350 Hp 318?

Rifleshooter

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Ok, what can you tell me about putting different heads on just any block really. I've seen some head have a higher cc number than others, what does this mean, is a higher cc better or a lower cc?
 

brotherGood

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Throw magnum heads and a nice cam on your 318..youll be happy. That's what I've got in my car now and it's night and day versus the AHB engine that came out.

That being said..I couldn't tell you what the numbers are, I've not dyno'd it yet, but it pulls hard.

To follow up though, I'm working on dropping a 360 mag in there shortly..but it's because I'm greedy

If I had an 833 and 3.55s in my car, I don't think I'd worry about a 360 OR having 350 HP

If you don't have to rush to throw it together, spend time on c/l..get some magnum heads, summit 6900 cam, headers, 4bbl. I've got part number for the gaskets, pushrods, etc. I got a stupid deal on magnum heads (35 bucks).

If you were closer (and it wasn't turning winter) if show you what you can do with next to nothing with a 318
 

BudW

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The only parts that will not swap are the pistons,the crank, and the damper.
And the engine oil pan and Left motor mount. The oil pan is slightly different where it touches the rear main cap.

Also 340/360 Left motor mounts are different widths (about 1/2" difference) than 273/318 engine mounts are. I have heard of people using washers to make up the mount difference – which will work but is not preferred.

1 cubic inch = 16.38706 cubic centimeters. Combustion chambers are always measured in cc’s.

You can get 340/360 cylinder heads to bolt onto a 318 (which is what the police 318’s have) – but for some reason the factory made the 340/360 heads with larger combustion chambers (higher CC (Cubic Centimeter)) – which effects the compression ratios, and a more.
A person can install 340/360 cylinder heads and manifolds to a 318 – but you will also need to change pistons because compression ratio will be way low, otherwise.

It comes down to a well-used, but true phrase – there is no replacement for displacement.

The 318 is a great engine – except for performance usage.
All 340’s are high performance engines. Many 360’s are also high performance (but not all). The larger displacement is another plus.


Stroker crankshaft kits are the way to go, now.
273, 318 and 340’s all share the same crankshaft stroke of 3.31”. The three different engine sizes have different bore sizes (3.63”, 3.91” and 4.04” respectably). 360 engines have a 3.58” stroke and 4.00” bore.

What a stroker crankshaft kit does is increase the crankshaft stroke (according to size you request). The common size is 4.00” stroke (up from 3.31” on 318 / 3.58” on 360) – which would give a 318 a new displacement of 390 ci or 408 ci on 360. The down size is a stroker crankshaft kit (consists of crank, rods, pistons, rings and crank bearings) run about $1,500-2,000 (US).
They also get the compression ratio back up to a better place.

To make use of the displacement, 340 or 340 cylinder heads (or Magnum) are now needed (so engine can breath) – or the engine using 318 heads will run out of steam at about 3K RPM (again – think small straw size and trying to push more air through it).


All AJ is saying, is if you already start with a 360 – you will already be ahead of the game.
Also, the 360 engine is a lot easier to make faster far easier (and far cheaper) than a 318 is.


I have a pair of 360 engines in my garage that I’d be happy to sell, cheap – but freight from Oklahoma City to PA will not be cheap.

I also agree with AJ, if you are looking at more than stock performance, you can’t go wrong with a 360. Add a 4-bbl, and you might be happy to stay there.

That said, I wouldn’t spend that much $ into a 318 just because you have to fork over tons of $ to get what is almost free on a 360. Also, if you want more, you already have a strong base to build upon.

Go find a used engine on Craigslist or at a salvage yard, even better, go find a 360 Magnum engine, transfer the timing cover, get a car 360 oil pan and a decent 4-bbl intake and you will be almost set. At that point – the sky is the limit.
BudW
 

BudW

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BTW, with an A833 and 3.23 (or 3.55) gears – that alone will make a huge difference, with any small block (including stock).

For what you are describing, I would recommend dropping in a “stock” 318 2-bbl, A833 w/Overdrive, some gears (maybe) and drive it that way for a couple of months.
After that time, come back to the table to see where you want to go, at that point.
BudW
 

Rifleshooter

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If I can get a good price on a 360 or 340 after shipping and all, I'd consider buying one. But as for the cc's, is more cc's better or is less when it comes to selecting a desired cylinder head?
 

mike2

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Build a 318 or 360 magnum, 318 2-300$ all day on craigs even 360 magnum4-500$ , cam and springs 400 high lift short duration , air gap intake ,360 oil pan carb and headers 1200=1500$ done, tons of bottom torque idle to 5200 good to go, can even have serpentine setup if wanted
 

AJ/FormS

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If I can get a good price on a 360 or 340 after shipping and all, I'd consider buying one. But as for the cc's, is more cc's better or is less when it comes to selecting a desired cylinder head?
Go straight to a 360, skip right over the 340
As to ccs, neither,.....you can't(or at least shouldn't) use that criteria to choose a head.
The compression ratio has to be matched to the cam . The head ccs is part of the tool kit to do that.
If you want to hop up that 360, pistons are available to use big CC open chambers, and also for small CC closed chambers. So If you're "stuck" using LA heads you would use one piston, and if you spring for better aftermarket heads, then you can use another. And depending on how much cam you want to put into it,you adjust things to optimize the running compression ratio. In this way you can build your combo. If you screw it up, you can have a so-so engine, or even less. If you get it right, it will be dynomite.
Your 360,lol, can be built from 250hp to 350 pretty easy and cheap,and is still very streetable at 400(not so cheap) with a manual trans.
But again these power numbers are almost meaningless for a street car that is limited to 60 mph and stock wheel tubs, and street tires. Once you have enough power to break the tires loose, more power is not the answer. More power always takes more airflow. And in a given engine,that almost always takes more rpm.
brotherGood said; "If I had an 833 and 3.55s in my car, I don't think I'd worry about a 360 OR having 350 HP". In an A-body, that's hard to argue with.
I have about 400 hp, and I bet I rarely use the half of it. If I use it all, in about 5 seconds I'm speeding, and the 295/50-15s never stop spinning. That's just waaay more power than my suspension can handle.
 
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mike2

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hp is great but torque is better, in my opinion , stock magnum 318 net hp is 225-230, torque 300, 360 hp 245, torque 330, these are net hp ratings, i bet with cam,210/220@50 lift 510 just an example,springs, intake, carb, headers, you would be very happy with either motor ,im sure the torque ratings should go up 30-40 ftlbs at least
 

Rifleshooter

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What would I have to do to get 350 hp out of a 318, or more like how much hp would I get out of putting Magnum heads on with a 4bbl carb, dual plane intake manifold, and headers?
 

AJ/FormS

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With the stock cam and compression, not much, I'll guess 260tops.
BUT
your low-speed torque will be much improved, and it will be a very fun combo with either trans and 3.55s. And the bonus is 65 will be about 2100 with the od trans. By not changing the cam, your fuel mileage on the hiway will be very little changed.
 

BudW

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But as for the cc's, is more cc's better or is less when it comes to selecting a desired cylinder head?
The amount of cylinder head CC’s – should not dictate which cylinder head to use – but is used to determine compression ratio. That and along with CC’s is used to determine what pistons to use.

This is a picture of ’67 318 (small port) heads. You can see the size of the combustion chamber is rather small. These are called closed chamber heads.
67 318 head.jpg

Picture swiped from internet.

This is a picture of 340 or 360 cylinder head being ported. You can see how deep the chamber is on this head. This is called an open chamber head. On this engine, the piston top actually comes close to the top of the cylinder block. I had a 340 and the piston top actually measured 0.015” (or 0.0015") above the cylinder block – so if I had used a closed chamber head – the piston “could” hit the cylinder head. The open chamber heads allowed for piston to go higher. The exact reason why manufactures use open chamber heads – IDK.
340 head.jpg

Again, picture swiped from internet.

The closed chamber 318 heads (which I have a set, way deep in my garage) – the pistons do not get that close to the top of cylinder bore.

I saved my ’67 318 heads (um, over 35 years ago) in thinking I could toss them onto a low compression open chamber engine thereby raising the compression up.
It will do that – but that project got shelved (literally) decades ago (a complex answer to what seemed to be an easy solution. – at the time)

The typical 340/360 cylinder heads have more CC’s than the typical 318 head has.
If a person was to install a 340/360 cylinder heads onto a 318, the compression ratio would be horrible (in the 6’s or 7’s to one, maybe).
Installing typical 318 heads onto a 360 would raise compression (if leaving pistons the same) – but the port size would choke the engine over 3,000 RPM, or so. Think of running a mile, with your mouth taped shut and your nose pinched almost closed.

The CC measurement is used to calculate your compression ratio and to make sure everything is where you want it to be.
Example, I’m building two big block stroker engines. The details on this link http://www.forfmjbodiesonly.com/classicmopar/threads/the-long-and-short-tails-of-a-4-speed-od-with-the-j-body-console.6800/#post-75565 are measurements provided by he different part manufacturers.

Next: input those figures into a compression ratio calculator, like this one (there are several of them on the internet) http://www.diamondracing.net/tools/ .

The numbers is what I had calculated things to be – but I will confirm my measurements before building the engine. My goal is to be at or slightly less than 9.5 compression ratio. Big blocks have a large number of head gasket thicknesses out there – so if actual measurements show different numbers, I can increase (or decrease) the head gasket thickness to get my desired compression ratio.

Even with the cylinder heads, if a core shift or machining mistake, or whatever, my cylinder head chambers might not be 80 CC. The list goes on and on and on what might be different – but so far – if the manufactures measurements are correct – I should have a hair less than 9.5 compression ratio.


Speaking on 318’s only at this point, I had not counted but but I bet that Chrysler has made pistons with 20 different Compression Heights (the distance from (center of) piston pin to top of piston. That means that factory pistons the top of comes up to a different height compared to the top of block – over the years. That distance (the Compression Height) along with style of cylinder head (open or closed chamber has a lot to do with compression ratio. Every once in a while changing cylinder heads will get the compression one is looking for – but I would say the other 95% of the time (or higher) – a person will need to find and replace the pistons, to match.


BTW, in my case, the Compression Height is only 1.483” (½” of that is piston pin). That means the area that hold the cylinder rings is less than 1” tall (which is not much).
20171029_123233 R.jpg

Also note: the custom pistons have a moly coating on sides and ceramic coating on tops, and is not something you normally see.
20171029_123213 R.jpg

BudW
 

Rifleshooter

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Ok thank you for the explanation on cc's. You told me everything I wanted to know and more too! As for the pistons, I'd rather not accidentally go too high of a comp ratio and blow the entire engine up. That would be most undesirable. How would I be able to find out head gasket thicknesses to do a pre-determined ratio check.

Also, I know that the higher compression ratio, you'll need to use higher octane fuel to prevent a knock. What is the limit when it comes to the fuel, how high of a ratio can I go before I exceed the 92 or 93 octane use?
 

BudW

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Compression ratio means what octane fuel you will need to use, to prevent pinging/pre-detonation. Pre-detonation (pinging) means every time it pings, it is like someone is taking a hammer to the top of the piston. The pistons will eventually fail (which a rather large hole in the middle).

Almost all newer cars have knock sensors in them to adjust ignition timing to prevent pinging from happening.

For pump gas, I would not go higher than 9.0 to 1 – maybe even less than that.
Note: aluminum cylinder heads “can” allow you to use up to 0.5 points higher compression ratio.

Engines with higher compression, will run better.

Having too much compression will not cause you blow the engine. Pre-detonation will (see above) break the piston tops, eventually. There are other factors on this that I won’t go into at this time.

Basically, the rule of thumb is: the higher the compression, the higher octane of fuel you have to use - to keep it from pinging.

I will need to let someone else answer:
What is the limit when it comes to the fuel, how high of a ratio can I go before I exceed the 92 or 93 octane use?
BudW
 
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