Mopar 318 engine upgrades

[stinkwheel]

OK,

so i know that alistair is the man to know this mainly, but i will post publicly to hopefully get a broad knowledge base.

Ive heard on the mopar 318 engine a good upgrade is to stick on 360 heads and a 4bbl intake and carb. just allows a bit more umph to come free. Do i need to change pistons etc to retain compression ratio or anything?

So basically is it as simple as that? Will just sticking these on help out a nice amount? will my exsisting exhaust headers etc bolt up to the 360 heads etc etc?

are all small block parts the same? i.e is a 318 crank really the same as a 360 one etc?

Thanks folks, have some pics............

[akku]

I’m going to be a little bit politic here because if you unduly praise or diss the 318 then someone somewhere will jump on you and Mopar guys are FIERCE.

The 318 has one notable Achilles heel, and that is that it suffers from horribly low compression ratio as standard. This is considered by pretty much everybody to be a bad thing in a normally aspirated performance engine. Mopar never sold the 318 as a performance engine. That was the job of the 340. Compression ratio varies with year slightly but generally runs from like 7.9:1 to about 8.5:1

The 360 heads have larger ports which flow better than the 318 however they also have larger combustion chambers than the 318 heads which leads to an even lower compression ratio. You can probably run a 318 with 360 heads on kerosene.

There are ways to bump the compression when using 360 heads on a 318 and these include milling the block deck, skimming the heads and such. Mopar Performance sell a thin head gasket which will also slightly increase CR. One problem with this is that you will require custom length push rods and adjustable valve train and will also need to modify the intake manifold if this is done to excess. The other is the cost of the machining work and finding someone to do it.

You could order up some custom made forged pistons from Mahle or someone. All the cast and hypereutectic pistons I’ve seen for the 318 are factory style flat tops. I’ve not seen off-the-shelf high compression pistons for the 318, but then I’ve not looked in a while. You may think that because the 340 shares the 318’s bore size that you can use 340 pistons in a 318. You can’t because of differences in compression height due the different stroke. Maybe you could do it with some custom forged con rods but it would be cheaper to go with the custom pistons. Probably.

I have never investigated installing a 360 crank in a 318 but you would need custom pistons as a minimum I would guess.

All doom and gloom?

No.

You can make a decent bit of grunt with a 318 wearing the right 360 heads and a 4 barrel. Add headers and don’t fit a wild cam and it will be a nice driver. You just have to understand the limitations of what you can do with that compression ratio (re cams and the like) and make sure you don’t get nasty smog heads with really huge chambers, so know your head casting numbers.

There were “good” 318 heads done late in the production run, used on Dodge Diplomat cop cars and the like in the 80s. You may luck out and find a pair. These give good compression when used with the MP head gasket set and you just need a little port work on them to get them flowing well.

One of the magazines built a 318 with these heads and some extensive porting and saw 450 BHP on the dyno. Not sure how drivable the engine would have been TBH, but you can tune them.

You have options to go further. Speedomotive and others do strokers on the 318 which take it to 390. Increasing stroke will tend to increase compression, all other things being equal. Add a hot cam, intake and headers and away you go.

I saw a build article on a guy’s 340 with a lot of power just recently (485 BHP or so). I **assume** that the 340 crank, rods and pistons will insert in a 318 block but don’t know for sure. Otherwise this build could be easily replicated with your block. I think he’d taken it to about 355” as well.

What is considered the hot factory swap is the later EFI Magnum heads. These engines are LA based but a fair bit different but they have great flowing heads and maintain good compression. Its like the Vortec swap on a small block Chevy. They also have their own intake flange pattern but as I recall its just how the bolts are aligned into the heads and some users have just used epoxy, redrilled and tapped them and used a stock type intake manifold on them. However Edelbrock and others now offer carb intake manifolds based on conventional LA designs but to fit the Magnum heads.

Getting hold of a good pair of Magnum heads in the UK for cheap may be tricky. However a cost effective option is available from Enginequest who offer a new casting of the Mopar Magnum head – with LA style intake manifold bolt! Job done. aaeq.net/Enginequest/

Dunno why you think I know anything about these things...

[stinkwheel]

[quoteDunno why you think I know anything about these things...][/quote]
Its something to do with the hugely helpful amount of info in your above paragraphs.

You sir are a legend when it comes to this info Many thanks.

It gives me plenty to think about...........

[dude]

I read alot about this a while ago, when i almost bought a dodge dart with a 318, and the conclusion was that the best oomph for the money upgrade for a 318 is a 360. ;D
340's and 340 heads are getting rare and expensive, but 360 are still plentiful and cheap, every cent you'd put at more power in a 318 would give twice the effect on a 360.. etc...

If i recall correctly all the 340/360 stuff should fit in a 318 block, 'cept ofcourse if it's a "truck" block. Sorry, i don't recall the correct name for them.

[stinkwheel]

OK, been looking into this a bit closer. All good info, thank you gentlemen.

What if i leave it standard 318 heads etc but whack on a edelbrock performer inlet, 500cfm edelbrock carb and maybe a cam and exhaust headers. Its priob a little more expensive to do this than 360 heads etc etc but maybe more sensible. I dunno. Maybe i should stop thinking about engine mods until i actually finish the welding, but where's the fun in that i ask you?

[akku]

No reason not to do that. Some 318 heads have the intake ports in an inapporopriate position and Edelbrock used to advertise their manifolds for "340, 360 or for 318 using 340 or 360 heads" but now seem to list them as "for 318, 340 and 360".

I put the regular Performer onto a 318 retaining the 318 heads. You probably want a 600 cfm carb rather than the 500. As much for cost as any other reason LOL. Used Holley and Edelbrock 600s can be picked up cheap. The Edelbrock/Weber 500 is a premium as all the Rover guys want them ands its a supply/demand thing.

The 318 which is "different" is the Poly engine made something like 1962-1967

The Truck Engine thing usually applies to the mopar big blocks (413 and 440)

[sammm]

Do you know anything about the Aussie 318 AK?

known here as the Fireball and much more common than the 340 or 360 and they don't have anywhere near as bad a reputation.

Pre '76 had 9.2:1 comp ratio too.

I'd be interested to know if there were any other differences.

Quite a bit of Mopar knowledge here

www.moparmarketforum.com/forum/viewforum.php?f=11&st=0&sk=t&sd=d&start=40

[stinkwheel]

Now I'm confused, not difficult i know but dumb question time..........

stroker kits, a lot of places do them for the 318 LA engine it seems. Is it as simple as buy stroker kit (crank, rods, pistons) and fit to my block, job done ??

Or do i need to have my block machined to accept all this stuff first?

[akku]

Aussie engines may have some differences, I don't know much about them except that they have some different manifolds, something to do with reloacting the oil filter to clear the steering in a RHD application, or something.

I forget, I used to know a couple of guys with Valiant Chargers.

I also know that some of the US 318s did have a claimed 9.2 CR but when you check them out in real life they were less that that by anything up to about 3 points. Or so I am told.

The stroker kits will either fit without machining, or not. Some do, some don't. Best speak to the supplier about that. many just require a little notching of the bore skirt which can be done with a die grinder so that the man bolts can pass by OK. ARP do "stroker" bolts with low profile dome heads for this purpose.

Some may require the use of a low base circle cam as well to stop interferance there.

Best speak to the supplier of the kit you are looking at

[datman]

I'm looking for a complete 360 EFI engine by the way if anyone knows of spare.