I have a 69 with 454,409hp,T-400,3.08 gears and 27.5" tall tires.I would like a lower gear, but I don't know how much RPM's I should be running on interstate at say 70 mph.The motor falls off at 5300 RPM's.How much RPM's are to much at this speed,3500,3000? what are your cars running at 70 mph?

I have 3.42 gears, and with a TH350 and 215-70R14 tires, I was spinning nearly 4000rpms at 80mph in traffic. I hated it. Taller tires would have helped, but I eventually went with an overdrive transmission. With no overdrive, 3.08 sounds like a nice compromise to me. But really, it all comes down to personal preference. Before this thread is completed, someone will tell you they run 4.11's on the interstate with no overdrive and they love it.

What can you live with, and do you want extra wear and tear? I run 4.11's and they are great in town, but even with a 28" tire, they have me spinning at 3K RPM at 60 MPH. I try to avoid the highway with them, but have done it on occasion. I love the kick in the ass though, so I'll live with them. smile.gif It's funny, but every time I drive the car, I keep waiting for it to shift into 4th, and it never happens :D Overdrive spoiled me in my other cars.

EDIT: with your current gears and a 700R4, you'd still have a very low 1st gear making your car launch like it had 3.73's, while improving final drive to be like having 2.56's or so. Just something to consider

I had 3.42's in my truck. 454 with th400, it did about the same as the fella above, about 4000 at 80, and around 3000/3200 at 60/65. It was ok for get up and go, but annoying on a long trip. I put the motor in my wagon with 3.08's and i like it better already, although I have not driven much yet. It still gets up and goes, but now i can cruise somewhat comfortably. i have a blower though so it kinda helps with the gears.

On a 454 that is set to spin to 5300, 3:31's are the most I would go with. I have usually used a relative comparison of engine rpm max operating range to gear ratio:
4800-5000 RPM 3:08 rear
5500 RPM 3:31 rear
5500-5800 RPM 3:55 rear
6000 RPM 3:73 rear
6500 RPM 4:10 rear
7000 RPM 4:56 rear

This is of course just a ballpark starting point for non overdrive trans and a 27-28" tall tire. For the most part though, these are pretty close to what the factory did when the cars were new.

Thats why I love my 2.73's..I'll take the ET loss for a very mild street driven car.
2300 rpms and I'm cruising at 60 MPH..when I cross the stripe at the track,I'm at 4100 doing a hair over 103..around town,1500 rpms idling I'm doing 40 MPH..best thing is,I get to harass people who's cars have alot more gear than me and more times than not,they're usually a little slower than me,or a little faster than me at the track..it's even worse when they're alot slower than me :D and I get to do outrageously,long stupid burnouts with those gears too ;) ..ever try to keep up with a car that runs low 13's with 2.73's on the highway when you got 4.10's? :D
But seriously,3.31's w/a big block are the limit in my book for sensible street cars that are planned to be driven quite a bit,unless you have an overdrive trans.

I have 3.55s in the Lemans, and that's plenty annoying on the fwy if you're used to a modern car with an OD trans. Wish I could have found me a set of 3.31s....

That all depends on the individual.

I ran a 454 that is shifted around 6500 rpms and I run 4.30 gears with 29" tall tires. It sounds like a lot, but believe it or not it is not that bad on the interstate. At 60 mph, the motor turns between 2900-3000 rpm's. At 65 its about 3200. At 3200, the engine seems to run real good. It seems to be a "sweet spot" were it just cruises right along and doesn't seem to "strain" or being pushed to hard.

I think the fact that I'm using 29" tires helps along with the fact that it is a manual transmission (NO torque converter slippage).

I don't drive real long distances on the interstate, usually an hour at the most and I keep the speed under 65.

I was even thinking about driving it down to CB'04 this year! graemlins/beers.gif

That is weird about those bbc. mine has that same spot. It's like it's an airplane just flying along, but then with the touch of the pedal it's in burner.

Darren,
What tire are you running that is 29" tall? Do you have any pics of the car with that setup?

Funny that this topic should come up. I'm pulling my 12 bolt@4.11's to put in a 10 bolt with 3.08. I've got 29.6" tall BFG's. Highway cruise was 3400 rpm to keep in the flow (60 mph). Can't wait to cruise extended trips! :D

Once again, Mr. Newby was right!

I think 3.31's and a 28" tire are max for me. As you know, I don't hesitate running a 5-10 hour trip for some bench racing! And on long hauls, well,55 isn't the number. 3000 rpm cruise is around 62. I'll bring it up to 3400 and let it run for a few hours....

Also have a 'modern' first gear of 3.04. Could use a bit more. Can't have too much gear in a stick car I believe; the natural limit is how fast you can pull the stick and what you want to be spinning at crossing the stripe.

Originally posted by chevywidow:
I'm pulling my 12 bolt@4.11's to put in a 10 bolt with 3.08. I've got 29.6" tall BFG's. Highway cruise was 3400 rpm to keep in the flow (60 mph). Can't wait to cruise extended trips! :D ??? I have 27" tall BFG's (275-60-15) with 4.10's and my 60MPH RPM's are only 3000. How can you be 400 RPM faster with 2" taller tires?

Darren,
What tire are you running that is 29" tall? Do you have any pics of the car with that setup?

Jim,

I am running a set of M/T Sportsman Pros (29x12.5) on a set of Weld Draglites (15x10, 5.5" BS). I had a pair of M/T ET Streets (28x12.5) that I had been running for a couple of years but they were not wearing so well and I wanted to save them for when I go racing.

I was looking for the tallest tire with around 10" tread width, full tread in case I got caught in the rain, that would still hook "fairly well" on the street. I thought about the BFG Drag radials (the one that is 29.6" tall) but I didn't think they would do very well in the wet.

I was also wanting to take a little gear out of the car and I thought it would be better to do that by using taller tires than higher gears.

My plans were to make it a little more live-able (streetable) on the road so I could take it to Nashville (CB04) this summer. As it turns out, I don't think I will be able to make anyway. :(

As far as pictures go, I need to purchase a digital camera so I can post some pictures. Hopefully will have one soon.

I once ran a V8 Vega with 4.11's and short tires (I can't remember the size). I was running 4000+ rpm on the highway all the time, and it never bothered me.

Now I'm running a 700R4 with 3.55 gears and 26.5" tires. Right at 2000 at 70. I like that too, but it's much more fun running in 3rd gear at ~3000. Still doesn't bother me a bit.

So it's definitely a personal preference thing. I love the sound of a revved up engine.

Speedo calibration no doubt Jim. I ASSUMED I had 3.55s by running alongside my wife's new car at 55, registering the rpms, measuring a tire and solving for X. I was told 3.31.

Well, X was really 3.31, but I had already picked up the speedo gears for 3,55 and 28" tires. Now, the tires are really 27.5, but still, my speedo is a bit off. At least I know how much and which way. Unless gears are checked to ensure they are corect ofr the gear/tire dia, how do you know the speedo is even right?

Oddly enough, with my slight miscalculation, when the local fuzz set up the unmanned Explorer with the mph readout, my speedo is spot on. ??? I even asked the dispatcher who lives across the street when it'd be out, so I could check it again. Spot on. But thats at 27-33 mph. I'd like to see 55-60 mph.

Now there's a cool deal. Jim, can an officer 'borrow' a speed gun? I know you can buy the things, but it'd be cool to check a bunch of cars at once. All passing by at say , at least 50, to be fast enough to show error. Hmm, maybe we'll include a speedo check in one of our cruise events!

26" tire with 3.23's was one of my favourite combinations. Would equal roughly a 3.42 with your 28" tires.

I have 3.73's with a 14" Rim and a 26" tire in my 67ss L78, 60mph at 2700 rpm. The 66ss 360hp I'm doing now has 4.10's 60mph would be 3000 rpm. I'm dating myself on this one but when I was in the navy in the late 60's I did a lot of street racing in Va Beach VA. At the time had a 67 302 Camaro which I ran as low as 5.13's on the street. Sold that and ordered a 69 L78 nova that had 4.56's. Both cars were 4 speeds. Wouldn't think of doing that today. The street racing that is.

I have 4.10 gears, a Muncie 4 speed and 25.6" tall 14" tires. I get used to running about 3200rpm on the highway and still love it around town (if you are hard core and have another car like me). The farthest highway trip was about 4 hours to Ocean City Maryland and the annual trip to Wildwood, NJ that is about 2 hours. It all depends what you want. I liked the 4.10's better on the small block on the highway than with my big block. I would probably do 3.73's or 3.55's with a 454.

Bob, I can't wait to try the 4.10's in my 66.

Hey BBBadboy here THANKS for all the input.Sounds like I'll have to get it out on the road,pull it down in 2nd gear and hear what it sounds like at different RPM's 2800,3000,3500.I'll see what the car likes and what I could live with.

My 454 powered ragtop has one of those sweet spots just crusing at 65mph. I'm turning just a tick over 3,500rpm with my turbo 400 and 4.00 rear gear. graemlins/thumbsup.gif

I had 5.13's with a 32" tall tire and a 5500 stall converter w/PG trans in my prostreet nova,and at about 50 mph,I was hitting about 3100 rpms.

I had 3.73's with 26" tires and it was terrible on the highway at 60. I switched to 28" tires and still not good watching everyone cruise by me.

I am now in the process of switching my 3.73's to 3.42's. in hopes of keeping up with traffic and being able to hear myself think.

bill

Just to reply to Jim's question about our different rpm ranges. I have BFG rating the 275-60-15's @ 28" dia. Goes to show you that a 4 gear is more efficient than a 3500 stall convertor! graemlins/waving.gif

Originally posted by chevywidow:
Just to reply to Jim's question about our different rpm ranges. I have BFG rating the 275-60-15's @ 28" dia. Goes to show you that a 4 gear is more efficient than a 3500 stall convertor! graemlins/waving.gif Aaahhhh, I wasn't thinking about an automatic with convertor slippage. You are correct.

I run an early 27 spline 700r4( supposed to be weaker than the 30 spline) with a Buick GN converter. The 200r4 converters will fit the early 700's. I run a 26" tire with 3.73's. The final drive works out to 2.61. With the lockup engaged it Idles at 60mph = 2024 RPMs. I have abused this tranny at the track for about 5 years running high 11's low 12's in a 3900lb car. One of the tracks I run is about 80 miles each way on the interstate. The looks on some peoples face as you cruise along at 75-80mph in an old muscle car is priceless. My vote is for modern overdrive, no need to compromise.

For comparison, the '95 Z28 we had, ran 3:73's. I used to run that down the highway in 3rd all the time, it never seemd to be that annoying. I think the 3.76" stroke motors are much more forgiving in terms of running at highway RPM with a bigger gear. This is probably one of those scenarios when the added rod ratio plays in. Another big issue in highway engine cruising is how well balanced the engine is. A drag race is much more forgiving of an engine that is out of balance than a motor running down the highway at 3000 RPM+.

im running 255/60/15s with 3.23 and am about 2500+/- at 60mph

At the moment,I'm running a 3.50 rear cog in my 69 El Camino with 26" tires and Viper T56. At 70mph in 6th,it's only spinning around 1,750rpm. Per my figures,a 4.30 cog will raise that to around 2,100rpm. Cool,huh.