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Veteran
Posts: 189
 
Location: Northern Illinois | hello all, just aquired a 56 dodge custom royal lancer with the 315 poly (semi hemi) power pack motor. good for 230 horsepower. my goal is to build the motor up to 300 horse if possible. i know the basic h.p. increase (port and polish heads and intake) boost compression ratio and different cam profiles. i dont want to make a drag engine just something with a little more umph. i realize performance parts for this engine is scarce and expensive. any tips or tricks would be greatly appreciated. also will a powerflite handle the h.p. increase? thanks in advance!!! Tony |
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Expert 5K+
Posts: 9900
  
Location: Lower Mainland BC | .
Tony: Be aware that what you are calling a "poly" isn't necessarily what others might call it.
While I think that you are correct in calling the single rocker 1956 315 Dodge engine a "poly" (as in one that has a single rocker shaft and polyspherical heads), I think most people
will think of a poly as being a 318 Plymouth "A" engine (which later became the corporate 318 "A" (until the 318 small block "LA" was introduced in around 1966-67).
Those 318 "A" engines had the valve covers with the sawtooth lower edge (not the same as your 56 315 "poly" with the curved scallop valve covers).
All that said there are "Poly" experts out there who have general poly knowledge that might translate from the 318 "A" to your 315 poly.
Specifically I am thinking Justin L (PolyJ here) and Gary Pavlovich from Chrysler Power.
Here is information that Gary P wrote about improving performance of the 318 "A":
https://1962to1965mopar.ornocar.com/poly318.html
Don't expect to find much in the way of performance parts for your 315.
Not like this for a 318 A poly:
https://cpwebstore.com/Poly
Good Luck.
Edited by 56D500boy 2023-09-27 11:17 PM
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 (Extra 315 Poly Motor_Small.jpg)
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Veteran
Posts: 189
Location: Northern Illinois | thanks dave for the info. thats why i put the "semi hemi" phrase in. i do know about the difference in the engines. the "A" poly is a different animal than my 315, but maybe some tricks can transfer over. |
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Expert 5K+
Posts: 9654
Location: So. Cal | As far as I know, there are no cams available for it. You'll have to regrind your original. That will limit you in terms of the profile that you can create. You'll need adjustable or custom pushrods to compensate for the base height change. Make sure you use new valve springs with the proper amount of spring pressure, not the weak originals. I believe HotHeads sells a little larger valve for it, but not sure.
You'll need custom pistons of course, but probably best to get them anyway. I recommend running a true 10:1 or 9.8 if you want to be more conservative (based on a modern, thick head gasket, not the original thin steel gasket). The powerflite will be fine with 300 hp.
Building custom headers would be recommended to get better performance than the restrictive log style manifolds. I think Sanderson makes a shorty header for it, but not sure if it will fit on the driver's side. You can give them a try. For the intake, you have a choice of stock 4bbl, Offy 6 pack, or Offy 2 x 4. I think they recently stopped selling the Offys, but they are still around if you look for them.
If you want a little more grunt, you can try offset grinding the crankshaft to a small block chevy size, using small block chevy rods & custom pistons. This should get you a larger stroke & displacement.
Edited by Powerflite 2023-09-27 10:18 PM
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Veteran
Posts: 189
Location: Northern Illinois | thanks nathan for your input. all good tips but does sound expensive!! to increase compression ratio would decking the heads help with the original pistons? could i use d500 hemi pistons with the poly heads? just trying to figure out what i want to do. Tony |
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Expert 5K+
Posts: 9654
Location: So. Cal | No, don't do it, and no. Don't turn it into a hack job that you will regret.
If you can't afford it, stick with stock pistons - that will get you 9.25 - 0.5 (for thicker head gasket) = 8.75:1 compression. Lousy compression that isn't compatible with a decent lobed cam. Not good. You can offset grind the crank to .03" undersize specs (make sure you can get the bearings first!) to get you .05" more stroke, which should get you back up to around 9.5:1 or so (I haven't done the math, but it's around there), using the stock pistons & rods. With that compression, you should be able to run a decent cam profile. That's probably the cheapest way of doing it.
Or you could have the crank welded and offset ground to stock bearing size. You could design it for any compression you want that way, and you are putting all the extra expense into the crankshaft.
Edited by Powerflite 2023-09-29 9:37 PM
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Expert 5K+
Posts: 6498
Location: Newark, Texas (Fort Worth) | Speed dome Is making new heads, water pump housing and other parts for the Dodge 315/325 which I believe is the same engine with the scalloped valve covers except he went with the HEMI. https://inthegaragemedia.com/a-look-behind-the-scenes-of-building-th... .
Edited by mstrug 2023-09-29 5:16 PM
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Expert 5K+
Posts: 9654
Location: So. Cal | There you go, that's how to make it cheaply! 
So he was able to get a 4" stroke out of offset grinding the crank down to small block Chevy size, giving 354 cubic inches. That's only offset ground by 0.1", he should have been able to get closer to .15" out of it. He must have really bored it out to get that big of a motor, or their numbers are off. A .06" overbore 315 should get you around 345 cubic inches with a 4" stroke. It looks like he really started with a 325 engine instead, unless it was a truck engine with excess wall thickness.
I would hope that there are better alternatives than purchasing a $2000 set of rods with a 22mm pin diameter like he supposedly did. That's pretty excessive. I don't see any reason why you would want to do that. Chevy rods are .94" wide, while the Dodge rod is .901" wide. So it should be a no-brainer to have some cheap Chevy rod cut down to fit properly. You could also use a small block LA rod that is cut down to fit, but there are likely less length variations available for them.
I looked for the aluminum heads they were mentioning, but didn't find a website for Speed Dome Engineering or any link to purchase them. |
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Expert 5K+
Posts: 6498
Location: Newark, Texas (Fort Worth) | https://opencorporates.com/companies/us_tx/0800034620
No matter how quickly you think you will be able to build your dream hot rod, the fact is it’s a lifetime in the making. There is no getting around the idea that Jack had the inspiration and put forth the effort to come up with the overall design. He then sacrificed countless days and nights to support the effort it took to build his ’32 Ford highboy roadster. Now, any project of this magnitude requires help … Jack was wise enough to enlist the help of George Hagy, who worked with Jack for much of the fabrication. To Jack’s “crew,” Gary Gates machined the bellhousing, firewall, and torsion bars that were added. A great deal of the mechanical work was handled by Mark Grohman, Donnie Anderson was the engine machinist and builder, Cody Chapman worked his magic on the EFI, Darryl Hollenbeck performed his masterful and artful touch on the body- and paintwork, Jimmy Shine and his staff worked on the many louvers found throughout the hot rod, and Sid Chavers handled the interior—another of the roadster’s strong points. To wrap up this project there was some “heavy lifting” handled by Roy Brizio and the team at Roy Brizio Street Rods as they completed the final assembly and finishing details. And, of course, not all work is physical and in Jack’s case he received a great deal of support and inspiration from Jackie Howerton who knows a thing or two about hot rods and race cars. All this from a lifelong dream of Jack’s that began to take shape back in 2000 from artwork by Thom Taylor.
For a hot rod that has undergone significant modifications it is conspicuous to see that Jack began with an original ’32 Ford frame. At this point Jack and Hagy teamed up to wholeheartedly modify the frame and work their collective magic. The front and rear of the frame is stepped while in back there is a two-piece hoop that allows for the rearend to be removed and replaced.
Powering the Deuce is a 355-cubic-inch (5.8-litre) early Dodge Hemi built by Donny Anderson and good for 420bhp at 5500rpm. It features a heap of custom parts, including cast aluminium heads and one-off stack injection machined by Cody Chapman.
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Veteran
Posts: 189
Location: Northern Illinois | thanks nathan and marc for your input. like you said nathan, maybe offset grind the crank may be the way to go. i was hoping there would be an easier way to build horsepower in this engine. i used to fool around with 318, 383 440 engines in the past. simple head swaps and different cam choices seem to bring these engines alive. 30 years ago parts were easier to obtain. have to figure out what to do with the cam, lobe and duration figues. not for sure what i want to do yet. Tony |
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Elite Veteran
Posts: 888
Location: Peoples Republic of Oregon | I'll add my 2¢
You basically need a complete rebuild with forged pistons @ 10:1, and a reground cam in the .450 lift x 220° @ 050 range. This, of course, then requires adjustable pushrods if you stay with hydraulic lifters. The heads could benefit from a minor cleanup in the ports and slightly bigger valves. Do not go overboard on springs. Yes, offset grinding the crank will give a few more inches and will use cheaper gm bearings but the rods will cost something...everything is a trade off. Make dam sure the rod big end matches the width of the oem or you will lose oil pressure.
You should budget at least $5K and expect more. |
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1956 dodge crl 315 poly performance
