Reg Evans

Just bought a '39 Royal

Recommended Posts

Hello there,

I just purchased a '39 Chrysler royal and wondered if anyone here knows what the standard rear end ratio would be.

I'm hoping it's a little better than 4.11 for an occasional freeway run.

Thanks in advance !

Reg

 

 

post-79638-0-73151600-1440176342_thumb.j

Share this post


Link to post
Share on other sites

Congrats, Reg!

 

 

Cort :) www.oldcarsstronghearts.com

1979 & 1989 Caprice Classics | pigValve, paceMaker, cowValve
"My heart takes off on a high speed chase" __ Lifehouse __ 'Falling In'
  • Like 1

Share this post


Link to post
Share on other sites

Gorgeous car. You could probably find some stock wheels, hubcaps and trim rings on this website. I have the trim rings. Some of the mounting tabs are missing....

post-81542-0-08620800-1440183489_thumb.j

post-81542-0-26956300-1440183502_thumb.j

post-81542-0-95001500-1440183513_thumb.j

post-81542-0-87410600-1440183528_thumb.j

Edited by keiser31 (see edit history)
  • Like 1

Share this post


Link to post
Share on other sites

The rear ratio is 4.1:1 for a standard transmission and 4.3:1 for an overdrive transmission. 

MIne has an after market 4.1:1 incorrectly fitted and makes it a bit "sluggish' with my overdrive engaged.

Luckily I have been able to find a brand new 4.3:1 Crown and Pinion set for later fitment.

  • Like 1

Share this post


Link to post
Share on other sites

Wow, The car just arrived today and is better than expected.  I also discovered it is equipped with an overdrive !!!  The seller never mentioned that in his ad.  I haven't driven the car yet so I don't know if the OD actually works. Got my fingers crossed though.

Share this post


Link to post
Share on other sites

You should have no trouble with the occasional freeway run especially with OD. Your car is equipped with aluminum pistons and insert bearings with full pressure lubrication. Niceties not all cars had in those days. Also, the large diameter wheels make up for the low gearing to a certain extent.

 

Do a compression test. That type engine is prone to broken pistons for reasons I have never been able to figure out but probably not connected to high speeds. As long as you have good compression and good oil pressure you should be good to go up to 60 - 70 MPH.

  • Like 1

Share this post


Link to post
Share on other sites

Today she's going up on my car lift for a brake bleed, adjust and inspection.  After that I'll warm her up and do a compression test.

I'm assuming somewhere around 90 to 100 psi would be healthy.  Anybody know what the psi would be when new ?

 

On another note the dash knobs have mostly crumbled away. Is anyone reproducing these. I tried the search function and nothing turned up.

 

Thanks

  • Like 1

Share this post


Link to post
Share on other sites

???Who is Wayne???

 

I did a compression test and they all range between 90 - 95 psi. Yahoo....Good news !

 

I'm going to have to buy new tires for the car.  Right now it has some old polyester cord bias ply L78-15's on the "Truespoke" wire wheels. Too wide in my opinion. What would a narrower size be in a wide white wall radial ? The taller the better.

 

Or ,better yet, who has a set of original 16" rims for sale for this car ?

Share this post


Link to post
Share on other sites

The closest to original size in a radial, would be the cheapest ones you can find. I used to buy Marshal 791 tires from Walmart in 205 75 R 15 size. They are nearly the same size as a 6.70 15 bias ply. The cheap tires are noticeably taller and narrower than the expensive name brands.

 

Or you can go to a specialist like Coker.

  • Like 1

Share this post


Link to post
Share on other sites

There are some original 16" wheels on E bay now, well,.... last time I checked, or try Moores salvage yard.

An almost correct radial replacement is a light truck radial 185 85 16, but it seems they are strangely not available in the States,but most every where else including Down Under.

Rich

  • Like 1

Share this post


Link to post
Share on other sites

Another question.........?

With the overdrive engaged what would the final drive ratio be ?

A standard trans would be 1 to 1 final drive. 

I'm just trying to calculate the rpm's with my new 205/75-15 tires at 27.11" diameter when in overdrive.

Edited by Reg Evans (see edit history)

Share this post


Link to post
Share on other sites

I found the answer thanks to FORDification.com of all places.

When a 4.3 rear end car is in OD the ratio becomes 3.01.  This is determined by simply multiplying the 4.3 x .7 ......  Yahoo !

Edited by Reg Evans (see edit history)

Share this post


Link to post
Share on other sites

Reg,

Different trannys may have different OD ratios.

Hi gear is 1 to 1 and an OD gear may be 1 to 1.15, 1 to 1.2 or 1.3 etc. out put from the transmission. (these numbers are just for an example)

I suspect that the OD ratio of your tranny is listed in some manual somewhere. Maybe someone on this forum could determine that for you.

You can divide the gear ratio in the rear end  by the OD out put from the tranny to achieve a final ratio.

 

In doing the math that you provided yours would be a 1.428 OD gear. This seems like a pretty high number to me. Although could be correct I don't know.

 

If there is a way to lock your transmission in the OD gear and mark the drive line and the rear tires (or drums) if easier. Then turn the rear wheels TOGETHER and count the number of times that the driveline turns (it will be a few turns and a fraction of a turn) for one full revolution of the rear wheels it will result in a final ratio and give you some numbers to work with to determine your OD gear ratio. Just make sure that the wheels are rotated at the same speed as each other.

So if your drive line turns 3.01 turns in the experiment then you indeed have a 1.428 OD gear.

You could do this in high gear and the drive line should turn 4.3 times for one full revolution of the tires.

 

Final drive is usually the revolutions of the wheel to revolutions of the engine. A transmission in high gear is indeed 1-1 but this is not considered the final drive ratio.

 

Kind of fun figuring this stuff out.

Edited by JACK M (see edit history)

Share this post


Link to post
Share on other sites

Today I installed a Spitfire head on the '39 Royal.  The average compression reading on the original head was 92psi.  With this new head milled .050 the compression has gone up 13% to an average of 104psi.  Anyone know what the higher reading did to the original 6.5 compression ratio ?

 

 

 

post-79638-0-28764000-1444256298_thumb.j

  • Like 1

Share this post


Link to post
Share on other sites

My wife I did notice that the car had an easier time climbing the hills around here on the way to town the other day. No down shifting where I had to before. :)

Now I'm thinking I'll mill the original head with the Chrysler medallion riveted to it to -.80.  I've heard they can be milled even more but I don't want to push it.

Share this post


Link to post
Share on other sites

If you have any doubt about how much the head can be milled you first to do a valve clearance check. Pull the head, don't damage or throwaway the gasket. Clean the combustion chambers in the head to remove all of the carbon build up. Get a package or two of modeling clay (yes the stuff kids used to play with). Press clay into the area of the combustion chamber that is above the valves, put enough to cover an area larger than the valves, make it a least 1/4 inch thick.  Maybe rub some Vaseline or spray WD-40 on the valve heads to assure they won't stick to the clay. Put the gasket and head back on the engine and snug down the nuts on the head studs. Then rotate the engine by hand or by bumping the starter. Rotate it enough that all cylinders make a full cycle. Remove the head being careful not to disturb the clay.  Finally, using a depth gauge of some type, like a tire tread depth gauge, or, some makeshift method of your own that can be measured with a caliper, and measure depths where the valves have squished the clay. The center of the valve impression should be the thinnest because that should be the high spot of the valve.

 

Using the thinnest measurement you find you can do some ballpark arithmetic. Depth measurement of the clay less thickness of the head gasket, and less a few thousandths for heat expansion of the valve, should give you the number of thousandths to work with milling the head. Someone a little smarter than me should be able to tell you about how much to allow for heat expansion of the valve.     

Edited by Bob Call (see edit history)
  • Like 1

Share this post


Link to post
Share on other sites

If you are serious see if you can find a head off a 1958 up Dodge truck. They used the 251 engine in 2 ton and larger trucks until 1962. They have the highest compression and best combustion chamber shape. If you live outside the US, Canadian made Plymouth and Dodge cars and light trucks used the same engine till 1959.

Share this post


Link to post
Share on other sites

My wife I did notice that the car had an easier time climbing the hills around here on the way to town the other day. No down shifting where I had to before. :)

Now I'm thinking I'll mill the original head with the Chrysler medallion riveted to it to -.80.  I've heard they can be milled even more but I don't want to push it.

I know of a head with the Chrysler cloisonne ribbon on it... a part # 635...  IE...# 635987  or something close to that  .

What were these cloisonne Chrysler Ribbon heads off of?

Two small brass pins staked the medallion ribbon to the head right behind the thermostat housing.

Share this post


Link to post
Share on other sites

The head on my 39 Chrysler had that medallion staked to it when I got the car.  Not sure how many years they used that medallion or even if it's a factory head for my car.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...