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 Post subject: RPM's
PostPosted: Thu May 19, 2022 1:06 pm 
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3 Deuce Webber

Joined: Sun Jun 05, 2016 12:18 pm
Posts: 69
Location: San Diego Ca
Car Model: 1965 Dodge A100 Pickup w/Super Six
I recently put a tachometer in my Dodge A100 pickup, and now I am seeing that my RPM's at speed are pushing 4,000! Now that's at 80 mph- at 70 mph it is closer to 3300. My 225 is sporting a super six 2 bbl with the matching intake and exhaust manifolds, magnaflow exhaust, and a shaved head, with mild port work. Tranny is a 727. The truck runs great and feels very comfortable at that level, but I wonder if I am pushing it too hard. Should I have any concerns???

Thanks.........Gary


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 Post subject: Re: RPM's
PostPosted: Thu May 19, 2022 1:33 pm 
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Board Sponsor & SL6 Racer

Joined: Wed Oct 23, 2002 7:57 pm
Posts: 7408
Location: Waynesboro, Pa.
Car Model: 65 Valiant 2Dr Post
I can fix your problem. Don't run 80MPH. :D :D

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 Post subject: Re: RPM's
PostPosted: Thu May 19, 2022 2:10 pm 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3566
Location: Indianapolis
Car Model:
Are you sure the tach is set up correctly?

Typically there are jumper wires that are cut or a selector switch that is re positioned to use a tach with a 4 or 6 or 8 cyl motor.
3300 RPM’s cruising at 70 mph would be a lot of commotion with a slant.

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 Post subject: Re: RPM's
PostPosted: Thu May 19, 2022 3:46 pm 
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Board Sponsor & Moderator
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Joined: Thu Oct 17, 2002 7:27 pm
Posts: 13341
Location: Park Forest, Illinoisy
Car Model: 68 Valiant
What gear is in the rear end? That would be consistent with a 3.91.

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 Post subject: Re: RPM's
PostPosted: Thu May 19, 2022 5:59 pm 
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Supercharged
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Joined: Sat Nov 27, 2004 8:03 pm
Posts: 7735
Location: IRWIN PA
Car Model:
I spin my engine in the 3.91 Equipped '64 Dart regularly past 4000 on the track and in the Mountain twisties. (Lou's Short Block). and have put ~5000 Miles on it so far.

I do have a 5th gear for the highway with 245 45 17 tires ~25.7" Diameter.





Greg

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 Post subject: Re: RPM's
PostPosted: Thu May 19, 2022 7:42 pm 
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Board Sponsor & SL6 Racer

Joined: Wed Oct 23, 2002 7:57 pm
Posts: 7408
Location: Waynesboro, Pa.
Car Model: 65 Valiant 2Dr Post
4000 rpm's for long periods of time can't be good on anything. Yes you may get away with it for a long time, but you might not too. :D That little troublesome oil pump gear comes to mind. :D

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 Post subject: Re: RPM's
PostPosted: Thu May 19, 2022 10:16 pm 
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3 Deuce Webber

Joined: Sun Jun 05, 2016 12:18 pm
Posts: 69
Location: San Diego Ca
Car Model: 1965 Dodge A100 Pickup w/Super Six
Since I found out how high I was revving my slant I have calmed down a bit, BUT, when this bright red, unusual vehicle goes past you on the freeway, the only thing you can say is "WTF"! And I like that!!


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 Post subject: Re: RPM's
PostPosted: Fri May 20, 2022 4:04 pm 
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Board Sponsor
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Joined: Wed Nov 06, 2002 1:57 pm
Posts: 2097
Location: Everett, WA
Car Model:
An A100 at 80mph is a scary thing. What with the crappy suspension and drum brakes. Not to mention the large surface area that the wind could use to blow you into the other lane.

I know when I has one, anything over 50mph was an adventure.


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 Post subject: Re: RPM's
PostPosted: Mon May 23, 2022 12:24 pm 
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Turbo Slant 6

Joined: Thu Jun 07, 2012 4:29 pm
Posts: 726
Location: Houston
Car Model: 68 Valiant
This topic has always fascinated me.

4000RPM is way too much for long durations. Not only is is bad for the engine, it's a direct cause of insanity in drivers.

I've noticed even on 4 cylinder cars with short strokes and the resultant low piston speeds....most manufacturers like to spin 2000-2500RPM at highway speeds. By highway speeds, I mean 70-80MPH.

My rule of thumb for any of my 'old' Mopars is 3000RPM max. And even that is a compromise, giving a nod to the fact I'm just not gonna run 2.76 gears.

I am always amazed when I see a 'Super Track Pak' Mopar that left the factory with a 440, 4 speed, and 4.10 gears. All I can think of is....no way was anyone gonna drive that car much over 55MPH. Not for long.

All of this sort of swirls around an undeniable truth. While people of 2022 love to rag on the drum brakes and death-for-sure suspension of old cars, the lack of overdrive gearboxes was probably the only real shortcoming of the 60's and 70's. By the 80's, of course, cars had millions of shortcomings, but that's a different story.


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 Post subject: Re: RPM's
PostPosted: Mon May 23, 2022 3:34 pm 
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Board Sponsor & SL6 Racer

Joined: Wed Oct 23, 2002 7:57 pm
Posts: 7408
Location: Waynesboro, Pa.
Car Model: 65 Valiant 2Dr Post
I ran 3.91's on the street for about 3 months with no Od and load exhaust. I about lost my mind and I was 40 years younger! :D

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!
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 Post subject: Re: RPM's
PostPosted: Mon May 23, 2022 3:41 pm 
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Board Sponsor & Moderator
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Joined: Thu Oct 17, 2002 7:27 pm
Posts: 13341
Location: Park Forest, Illinoisy
Car Model: 68 Valiant
I drove my Duster to Kearney and back with 3.91's. Drove the Valiant to Clay City twice. 904 with a 3500 stall.

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 Post subject: Re: RPM's
PostPosted: Mon May 23, 2022 4:03 pm 
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Board Sponsor
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Joined: Wed Nov 06, 2002 1:57 pm
Posts: 2097
Location: Everett, WA
Car Model:
GregCon wrote:
This topic has always fascinated me.
All of this sort of swirls around an undeniable truth. While people of 2022 love to rag on the drum brakes and death-for-sure suspension of old cars, the lack of overdrive gearboxes was probably the only real shortcoming of the 60's and 70's. By the 80's, of course, cars had millions of shortcomings, but that's a different story.


Have you ever drove an A100? i have, 25 years ago. Even then the front beam axle was wore out, the steering was rather vague and it would follow all the ruts in the road. A passing semi could push it into the next lane. An "adventure" for sure.

Stupid car to drive on the freeway. A '66 Dart, 318, dual quads, 4 speed with 4.56 gears in the rear and G50x14 tires. 3000 rpms was 55 mph. The national speed limit at the time. It got 13mpg. On the plus side, i out ran a '66 GTO with a tri-carb 389 by 4 car lengths in "Mexico".


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 Post subject: Re: RPM's
PostPosted: Mon May 23, 2022 4:59 pm 
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Turbo Slant 6

Joined: Thu Jun 07, 2012 4:29 pm
Posts: 726
Location: Houston
Car Model: 68 Valiant
Well..I was really referring to cars. But still....any vehicle with worn out suspension and/or brakes can't be judged fairly.


Right now, my trusty 68 Valiant has about 135K original miles and ALL of the suspension is the same it rolled out the door with. It drives pretty well, though I am aware that it's one of those deals where if I were to touch any part of it, it would never be the same again.


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 Post subject: Re: RPM's
PostPosted: Mon May 23, 2022 5:47 pm 
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Board Sponsor & SL6 Racer

Joined: Wed Oct 23, 2002 7:57 pm
Posts: 7408
Location: Waynesboro, Pa.
Car Model: 65 Valiant 2Dr Post
Quote:
I drove my Duster to Kearney and back with 3.91's. Drove the Valiant to Clay City twice. 904 with a 3500 stall.


You are a much tougher man than I ! :D

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!
Image
12.80 @ 102.88
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 Post subject: Re: RPM's
PostPosted: Tue May 24, 2022 6:48 am 
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EFI Slant 6
User avatar

Joined: Thu Jul 24, 2003 4:51 pm
Posts: 452
Car Model:
kesteb wrote:
What with the crappy suspension and drum brakes.


What crappy suspension? It's a truck suspension for cryin out loud! That so called crappy suspension as you call it, I bet that my A100 will outperform, and take tons more abuse than your wimpy ass sedans suspension could ever handle!!


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