318 Poly Stroker

There's a fella over on Bbodiesonly.com that just built one with a dyno session. Head over and check it out.

That poly motor weights about 30 lbs. more than an LA motor. They can be built to make torque but the hunt for real HP is too much $.

Never built one but the heads limited flow are going to ultimately hold you back, depending on what kind of power you're after. It's kind of funny but I personally think the aftermarket shouldve hooked onto the Poly head, an aftermarket canted valve SB Mopar head would be sweet

If you really want to build a small displacement motor of the Hemi variety that has some relevance to today's world I would suggest you go for a 5.7 Hemi. They are plentiful now in the yards as cores, you can use a conventional intake, carburetor and distributor to eliminate swap hassles and they fit the late O/D transmissions. Remember Chrysler dropped the Poly in favor of the LA motor to save manufacturing costs and there really is no need to build an antique motor just because you can.

There are several major impediments:

1. You will need custom pistons, as AFAIK there are no stroker Poly pistons out there. The intake valve needs a relief pretty close to the edge of the piston.
2. Camshafts are quite hard to come by. Camcraft has some new cores, but their hydraulic flat tappet grinds start at about 242 degrees at 50 lift. The other alternative is regrinding, and you are limited by what the lobes look like on the cam.
3. Intake manifolds are very high priced. There are only a couple of aftermarket manifolds, the Weiand 7503 and Edelbrock P-600. Weiand 7503s are selling for around $500. The P-600 is an antique design that for the most part runs Stromberg 97s, although a few were made that used a Rochester two-barrel. Neither intake is available new.
There is a factory four-barrel, found on 1962 and older. This is also selling at about $500. The factory dual four barrel intake is currently the lowest priced, running around $250 last I checked.
There is SUPPOSED to be a new intake that looks superb, but I don't believe it's hit the streets yet. It is around $600.
4. Then there are the heads, which flow quite equivalent to a 360 smog head, around 200 cfm at max. They also have the same problems as LA motors, with short installed height making spring selection more difficult.
5. Exhaust will also be problematic. All Poly exhaust manifolds are logs, definitely low performance, and there are no headers readily available for the Poly exhaust port layout. Cleveland Ford comes closest.

Now put this together with an engine assembly weighing around 60 lb more than an LA motor and you will see why it's not a solution to your problem. Also, like the Hemi, the Poly stroker will take a lot of $$$$$$ to make a horsepower.

Pavlovich's Poly stroker made 400 hp, not exceptional.

I say all this and I like Polys, ran one for years.

If I was going to start a new engine family it would be GIII Hemi. Makes no sense to go anywhere else.

R.

http://www.forbbodiesonly.com/moparforum/showthread.php?88085-Poly-Stroker-Dyno-Numbers

405 HP 4900/ 472 Lbft 4100

Here's the articles from the guy that is sort of a pioneer in building the Poly stroker. Another person who is an expert on the Semi-Hemi is Bill Richardson at Ram Racing. http://www.1962to1965mopar.ornocar.com/poly318.html

http://www.forbbodiesonly.com/moparforum/showthread.php?61890-CNC-Ported-318-Poly-Heads/page2

CNC heads

Heads and cams hold the Poly back. Intakes are avilable but as said, a bit crazy in price.
A new intake from Chrysler Power is available. At $600 (or so) that is really expensive! But a low run (basically custom) intake is allways going to be that way. And for any antique engine. The Poly was not what I'd call popular ether. That's 3 strikes on it. The only benifit to it is that it shares parts with the LA. While a real plus, I don't consider it a great one.

The CNC heads are nice. The rocker issue isn't sorted out just yet. Once the rockers are fitted, that guy could brake 500HP with the right cam.

The poly uses the same cam length as an LA. It's IEIEIEIE prove to be the problem. I myself have not looked into this.

TTI makes Poly headers and exhaust to hook up to it for many makes and models.

Truly, this "A" engine is one that you want to build. Other engines are cheaper.

I gave some thought to that idea years ago, and by the time I had crunched the numbers, I realized I would be cheaper to build a nice 440 and do the entire big block swap. And of course, you can build a 500 horse 440 with your eyes closed.

That being said, I would enjoy the heck out of seeing a stroker poly come together.

I am a Poly kind of guy, I own a Weiand 7503 and have been all through the Poly stuff. I can rattle off part numbers for pistons etc with the best of them.
Years ago my little brother told me the Poly 318 was stouter than an LA 318 and stock for stock, 2-barrel against 2-barrel, the Poly wins. It has much better heads than the 318 and its cam is about the same as a 360. So it runs pretty well.
BUT, building a stroker that maxes out at 405 horsepower? You can build a nearly stock 360 that will make that kind of power, and a lot more. Torque? that wasn't a boatload of torque.
So you take the expensive intake and the custom pistons and the stroker crank and the $1000 or much more for headwork and paying more for headers and you have an engine that any carbureted 5.7 Hemi will beat and weigh 150 lb less, be much easier on fuel, and cost less to boot.

What really pi$$es me off is all this ignorant hot air being blown around by people who are fooled that the engine really compares with a Hemi, because someone called it a semi-hemi.
This kind of horse crap has caused these giveaway engines to all of a sudden be advertised for $500 for a core.

Now let's get into the wonderful CNC heads referenced above. Big honkin deal. So it's a CNC program. Read the writeup. Every intake port has a pushrod tube in it. They broke through one intake port in another place but that's okay, because it isn't an exhaust port so you can stuff some epoxy into it.
What this tells me is that those heads are max ported and thus:
a. They are really expensive, and
b. They are about as durable as a potato chip.

It just doesn't add up. Years ago I corresponded with E-berg about this subject, and he said don't waste your time. I didn't want to believe him back then, but he was right. And that was way before the new Hemi. At that time the Mag motor was the way to go.

So guys, let's not fool ourselves into thinking the Poly is some kind of hidden gem that's been ignored for 55 years because everybody was just too stupid.

People will do what they want, it's a free country. I may still build a Poly stroker, but it'll be because I want to be different. Heck, I might just decide to build a 273 stroker! But I won't be kidding myself about how totally gnarly my motor is, it'll just be something I did for myself.

And, if I didn't have enough money to contemplate a GII Hemi, I for sure wouldn't go back in time to the Poly when the GIII Hemi rolls out of the factory door with a roller cam and heads that flow as well as those max-ported Poly heads. No way you can't build equivalent horsepower with the new Hemi for less than the stroker Poly motor.

R.

Anybody want some flathead Ford stuff? It's just a little bit older.

I have a poly engine in my Valiant, runs pretty decent.This engine has ported heads, a four barrel intake and a mild Scneider cam, the engine will in the next couple of months be replaced by a 340, it is for sale cheap.

Joey

As much as the above is right, I would much rather look under the hood and see the old poly as opposed to any new gen hemi engine. Just looks more at home.

stuff an f3 on it and see how much power it makes.....

I was going to look at a boat his weekend with an A318 motor. After checking into Poly performance parts, I decided against it. The boat was a 1966, if it had been 1 year newer with the LA318, or had a 273 in it, I'd probably buy it.

Yes, first car I ever drove was my dad's 66 Coronet with a 318 poly. Which we rebuilt. So I know prices and parts limitations.

The price of a custom poly piston notwithstanding, it won't cost a nickel more to stroke this out to 426 than an LA. Of course as others have pointed out a stone stock 440 swap will get you the same results for less $$, but where is the sport in that?

I have a 65 C-body wagon with a poly and an extra 100 cubes of bottom end torque would be most welcome. Will the heads limit horsepower? Absolutely! With the heads cleaned up with bigger valves and a good valve job I would expect it to be completely out of breath at 45-4800 or less but guess what, it's a 5000 lb cruiser that never sees the high side of that rpm anyway. 340 ft/lbs to 450-475 will cause tires to protest.

As for those CNC heads $2800?? Most shops that I see advertise CNC ports are around $1000 +/-. I realize these are max ported because they have to install tubes etc but does that really add $1800 to the job? I suppose cast iron causes more wear and tear on the equipment than aluminum but the price seems to be a tad extravagant.

Kevin