Max revolutions for a 1939 320 engine?

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DrMorbius
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Max revolutions for a 1939 320 engine?

Post by DrMorbius » Wed Aug 24, 2016 12:57 pm

Hi, I just wondered if anyone knows what the redline is in general for a 39 Super-8 engine. I can't seem to find the answer anywhere but I'm guessing between 3,500 and 4,000 revs. Am I correct? That's with the 9 main bearing motor.

Thanks,

Steve

DrMorbius
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Re: Max revolutions for a 1939 320 engine?

Post by DrMorbius » Tue Aug 30, 2016 9:25 am

My mechanic informs me that this engine redlines at 4500 to 5000 rpm, I myself feel that's a bit high. I would try to keep it under 4000, wish it came equipped with a tach like a Duesenberg.

Steve

Dave Czirr
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Re: Max revolutions for a 1939 320 engine?

Post by Dave Czirr » Tue Aug 30, 2016 10:32 am

Redline was not a specification or even a common concept at the time; with a 5" stroke these are high torque engines, not high-rev engines!! For my '34 320 with poured babbitt bearings, I try to keep below 2400 rpm for prolonged highway cruising - I'll occasionally go up to the equivalent of about 3000 rpm but have no desire to maintain that rpm. And for your '39 with no source for OEM-style connecting rod bearings I'd be just as conservative if I wanted to maximize engine life.

Easy to calculate your engine rpm in direct drive at different road speeds, all you need is 8th-grade math, the differential ratio, and the tire diameter or circumference.

Adam
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Re: Max revolutions for a 1939 320 engine?

Post by Adam » Wed Aug 31, 2016 12:23 am

Why do you need a tachometer? You really should use your ears and other senses to tell when it is running most comfortably. That should be the speed at which you run it. Mechanical sympathy is the order of the day !! :) :) :)

I use a strobe timing light that provides a tachometer function. That is very interesting to try out.
"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

dak955
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Re: Max revolutions for a 1939 320 engine?

Post by dak955 » Wed Aug 31, 2016 1:05 pm

I agree with Adam 100%. You will "feel" when your engine is at a good pace where it is not overworking. It varies a little in each car depending on the engine, rear end ratio etc.....get the car on a nice stretch of road and once you start approaching 50 mph or so and start listening to the engine work. Push it a little at a time until it feels like it is starting to overwork...back off a little from there and see how it sounds and feels.....good luck...

5682-4775
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Re: Max revolutions for a 1939 320 engine?

Post by 5682-4775 » Thu Sep 01, 2016 3:51 am

Hi

For what its worth as an rpm guideline, the maximum torque listed for a '35 320 ci engine is as follows: 260 lb/ft @ 1,600 rpm. Your '39 Super 8 320 is essentially the same engine. The advice given about mechanical sympathy is spot-on; listen closely how the engine sounds and reacts at various speed ranges. You'll develop a good feel for what is reasonable, what's not. Average road speeds are higher now than when these cars were in general usage, just the same, drive what is not over-stressing the powertrain, and you'll be fine.

Steve

DrMorbius
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Re: Max revolutions for a 1939 320 engine?

Post by DrMorbius » Thu Sep 01, 2016 2:42 pm

Thanks for all your inputs, everyone - I will follow your advice. Now about those connecting rod bearings, are Kanter out of them at this moment, or is someone out there making them, or are they, like totally made of unobtainium?

Steve

Dave Czirr
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Re: Max revolutions for a 1939 320 engine?

Post by Dave Czirr » Thu Sep 01, 2016 3:02 pm

They are flanged bearings to control side thrust; they've were scarce even 40 years ago. I don't know that Kanter ever had much of a stock, last time I asked they only had 1 or 2 sets for individual rods. There have been rumors of reproduction runs on and off for decades but I don't know that any ever reached fruition. General options are to remetalize the old shells or convert the rods to a common slipper bearing and make other provisions to control side tolerance such as brazing buttons to the sides of the rod big end.
Attachments
Rod bearings senior 35 39.jpg

dak955
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Re: Max revolutions for a 1939 320 engine?

Post by dak955 » Fri Sep 02, 2016 8:25 am

Hello. For what it is worth, I just checked ebay and there is a set of connecting rod bearings in the original Packard box which shows a part number and group number. The info in the ad claims they fit the 8 cylinder motor that you have.....the price is $74.99......maybe you can cross reference the numbers to make sure they are correct.......good luck....

DrMorbius
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Re: Max revolutions for a 1939 320 engine?

Post by DrMorbius » Fri Sep 02, 2016 12:46 pm

I saw them on eBay, it looks like they are made for the Packard 120 with the 282 engine - I have the 320 engine. Pretty close though.

Steve

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