318 Poly

[Inspector71]

I have a 66 Sport Fury. It used to have a 318 Poly. My recollection is the motor is wider and much heavier than a 318 LA motor. Well, I stepped into now. I posted this on For B Bodies Only in response to a question about swapping a poly for an LA. The people on their told me what I said was BS. I might be wrong, but BS? I am going by what I remember. They say the blocks are the same, the 318 Poly is NOT wider or has any different dimensions than the LA, and ALL parts interchange. My experience was:

the block was wider,
it was so heavy when it was pulled and a 440 put in its place, the front of car raised not went down
The 318 LA intak manifold did not work on a Poly. I had to get a Weiand (spelling)
The 318 LA cam didn't work and I had to get one from ISKY

The Crank would interchange and that was it.

Now that is my experince but I'm being told I'm wrong and putting out BS. Maybe I'm wrong but that is what I recall and I had that motor from 1984 to 1996. Can anyone help me out on the facts?

 

[commando1]

Umm.. Inspector, why are they debating you? You're right and it's trivial.

 

[strokerpost]

I have a 66 Sport Fury. It used to have a 318 Poly. My recollection is the motor is wider and much heavier than a 318 LA motor. Well, I stepped into now. I posted this on For B Bodies Only in response to a question about swapping a poly for an LA. The people on their told me what I said was BS. I might be wrong, but BS? I am going by what I remember. They say the blocks are the same, the 318 Poly is NOT wider or has any different dimensions than the LA, and ALL parts interchange. My experience was:

the block was wider,
it was so heavy when it was pulled and a 440 put in its place, the front of car raised not went down
The 318 LA intak manifold did not work on a Poly. I had to get a Weiand (spelling)
The 318 LA cam didn't work and I had to get one from ISKY

The Crank would interchange and that was it.

Now that is my experince but I'm being told I'm wrong and putting out BS. Maybe I'm wrong but that is what I recall and I had that motor from 1984 to 1996. Can anyone help me out on the facts?

You are right except about the block being wider, dimensionally the block is basically the same, it starts getting wider when you bolt on the poly heads. if you've ever noticed, on the poly motors the pushrods are a straight line from the lifters to the rocker arms, where on an LA there are angled upward leaving the lifters. That's because when they put the redesigned LA heads on they didn't reconfigure the lifter valley in the old style block. As for weight, I cant imagine it being as heavy as a 440, but probably is a bit heavier than the LA, and all of it from those big heads and intake. I currently have a poly motor in my shop right next to a 440 and one is as wide as the other. I've heard a bunch of people refer to it as the old 318 big block.Lol.

 

[Inspector71]

Thank you both for helping. I never posted that I was right or someone was wrong. The thread starter simply said he had purchased a C body from out of state and the seller said the poly 318 made a knocking noise when it warmed up. He was weighing whether it made more sense to fix the motor or replace it with an LA318. I didn't know how he could make such a choice if he didn't have the car yet and didn't know what was wrong. Several posters said it was probably the adjustable valves. I simply chimed in that he needed to make some measurements to ensure the LA would bolt in to the same engine mounts as the poly is wider. What I meant, which Strokerpost explained, is the block is not wider but with the heads on it is. That is what I meant but fumbled in my explanation. I added that my valves clacked a little but only when cold. I suggested he find out what is wrong first. Another poster got all bent out of shape saying half of what was posted was wrong and BS and he met me. He said the blocks are the same, and, well, I explained that. I wasn't looking for an argument, I was trying to help someone out because I had the same motor too until the heads and block cracked (possibly the result of mistakes made by the Chrysler place that rebuilt it). I'm not kidding about the weight. I can't tell you what the difference is because I have no idea. I only know the front end raised with the 440 in once the 318 poly was pulled out. But your explanations are a big help. I will post it directed to the thread starter, to help him out, and then I'm out. I sold my car to a younger brother (for $0) because we are close. Someday I might pick up another one. I like the C bodies. Again, thanks a million for helping me out with the facts.

 

[bluefury361]

The later 318 LA, (as well as the 340 and 360's) are a direct changeover with a 318 A, (poly), engine.
Your correct in that the heads and intake differ. Pulling a poly head is about like pulling a hemi head.

You better cross your I's and dot your T's over at the FCBO site...... More self proclamed experts over there.... Most who have "SEEN" a poly 318 once.

 

[strokerpost]

Thank you both for helping. I never posted that I was right or someone was wrong. The thread starter simply said he had purchased a C body from out of state and the seller said the poly 318 made a knocking noise when it warmed up. He was weighing whether it made more sense to fix the motor or replace it with an LA318. I didn't know how he could make such a choice if he didn't have the car yet and didn't know what was wrong. Several posters said it was probably the adjustable valves. I simply chimed in that he needed to make some measurements to ensure the LA would bolt in to the same engine mounts as the poly is wider. What I meant, which Strokerpost explained, is the block is not wider but with the heads on it is. That is what I meant but fumbled in my explanation. I added that my valves clacked a little but only when cold. I suggested he find out what is wrong first. Another poster got all bent out of shape saying half of what was posted was wrong and BS and he met me. He said the blocks are the same, and, well, I explained that. I wasn't looking for an argument, I was trying to help someone out because I had the same motor too until the heads and block cracked (possibly the result of mistakes made by the Chrysler place that rebuilt it). I'm not kidding about the weight. I can't tell you what the difference is because I have no idea. I only know the front end raised with the 440 in once the 318 poly was pulled out. But your explanations are a big help. I will post it directed to the thread starter, to help him out, and then I'm out. I sold my car to a younger brother (for $0) because we are close. Someday I might pick up another one. I like the C bodies. Again, thanks a million for helping me out with the facts.

Never stop trying to help folks in the hobby, even though sometimes you butt up against "guys like that" now and then. I know I love to help if I feel I know what I'm talking about or have experience with whatever the topic, that's why I spend a lot of time on these kinds of sites, lotta guys willing to share what they know and help out. Glad we could help you a bit. Have a good one.