What is the horse power benefits

-

moparmikie

Member
Joined
May 9, 2024
Messages
13
Reaction score
13
Location
Montana
Read an article about putting a 360 crank in a 318. Isn't that just a smaller bore 360? Wouldn't it be better to keep the cubic inch and work on upper end stuff and 10.5 or better pistons? Or turn the 360 into a 408. I am not upto date on strokers.
 
The 360 has a much bigger Main bearing size!
As I recall it is 2.81
The 318/340/273 has a much smaller Main Bearing size.
As I recall 2.50

You can buy longer stroke cranks with the 2.50 Main size.

A 4 inch would get you 391 CI as I recall.

The 408 converted 360 is a good combo!

The main caps are weaker and smalller on the 318 and we have
broken several when the HP gets close to 500HP or more.
 
Last edited:
Read an article about putting a 360 crank in a 318. Isn't that just a smaller bore 360? Wouldn't it be better to keep the cubic inch and work on upper end stuff and 10.5 or better pistons? Or turn the 360 into a 408. I am not upto date on strokers.
There's really no plus of a 318 with 360 crank over a 360. But built similar they will make similar power and torque since there now fairly close to the same size.
 
LISTEN to GTX John!! He's been going very fast for 50 years, and still is.
If you want to stroke a 318, a 360 crank is NOT the way I would do it. For really high performance application, get a 4" all forged kit FOR a 318. For budget street use, cast crank kit with hyper pistons would be fine.
But if you expect a big horsepower boost, heads will have to be MUCH better than 318s, and a cam will have to match what you plan on doing with it..
With good heads,, decent cam 400+ hp should be easy.
 
A more fair comparison would be the 318 with the 360 stroke crank to a 340.
 
LISTEN to GTX John!! He's been going very fast for 50 years, and still is.
If you want to stroke a 318, a 360 crank is NOT the way I would do it. For really high performance application, get a 4" all forged kit FOR a 318. For budget street use, cast crank kit with hyper pistons would be fine.
But if you expect a big horsepower boost, heads will have to be MUCH better than 318s, and a cam will have to match what you plan on doing with it..
With good heads,, decent cam 400+ hp should be easy.
No kiddin! He's da man!
 
Without good heads, a stroker won't get you much.
Good heads, decent cam, improved compression can get you 325-350 out of a stock stroke 318.
And in case you were wondering, John's 318s, stocker type, make somewhere around 400-500 depending on stock eliminator or super stock.
 
Without good heads, a stroker won't get you much.
Good heads, decent cam, improved compression can get you 325-350 out of a stock stroke 318.
And in case you were wondering, John's 318s, stocker type, make somewhere around 400-500 depending on stock eliminator or super stock.
Yeah, you start using more lung power with a stroker and you're gonna need better heads real quick.
 
Thanks for the info. I have been building mopars for close to 50 years mostly RBs and chevys before that. Got hooked on mopar when I bought my 69 road runner have driven nothing else since and all kids drive mopar also. Trained them well!! So I am thinking 360 bored 30 over good heads that breath, purple shaft, AVS on top of a performer intake. Y tube headers 3 inch exhaust. Don't need a fire breather at 73. Just something to put these modern cars in there place once in a while. Thanks again may stroke the 360 not sure yet.
 
the purple shaft cams are good and work, but the grinds are antiquated by today's standards. there's TONS of newer split pattern grinds that would be absolutely great in that type of motor (the 360 with some decent heads).

the AVS on top of a dual plane is a great combo.
 
I already have the purple shaft along with all the parts nessecery except pistons. Including 273 adjustable rockers.
 
Putting a 360 crank in a 318 block will give you more low end tq. If 318 heads are used, hp peak will be at a correspondingly lower rpm.
If more low/mid range tq is all you require, then a good move.
You might be able to grind down the mains on the 360 crank, depending on where the oil holes are.
 
Thanks for the info. I have been building mopars for close to 50 years mostly RBs and chevys before that. Got hooked on mopar when I bought my 69 road runner have driven nothing else since and all kids drive mopar also. Trained them well!! So I am thinking 360 bored 30 over good heads that breath, purple shaft, AVS on top of a performer intake. Y tube headers 3 inch exhaust. Don't need a fire breather at 73. Just something to put these modern cars in there place once in a while. Thanks again may stroke the 360 not sure yet.
That's not gonna be so easy, many modern cars are putting out enough hp/ci, that Your 'teener'd have 457hp. That's NA, they're runnin' 13:1 on pump regular, sooo I'd set the dial on 'FUN' & roll...the plus for You is most new cars are heavy by comparison.
 
I didn't know the 318 has weaker mains... i plan to do a 390 next spring but don't think i will get over 430-440hp.. unless a 360 block falls into my lap but not gonna hunt for one..
 
I didn't know the 318 has weaker mains... i plan to do a 390 next spring but don't think i will get over 430-440hp.. unless a 360 block falls into my lap but not gonna hunt for one..
273/318 main caps are physically shorter than 340 main caps. Less "meat" and shorter bolts.
 
There was an article in one of the mags when I was a kid in the 80s's about doing this. My buddy built one and it ended up being a nice little motor for the time. Relatively cheap street motor since he and I worked at an auto parts sore with a machine shop. However as everyone keeps saying, there are much better options now that we didn't have back then, like 4" cranks etc.
 
Read an article about putting a 360 crank in a 318. Isn't that just a smaller bore 360?
No, I’d call it a destroked 360. (345 cid IIRC)
The problem with this 360 crank into a 318 is pistons. Not the displacement.
Wouldn't it be better to keep the cubic inch and work on upper end stuff and 10.5 or better pistons?
Yes
Or turn the 360 into a 408. I am not upto date on strokers.
That would be fine as well. This is one place I’d take advantage of. Increasing the engine size over a modern car. Be it the stroker route or just an over bored 360. .030 = 365, .040 = 367 etc.


Stroker kits are pricey. (As we know) You could do very well with simply over boring the 360. The 360 vs the 408 will require the next step up in gear ratio to remain competitive due the strokers toque advantage. Piston selection is very good in ether forged or hyperutecic for ether sized engine. 10.5-1 is a little harder for the 360 with a flat top piston. A dome is required, or a really small chambered head.


So I am thinking 360 bored 30 over good heads that breath, purple shaft, AVS on top of a performer intake. Y tube headers 3 inch exhaust. Don't need a fire breather at 73. Just something to put these modern cars in there place once in a while. Thanks again may stroke the 360 not sure yet.
Going with a 4 inch arm provides a good amount of low end grunt over the short stroke. I can see an easy 40ft. lbs. (build dependent) once you reach peak power, the longer stroke drops off in power quicker while the shorter stroke tends to hang on to the HP a bit longer. Of course, this is build parts dependent.

Personally I wouldn’t do a (Tri) “Y” header or a 3 inch exhaust unless the muffler was a turbo muffler. The Performer is a decent street driving intake. However, for putting some modern cars in there place, it’s not what I would use.

Here’s the question.
What size AVS?
What purple shaft do you have?
What are the other parts? The build looks idea/plan?
What car?

The biggest problem to match and exceed a modern cars performance is they have every advantage with the exception of cubic inches in many cases. Our biggest limitation is only a 3 speed transmission. Or just simply ending in a 1:1 final drive.

We can upgrade to most any part they have. Variable intake runner length, cylinder shut down are not an easy task and one I’ve seen no one try to copy. Variable cam timing is another trick that is difficult to copy.

Everything else we can match or come very close to.

On the cylinder heads, if your not lifting the valve up as high as the heads can flow air, your leaving power on the table. The modern cars do this a bit but when fellas add in a cam, there lifting the valve up as high as possible to extract as much as possible.
 
Last edited:
I would have a concern with cutting the mains down over
.300 on a 360 cast crank. I would also be concerned with
the opening up of the 318 block to 2.810. It would be quite
a machining job for me and it would make the skinny 318 Main
caps even skinnier yet. I have seen a 360 stock eliminator car (450HP
or maybe a bit more) break the cast 360 crank in #3 Main. The front 1/2
kept turning and the back stopped = Epic Explosion!!

If you are going to buy Pistons anyway, There are some decent
4 inch cranks that are not a fortune. even a cast one is fine for
most street builds.
 
Last edited:
If you want a stroker SBM the best option is to start with either a 340 or a 360 block. This allows a really good selection of quality off the shelf pistons.

Building a 318 stroker will not allow cost effective piston options. Custom pistons are really expensive and take a lot of time to get. Real pain if you hurt one.

Using a 4.00" stroke crank in either a 340 or 360 gives you a great short block, ease of parts selection, and is the most cost effective.

Tom
 
If you want a stroker SBM the best option is to start with either a 340 or a 360 block. This allows a really good selection of quality off the shelf pistons.

Building a 318 stroker will not allow cost effective piston options. Custom pistons are really expensive and take a lot of time to get. Real pain if you hurt one.

Using a 4.00" stroke crank in either a 340 or 360 gives you a great short block, ease of parts selection, and is the most cost effective.

Tom
Tom, i'm curious. how has the molnar stuff been holding up?
 
-
Back
Top