I got a note from my good friend Gary Pavlovich about his most recent dyno run with a stroker poly, here is what he had to say: Had a nice engine break-in session on the dyno the other day with one of my 390" Poly Stroker builds. We made 412HP@5600rpm and 438ft.lbs.torque. As is common with the Poly 318 engine the HP and Torque curve was very high and flat. We averaged 428ft.lbs. of torque from 3400rpm to 5400rpm...now that will set you back in the seat and keep you there; not bad for a "throw-away" motor. Cast iron dual quad w/500cfm Edelbrocks, 9.5compression, Hyd. Poly Cam with 290/.482" Advertised and 232@.050" , 1.94/1.60" 11/32" Stainless Valves, a modest head flow of 208/151cfm @.500" lift, 16deg. initial adv. 34total...should make a few more HP and Torque once the rings get used to their new home. So, for those who want something a 'little' different, one of those old throw-away polys may be the ticket.
Those seem like some pretty impressive #s for a Poly. I've always loved these motors and found them to be pretty impressive even in stock trim with a 2bbl Carter and restrictive heads and exhaust. I've only seen one stabbed into a traditional hot rod but it caught my eye right away.
The guys who usually bash Poly's have their heads so far up a small block chevy's girdle they don't know anything else. I've heard them (the Poly's) called 'mini max wedges'. They are different, and Mopar (which means more durable than any GM product) and that's all good.
I'm betting there's a lot more power to be had in the heads. That cam [232@50] is probably about as hot as you could go with those flow numbers feeding 390 cubes. Still damn impressive... And with the dual quads and them purdy valve covers... Drool!
Polyspheric. They were basically de engineered hemi. The hemi heads were heavy and expesive, so MOPAR engineered thes single rocker heads that were designed with a less than hemisperical spaed combustion chamber. Sometimes ther are referred to as Semi Hemi's. The blocks were the same and the heads are generally interchangable within engine families. There was a change in block and head designs that did not interchange. Had to be on your toes to keep up with chrysler's engineering dept. http://www.allpar.com/mopar/poly.html
Send a note to Gary Pavolich, maybe he has something from the assembly part of the job. Externally, it will look just like any other 318P. .
The main poly engine was the 277,301,303, 318 Plymouth "A" series engine which ran from about 1956 to 1966. There was a dodge poly that ran from 1953 through to 1958 and a similar type of poly in the Chryslers. Dodge did use the Plymouth style of poly from 1959(?) onwards when the "families" were brought back together again with a common series of engines across all Mopars NONe of the heads are interchangeable from one "family" to another with the exception of the desoto 325 ci poly engine which was a Dodge 325. Plymouth fits plymouth and Dodge fits Dodge in their early distictive own poly engines. Even in the Hemi's the Families Heads were not interchangeable. The engine GAry is talking about here will of come from the Plymouth range or maybe later model (59 onwards) Dodge vehicle.
I had a polyhead, seized up... never could get it apart. Finally got rid of it, still got the factory dual-quad setup and stock linkage tho.
People have a tendency to bad mouth what they don't understand. The same can pretty much be said about any engine family. Its just a shame that you fellas have to bad mouth the SBC every chance you get, you should all just get over it. 73RR, Those are good numbers from from the little almost a hemi. They are just sweet motors to work with, and there is an upside the little poly weighs less than a baby hemi by a couple of pounds. Anytime you can squeeze comparable numbers out of a lighter package you are in pretty good shape.
I love those engines! I had thought about putting one in my Model A years ago, but at the time the running Polys I saw for sale people were asking the same price that I could get a runner 440 for, so it was kind of a no brainer. Still, if one falls in my lap... I'd have broken legs...
Basicly what some call a pent roof design with canted valves, some have said a prerunner to the BB Chevy & Ford Cleveland/429/460 series.
Boy, I'm not sure how all of the extraneous 'poly' info got into this discussion since it started with something very specific; Poly 318, as 35desoto notes.
If we're playing the "let's see how many polys we can add to this post" game, these polys get pretty good numbers, too: http://www.allpar.com/mopar/new-mopar-hemi.html The Mrs has a new black-on-black with black stripe '11 "Moparized Challenger" that I'm not allowed to drive. Trust me, I know they can perform. ~Jason
Gary's done a great job here with this engine - some good numbers there. The limiting factor in this engine is the head flow - 390" with more cfm in the low -mid lift range would make a lot more power from this combo. I wonder what kinda CR & VE this engine had with that combo of parts. Do you know Gary ? Unfortunately, others do not agree with this logic......"strokers are for wankers who like to lean on the bar and brag...." Rat
Read all about it and more, plus talk to Gary & the rest of us at the 318 Poly Yahoo Group: http://autos.groups.yahoo.com/group/318poly/
Impressive. I always like to see guys doing things different. I wonder how much it cost to get those numbers?
The 390 Poly stroker that 73RR refered to is my engine that Gary P, has built for my 1926 Chrysler 2 door sedan project. I have to say that I have nothing but good things to say about my experiences working with Gary. He is very knowledgable and a truly outstanding guy. The engine was bored 0.030 over to 3.94", compression ratio is 9.5:1 to keep the engine pump gas friendly. Pistons were custom made for this application. The engine itself is not as pretty as you might think, it is currently wearing a coat of black primer, until I figure out where I am going colorwise. I don't have plans to dress it much, I would rather keep it fairly stock in appearance. I have another poly (stock 318) that will end up in my wife's 1928 Essex 4 door sedan that will be running a nice Edelborck P600 three duece intake dressed with 3 Holley 94's and a mild cam. Can't wait to get this stroker poly screaming down the road, but that will be at least a year off as I have a lot of work still to do.
I don't know why anybody would diss on the poly 318. It doesn't cost that much to build over an LA 318. Much of the LA 318 stuff will interchange right over to the poly engine. I know good intakes are expensive for it which is a downfall and I think the cam's are different as well. They are reliable engines and they make around 40 more foot pounds of torque than a similar based LA 318.
Nice, big block torque curve out of a small block (sort of). My experiences with poly's has always been good, although I have never "built", just stock rebuilds, one with a four barrel added. Smooth torque that will shove a fairly heavy car around nicely. Once you learn it ain't gonna rev like a 340, you gear to use the massive torque output, you have a winner that is pretty much indestructable for decads and decades. And they look so freaking cool!
It is the design the Big Block chev and 351 Ford , 429/460 Ford were copied from. Angled valves toward the port. If you would suggest I am wrong I must tell you I once took a BB chev head and a poly 318 head and set them with combustion chambers showing. My friend "The Expert" said he could tell the difference and proceeded from about 15 feet away to pick the wrong one. I have one underway here just for "sumthin to do." I am using 400 ford pistons BTW> Bored it to 4 inch , stock stroke. (I am anti stroker in this case.) Gary BTW is a friend and we often talk long into the night since he is in a different time zone. Interesting guy. Deserves a lot of credit. He sent me a birthday present once I will never forget. Ask him about it. :>))) Don.
What is the compression distance on the ford slug? Are you fly cutting valve reliefs? How deep is the first ring? .
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