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361 to poly 318.

35desoto said:
And I'd be happy to be proved wrong
BUT
the engine mounts for a LA block are located differently onto the K frame in comparison to the Poly 318
If the blocks were the same you could swap the rubber mounts and bolt out / bolt in without any change however thats not the case
Schumacher makes a conversion kit to swap the later LA engines into Poly frames because of this very issue. The block ear tags are the same so thats not the change plus if I get my act together this difference is recorded in a MOPAR publication buried in my library.
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Mate I think all American V8's back in the day were 90 degree. Have a look on Google. 60 degree V8's are not common. There's no way an LA 318 is a 60 degree V8.
 
Ron H said:
My poly has been rebuilt costing a lot of cash. Put in a medium cam, solid lifters, bored .60, some 340 internals, heads redone…etc. and etc. It’s peppy and it was before too after a few adds. To make it more peppy more needed doing. These motors can be bored out considerably more yet. Yeah the poly’s were reliable as all get out and mine runs like a clock – but – it is a 318. A do-over would be my choice; but too damn old now to redo. Nice cruiser. If I had a decent running 361 I’d keep it or rebuild it before going 318, IMO.
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Ore it to a 340 size or bigger. They make lots of pistons. Kim
 
If people think the poly weighs less than a 361, try lifting one!That poly goes back to the mid 50's. Not only are the heads heavier, the Intake as well. the 315 dodge hemi was one heavy unit, and the poly wasn't much less. The best poly was the 1959 325 V8 265 HP two barrel. My 66 coronet had the 318 poly, and it had the same torsion bars part # as the 383 four barrel engine. so they were heavy, a 440 was in it for a short time, and that front end didn't drop a bit. I put in a1968 340 engine and softer bars, and it now drives like a dream.
 
If the Poly is still available, where are you located or could you point me in the direction of it. I could use the motor. Let me know, thanks
 
35desoto said:
The Poly 318 is cast on a 90 degree block (ie the cylinders are spaced 90 degrees apart) while the LA 318 is cast on a 60 degree block. This accounts for a fair percentage of the weight saving along with the thin wall casting techniques and lighter heads used in the LA casting. The 361 big block is cast on a 90 degree casting block so sitting a 318 Poly beside one will look similar in size. I will never ever knock a poly 318 - they were one of the most underrated and underdeveloped engines from the Chrysler fold yet if you have a 361 in place the upgrades to 383/400/413/426/440 is so wide for any Chrysler enthusiast.
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I 'liked' your post for what you said for the most part but the LA engines are all 90* engines.
 
the biggest advantage of a 361 is you can go larger, but the 318 can't.
 
monaco66coupe said:
the biggest advantage of a 361 is you can go larger, but the 318 can't.
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You can go larger with a 318 poly. I'm stroking mine to 360 (3.58" crank) and Gary Pavlovich routinely helps people with the 402 stroker (4" crank). They can safely be bored 0.060" and even larger with a sonic check.
There is a lot of misinformation around regarding these engines.
 
What I meant to say is the Big block engine Family has the potential to be Increased to a much larger size, and a person can also do many simple add ons to Improve the big block, VS what is available for the the 318 Poly.
In my opinion I would rather start at 265 HP than 230 HP right out of the gate, Plus the 361 has many more parts choices,,,Sorry for the poor explanation.
 
Depends on which Poly you start with...right out of the gate. Factory 318s sometimes came with 290 hp. in the 1950s.
 
Photon440 said:
Depends on which Poly you start with...right out of the gate. Factory 318s sometimes came with 290 hp. in the 1950s.
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true, but two four barrels, and the 361 could also be had with the package. in the end the 361 always had more going for it. Now the 1959 325 poly was the exception, at 265 with a two barrel. but chrysler discontinued that engine, as they had their minds on the future, which was 361-383-413. Now If I could find that engine, I would put it in my 56 Plymouth in a heartbeat.
It would be a a direct drop-in replacement of my 277 V8 presently.
 
Cool thread a lots of mis-info everywhere lol.

Later 361 is an under-bored 383 same castings.
So you can safely bore that and put a stroker kit in from 440-source.

We have done a 402ci Poly with the help of The Poly Guru Gary!
This is a 90 thou overbore, with the LA 4.00 crank.

All Mopar blocks can go +100 overbore they is super thick in the cylinder area!

All LA blocks can be converted to Poly heads with some clearance work for the pushrods.

This is where the 60 degrees comes into play, with lifter bore angles!
The 318 wideblock was the first to get the 59 degree lifters.
When the redesigned the lightweight LA block they left the lifter angle the same DOH.
Only aftermarket R3 have the revised 48-degree lifter angles.
It’s the biggest drawback for hipo LA engines is POOR lifter angles a Mopar foo-pah (faux pas)...
 
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Back in the day, I would have told you to go to the wrecking yard and get a running 400. The yards were littered with them. But now, I’d look into a Gen 3, and the trans with it. Sure wouldn’t be a bolt in though.
 
Too true Phixx!

I will be doing an old school 400 build with a turned down 440 crank.
This will give at 30 overbore a capacity of 451ci.

The first gen 71-72 400 blocks are the strongest ever made by Mopar from that era.

My Moparmate had 547ci that made 1200hp in a 71 400 block...
 
Just checked the 440 Source site for 383 stroker.

The best one I think is the 438ci it’s the smaller version of the 451 that I’m doing.

If you want Chevy rods and more capacity in the 361, you can have 496 cubes!!!
 
polyjohn said:
Cool thread a lots of mis-info everywhere lol.

All Mopar blocks can go +100 overbore they is super thick in the cylinder area!
Click to expand...
That's 'mis-info' right there. You had better sonic test any block that you plan on taking +.100 out of or you could end up with a home made 'thin wall' block. The last 400 block that I had sonic checked had a pretty good amount of core shift in it and it wasn't to the good side either.
 
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