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Question for early (55-57) Poly engine experts
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56D500boy
Posted 2019-03-12 12:17 PM (#579238)
Subject: Question for early (55-57) Poly engine experts



Expert

Posts: 4993
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Location: Lower Mainland BC
Canadian built 56 Custom Royal (D63) Dodges supposedly got the 303 Plymouth engine, not the 270 or 315 Dodge polyspherical engines. One of our forum members (Steve B) is in Australia and has a RHD Custom Royal that he thought had a 303 V8 because he (and I) understood that the RHD export cars were built in Canada and therefore a RHD export 56 Custom Royal would have a 303. I was reviewing his photos today while cleaning out my email inbox and decided that something was wrong with our understanding and the he might actually have a 218 hp 315 2bbl poly, not the 303. This is what I just sent Steve:

"1. Your engine number D633-48597. That is a 315 poly number. *HOWEVER* I also notice the "L C" below the number. Other than "low compression" I don't know what that means. (See photo below)

2. Your intake manifold sits high and above the valley cover. That is not a 303 feature. Based on what I read "The A-engines had polyspherical heads, like the “semi-hemis;” one major difference is in the way the “valley” is covered. The older engines had a separate valley cover; to save time and money, the A-engines used the intake manifold to cover the valley, instead. Both series of polyspherical-head engines looked rather similar otherwise, with their scalloped valve covers and rear-mounted distributors, but looks can be deceiving."

REFERENCE: https://www.allpar.com/mopar/a-engines.html"

Since I sent him the email, I see that he has a Detroit style cowl tag, which is different than a Canadian 56 Dodge cowl tag (see below) (Thanks Kent).

Bottomline: I think that Steve's car was built in Detroit and has a 315 poly.

But what do the experts think?





Edited by 56D500boy 2019-03-12 3:17 PM




(SteveBsCustomRoyalEngineInAustralia.jpg)



(SteveBsEngineNumber.jpg)



(SteveBsCustomRoyalSedanCowlTagInAustralia.jpg)



(KentKsCanadianBuilt56DodgeCowlTag.jpg)



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Attachments SteveBsCustomRoyalEngineInAustralia.jpg (183KB - 29 downloads)
Attachments SteveBsEngineNumber.jpg (145KB - 30 downloads)
Attachments SteveBsCustomRoyalSedanCowlTagInAustralia.jpg (64KB - 30 downloads)
Attachments KentKsCanadianBuilt56DodgeCowlTag.jpg (106KB - 30 downloads)
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Mopar1
Posted 2019-03-12 6:16 PM (#579257 - in reply to #579238)
Subject: Re: Question for early (55-57) Poly engine experts



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Location: N.W. Fla.
Obviously not an A Poly. D633 is listed as a Dodge 315 Poly.
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56D500boy
Posted 2019-03-12 9:19 PM (#579264 - in reply to #579257)
Subject: Re: Question for early (55-57) Poly engine experts



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Posts: 4993
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Location: Lower Mainland BC
Mopar1 - 2019-12-12 3:16 PM

Obviously not an A Poly. D633 is listed as a Dodge 315 Poly.


I agree. I was just hoping that somebody with a Plymouth 303 would post a photo or at least comment that the intake shown in the photo above that I posted is NOT a 303 intake.

Here is a photo of a US 56 Dodge Custom Royal with a D633-60nnn engine (Jan. 56 build date for the car). It is a 230 hp 315 Super Powered Super Red Ram 4bbl dual exhaust Poly power pack engine. On that basis, based on the similarities to the Australian 56 RHD Dodge's engine, I think that it is safe to say the Aussie car's engine is the 218 hp 2 bbl Super Red Ram 315 poly.

Thanks go to George B. for the engine photo.





(engine right.JPG)



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Attachments engine right.JPG (107KB - 29 downloads)
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58coupe
Posted 2019-03-12 10:09 PM (#579267 - in reply to #579238)
Subject: Re: Question for early (55-57) Poly engine experts



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Location: Alaska
As to the LC, i think you are right to assume low compression. I have seen GM engines for export also listed as low compression. It could be that high octane gas was not very available in the 50s in foreign countries. Do any of our members from "down under" have any info about this?
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56D500boy
Posted 2019-03-12 10:46 PM (#579268 - in reply to #579267)
Subject: Re: Question for early (55-57) Poly engine experts



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Posts: 4993
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Location: Lower Mainland BC
58coupe - 2019-12-12 7:09 PM

As to the LC, i think you are right to assume low compression. I have seen GM engines for export also listed as low compression.


I think that is going to be the answer. It would have been fairly easy to drop the compression ratio a bit by just installing two head gaskets per head. I know that has been done on some turbo engines when they want to go to higher boost levels with a fairly high native compression ratio, e.g. 9.3 gets dropped to 9.0 with two head gaskets.

Hopefully some Aussie bloke will chime in with some octane history in Oz.

Maybe even Steve.

(Steve???)



Edited by 56D500boy 2019-03-13 8:58 AM
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Steve1956
Posted 2019-03-13 7:30 PM (#579301 - in reply to #579238)
Subject: RE: Question for early (55-57) Poly engine experts


Member

Posts: 16

Hi Everyone, I am no expert on this, but just on doing some goodge research, it seems that the HIGHEST octane rating in Australia in the fifties was 89 RON.

In most countries in Europe (also in Australia, Pakistan and New Zealand) the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2. It may also sometimes be called the Posted Octane Number (PON).

So I am not sure what the 315 V8 would have needed , but if the LC does stand for low compression, then maybe there was a higher equivalent available in the USA at the time ?

At least it won't need to be LC when restored in the next couple of years !!

Steve B
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56D500boy
Posted 2019-09-07 11:07 AM (#587210 - in reply to #579301)
Subject: RE: Question for early (55-57) Poly engine experts



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Posts: 4993
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Location: Lower Mainland BC
Steve1956: I got your email last night but had to deal with an attempted break in at our house (discovered after we were out for the evening) so I couldn't help you then. (House is secure again now - they did not get in anyway).

Your WW3-133 E Stromberg 2 bbl carburetor seems to be from 1955 Dodge (smaller poly engine, 2 bbl). The dashpot would be because of the Powerflite. (Oddly my 4 bbl carb on my 315 hemi in my 56 Dodge with Powerflite does NOT have a dashpot).

The WW3-140 2bbl Stromberg is, I think, what the 218 hp, 315 cu in 56 Polys used. But they weren't "LC" (low compression). So the WW3-133 E might be appropriate for your 56 LC Poly *OR* it is just something that worked and somebody swapped it on, back in the (some?) day.

Maybe some one (Del??) can chime in a post up their 2 bbl 56 Poly 315 (or 270 Poly) carburetor numbers (or photos that show info). I know George B and Dave N have the 4 bbl Powerpack 315 engines.

55-58 Dodge Carburetor Part Numbers:

3-nnn = Stromberg 2bbls, 2nnn = Carter 4 bbls.



Edited by 56D500boy 2019-09-07 11:43 AM




(55-58DodgeCarburetorPNs.jpg)



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Attachments 55-58DodgeCarburetorPNs.jpg (166KB - 2 downloads)
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