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  #1  
Old 08-18-2003, 11:15 PM
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Default i have a question...maybe a good idea that is cheap!!!

IF IT WORKS...

i have the book "how to hot rod small block mopar engines"...new edition...

it says the 360 stroke is longer than the 273,318,340 engines...but the mains on the 360 crank are bigger

my idea is can i machine the mains on the 360 crank to the smaller main sizes and drop it it the 273,318,340 block?

seems like it would be a cheap effective way to add power and cubic inches...

thanx
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  #2  
Old 08-19-2003, 12:19 AM
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It's been done. I don't now how cheap it is/ how much the required pistons cost.

Use the search feature. I think this topic has come up a few times
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  #3  
Old 08-19-2003, 01:31 AM
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Standard deal any GOOD crank shop can fix you up....Diamond has pistons and ring sets sittng on the shelf

While your at it have the thows offset ground and widened to use a 6.125 Chevy Forged rod......it makes a big inch motor out of a 318.

But do the ratio calcs and you'll see that the bore to stroke ratio's don't look very good..
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  #4  
Old 08-19-2003, 02:14 PM
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also...the 340 bore is 3.98?

can the 318 be bored to the
340 bore?

thanx for the replys

laters
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  #5  
Old 08-19-2003, 07:27 PM
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No, a 340 is a 4.040 bore and a 318 is a 3.9100 bore, I don't think you can squeeze that much out of a 318.

This link may help you in calculating engine displacement

http://victorylibrary.com/mopar/a-bs.htm
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  #6  
Old 08-20-2003, 04:01 PM
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thanx for the reply guys...

the moparpages.com forums kind of sucks cuase no reply's

this is a good one

ONE MORE QUESTION!

what cars came with a 340?

is it easy to find at the junkyard?

are they expensive?

thanx!!!!
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  #7  
Old 08-20-2003, 04:42 PM
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340's were a performance motor, so the numbers are much lower than the regular production 318's and 360's. They were built between 1968 and 1973, with the 1968-71's being high compression steel crank units, and 72-73's being low compression cast crank units. I don't know about where you are, but around here they are getting scarce and command a good dollar in decent (rebuildable) condition.

The hot ticket here if you want the big bore block with the 360 crank is to find a pre 74 360. They were made with the same mold as the 340 and have enough meat to be bored out to .040 over 340 (4.080) bore size and that comes out to about 372 cubes. You would need to have the block sonic checked to be sure though. I have seen a few early 360 blocks in early 70's C-bodies, a more likely find than a 340 in a scrappers.
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  #8  
Old 08-20-2003, 04:48 PM
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Pantera, ever see a Pantera in a junkyard? Well, the 340 equipped car will be sitting right next to it. Seriously though, the 340 is pretty a pretty sought after piece, so chances of finding one in a junkyard in useable shape are pretty slim. Look for a 68-73 Mopar A or E-body. Occasionally they were in Roadrunners. Good luck, easier to get is a 360 and they can be built up in pretty much the same manner. Welcome to the board.
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  #9  
Old 08-20-2003, 09:03 PM
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hey thanx...i love the sarcasm...SERIOUSLY!!!


anyway...i heard the 340 is better because it has larger bore and smaller stroke so it'll spin up better...but can be semi-economical...compared to the 360...i heard the 360's waste a lot more gas, even in stock or mild form...but...u guys are the one's that know and have experience

so...it would NOT be a good idea to get a 360 block, overbore it to 340 bore size, and but the smaller stroke of the 340 in it?

thanx

and

thanx
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  #10  
Old 08-20-2003, 09:46 PM
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The 20 extra cubes of the 360 do not eat up gas in a big way. Fuel mileage is determined by more factors than cubic inch displacement. (I could write a paper on this.) I had a 360 getting 20 mpg's without headers and it had cats. Imagine what a set of headers would do and then drop the cats. Free up some power with out adding gas guzzleing parts. This equals more mileage. (And performance.)
For the best way to do a stroker useing old parts, get a 360 crank turned down for the 340 mains and bore out a 340 .030 for a 4.07 bore and get 372 or .060 for a bore of 4.1000 to get 378 cubes. (Stay with a .030 bore. It keeps the walls thicker = stiffer = HP!)
A .040 360 block is OK if it checks out with a sonic test. Reason being is to insure it has the meat there. It should, but it pays to check. Beats doing it twice!
MoPar sells 360 stroke cranks in the small main size. They also sell the small stroke with the bigger main size.
If thats not tasie enuff, the 4.00 inch crank sells cheaply and will make 400+ cubes in ethier 360 or 340.
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  #11  
Old 08-20-2003, 11:20 PM
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how much does the 4 inch crank sell for and it'll drop into the 318 too right?


just exploring my options

the reason i want the 340 is because i hear it has the best bore to stroke ratio..i heard the 360 is too much stroke..therefore being less economic than the 340 even when built mildly hi po

thanx for all guys!!


this forum kicks ASS!!!
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  #12  
Old 08-20-2003, 11:38 PM
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Default Buy a 360

I'd just buy a 360 engine, and it that's not enough, you can buy the 4.00" stroke cast iron crank and pistons from a variety of places. Then you'd have 400+ CID. Top with a decent set of heads and enjoy the torque.
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  #13  
Old 08-20-2003, 11:45 PM
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Default Junkyard 340 story

Pantera, Sorry I'm not offering help...but I gotta tell you guys my junkyard 340 story.

O.k....Bought the Chal. with a trashed 2 brl. 318. Tossed the motor, going to get a 360. I hunt the yards in my area, which suck for Mopar people. One of the yards near me has a 360 from a 74 Charger, and a 340 from a 73 Valiant!?! Blew me away.

Both motors had been there forever. The guy says not to worry, I'm the first person in years to even ask about them. So, I don't worry.

The day before Thanksgiving (whatever year it was) I go to make the decision and buy one of them. The whole frikkin' yard is practically empty. I have shown up in the last hour of the last day before this place is history!

I want the 360...nada, it is gone. O.K. gimmee' the 340. It is sitting in the back of one of the employees' el camino. The owner was just giving it to him (severance pay?).

Screw THAT! I buy it from the back of the car and we load it into my truck. Owner sells it to me for $50 more than original price and hands the $50 to the el camino guy, who was only going to try and sell it to a Mopar guy because he knows...You never find a 340 in a junkyard!

I used it for a year and sold it to a guy for the same $ I bought it for!
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  #14  
Old 08-21-2003, 12:41 AM
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First you say....Quote
"the reason i want the 340 is because i hear it has the best bore to stroke ratio..i heard the 360 is too much stroke.."

Which is a relatively true statement

Then you ask.....Quote

"how much does the 4 inch crank sell for and it'll drop into the 318 too right? "

But you've already determined correctly that the 340 makes more power per cubic inch of Mopar nostalgia than the 360.

But we could get into a long disscussion about HP vs. Tork and stroke Vs Bore and how it affects the air flow...and we'd be here for a month with everyones opinions,,,,,so let's just say that all your assumptions are correct to a degree, before you decide on what motor to stroke or not to stroke you need to look deeper into your project and see what heads your going to use and will they work best on a 318 plain jane or stroked, a 360 plain vanilla or stroked or do you want to search for the 340.

Better to look at it as a target...what do you want from the finished product and how much do you want to spend.

Just one example:

You have a 323 rear gear and a nice sure grip that you just spent $1000 on.

So now you build a 340 and it's a pig ..it needs a 430 rear end and 3500 stall convertor just to drive on the street....get out the checkbook...

So now let's build a 360, longer stroke, more low end tork and it works fine with a streetable 2500 convertor and a 3.23 gear...you just saved $1000, your time slip is almost the same and driveability is excellent.

Set your goal first, come up with the plan and stick to it.

Just my 2 cents worth

Ohh and welcome aboard
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  #15  
Old 08-21-2003, 11:17 AM
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Cuda66273. I totally agree. well said.
There is little benefit of putting a 360 crank in a 340 or 318. You should just use a 360. Grinding the crank for 350 rods is always a great way to lessen the cost of rods. (chevy parts are cheaper)

The 4 inch stroker crank is about $300 plus balancing. There is a 360 version and a 318-340 version.
Check for piston availablity prior to any decisons.

Here is my 360 (4 inch stroke) build ... equals 408 cubes

Stroker 408
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  #16  
Old 08-22-2003, 06:34 AM
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Before you invest, investigate ...where are those $300 cast stroker cranks made?

Do you like Chinese food?
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  #17  
Old 08-23-2003, 03:48 PM
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thanx for all the suggestions guys...

does anyone knwo what type of trans i have in my 1977 dodge aspen se 2 door?

can that handle hi power engine?

thanx all!!!!!!!
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  #18  
Old 08-23-2003, 11:25 PM
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Those $300 have been used now behind some pretty stout engine. My 400-450 hp version should be fine. If you are looking for really big numbers, forged is the way to go.
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