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Re: Highway RPMs
[Re: MoparJ]
#1773456
03/07/15 04:42 PM
03/07/15 04:42 PM
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Joined: Jan 2006
Posts: 706
USA
rftroy
super stock
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super stock
Joined: Jan 2006
Posts: 706
USA
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Quote:
The A-833 with OD swap will take place sometime before the year is out.
You may not like the OD4 behind that engine. It will cruise nicely, yes, but the ratios are such that it is no fun getting going.
The ratios are 3.09, 1.67, 1.00, 0.73.
1st to 2nd is getting very close to a 2 to 1 ratio change.
I had a 318 with 360 heads, thermoquad, and a DC hyd. with specs right between the stock 318 and 340 cams, and an OD4.
It was miserable to drive because of the torque curve. It winds out fast due to the low first, but then 2nd gear puts you way down on the torque curve, and you just lug for a while. If you shift at 4500 from 1st, you start 2nd at 2432.
It was especially no fun in stop and go traffic, and you know what that's like here in SoCal.
I ended up pulling the OD4 after just a few months and put the std 4 speed back in.
I have the OD4 behind my slant 6, and it runs great. But that's when you find that the stock slant 6 has a really wide torque curve, and it can pull comfortably at low rpm. A warmed over 318 is going to be more "peaky", and that's where the wide gear spread works against you.
Not saying it won't be right for you, but keep in mind that acceleration runs aren't going to be as much fun.
Robert
AAR 4-speed 3.91, Tor-Red;
70 440 6 pack Roadrunner 4-speed 3.54, Plum Crazy;
68 Formula S conv 383 4-speed 3.23, Electric Blue;
69 Barracuda conv Slant 6 OD4 2.94, 71 B5 Blue;
78 Lil' Red Truck, Red;
70 Challenger S/E. 505 6 pack, Passon 5-speed, 3.55, B7 Blue
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Re: Highway RPMs
[Re: Von]
#1773465
03/10/15 03:32 PM
03/10/15 03:32 PM
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Joined: Jun 2006
Posts: 5,186
CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,186
CT
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Quote:
Quote:
As far as will high rpm on the highway hurt it? Eventually, yes: there's a reason why new vehicles with overdrive are hitting 300,000 miles and the old girls barely made 100,000.
No offense, but considerably more involved than just final drive ratio....
 The gear ratio helps but is probably one of the least important factors. Harder bores, moly rings, oil technology, and fuel injection have helped to make big strides.
Also theres lots of 4 banger cars that turn 3000-3500 @ 70 in overdrive.
Last edited by GTX MATT; 03/10/15 03:36 PM.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: Highway RPMs
[Re: Magnum]
#1773468
03/10/15 10:33 PM
03/10/15 10:33 PM
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Joined: Aug 2005
Posts: 6,053
Salem
Grizzly
Moparts Proctologist
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Moparts Proctologist
Joined: Aug 2005
Posts: 6,053
Salem
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A Member who I have not seen on here for quite some time, had an 833od in an A-body with a 360. I asked him about it and he said he never noticed any drastic difference: the 360 pulled the wide-ratios with ease and still did low 13's in the 1/4. 340Shorty had the same set-up in his truck and he liked his as well. I just got one in an '84 Ram with a 318 2bbl. With 2.94 gears, 30" tires, and at 4000 pounds that 833od is fun as heck to drive. I got back into one of my close-ratio ratio cars and it felt like you had to shift all the time. It seemed like it was wasting power. The 1st to 2nd is not an issue at all, 2nd to 3rd is a little much but nothing you can't get used to. 
Mo' Farts
Moderated by "tbagger".
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Re: Highway RPMs
[Re: 70Cuda383]
#1773474
03/16/15 03:04 AM
03/16/15 03:04 AM
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Joined: Dec 2010
Posts: 12,375
SoCal
MuuMuu101
I got lucky at Woodward!
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I got lucky at Woodward!
Joined: Dec 2010
Posts: 12,375
SoCal
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Quote:
Quote:
I think there is a huge difference between a 4 banger and a big block spinning well over 3 grand for hours at a time.
Yes and no
Smaller engines usually have shorter strokes which is conducive to high rpm cruising. But, 3000 rpm is 3000 rpm... The piston sweeps the bore just as many times regardless of the bore/stroke, and rings/pistons sweeping up and down is what adds to engine wear.
Again, yes and no. With the smaller bores and stroke, there's less moving mass that doesn't move as far and that allows the engine to have a higher natural frequency (otherwise known as red line). But I don't really see a difference from a wear standpoint. Also, 4 bangers need to spin at a higher rpm at higher speeds in order to keep the car moving. It's actually a little wasteful for a v8 to be cruising at 3000 rpms (all depending on the vehicle's weight and aerodynamics).
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Re: Highway RPMs
[Re: MuuMuu101]
#1773475
03/16/15 10:47 AM
03/16/15 10:47 AM
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Joined: Jan 2003
Posts: 13,040
Benton, IL.
DaveRS23
Master of nothing...
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Master of nothing...
Joined: Jan 2003
Posts: 13,040
Benton, IL.
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I was thinking of the weight stopping and starting with each stroke in the 8, especially big blocks. Our stuff is usually bigger and heavier inside and really wasn't designed to spin that high that long. Which is at least part of the reason why anything but a performance car got 2.76s or so. Of course, newer, lighter reciprocating assemblies lessen the impact. And doesn't the load increase exponentially with RPM? I just think that after a certain point, the higher the RPM and the longer it is held there, the more impact it has on our engines. So I don't cruise my big blocks over 3,500 for any length of time and usually try to keep it closer to 3,000. Too old school? 
Master, again and still
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I was in California this week everyone goes about 80 on the freeways!! There is no need to run your RPM's that high on a street car
