Hello I'm new here and this might be the end of me for even bringing this up but...... after a long search on the web I have not found what I'm looking for. I have a LA 318 that is sentimental to me so it is what it is. I am looking to stroke it 340-349 Cid. No more no less. I see a lot of stroker kits to get 390 but it's not what I'm looking for. I understand that this is a dumb thing to hash through but any help would be much appreciated!
Oh dear God! 318 stroker
- Thread starter slick69
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Welcome aboard from Ga mtns.
This is best place on web for good info.
Good luck!
This is best place on web for good info.
Good luck!
Part of what we live with is working with the parts that are available and affordable, unless you have unlimited resources. If you are going to bother stroking it, 390 is where it's at. You can get a kit that is already all scienced out or you could probably send your block to Blueprint and they can return it as a 390 complete with a warranty, rather than spending a fortune on machining something that is otherwise unavailable.
You will find lots of experienced folks here willing to help you out and sell you parts that you need - Welcome Aboard!!!
You will find lots of experienced folks here willing to help you out and sell you parts that you need - Welcome Aboard!!!
There probably no kits anymore, theres 3.58 cranks with 318/340 main bearing size.
You'll probably need custom piston, but you could have the block check for a possible 4 inch bore or mill down a 318 piston are possible options.
You'll probably need custom piston, but you could have the block check for a possible 4 inch bore or mill down a 318 piston are possible options.
33IMP
Well-Known Member
By the time you get done cobbeling together a cut down 360 crank, paid for the crank maching and custom pistons, redoing stock rods, and balancing the mess, you WILL be sorry you didn't just get the 390 kit and an extra 50 inches MORE than an ordinary 340.
That's kinda like stroking a 383 to 426 (only!). Why bother?
That's kinda like stroking a 383 to 426 (only!). Why bother?
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buy a 360LA or 5.9 core and save yourself some money and headaches
What year of 318 block? If sonic testing checks out, this will get you to 333.
SRP, Chrysler, 4.000 in. Bore, Kit
SRP, Chrysler, 4.000 in. Bore, Kit
340sFastback
Well-Known Member
4 inch crank in 318 block get an off the shelf kit and probably cheaper. 4 inch arm is like a long wrench compared to a short wrench - more leverage - more torque. And 4 inch stroke has shorter lighter pistons which makes them rev a whole lot faster. Its the hot setup for small block mopars they drop right in no special machining required. Make big block torque without the size and weight of a big block.
Welcome aboard.
And it seems that the stroke it people have already attached themselves to your thread here. All they can think of is put a 4-inch arm in it. Personally I would say put a 360 crank in it check and see if it'll go to 4 inches on the bore and have a 360 that's my personal preference in this case. Once again welcome board have fun.
And it seems that the stroke it people have already attached themselves to your thread here. All they can think of is put a 4-inch arm in it. Personally I would say put a 360 crank in it check and see if it'll go to 4 inches on the bore and have a 360 that's my personal preference in this case. Once again welcome board have fun.
Welcome to FABO. Have it sonic checked and bore it .130 thou to 4.04 which is the 340 bore. Then get some good pistons, have it balanced and away u go. Kim
Welcome,
As you have seen you have gotten 318 answers from 273 people on how to not get to 340
And 440 answers from 360 people in how to get to 340.
Just a little cubic inch humor.
I have no idea how to get to 340 but the real question is why do you need to get to 340.
Is it a rules thing?
Professor Fate
Push the button, Max...
Welcome.
Sentimental attachment to the block, okay. 340-349 c.i., period. You got your reasons, who am I to argue, if that's what you want?
As mentioned, I wouldn't stroke it. Too many custom ($$$$) and discontinued parts involved. Have it sonic checked and see if it'll go to 4.040, some early and truck blocks will. You wouldn't be the first person to build a 340 out of a 318. And it'll all be common, off the shelf parts. If it won't go 4.040 and you still want to keep the block, sleeve it and get your bore. Sleeving 8 holes and using standard parts is easier and cheaper than custom pistons and offset grinding cranks.
Sentimental attachment to the block, okay. 340-349 c.i., period. You got your reasons, who am I to argue, if that's what you want?
As mentioned, I wouldn't stroke it. Too many custom ($$$$) and discontinued parts involved. Have it sonic checked and see if it'll go to 4.040, some early and truck blocks will. You wouldn't be the first person to build a 340 out of a 318. And it'll all be common, off the shelf parts. If it won't go 4.040 and you still want to keep the block, sleeve it and get your bore. Sleeving 8 holes and using standard parts is easier and cheaper than custom pistons and offset grinding cranks.
dano
Evil Handy Man
Are you planning on better heads? If not you'll just choke it.
Ah, what the heck, build what ever you want. Do your homework and search for the proper parts. I have read about some strong 318/390's here. Just a few. Most aren't that attached to the original Teen though. Remember, if you modify it it won't be original any more. Pull it, stuff it in the corner, and build a 360/408+ Magnum stroker. (I can't believe I said that) I rebuilt the 273 in my 66 with no regrets. I like the 318 in my 70 Swinger so much I might not even out a 4 barrel on it. I have a LD4B, a 650 AVS2 , 68 340 manifolds, and even a set of Speedmaster heads. I might just leave it all as originally designed. No reason to mess with perfection.
Is the 318 still together? If it is, get a depth mic with an extension on it. Put a timing tape on the balancer so you can index the 90 degree points from TDC #1. Measure how far the pistons are below deck at 1, 2, 7, & 8. Then measure BDC on each one to see the actual stroke on each hole to see how far the crank is off from 3.31 inch stroke (some sources list as 3.306). A little subtraction from there will give you your actual deck height. I’ve got several 318 blocks I’ve measured out deck height closer to 9.97 than 9.96 after checking stroke, piston compression height, and rod length. With a typical 1.72 compression height replacement piston CHRYSLER 5.2L/318 Mopar small block LA Pistons - 1.720 in. Compression Height (in.) - Free Shipping on Orders Over $109 at Summit Racing
Some of the aftermarket cast 318 pistons are far enough down the bore or that close to it that you could run a 360 (3.58) stroke crank with them and be at zero deck and 349 cubes at 30 thou over.
I know someone who did this before stroker cranks became popular.
If you have a 360 crank already, suitable cast pistons and are happy with a small lift cam then it might be ok, if not you will spend as much or more on buying a 360 crank, machining it, buying cast pistons and fly cutting them for valve reliefs than you would buying 318/390 stroker pistons and a stroker crank.
I know someone who did this before stroker cranks became popular.
If you have a 360 crank already, suitable cast pistons and are happy with a small lift cam then it might be ok, if not you will spend as much or more on buying a 360 crank, machining it, buying cast pistons and fly cutting them for valve reliefs than you would buying 318/390 stroker pistons and a stroker crank.
One other noteworthy mention if you use higher compression height 1.72 CH sealed power pistons. If you’re planning on using iron open chamber 360 heads, you can run at positive deck like a 340. But you do have to start carefully planning for piston to valve clearance and having a solid plan on what compression you’re planning on. On that note, I’ve been collecting parts for the same type of build using some full float 318 rods and some eBay Zollner pistons with 1.746 CH, steel expansion limiters, and over .400 crown thickness. Going to get them cut for snap rings for pin retention and cutting a large dish similar to a 360 piston in the crown for piston to valve clearance and to keep the compression in check.
Phreakish
Well-Known Member
Just checked and the stock replacement Silvolite pistons are a 1.658 compression height.
With a nominal deck and 360 stroke, the pistons would still be about .030 in the hole.
No valve reliefs and no idea how thick the crowns are, so the cam would probably have to be pretty small but it's doable and the pistons are only $300 per set of 8.
They're supposedly good for stock replacement, so measuring the crown of a stock slug might give an idea of thickness available for some eyebrows.
MOPAROFFICIAL
Oogliboogli
.030 over 3.58 stroke 318.
Ok, go order the pistons.
Je,Ross, etc.
Or spend on Machining of stocker type cast Pistons. 8, probably -145 bucks to mill all 8 .
Ok, go order the pistons.
Je,Ross, etc.
Or spend on Machining of stocker type cast Pistons. 8, probably -145 bucks to mill all 8 .
And add valve reliefs././/
Your cubic inch requirement means a std. bore, up to .030 bore. Hope you have a Magnum block..... What you ask of can be done. Hope you have friends with machines, you're going to need them. I've done this very engine. If not for thlose friends with machines, it WILL get costly. We started with a std bore 318 Magnum block. 360 stroke crankshaft(3.58) with 318/340 main journals can/could be had. Std length connecting rod. Early 318 pistons used for the compression height. Skirts milled off to clear crank throws. Basically made a gen 3 hemi piston out it. Deepen the valve reliefs a little after machining tops down for street friendly compression ratio. Ran lightly touched Magnum heads. Air Gap Magnum intake. Only cam we had around was an old Direct Connection Hemi grind flat tappet. Long tubes and a ThermoQuad. Damn little thing ran like a scalded dog. Went into a 70 1/2 ton D-100 with a 3000 convertor and 3.91 gear.
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