Reliability vs. Performance

[Cooper04226]

hello all! i'm a bit new here so i have kind of a vague question, i'm planning on putting together a 1949 dodge wayfarer and i'm looking for some help, 

 

my question is this:

is there a way to build the motor where it can handle 65mph for hours at a time, i do alot of road tripping between where i live and my home town because of my love of driving, but do y'all have any advice on how to build a 230 or 218 for extended driving? i should also mention this is going to be my first time building a motor.

 

thank you in advance

-Cooper

[Plymouthy Adams]

keep it stock keep it running....the higher rpm and lower speeds are relevant more to gearing than HP/torque limitations.   Based your changes in gearing on terrain of travel area.  Many are happy with rear gearing changes,  many opt for factory style OD or other transmissions with OD incorporated.  Based on how much change you wish to do to other segments of the car if this will or will not work for you.  If concours is important to you.....apply none of the above.

[Kilgore47]

The old flat 6 engines can handle running for hours at a time.  If you want to drive at 65 for extended periods you need to keep the engine revs down.  Old flat heads are not high revving engines.  This can be done with an overdrive transmission or by changing the rear end ring and pinion gears.  I have a 1947 P15 and it came with a 3.90 rear gear.  At 65 this gear would over rev the engine.  I plan on changing that to a 3.54 gear.  To keep the revs down on longer runs.  And the 3.90 has seen better days.  BUT you will want to make sure you have the stopping power to go along with the higher speed.  A front disc brake conversion could help with that.  The original brakes can work very good if adjusted properly.  But adjusting these old brakes is not as easy as it sounds.

 

There is a lot of good info on all these subjects on this site.  And many people that will answer all of your questions.  

 

Go for it.

[Sniper]

As mentioned above, RPM is the key.  My 51 has 28" tall rear tires and a 3.91 gear ratio.  At 65 that works out to 3042 rpm at 65.  With an OD trans, ratio 0.7, 65 becomes 2130 rpm.  75 is 2457 rpm, highway speeds are 75 around here.

 

Now, the issue becomes braking, as mentioned, and high speed stability.  When I first got my 51 is was squirrely at 65.  A front end redo and a good alignment took care of that.

 

 

[TodFitch]

Chrysler tested these engine designs at max BHP in 50 hour tests. So basically it can run at 3600 RPM at full throttle for hours on end. Back that RPM down a few hundred for longer life and keep your cruise speed to maybe 3200 RPM.

 

At that 3200 RPM with 4.11:1 rear and 600-16 tires you will be moving at 65 MPH.

 

It will not be a quiet as a modern car but a lot of the noise will be from the fan. And if you weren’t used to driving in cars from before the early 1970s gas crisis it will sound like you are beating it to death. But you aren’t, that’s just how cars of the late 1930s through the early 1970s sounded when at speed.

[dpollo]

I concur with what has been posted ,  I have driven these cars since I was a teenager (1960s) and have logged a lot of highway miles.

Any of the engines combined with a Warner R10 overdrive and a  3.9 to 1 rear end will take you where you want to go at highway speeds.

 

My favourite combination is a 228 , (4 1/4 stroke)  Warner OD (.7 ratio)  3.9 rear and P205 R 15 tires)    In the early days I discovered 11 inch brakes from a Desoto or a Chrysler Royal eliminated fading .  

[greg g]

My machinist told me that his rule of thumb for sustained cruising engine speed for these long stroke engines was to be at 80 to 85 percent of factory hp rpm.  So you can put your details for rear end ratio, and tire diameter into one of those on line calculators and see where your engine sits.  I have 4.11 with 225r75 15 tires.  This comes to 3280 rpm at indicated 65 (63 on GPS).  Engaging overdrive pulls out around 900 rpm, putting it at about 2400 rpm.  Compared to modern short stroke engines geared to go 70 just off idle, I would say these old flat heads are the high rpm engines.

Edited November 13, 2023 by greg g

[Hickory]

I see the title performance vs reliability, with that said the easy performance upgrades are dual exhaust manifolds, shave the head .05-.07 and the rebuild. New pistons may be needed. Thats reliable now you can add dual carbs and reground cam but i think that can get expensive quickly. The best upgrade is brakes and rear end as mentioned. With the taller rear gears(i used a jeep rearend, easy change and lots of info here) a fresh engine is the best way to utilize the speed increase.

[Sniper]

I just got back from a trip out shopping, well trying to shop but it seems I was up before the stores were open, slackers, lol.

 

Got the old Plymouth up to 65 today.  She likes to run.  A totally different experience from my work truck (2022 Chevy).  She talks to you, you feel the road, the wind, the whole shebang.  In the WT you are isolated, really isolated.   Heck the Plymouth has much better visibility too. 

 

 

[Sam Buchanan]

Here are a couple of videos that should be interesting for those who are considering driving our old cars at modern speeds on congested highways. 

 

I know, I know......live life to the fullest, but still.........these cars were designed for a vastly different day and age.

 

https://www.youtube.com/watch?v=Tlvl8fXuuVg

 

 

 

 

 

Edited November 14, 2023 by Sam Buchanan

[Hickory]

I love it when she talks to you ?