RAMM
Well-Known Member
Nothing other than I finally received the pistons. Still waiting on oilpan, balancing etc.... It will probably be awhile until it hits the dyno...Just too busy. J.Rob
New life for an old 340 (stock stroke)
- Thread starter RAMM
- Start date
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Nothing other than I finally received the pistons. Still waiting on oilpan, balancing etc.... It will probably be awhile until it hits the dyno...Just too busy. J.Rob
RAMM
Well-Known Member
More progress has been underway. Probably have the rockers next week and then its breakin on the dyno. Looking forward to having this one buttoned up. Deck height worked out perfect as does intake manifold fitment. Whoever worked on this intake did a pretty nice job and I won't be able to take credit for it. J.Rob
Purdy. What color did you paint the block? Hope that is not a chevy color, you will have all kinds of mechanical issues with it.
Funny thing about cameras, lighting and the internet is sometimes red looks orange and orange looks red.
Both colors used by Ma MoPar.
Both colors used by Ma MoPar.
RAMM
Well-Known Member
It is Valspar Chrysler Orange #226 . J.Rob
jeffnmo
Just another Mopar Maniac
I need to send you my 340, really like what you are doing, its gonna be a screamer for sure. I'm going to switch over to a solid cam soon to hopefully wake mine up a little.
Jeff
Jeff
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MOPAROFFICIAL
Oogliboogli
The x heads do these numbers with little effort. People just cant seem to wrap their minds around it.
nm9stheham
Well-Known Member
RAMM, the end counterweights look to be polished or machined down. Has this been done as part of removing weight for balance? Or did it just come this way from the factory?
RAMM
Well-Known Member
Looks like every other factory forging to me. J.Rob
RAMM
Well-Known Member
Wow, thankyou so much Lobsterman. This is nice to hear as this is one fickle f*%$ing trade. J.Rob
MoparMark91
Well-Known Member
Where do you get trw replacement pistons and a decent stock stroke crankshaft all I find is used ones and eagle brand but idk if their any good
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Summit Racing or Jegs has them.
However how above a 360 (3.58) stroke 340 crank with .060 360 pistons that equals a .020 over 340 bore. Turn that 340 into about a 366. Since your thlnking about a new crank anyway be the same price and you pickup more cubes and more power.
MoparMark91
Well-Known Member
Well I'm still paying off the block but as for crankshaft I dont have one so I'm looking who's a good source for one when I start the build in december. I have a 318 crankshaft but its cast out of a 69. I'm trying to keep the cylinder walls as thick as I can but I will admit I'm still debating on the build and everything on how I want to go about it
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Never knew they put cast cranks in 69 318s. Besides that what is wrong with a cast crank.
A 340 @ .020 is the same bore size as a 360 @ .060.
MoparMark91
Well-Known Member
That's what I said I checked it the other day and I always thought those years mainly had forged but I guess not. And i just like the peace of mind with durability honestly, I'm still thinking though. I dont mind cast crank just if I am going to build it just thought I'd play it safe with forged. I'll double check but I'm pretty sure it's a cast crank cause it has a fine line from the cast molds. And I did not not know that about the bore sizes hmm got some thinking to do.
TRW stock replacement forged pistons are part#2316 from memory and not all that expensive.
Stock forged cranks turn up from time to time.. sold one that was fresh cut 10/10 a month or so ago for about $120 just have patience and you will find one.
MoparMark91
Well-Known Member
Yeah I see them on Ebay that have been 20/20 grinded for about 400 so I'll just be patient with this build
nm9stheham
Well-Known Member
MoparMark91, if you are doing a 340, then the 318 crank has one problem: the counter-weighting is not set up on the 273/318 cranks to balance the heavier stock 340 pistons and rods. To use those heavy pistons with a 318 crank, you will need to have a shop balance it and ADD weight to the 318 crank; adding weight tends to be pricey.
So you either:
You may actually do yourself a favor for longevity by going to lighter rods and pistons and staying with the 318 crank. My son and I did that on his 340: we used KB pistons, and SCAT rods, and the 273 cast crank balance was simple and cost only $100. That combination reduced the bobweight on the crank by almost 20%, from 2326 to 1893 grams; that is a LOT, and takes stress off of the crank and rods. That engine is set up for around 400 peak HP.
The KB pistons are around the same price as the L2316F's and the SCAT rods are just under $300 for a set of 8, which is not much more than re-conditioning a set of stock rods. Both pistons and rods are already weight matched out of the box, so that cuts out the majority of labor time and cost for the balance work; you end up only balancing the crank.
So there are options.
And here is another source for crankshafts:
Crankshaft Supply, Inc. -- Experts in Crankshafts & Cylinder Heads
So you either:
- Find a 340 crank to use with those L2316F pistons, which are stock piston weights. To not re-balance the crank assembly, you would need the heavier late-318/340/360 rods, (not the earlier, lighter 318 rods, like came in 1969 318's) to use these pistons with a stock 340 crank.
- If this is not an all out race machine, then the cast SBM cranks have a reputation for being quite durable. That gives you another option. You use lighter pistons/rods that will be balanced with the 318 cast crank at a shop. You spend $$ on new pistons and rods that are already weight matched out-of-the-box, and then save $$ since the shop will only have to weigh a set, compute the bobweight, and then take weight off the crank.
You may actually do yourself a favor for longevity by going to lighter rods and pistons and staying with the 318 crank. My son and I did that on his 340: we used KB pistons, and SCAT rods, and the 273 cast crank balance was simple and cost only $100. That combination reduced the bobweight on the crank by almost 20%, from 2326 to 1893 grams; that is a LOT, and takes stress off of the crank and rods. That engine is set up for around 400 peak HP.
The KB pistons are around the same price as the L2316F's and the SCAT rods are just under $300 for a set of 8, which is not much more than re-conditioning a set of stock rods. Both pistons and rods are already weight matched out of the box, so that cuts out the majority of labor time and cost for the balance work; you end up only balancing the crank.
So there are options.
And here is another source for crankshafts:
Crankshaft Supply, Inc. -- Experts in Crankshafts & Cylinder Heads
MoparMark91
Well-Known Member
I do have some thinking to do on this build and I greatly appreciate your input and opinion and locknut really helps. I've also thought about just getting a scat rotating assembly package from summit what are your thoughts on that if I may ask
1-48005BI
I personally love the idea. A kit in the box.
Home run as far as I’m concerned. As long as it fits the bill for the build, your in.
I am looking at kits myself. It is the ez button.
Once I get my 340 blocks sonic checked and know exactly where I stand and can go, I’ll order a kit or two.
Just pay attention to the compression ratio with the spec’d Cylinder head cc amount. Also, it is a nice to know of the block needs to be notched with the kit your looking at though once the machinist has it all, it is a simple thing to adjust for. It’s just nice to know ahead of time instead of being a surprise when you get there.
If you have the coin (to anyone considering this move) go to a forged crank set up. Then pistons if so desired. IMO, how I see it is it would be almost crazy not to go with a forged crank.
Home run as far as I’m concerned. As long as it fits the bill for the build, your in.
I am looking at kits myself. It is the ez button.
Once I get my 340 blocks sonic checked and know exactly where I stand and can go, I’ll order a kit or two.
Just pay attention to the compression ratio with the spec’d Cylinder head cc amount. Also, it is a nice to know of the block needs to be notched with the kit your looking at though once the machinist has it all, it is a simple thing to adjust for. It’s just nice to know ahead of time instead of being a surprise when you get there.
If you have the coin (to anyone considering this move) go to a forged crank set up. Then pistons if so desired. IMO, how I see it is it would be almost crazy not to go with a forged crank.
MoparMark91
Well-Known Member
Yeah I'm leaning heavy towards the kit it come with everything except bearings I'm already going 30 over and a little extra stroke should be nice. I'm going to talk with my machinist first make sure everything checks out
nm9stheham
Well-Known Member
The easy part is good. It is a lot of what you are paying for. SCAT's reputation seems to be pretty good. Just so as you will know, the cast 318 crank route with KB's and Scat rods will run about half the price.
The forged pistons on that kit will buy you some extra toughness if things detonate, but don't think that forged pistons are proof against detonation. Forged crank will buy some insurance, but again, it depends on the use.
As noted above, this has a pretty high compression ratio; that comes partially with stroking. It may be OK but it depends a lot on the cam and heads, and that depends on the use and the rest of your parts. What ARE you going to be doing with this car/engine?
MoparMark91
Well-Known Member
Just a little street beast with drivability. My buddy has stock j heads, so I was going to use those 1.8 valves. And havent decided on intakr but a lunati cam like a step above stock. So will that kit put a big impact on cr like what else would I have to do? Just want a solid new setup. I didnt think it would put a huge impact on cr? But I could be wrong
nm9stheham
Well-Known Member
Stroking always raises CR, all else being equal. Just looking at that tabulation of number on the SCAT website shows static CR's between 10 and 11. With a small cam like that, the dynamic CR may well work out too high.
Running some numbers quickly for that crank and piston setup.
Dynamic CR accounts for the cam size and ought to stay at or below 8.0 or so for iron heads to be able to stay away from detonation on premium pump fuel. A smaller Lunati Voodoo cam would be a 10200702, at 265 advertised intake duration, and .475 lift. Pretty easy to work with. dynamic CR would work out around 7.9-8.0. So that is as small as you would want to go on the cam. A very nice, torquey street engine at that; you would want to approach the tune-up carefully; I assume you are in CA near to sea level...yes???
And the nice thing about keeping the CR up is that you can go with a bigger cam and not hurt your low RPM torque.
BTW, with the heads you mention, you're not going to be stressing a stock cast crank, IMHO. They just are not going to flow the air.
Running some numbers quickly for that crank and piston setup.
- That kit with the ICON 741 pistons (which I think are what they are using)
- Typical J heads, not milled
- .039" thick head gaskets
Dynamic CR accounts for the cam size and ought to stay at or below 8.0 or so for iron heads to be able to stay away from detonation on premium pump fuel. A smaller Lunati Voodoo cam would be a 10200702, at 265 advertised intake duration, and .475 lift. Pretty easy to work with. dynamic CR would work out around 7.9-8.0. So that is as small as you would want to go on the cam. A very nice, torquey street engine at that; you would want to approach the tune-up carefully; I assume you are in CA near to sea level...yes???
And the nice thing about keeping the CR up is that you can go with a bigger cam and not hurt your low RPM torque.
BTW, with the heads you mention, you're not going to be stressing a stock cast crank, IMHO. They just are not going to flow the air.
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