Max revolutions for a 1939 320 engine?

Discussions related to engines, transmissions, rear axles, suspension & steering.
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Re: Max revolutions for a 1939 320 engine?

Post by flackmaster » Fri Sep 02, 2016 1:56 pm

Forget rumors....the 320 bearings have been reproduced and available for something in the order of 4 years now. They used to be unobtainium. Now they are reproduced, contact Dave Schumacher at 818 six four zero 37 ninety.

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Re: Max revolutions for a 1939 320 engine?

Post by DrMorbius » Sat Sep 03, 2016 11:03 am

Mr Flack, you are the Master and I thank you again for the information. I have to ask - is there anything you don't know about Packards??? I for one am glad you appear on this website.


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Re: Max revolutions for a 1939 320 engine?

Post by Adam » Thu Sep 08, 2016 4:43 am

5682-4775 wrote: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.

Interesting Steve. If maximum torque is at 1600 rpm, then the likely 'sweet spot' will be about 1800 or 2000rpm. This will allow the engine to 'lug-down' to peak torque as you begin to climb a hill. In other words, as the revs drop, initially the torque output will become greater all other things being equal, such as the throttle position. But at the end of the day, listen to when the engine sounds least stressed and go with that.

"Do not underestimate the English cousin.....they are not as stupid as they look!" - Signor Altabani in The Italian Job.

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Re: Max revolutions for a 1939 320 engine?

Post by Packard V12 » Thu Oct 06, 2016 3:05 pm

[quote="DrMorbius"]My mechanic informs me that this engine redlines at 4500 to 5000 rpm,.....
I strongly recommend your mechanic go back and re-take that basic engineering course he obviously got nothing out of.

Your "320" motor's design dates from the mid 1920's, when Packard did away with its six cylinder motor, going to a smaller (compared to its large luxury car motors) eight cylinder. Like the "Super Eight" it has a stroke of 5".

How long would you expect your modern car to last, if you drove it at 120 miles an hour for any length of time ? 120 mph, the shock-loadings on the connecting rod bearings and "crank-pins" on a modern motor are significantly less than the abuse the rods and bearings of a pre-war "big" Packard are taking at 60 mph. It is a simple problem of physics.

As a side-note, once you spin a pre-war Packard motor much past, say...around 1800 rpm, its actual torque output starts dropping markedly.

It is difficult for todays drivers to comprehend what the roads were like when these motors were designed. People THINK if they find old sections of what WAS U.S. Highway 66, they have an idea. Wrong. Virtually every section of what WAS U.S. 66 was re-built to wider surfaces with more gentle curves in the immediate pre-World War II and later years. So it logically follows the cars were designed and geared for the kind of roads they faced.

The introduction of "insert-type" connecting rod bearings for the entire Packard line in 1935 made it POSSIBLE for a pre-war Packard motor to SURVIVE extreme speed driving. Want an idea of the difference ? Simple mathematics. Take a typical mid 30's final drive ratio of 4:41 to 1. Compare that with today's cars (again...note how much shorter their connecting rod "stroke" is, meaning so much less shock-loading on bearings)....which typically are geared 2.5 to one. That means, to drive a 1,000 mile trip....the old Packard would have to drive another 500 miles for the engine to go the same distance. Or how about match the engine speed of a pre-war Packard with a 4:41 final drive ratio at 45 mph..., a modern car would have to go well over 100 !

I strongly recommend that no "stock-geared" pre-war Packard (unless you are one of the lucky ones to have been equipped with over-drive) be cruised at much beyond 45 mph. That is...if you want to avoid problems. Remember..attached to..and spinning furiously with that horribly over-geared rear axle...are the transmission, generator. distributor, water pump...etc.

A properly maintained / restored pre war Packard has superior brakes, handling, and steering to the typical ordinary car of its era. There is a reason why Packard had such an incredible reputation. Compare a pre-war Packard of ANY price class with any mfg's product IN THAT PRICE CLASS and you will see why Packard was so beloved and famous.

With proper re-gearing to lower the engine rpm down to what modern cars enjoy, and you can cruise all day at modern speeds. Otherwise......stay on the country roads...and OUT OF MY WAY !

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