318 Poly Flow Test

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Earlie A

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Not really an A-Body thing, but a cool engine none the less. My first car was a 1966 Coronet 440 with a 318 poly. My father bought it new. I've had the heads in the shop for quite some time, and I finally took the time to rig up the valve opener and flow test the intake. Small ports and not much flow, but these are cool heads. Nice, centered, unobstructed intake port. Combustion chamber with canted intake valves and quench area on both sides. Short, direct exhaust port. Nice design for the 1950s.

Flow numbers are attached. Flow numbers from an iron 360 head with 1.88 valves are included for comparison. Poly has 1.84 intake valve.

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THat's really interesting. Thanks for taking the time to do it and post results. I wonder what thr poly head would do fully ported with big valves?
 
RustyRatRod said:
THat's really interesting. Thanks for taking the time to do it and post results. I wonder what thr poly head would do fully ported with big valves?
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Other people have gotten 250-260 cfm out of them. Even saw one report of 270 cfm. There are some strokers making 500hp. Cams and intake manifolds are expensive.
 
Earlie A said:
Other people have gotten 250-260 cfm out of them. Even saw one report of 270 cfm. There are some strokers making 500hp. Cams and intake manifolds are expensive.
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Yeah I've seen Gary Povlovich articles about them. The 4" arm for the 340 is a direct drop in. They can be made into stump pullers.
 
Does anyone know if Gary Pavlovich is still actively working on the polys? Haven't seen anything from him in a few years.
 
I’ve only ever worked on maybe 5 sets of those.
Just general rebuild stuff.
I actually did a set over the winter.

Not a big fan, but to each their own.

I see it as a pretty big chunk of iron for only 170cfm.
 
Totally agree that they are big, heavy and in stock form don't flow much. Performance parts are expensive if they are even available. Valvetrain angles are wonky so not the greatest for high rpm use.

But the neat part is the advanced design for the 1950s. The port arrangement and chamber are similar to the modern hemi. It has dual quench pads and canted valves. It does not suffer from flow stall like the wedge head. The engine likes 30 degrees of total timing compared to the 35-36 that a wedge head needs. Volumetric efficiency can be better than a wedge head. Very little valve shrouding. No pushrod pinch. Head can be ported to make north of 500hp with a broad, flat torque curve. Block is a little stouter than the 318LA block. It has its advantages. Dollars per HP is not one of them.

IMG_2632.jpg


I bet there's 5 cfm of trash on the walls. That would get it all the way to 178!
 
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For me it’s a typical situation where, “the juice isn’t worth the squeeze”.

But I’ll follow along if you’re going to start carving on them.
 
Dartswinger70 said:
Weren't those engines real torquey? propelled the heavy cars pretty well like the C bodies?
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They were certainly low speed engines with small ports and 2-barrel carbs. Throttle response was good and efficiency was pretty good. Probably a little torquier than the later 318. I had my '66 Coronet up to 115mph once when I was a teenager. That was going down a big hill, lol. That was the only time it felt like it had power steering. Front end was very light.
 
Chrysler engineers in the fifties were good at spending extra money to obtain little if any real benefit. Canted valve poly heads that didn't flow as well as cheap wedge heads (at least the poly heads were cheaper than hemi heads, albeit not nearly as effective), ball and trunnion u-joints that were a bear to service and weren't any smoother (to my insensitive butt) than normal u-joints, dual leading shoe drum brakes that also were a bear to service and, even when adjusted correctly, of questionable benefit in the real world, and (late forties and early fifties) fluid drive transmissions that were more complicated than a real automatic transmission and killed performance - just so Chrysler products could keep their "safety clutch."

I say this as someone who owns several of these cars and loves them all despite their quirks.

My 56 Belvedere, with a 277 poly, factory four barrel and dual exhaust (not original carb or air cleaner). Motor looks just like a 318 poly.

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Earlie A said:
Totally agree that they are big, heavy and in stock form don't flow much. Performance parts are expensive if they are even available. Valvetrain angles are wonky so not the greatest for high rpm use.

But the neat part is the advanced design for the 1950s. The port arrangement and chamber are similar to the modern hemi. It has dual quench pads and canted valves. It does not suffer from flow stall like the wedge head. The engine likes 30 degrees of total timing compared to the 35-36 that a wedge head needs. Volumetric efficiency can be better than a wedge head. Very little valve shrouding. No pushrod pinch. Head can be ported to make north of 500hp with a broad, flat torque curve. Block is a little stouter than the 318LA block. It has its advantages. Dollars per HP is not one of them.

View attachment 1716257818

I bet there's 5 cfm of trash on the walls. That would get it all the way to 178!
Click to expand...

Hmmmm interesting intake port.
 
65 Cuda 340 said:
Chrysler engineers in the fifties were good at spending extra money to obtain little if any real benefit. Canted valve poly heads that didn't flow as well as cheap wedge heads (at least the poly heads were cheaper than hemi heads, albeit not nearly as effective), ball and trunnion u-joints that were a bear to service and weren't any smoother (to my insensitive butt) than normal u-joints, dual leading shoe drum brakes that also were a bear to service and, even when adjusted correctly, of questionable benefit in the real world, and (late forties and early fifties) fluid drive transmissions that were more complicated than a real automatic transmission and killed performance - just so Chrysler products could keep their "safety clutch."

I say this as someone who owns several of these cars and loves them all despite their quirks.

My 56 Belvedere, with a 277 poly, factory four barrel and dual exhaust (not original carb or air cleaner). Motor looks just like a 318 poly.

View attachment 1716257889

View attachment 1716257890
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That’s a beautiful Belvedere!
 
Earlie A said:
Totally agree that they are big, heavy and in stock form don't flow much. Performance parts are expensive if they are even available. Valvetrain angles are wonky so not the greatest for high rpm use.

But the neat part is the advanced design for the 1950s. The port arrangement and chamber are similar to the modern hemi. It has dual quench pads and canted valves. It does not suffer from flow stall like the wedge head. The engine likes 30 degrees of total timing compared to the 35-36 that a wedge head needs. Volumetric efficiency can be better than a wedge head. Very little valve shrouding. No pushrod pinch. Head can be ported to make north of 500hp with a broad, flat torque curve. Block is a little stouter than the 318LA block. It has its advantages. Dollars per HP is not one of them.

View attachment 1716257818

I bet there's 5 cfm of trash on the walls. That would get it all the way to 178!
Click to expand...
Looks like the port shape should work really well, just needs to be bigger.
 
Every single engine out there had its disadvantages. I like the poly regardless if those it has. The bottom line is, if it's what you like, build it. It'll respond to high performance mods just like any other engine.
 
I have an old factory 318 Poly dual-quad intake, & a pair of rough WCFB's to go with it, I've wanted to get a mill to go with it & go to town on the heads myself. There have been some nice one's offered here on FABO, but a looong ways away, too far to fetch for Me.
 
Earlie A said:
Totally agree that they are big, heavy and in stock form don't flow much. Performance parts are expensive if they are even available. Valvetrain angles are wonky so not the greatest for high rpm use.

But the neat part is the advanced design for the 1950s. The port arrangement and chamber are similar to the modern hemi. It has dual quench pads and canted valves. It does not suffer from flow stall like the wedge head. The engine likes 30 degrees of total timing compared to the 35-36 that a wedge head needs. Volumetric efficiency can be better than a wedge head. Very little valve shrouding. No pushrod pinch. Head can be ported to make north of 500hp with a broad, flat torque curve. Block is a little stouter than the 318LA block. It has its advantages. Dollars per HP is not one of them.

View attachment 1716257818

I bet there's 5 cfm of trash on the walls. That would get it all the way to 178!
Click to expand...
What was the test bore being used?
 
Killer6 said:
I have an old factory 318 Poly dual-quad intake, & a pair of rough WCFB's to go with it, I've wanted to get a mill to go with it & go to town on the heads myself. There have been some nice one's offered here on FABO, but a looong ways away, too far to fetch for Me.
Click to expand...
Don’t know how far you are from Cleveland, OH. There’s a guy on FBBO that had two 1960 complete engines for $150 each.
 
Just picked up a 318 poly motor and single 318 LA head. I'll try to do a 318A vs 318LA flow test soon. Should be fun.
 
Here's the results of the 318LA vs 318 poly flow tests. Both of these heads were old, came off of 100,000 mile engines and look to be bone stock. This test proves nothing, but it is a fun comparison.

Notice how the superior breathing capability of the poly shows up at higher lifts. This is because of less shrouding (a better utilization of the entire valve perimeter), less loss of short turn flow, a less obstructed port and a slightly larger valve.

It would be interesting to put the same valve job on both heads and retest. It's hard to compare the two heads now because the quality of the valve jobs is unknown.

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Grind the seat on the LA to accommodate the valve out of the poly head and see what happens.

Which LA head are you working with?
 
PRH said:
Grind the seat on the LA to accommodate the valve out of the poly head and see what happens.

Which LA head are you working with?
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It is a borrowed head from a 318. I don't own it. It would be a more fair way to compare ports however.
 
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