318 poly heads?

[no1newb]

This is probably a stupid question, but would a 318 poly engine head fit on a 318 LA engine, and if so would it be worth it, i dont know really that much about the LA engine heads but i always hear about how the hemi or poly-spherical heads are very efficient, but was it just for that time, or were they still really good, just more expensive to produce or what.

i ask because someone is selling a 318 poly near me for $150, and I have never really worked on an engine, let alone have the equipment to pull a motor, but heads seem like theyd be a pain, but able to do in the car still.

 

[RustyRatRod]

I dont think so. what intake would you run if it would? If you like the poly motor. build one. you can get performance stuff for um. they are super cool.

 

[Dusterdude72]

Im not sure either.......I have a 67 318 and it has poly pistons in it but it has the 67 318 heads on it.....but I am not sure what the differences would be in the heads.

 

[no1newb]

i get around 11 or 12 mpg on my 318. and these guys are saying that they are getting 22 to 23 mpg with a 318 poly....I may be wrong, but if this is true, i may buy the engine anyway lol.

http://autos.groups.yahoo.com/group/318poly/message/11528

 

[caferacerx]

poly 318 is not going to give better fuel mileage or performance than an LA 318
one of the reasons that the LA engine was developed is because the poly was to wide to fit narrower cars like the A-body

11 to 12 MPG sucks! you need to figure out why you are getting such bad fuel economy

 

[Dusterdude72]

yeah, like was said.....it sounds like the fuel mileage is an issue with your specific engine......318's get better mpg's than that on average.

also ,the poly engines are alot heavier of an engine because they had so much more iron in the block.

 

[Gryzynx]

A long time ago, I stuffed a 318 poly into a '56 Dodge 1/2 ton. Can't recall the exact #s, but the fuel mileage was fantastic. Of course, this was with the larger Canadian gallon. Donor car was a '66 Belvedere that I bought as insurance salvage. Used the complete driveline including the highway geared 8 3/4 diff. I recall using $3 worth of gas for a 100 mile road trip, but this was in 1975.

As to the heads, I have heard of the LA wedge heads being installed on the poly block, so it stands to reason that the poly heads could be adapted to the LA block, but why you would want to do this may be questionable.

 

[no1newb]

This is probably a stupid question, but would a 318 poly engine head fit on a 318 LA engine, and if so would it be worth it, i dont know really that much about the LA engine heads but i always hear about how the hemi or poly-spherical heads are very efficient, but was it just for that time, or were they still really good, just more expensive to produce or what.

it was the first thing i asked. i dont know anything about the LA engine / heads, i thought they stopped with the hemi partially because it was expensive to fabricate the rocker and other unique parts and it was cheaper to go back to the original style.

 

[67Dart273]

It's been a long long time ago, but even though the heads won't interchange, they are close. Evidently it's pretty easy to confuse a poly and LA shortblock "by sight."

 

[goldfish65]

This is probably a stupid question, but would a 318 poly engine head fit on a 318 LA engine, and if so would it be worth it

Not a stupid question, keep on asking and learning. BTW congrats on doing your disc brake conversion yourself.

 

[rumblefish360]

The heads will in no way fit a "LA" engine.

The bottom of the valve cover edge should be a dead give away to it being a Poly head because the valve cover edge is scalloped. (Wavey)

The Poly can perform, but some parts are ghard to come by if not impossible. Expensive they can be.

They'll take a "LA" parts, but NOT CAMS! LOL

 

[1wild&crazyguy]

The heads will in no way fit a "LA" engine.

The bottom of the valve cover edge should be a dead give away to it being a Poly head because the valve cover edge is scalloped. (Wavey)

The Poly can perform, but some parts are ghard to come by if not impossible. Expensive they can be.

They'll take a "LA" parts, but NOT CAMS! LOL

Yep, no worky on the head swap.

The crank/rods yes, but the consider the year for some had flat crank flanges with no register.

Other than valve layout, between the 2, the Poly castings weigh more, even the rotating assembly weighs more, 2 lifter angles...chrysler came up with a redesign based on the cid/Bore&Stroke but with lots of weight shaved of, It's called the Light Assembly or LA 318
IMO The poly valve layout is nice and are where the P series Race heads sorta came from.
They just weigh a ton for how small the cid is, stroking one would kinda make up for this, but then there is only about one intake available , maybe 2 if you cn find the dual 4 factory iron, otherwise it's the weiand dual plane.

 

[HemiEd]

Yep, no worky on the head swap.

The crank/rods yes, but the consider the year for some had flat crank flanges with no register.

Other than valve layout, between the 2, the Poly castings weigh more, even the rotating assembly weighs more, 2 lifter angles...chrysler came up with a redesign based on the cid/Bore&Stroke but with lots of weight shaved of, It's called the Light Assembly or LA 318
IMO The poly valve layout is nice and are where the P series Race heads sorta came from.
They just weigh a ton for how small the cid is, stroking one would kinda make up for this, but then there is only about one intake available , maybe 2 if you cn find the dual 4 factory iron, otherwise it's the weiand dual plane.

I built a three of them, back in the day. I had a 58 Plymouth, JSA forumla 5, AHRA, running a 2 barrel.
My first car, a 57 Fury had one, then I did a frame off on a 57 Fury in the mid 80s.

I don't think I could tell the short blocks apart, from an LA motor, except for the valve reliefs on the pistons. Both use 10 head bolts, rear distributor etc.

Even when those motors were in production, there were almost no speed parts. That was probably difficult to justify for the manufacturers because the Dodge Poly was a little different.

I always thought it was a shame, because the motors really did run good, and had a lot of high rpm characteristics of the Hemi. They were all solid lifter
motors, and I still think that the BBC canted valve design was stolen from the Poly.

 

[fishy68]

i get around 11 or 12 mpg on my 318. and these guys are saying that they are getting 22 to 23 mpg with a 318 poly....I may be wrong, but if this is true, i may buy the engine anyway lol.

http://autos.groups.yahoo.com/group/318poly/message/11528

Wow that's bad mileage for a teen. I get better mileage than that in my Cuda with a lumpy idling 360, 770 Holley, 3000 stall, and 3.55 gears. I've known several guys that got 20+ mpg. with a 318.

 

[no1newb]

...my speedometer is messed up, so there is a chance that i may be getting better than when i last checked. got a carter AFB 4bbl carb, stock pretty much everything else. could i have a major problem somewhere? or would it just be the speedo.. i got a new cable and have had it for a while, but i think my gauge is off too.

 

[fishy68]

The speedometer being off can definitely have a huge affect on it because you have to know how many miles you went to know the MPG. Could also have tuning issues so it may be a combination of things.

 

[67Dart273]

...my speedometer is messed up, so there is a chance that i may be getting better than when i last checked. got a carter AFB 4bbl carb, stock pretty much everything else. could i have a major problem somewhere? or would it just be the speedo.. i got a new cable and have had it for a while, but i think my gauge is off too.

Your speedo problem could be a number of things. In this day and age there are a few ways to check it. If you or a friend has a GPS you can use it for a speedo to check.

Your tire diameter will affect the speedo, as will the rear gear ratio

You can get different speedo drive gears that fit into the transmission to change it.

And of course, lastly, there actually could be something wrong/ worn in the speedo dash unit.

On this page are some shop manuals you can download. If you go down the page, there's one for 66

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download

 

[dodgetkboy78]

poly 318 is not going to give better fuel mileage or performance than an LA 318

Yeah hah! The Poly head is better equipped to make MPG...... No doubt about that.

 

[Rcuda2]

I'm pretty sure Poly heads will fit LA 318 block, you'll have to use a poly cam & pushrods that go with the poly rocker setup and of course a Poly intake. I think the Poly pistons had 1 valve notch for intake valve only.

 

[no1newb]

i found this, and i think its too much for me unfortunately. i would have loved to do this if i could.

http://autos.dir.groups.yahoo.com/group/318poly/message/6814

 

[Dustedu2]

If you want the facts, any facts about the 318 Poly go the poly wizard, Gary Pavlovich. he wrote the following article for Muscle Magazine in 2001. Currently builds 500hp stroker poly's and his own dual tunnel ram intakes. (one shown in pic below) You will get all the right answers with no "i think this or that". here's one link to the article. PART 1 http://www.moparmusclemagazine.com/...pp_0109_chryslers_poly_head_engine/index.html PART 2 http://www.moparmusclemagazine.com/..._give_a_318_poly_engine_more_power/index.html He is the one I got all my info from when I built mine. It's my avatar pic below. Dual quad poly. here's another link about poly's http://www.1962to1965mopar.ornocar.com/poly318.html Cool pic's of intakes too. Good Luck!

 

[67Dart273]

I'm pretty sure Poly heads will fit LA 318 block, you'll have to use a poly cam & pushrods that go with the poly rocker setup and of course a Poly intake. I think the Poly pistons had 1 valve notch for intake valve only.

Don't believe so. If memory serves, there is a minor difference in the blocks A Google trip around the www found nothing except that some poly parts can be used to build a hemi. Many LA parts fit, just not blocks or heads

 

[1wild&crazyguy]

TheLAblock would interfere with the poly push rod placement required to accommodate the poly valve layout, to start.
Poly block has the notches, windsor too..if Im not mistaken.

 

[1wild&crazyguy]

This was done around here and dyno'd in lakeside by Ed Hale mahine.

Good numbers for a tiny cam.

http://moparmuscle.automotive.com/1...-318-poly-engine-more-power/nielson-cams.html

 

[RustyRatRod]

There's an interchange list that comes right up when doin a search that lists all the parts that interchange between the A and LA engines. Heads are NOT on the list.