cruising rpm

[SMA390]

Just curious, When I cruise on the highway my galaxie turns 4000 at 70mph..This is a bone stock 352 no mods what so ever.
How long at that sustained rpm before damage might occur  in idea conditions, good oil pressure normal operating temps ? The motor runs perfect no issues and has about 9000 miles on it. How long would you feel comfortable driving at that rpm for a cross country trip? The car / engine is meticulously maintained

[machoneman]

That is a LOT of rpm's for sure! I'd feel comfortable at that rpm for a cross country trip for about 1 hour! No kidding! What the heck is your gas consumption? Also, are those 9K miles all highway? 50% city/local? If your highway driving is rare, your current rpms in that city/local driving may be just fine as I doubt you even approach 4,000 rpm in stoplight-to-stoplight driving. 

No doubt elevate rpms will wear out that engine sooner, much sooner than one where highway rpms are well below say 3,000 rpm. Heck, the closer one gets to even say 2,000-2,300 rpm the better. 

 

[cjshaker]

Cross country? At 4000 RPMs? I don't believe I'd even try it. My jaw would be hurting from clenching my teeth the whole way. Sounds like a very worthwhile investment to be changing some gears before that trip! And it'd be cheaper than an engine rebuild afterwards

Seriously though (although I was being serious), if the engine is in great shape, it'd probably survive, but a little worse for wear. Or a lot worse for wear. That's a lot of sustained RPM. I'd be doing something to get that down, like bigger wheels/tires, gearing or something.

[babybolt]

Engine oil temperature would probably peak out and destroy the oil.

That's why Ford put the oil coolers on the Boss and Dragpak cars, and "modern" trucks with tow packages get oil coolers - usually these days its a water (antifreeze) to oil cooler.

[MRadke]

What year galaxie, what transmission and what gear ratio in the rear end?  My 66 cruises at 70 mph at @ 3000 RPM with the cruisomatic and a 3.0 rear.

[cleandan]

SMA390, please tell us a little about your car. Also tell us what you want your car to do for 95% of its normal use.
I am with everyone else so far. 4000RPM is a lot of rpm for sustained driving.
Even if everything is operating at optimum levels, 4000 rpm just turns things more and this more causes more wear and tear.

As asked already some specs of your car would be helpful for us to get a better mental picture of what you have.
Engine, transmission, rear end gearing, rear tire diameter...tire size if that is all you have.

Thank and have a great day.

[SMA390]

This was just purely a  HYPOTHETICAL question..the car has never been driven longer than an hour to local car shows..that being said the car is in storage and has been for 6 years. 66 galaxie 500 cruise o matic   275/60/15 rear tires don't know the rear gear but would guess 4.11..it's just a sunday cruiser..79,000 original miles and mostly driven at around 50-55mph...It's just one of those curiosity thoughts like how would your stock motor hold up compared to the infamous Lemans motors that ran 24hrs straight. Could it run 24hrs straight as a stock motor.. I don't think anyone in their right mind would try to do that to restored a vehicle... I hope

[cjshaker]

I don't think anyone in their right mind would do that to any engine, let alone a stock, all original 352 that's been in storage for the last 6 years. Busted springs, busted rocker shafts, wiped out bearings....all things I would expect to happen.

[BattlestarGalactic]

What was the typical rpm of old pump motors?? 3200?  What's a few more??  Lol.   With a light load I can't see it being that bad for it.   Is it good for it?  Not the best but I don't see it as catastrophic as others.

 I do run my 428cj at 3500+ on highway jaunts and don't fuss.  It does have LeMans rods, but they are stupid heavy and I consider worse on things then light stock rods.

[Jb427]

My 66 fairlane with pretty much stock 390 c6 and 3.5 rear 265/50/15 use to sit at around 3000 and 100/110 kph 60/65 mph.

[Rory428]

This was just purely a  HYPOTHETICAL question..the car has never been driven longer than an hour to local car shows..that being said the car is in storage and has been for 6 years. 66 galaxie 500 cruise o matic   275/60/15 rear tires don't know the rear gear but would guess 4.11..it's just a sunday cruiser..79,000 original miles and mostly driven at around 50-55mph...It's just one of those curiosity thoughts like how would your stock motor hold up compared to the infamous Lemans motors that ran 24hrs straight. Could it run 24hrs straight as a stock motor.. I don't think anyone in their right mind would try to do that to restored a vehicle... I hope

No chance you could run it 24 hours straight. Even if the engine didn`t blow up, you would be stopping for gas every 2 hours or so!

[chris401]

My truck runs 3,040 RPM's at 70mph with a 1:1 4.10 gear and 31.73" tall tire. Some of the gear, RPM and tire size post don't add up. Here are some Wallace Racing Calculators.

http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php

[Joe-JDC]

The only problem with that scenario is pumping all the oil out of the pan.  I ran 4.10 gears in my Shelby, and on a drive from Ogden UT to Las Vegas, I was zipping along at 125-130 mph, and after several miles noticed a cloud of blue smoke behind me.  I looked around for the car that was smoking and realized it was me.  I pulled into a gas station just over the border into NV, and checked the oil level.  It was down over two quarts.  I added the oil, and checked it when I got to Las Vegas, and it was full.  It was about that time that Ford came out with the TSB on running 6 quarts of oil in the CJs, and not driving for long times without letting off the accelerator so the oil could scavenge back to the pan.  Changed out the 4.10s to 3.50s, 6 quarts, and no more problems.  Joe-JDC

[chris401]

The only problem with that scenario is pumping all the oil out of the pan.  I ran 4.10 gears in my Shelby, and on a drive from Ogden UT to Las Vegas, I was zipping along at 125-130 mph, and after several miles noticed a cloud of blue smoke behind me.  I looked around for the car that was smoking and realized it was me.  I pulled into a gas station just over the border into NV, and checked the oil level.  It was down over two quarts.  I added the oil, and checked it when I got to Las Vegas, and it was full.  It was about that time that Ford came out with the TSB on running 6 quarts of oil in the CJs, and not driving for long times without letting off the accelerator so the oil could scavenge back to the pan.  Changed out the 4.10s to 3.50s, 6 quarts, and no more problems.  Joe-JDC

I burned up the bottom end like that. Had a nice knock when I shut it down.

[RustyCrankshaft]

It's not ideal, but a lot of FE powered trucks did it for a lot of years. My 73 camper special runs 3600 at 65 empty and it's a bone stock 360/C6 with some kind of mystery cam the PO installed (he literally said it was one of those popular CompCams everyone was installing in the 80s.....cause that narrows it right down for me!). It's run all over the western US and made at least 4 trips to Alaska early in it's life from info I got when I was given the truck. Still running fine. Still sees a lot of freeway time at 60-70. Have a few other FE and 385 powered basically stock bump and dent sides that do the same thing. My 73 F350 ran about 4100 at 65 when it had the original axle in it.

As long as the oil pressure, temp and coolant temps are fine it shouldn't hurt anything if it doesn't fill the valve covers completely full of oil. I would prefer lower RPM on a freeway car, but sometimes you gotta run what ya got.

Or just slow down to 62mph! More time to enjoy driving the old iron on a cruise that way.