I own a 55 Plymouth 6 cyl 3 speed manual transmission. The speed limit on our highways is 70 mph. When I drive the car at 55 it sounds like the engine is screaming and ready to come thru the hood. Remember the highway system was not invented when this care was produced. Some have told me it is the fan that makes all the noise. I am interested to hear from others that have the same problems. Is it safe to drive at a higher speed? Do I run the chance blowing the engine at these high speeds?
Looking forward to your comments,
Chuck
Chuck,
My '40 Plymouth has the stock engine and drive train, I usually keep it about 45 miles an hour when driving as the old girl wines also. On the few occasions that I have been on four lane highways, I stay to the right, maybe 50 mph, but living in the country, I don't often get on four lane highways. I figure that 45 mph is fast enought because of the brakes and DEER in our area.
For the 1930s vintage Plymouths, my thoughts can be read at http://www.ply33.com/Misc/speed
Not sure what the rear end ratio is in your 55 nor your tire diameter, but I'd expect that car should be able to run 65 MPH all day. We had a 57 Plymouth when I was growing up and we certainly drove it at the speed limit. And in Arizona at that time there was a Day/Night speed system with 65 MPH being the typical rural highway daytime speed limit.
Engine RPMs were reduced considerably after the 1970s gas crisis to help increase fuel economy and I guess people have gotten used to the lower RPM at speed that was normal before that. Or they actually were born and learned to drive after that transition and never knew how older cars were geared. I remember in the 1960s the teenagers who were trying to hop up cars were keen to find 4.11:1 rear ends to put in their cars so they'd accelerate faster. Seems like the reverse is true now, want something in the neighborhood of 3:1 for quieter cruising. And then compensate for the lack of acceleration by putting in a 350 HP engine.
There are many factors that govern the top speed for older cars, e.g. car built prior to 1965... I use the year 1965 because after that period, cars generally were geared higher and the automatic trans became the more standard transmission.
Two major factors govern the top speed of a vehicle, the first being the gearing of the rear end and the size of the engine.... During the years prior to 1948 common gearing was around 4.11, 4.27 or 4.33 with 4.33 being on the low side where-as 4.11 was average. Higher gear ratios were available up to 3.54 in the Fords. Overdrives started appearing in the low priced cars in 1936, however, Chevrolet and Plymouth did not generally offer them as an option.
In reading through the old car publication I have found that several of the manufactures sold their more stripped down, Standard model cars with "high speed" gearing where-as the Deluxe versions usually have low gearing. The rational behind the gearing difference is that the Standard model would most likely be purchased by a company for salesmen use, therefore, fuel mileage and longevity could or would be a big factor. The Deluxe cars would most likely be driven in the city and/or country by a family man/women who would be more interested in low speed performance.
The average older car engine turns about 3,500 RPM's at 60-65 MPH, modern engines turn on the average of 2,100 PRM's... The average older engine of 80/85 HP get that amount of HP at about 3,500/3,800 RPM's with a top RPM range of 4,500 +/-... When all of this is taken into consideration, the older engine's are near the end of their "SAFE" range at 3,500 RPM's.
I use to know a man that had a '39 Plym conv. cpe which he purchased in 1940. Shortly after buying the car he tried to catch a Greyhound bus that was headed for Los Angeles, in a little over 50 miles he burnt the engine up. When the engine was replaced by the Plymouth Dealer, the service manager told Mr Cutler... " I don't want you to ever drive this car over 45 MPH again" Mr Cutler owned the car until 1998 and claimed he never drove the car over 45 MPH during all of those 58 years....Bill
I just put 200 miles on my '38 Chrysler today running 55 to 60. It has the 4.1 rearend and 650-16 tires. It was very comfortable at that speed and did not sound overworked. Engine is a newer rebuilt 251 CID flathead as the car had no engine when I got it. I think a lot depends on the condition of your engine.
due dillegence would suggest you put your rear end gear ratio and tire diameter into any one of the calculators on the internet.
They will take your information and give you an RPM per MPH. You are looking for a over the road speed that is 80 to 85 % of the 3600 RPM's that Chrysler used to rate peak HP. the 80 to 85% will give you a crusing speed and a driving margin for give road circumstances.
http://www.4lo.com/calc/gearratio.htm
this one is for radials but there are others out there, http://robrobinette.com/tire_diameter.htm
use 1 to 1 as trans and trasfer case ratio.
I run 4.11's and 28.28 inch diameter tires (225 75 15) and at 3087 RPM my car is at 65 mph. I run at an indicated 65 if and when I drive on interstates. (which is 64 mph by my GPS) I have driven from Syracuse NY to Vermont, Virginia, North Carolina, and Detroit, Maryland and elsewhere
Yep they are noisier than modern egines, the fan puts out most of it, and there is not much insulation between you and the engine.
Limiting yourself and your car to 45 is?? well it's up to you......
My engine is a recently rebuilt 230 out of a 56 savoy. It has about 10 K on it since the rebuild. It runs at 170 degrees with 40 to 45 lbs per sq in of oil pressure.
My '39 Plym conv cpe turns 2.100 rpm's at 70 mph... other than some wind noise the car is very quiet.. The entire inside of the body has been covered with "Road-kill", a sound deadening matting. My rear end is geared 3.23 and I am running 27" P205R60-15 tires. The car has an electric fan in lieu of a mechanical fan....
Life is good in the fast lane... 8) .... Bill