it seems like it should be shifting into another gear or something but its not there. its an automatic 350 turbo trans i dont know much more about the other stuff. i was thinking that maybe if i retarded the timing it would top out higher but then i would loose off the line speed.

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Old 08-21-2004, 11:08 PM
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Maybe your valvesprings are old.

You didn't really give us enough info to answer that question. What is your engine combo?
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Old 08-21-2004, 11:12 PM
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it almost sounds like you're running out of distributor or your gears are just to low but i can't amagine thats the problem.what kind of motor do you have ,rear gear and such.need more info
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Old 08-21-2004, 11:30 PM
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Yes, everyone might hate the thought

BUT! Go to a 200C and you will be able to run 3.08's or 2.73's and still have about the same amount of pulling power thanks to the 200's higher ratio 1st and 2nd gear.

OR Go to a 200-4R or 700-4R. Told ya, three speeds are really getting to be a thing of the past.

As far as not being able to get over 4500RPM, well... What heads, what type of dist, what type of cam and duration? Is everything good mechanicaly? All these are important to know in helping find you a possible answer.
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Old 08-22-2004, 12:03 AM
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Don't run a 200-4r metric,only thing you'll be running,is back to a tranny shop.IMO those are the worst GM trannys on the planet I've blown 4 so far behind stock engines.Everyone I know thats ever had them blew um up. If you want OD get a 700r4
Anyway need more info on your combo.
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Old 08-22-2004, 12:11 AM
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the distance is like 3 miles or so i dont know but the motor is a 350 carburated the rear end has 3.73 gears but like i said it only takes like 2 miles or like 1 in a half and the car is topped out at about 120mph it gets to top speed really quick but then it stops at like 4,5000 rpms it might keep going but 5,5000rpms is my redline so i dont want to blow the motor. could an exuast leak at the headers be a problem its not much but i feel alittle air from it when i rev it?
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Old 08-22-2004, 12:15 PM
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Now are you seeing the problem with 3 speeds?

And you tell that to any GN owner 78 monte, see how fast they try to throw something at you.

Go with a 200-4R and you can keep your 3.73... unless around 160MPH is too slow for you?
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Old 08-22-2004, 05:07 PM
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Olds442lover the top speed of most cars isn't dictated by the redline as you are indicating. The top speed has many factors that infuence it and gearing is only one of them, wind resistance is one of the biggest factors.
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Old 08-22-2004, 05:29 PM
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Robinson Robin
That sounds similar to a problem I had before. The problem on mine was I couldnt get a high enough air cleaner on the carb to clear the choke body because off stock hood clearance. Look and see if the top of the air cleaner is really close to the choke. If it is try pulling it off one time and see how it runs. If its a holley you might need to put a taller air cleaner on or cut the choke body off. My car would run into a wall at 5000 rpm. When I tried it without the air cleaner to check it , I couldnt believe the difference.
Kevin
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Old 08-22-2004, 07:21 PM
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Quote:
Originally posted by Robinson Robin
Olds442lover the top speed of most cars isn't dictated by the redline as you are indicating. The top speed has many factors that infuence it and gearing is only one of them, wind resistance is one of the biggest factors.
All right, I'm going to TRY and be nice here, I wont say that was a stupid statement or anything, but...

Yes I know that robinson, but a 5MPH increase in top speed by reducing drag, or freeing up some HP is not the answer to get you past 120, that would just get you to 125, right?

The ONLY REAL answer would be to lower the gear ratio, swap out tires for some bigger ones, or replace the transmission with an OD trans. THee unreal answers are do extreme things to an engine to get it's redline up further, or worrying about drag. I mean my uncle has his 512ci 64 chevy that goes 145MPH in the 1/4 mile at near 10,000RPMs. But then he can't use that as a daily driver now can he??? His trans is a powerglide 2 speed and 4.10's in the rear(I think).

So, once again, the only real option is to throw out the TH350 and go with an OD trans, wether it be a 700-4R, 200-4R, 4L60, 4L80 is up to you, but you need to ditch the 350 if you really want top end speed with out losing the low end side. Of course I sure there is someone out there that can custom build ya a 350 or other 3-speeds with an OD 3rd gear(below 1:1), but I'm just guessing on that one.

So long as you have got the power, dont even give drag from wind resistance a second look! BRUTE FORCE!
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Old 08-22-2004, 09:26 PM
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Quote:
Originally posted by 87442lover
All right, I'm going to TRY and be nice here, I wont say that was a stupid statement or anything, but...

Yes I know that robinson, but a 5MPH increase in top speed by reducing drag, or freeing up some HP is not the answer to get you past 120, that would just get you to 125, right?

The ONLY REAL answer would be to lower the gear ratio, swap out tires for some bigger ones, or replace the transmission with an OD trans. THee unreal answers are do extreme things to an engine to get it's redline up further, or worrying about drag. I mean my uncle has his 512ci 64 chevy that goes 145MPH in the 1/4 mile at near 10,000RPMs. But then he can't use that as a daily driver now can he??? His trans is a powerglide 2 speed and 4.10's in the rear(I think).

So, once again, the only real option is to throw out the TH350 and go with an OD trans, wether it be a 700-4R, 200-4R, 4L60, 4L80 is up to you, but you need to ditch the 350 if you really want top end speed with out losing the low end side. Of course I sure there is someone out there that can custom build ya a 350 or other 3-speeds with an OD 3rd gear(below 1:1), but I'm just guessing on that one.

So long as you have got the power, dont even give drag from wind resistance a second look! BRUTE FORCE!
Ok I'm not even sure where to start here. First of all over drive or 4th gear in 200r4 and 700r4's is not made for full throttle top speed. Infact with the
exeption of some of the vette version a stock 700r4 will not allow full throttle in 4th. Most cars will be over come by wind resistance longs before they run out of rpm range in 1:1. Over drive is designed for loafing along on the highway. As for you comment about reducing drag giving you only 5mph obviously you have no idea how much wind drag effects top speed.
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Old 08-22-2004, 09:38 PM
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I have to agree with Robinson on this one. I do have a 4 speed tranny but if you don't have the power to get the car over 120 in what I assume would be the top of the power band 4500-5500 RPM you certainly will slow down in 4th when the RPM's are like 2500-3500. I think the issue here is more power or less wind. Let's be honest a mile and a half to reach 120 with 3.73 gears doesn't sound like a powerhouse to me.
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Old 08-22-2004, 11:15 PM
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Something doesn't add up here. I did some looking into this and have to assume that he already has a four speed tranny in the car. My math shows that in order for a car with 3.73 rear and the engine RPM at 4500 the tranny final drive would have to in the .75 neighborhood ( depending and converter slippage). Now if he does have a three speed tranny with a 1 to 1 ratio in the final drive I cannot understand how he could even hit 120 because at 117 he would be at 5500 RPM. ???????????
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Old 08-22-2004, 11:18 PM
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ok it wasnt really a mile in a half to reach 120 i dont really know but it didnt take that long since i just checked out the 1/4 mile and i was doing about 104-110 but thats an estamite since my speedometer only goes up to 85mph but when i checked out the top end speed i was accelerated slowly and just kept going to see how the gears went and how my rpms went. but 120 is the top end right now and wind resistance doesnt seem to be a problem im pretty sure this motor will bring me to speeds of 160 if not more if i had the gears. i just didnt know too much about trans gears and rear end gears since im new to much of this. so i see now that if i had smaller gears in my rear end i would reach greater speeds but be slower off the start, and if i had more gears in my trans the same could happen. my rear tires are 14 in rims and including the tires its about 19inches. the power right now is nice but i kinda wanted to reach speeds of 160 for a top end with out loosing any of the power off the line.
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Old 08-22-2004, 11:21 PM
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I don't think 160mph is a realistic goal but you might be able to make 130
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