[389]

Originally Posted by Formulajones

We daily drive our 69 Z with 3.55's and 27" tire. Works just fine in my opinion, and my wife doesn't mind it at all.

We daily drove it I'm guessing 4 years like that with a stock Muncie and probably logged close to 40,000 miles with some long trips mixed in before this year eventually installing a TKO600

Just not a big deal, but I'm used to driving cars with 3.73's and going across country. I grew up with cars and gears so it's just not a huge deal.

Chevys love high revs even big blocks..

[Steve C.]

As does a Pontiac at 5800-6000+ peak power rpm with a 4.210 and popular 4.250 stroke !


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[Formulajones]

Originally Posted by 389

Chevys love high revs even big blocks..

Yep, Pontiacs aren't immune to it either. They were new back in the day with the same gear ratios, daily driven and never given a second thought.

As Steve eluded to, once built to make some HP, they'll make peak power around 5800-6000 and even higher. Peak rpm HP is just physics and will change as you push camshaft and head flow numbers higher.

Even dad's 571 Pontiac with a 4.750 crank peaked at 5700 on the dyno and carried it pretty flat to 6000. With a 6200 chip in it, he can't keep it off the limiter. It just zings up there quicker than he can move the shifter.

[PunchT37]

Originally Posted by Formulajones

Yep, Pontiacs aren't immune to it either. They were new back in the day with the same gear ratios, daily driven and never given a second thought.

As Steve eluded to, once built to make some HP, they'll make peak power around 5800-6000 and even higher. Peak rpm HP is just physics and will change as you push camshaft and head flow numbers higher.

Even dad's 571 Pontiac with a 4.750 crank peaked at 5700 on the dyno and carried it pretty flat to 6000. With a 6200 chip in it, he can't keep it off the limiter. It just zings up there quicker than he can move the shifter.

Iv`e got my 463 chip at 6500. It`s been 6500 a few times already. HR cam. No valve float yet. It goes to it`s proper red line of 5800 to 6000 with no problem. Factory crank/ block. 4340 I beam rod with a Ross full float piston.

[Formulajones]

Originally Posted by PunchT37

Iv`e got my 463 chip at 6500. It`s been 6500 a few times already. HR cam. No valve float yet. It goes to it`s proper red line of 5800 to 6000 with no problem. Factory crank/ block. 4340 I beam rod with a Ross full float piston.

.............

[punkin]

I hope this isn't considered a hijack but there were a few responses where it was suggested that you don't want the rpm to be too low when cruising on the highway. Some called it lugging down the engine. What would be considered the ideal rpm for long distance highway driving?

Thank you...this has been a very interesting topic.

[i82much]

Originally Posted by punkin

I hope this isn't considered a hijack but there were a few responses where it was suggested that you don't want the rpm to be too low when cruising on the highway. Some called it lugging down the engine. What would be considered the ideal rpm for long distance highway driving?

Thank you...this has been a very interesting topic.

depends on the engine. 455 with an 067 cam, you almost couldn't lug it. 326 with an 041, you'd probably need to cruise at 3k. And that is ignoring intake/exhaust/compression etc.

[PunchT37]

Originally Posted by punkin

I hope this isn't considered a hijack but there were a few responses where it was suggested that you don't want the rpm to be too low when cruising on the highway. Some called it lugging down the engine. What would be considered the ideal rpm for long distance highway driving?

Thank you...this has been a very interesting topic.

The larger the cam and smaller the cubes will determine a kinda minimum rpm for efficiency.


Example, one wouldn`t want a 400 cube with a 246 at 050 cam running around a 1500 rpms.

[Steve C.]

About 22 years ago Dave Bisschop built a .030-over 400 with ported 6X heads that were around 260 cfm, 9.3 compression and he used a Comp P296-AH-8 hydraulic flat tappet cam with 246 degrees intake duration at .050" lift. With 1-3/4" headers. Torker II intake and 800 cfm Holley carb. It made 451 ft.lbs. torque at 5000 rpm and 459 hp at 6,000 rpm. He suggest at the time it was about the biggest cam suitable for a street driven car, his opinion. Suggested a 3500 stall converter and 3.73 gears.


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[Ponchy]

Originally Posted by i82much

depends on the engine. 455 with an 067 cam, you almost couldn't lug it. 326 with an 041, you'd probably need to cruise at 3k. And that is ignoring intake/exhaust/compression etc.

^^^YES^^^
Hard to answer that question without some specifics.

[Formulajones]

What's going to play the biggest roll in lugging is how well you're able to tune that particular combination.

If you really spend the time to dial in the distributor, and you know your way around the carb circuits, particularly the idle and transition areas, you can make just about any engine and any combo pull at very low rpms without complaint, and with rather large overlap camshafts.

I have our little 302 with a 254 @ .050 cam putting around near idle in 5th gear without an issue. 3.55's out back with a .64 5th gear. It'll cruise through town at 30 mph in 5th gear without a single complaint, no bucking or kicking, and will gain speed pushing on the throttle without an issue. It easily does 50 mph in 5th or any speed above that, and will climb mountain grades, and actually gain MPH if you want, without downshifting.

Spending the time to get this combo running perfectly really makes it a pleasure to daily drive. My wife drives it all the time, it behaves like a kitten.

There is no reason anything larger, a 350, a 400 or especially a 455 couldn't accomplish the same thing with just about any camshaft you put in it.

[Tempest T-37]

I think it helps to clarify what you mean by lugging. To me, it's not that it's operating outside the camshaft's efficiency, but I've always understood "lugging" as high load, low rpm. Usually when the engine won't or barely gains rpm under throttle, and is associated with a low frequency vibration and groan/grumble noise...which is mostly the sound of all the journals bouncing around beating on the bearings. Usually you can safely cruise at light load at an RPM that the engine would be very unhappy with if you put the pedal down (especially with a modern OD transmission). But that is probably a below 2000ish rpm type of scenario. But, if the engine isn't happy down low, don't force it to lug if you can downshift/regear.

Anecdotally, I come from a turbo Subaru background, and low-RPM-high-load is a big killer of rod and main bearings. The engines can make way more torque than the bottom end can support at lower RPM/oil pressure and over time the bearings will take a beating until failure. Most steer away from the smaller super quick spooling turbos or tune the boost curve to come on soft when trying to make power with stock internals for this reason.

[Ponchy]

I define "lugging the engine" as you do, Tempest T-37.
My dad learned to drive during WWII.
He always taught me to "lug the engine". To him, winding it out is what kills them.....unless its a Detroit,, then it ok to push it against the governor.

Ponchy

[Steve C.]

"When you know that you are going to be driving at a steady speed, the fuel-saving strategy is easy—run your engine as slowly as possible. Those of us who learned to drive in the Sixties or Seventies might remember cautions against “lugging” an engine. That means not working your engine hard when the revs are low—generally below 1500 rpm—lest you damage the bearings and cause a major engine failure. This is still not bad advice, but modern engines are much more robust than they once were."

From an article about improving gas mileage... Lug and Coast ! And avoid those jackrabbit starts


.

[slowbird]

Well just to close out this thread, we got the 3.55 in and looks like 70mph is 2700-2800 now vs 3400-3500 before. It's a hair bit softer down low (pulling away from stop light) but that's to be expected vs the 4.11 it had. Real happy with the change. Now we just need to finish up the new engine and wait for warm weather to see how it really runs.

[Tom Vaught]

You dropped (for easy math), about 700 rpm with the change at the same 70 mph.

I expect with my 2.75 rear axle combination with the Nash 5 speed trans to do a similar drop. About 700 rpm from your 3.55 axle combination. BUT I have a much better 1st gear
ratio and second gear ratio to help me get the car moving off the line at the street light.

Modern vehicles (Like a Corvette or F-150 Truck) let the trans do the work with mild gear ratios in the rear axle. They cruise very happily at 1800-1900 rpm at 75 mph and get great mileage as well as very good performance at all speed ranges.

The converter helps with off the stop light drive-away but the trans with either a larger 1st gear ratios or Overdrive final gears do the same thing.

Tom V.

[FirebirdHank]

I think a lot of us who grew up in the sixties were just fine with 3,800 rpm or more @ 80 mph. Then we drove modern cars with o-drive and now it seems like the engine is screaming at those levels. I know after driving 3 &4-sppeds all of my life after driving a 5-speed as a daily driver for a while, when driving one of my 4-speeds I found myself "searching " for fifth on the high-way. My '69 Firebird now has a 5-speed with 3.08s and I love it. Certainly not a tire shredder but I did all of that back in the sixties. Twenty-two hundred @ 75 and if you want to pass just drop down a gear and go. Isn't that why we drive manuals anyway.
As I have stated in other posts If you want a lot of responses to a post just ask "what gear should I run" and sit back.

[Half-Inch Stud]

Drove the GTO today ( was 58 degrees); Overdrive uphill at 30 mph was just fine. was bumping 3rd-4th, 4th-3rd just to see what RPM was; 2100 to 1900 and no lugging.

Camed 236-244 9.0:1 as signed below.

[Skip Fix]

"I think a lot of us who grew up in the sixties were just fine with 3,800 rpm or more @ 80 mph. Then we drove modern cars with o-drive and now it seems like the engine is screaming at those levels"

Yep my old 409 Impala put a lot of miles on with 4.56s and 28-29" tall tires, but premium leaded was only about .30-35! Those dual quads sure sucked it down.

[PunchT37]

Originally Posted by FirebirdHank

I think a lot of us who grew up in the sixties were just fine with 3,800 rpm or more @ 80 mph. Then we drove modern cars with o-drive and now it seems like the engine is screaming at those levels. I know after driving 3 &4-sppeds all of my life after driving a 5-speed as a daily driver for a while, when driving one of my 4-speeds I found myself "searching " for fifth on the high-way. My '69 Firebird now has a 5-speed with 3.08s and I love it. Certainly not a tire shredder but I did all of that back in the sixties. Twenty-two hundred @ 75 and if you want to pass just drop down a gear and go. Isn't that why we drive manuals anyway.
As I have stated in other posts If you want a lot of responses to a post just ask "what gear should I run" and sit back.

You could start a cam thread...