A little help here? Smallblock build

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71dusterdan

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In need of some tech help outside of my circle of knowledge. First allow me to preface this question with 2 criteria... I do not want to throw good money after bad. Meaning I need to try and use parts I already have as opposed to just buying something else. Second, I do not want to leave easily acquired horsepower on the table, just because it costs a couple of bucks more.

So what is the best use of my available parts, for a good strong running smallblock, going into a 71 duster, 833 od, 3:55 gears. I want decent to good mileage, daily driver reliability, and enough power to be fun. How much power is that? Hell if I know, but figure to retain some semblance of mileage, need to keep it in a 13 second quarter mile range.

So the list of parts...
Complete 71 340, was frozen so it needs pistons and boring. J heads, 1.88 intakes, iron intake, thermoquad. Forged crank, full floating rods. Correct balancer
LA 360 block rods and crank, magnum heads, balancer.

Comp cams extreme energy 268 cam kit
Complete Milodon road race pan for a 340!!!
Edelbrock Performer
Schumacher Tri-Y's

So the Milodon pan dictates the 340 block.
Years ago the old High Performance Mopar magazine built a really wicked 340 with a 360 crank. Seemed the engine really liked the stroke. This is an option.

Like I said, I do not want to leave power on the table, 13's are really easy in an a body. I am not against more power and faster so long as I can still get mileage on the road. So will some of you with way more experience chime in on your ideas, to use what I have got and approach my goals? Thank you in advance.
 
You can get more cubes with a340 and 360 crank but it's a lot of money and work, and pistons? not sure, might be expensive.

Why not just build / bore the 360? What shape is the crank, it need work?
 
360 Crank mains will need to be machined down to 340 Journal size..... Your not going to get that much out of it though. 3.31 stroke to 3.58..... Pistons because of the bore size if you can find them. I am sure someone here has part numbers possibly.

I think you would be better off since you have to buy pistons is to stroke it to 4" or leave the 340 crank in it and spend your $$ on a good set of heads. OR Just use the 360 as your base to build on and again spend your $$ on Heads.
 
Yup A pan to fit the 360 is far cheaper than diddling that 360 crank to fit the 340. And you can sell the Milodon and buy a different pan
 
Just build the 340. That's a nice recipe. "Everybody" leaves power on the table, unless they are runnin a 14-71 and nitro. Just use what you have and you'll have a really nice small block. Don't get caught up in numbers. Just build it.
 
The use of a 360 crank in a 340 bored out some equals 372, the poor mans stroke back in the day. Pistons will be very pricey. I'd skip that option and ether stroke the 340 with a 4 inch crank (still pricey) or just build the 360. Which would be my choice since the heads you have limit the power available with a stroker in a big way.

What I would do is use the 340 heads and intake on the 360 with the cam you have. Build it with KB-107's pistons and a thick head gasket. If the pistons come to a zero deck height, then with a .039 head gasket the ratio will be 9.8-1. A thicker head gasket (.060) will drop the ratio enough for pump gas and no issues.

Now does the intake have the ability to use the TQ without a spacer? If not, swap for a factory TQ intake.

The rest ether keep for later or sell and roll the money over into paying for parts. That 340 and the road race pan should bring in some decent bucks.
 
67Dart273 said:
You can get more cubes with a340 and 360 crank but it's a lot of money and work, and pistons? not sure, might be expensive.

Why not just build / bore the 360? What shape is the crank, it need work?
Click to expand...

No ...just buy the 3.58 stroke crank with 340 mains from Scat......Or MP as that is a Scat crank too...the MP shows up 15 dollars cheaper at jegs

http://www.jegs.com/i/Mopar-Performance/312/P5007257/10002/-1

$361.99 shipped to your front door..
 
KB 107 are available at 4.07 ...which is a .030 340

KB IC 741 are good up to 4.08......040 340
 
I just had a reply typed up, then accidentally hit the wrong button on my keyborad (typing in the dark) and blew everything away..... :banghead: :banghead: :banghead:
 
Seems like a lot of work for 12 cubes over the 360 you already have to get the small main 360 crank.

Build a replica of Tony aka "70aarcuda's bad *** 360's and be done with it!
 
Mad Dart said:
Seems like a lot of work for 12 cubes over the 360 you already have to get the small main 360 crank.

Build a replica of Tony aka "70aarcuda's bad *** 360's and be done with it!
Click to expand...

I picked up a couple of those cranks years ago...at very good price went mopar dumped them...

just have not found the pistons at a price that I like yet...LOL....super cheap...lol
 
Take your cam, heads, intake, carb and exhaust and put them all in a good running 150 dollar 318. You will get your best gas mileage vs 340/360, you will get into the 13's with your gears and tranny, and you will spend way less than working with a frozen 340. There, ya go! Easy, cheap, and with tuning, mid 13's very possible :)
 
70aarcuda said:
I picked up a couple of those cranks years ago...at very good price went mopar dumped them...

just have not found the pistons at a price that I like yet...LOL....super cheap...lol
Click to expand...

Lol, shoot man you hand out car parts to your 3 cars like a Vegas black jack dealer with a full table! haaaa

I think you got the 360 game wired! No reason to go switching things up!
 
318willrun said:
Take your cam, heads, intake, carb and exhaust and put them all in a good running 150 dollar 318. You will get your best gas mileage vs 340/360, you will get into the 13's with your gears and tranny, and you will spend way less than working with a frozen 340. There, ya go! Easy, cheap, and with tuning, mid 13's very possible :)
Click to expand...

Ya so he has to buy yet another engine, and when done, those big heads will have about 7.5 compression. I think the idea here, was to use "the most" of 'what he has'
 
I would sell the 340 to fund the rest of the build (since you can get more $$$$ out of the 340). Then build the 360. 13's are no problem with the parts you have. There are a lot of factors, but for the most part power is all in the heads (and cam)...if you want more power, get better flowing heads.
 
good mileage and power
340 w/flat tops (9.5:1) j heads,stock style cam with a little less duration
thermoquad,3.23 and 2200 stall converter
 
67Dart273 said:
Ya so he has to buy yet another engine, and when done, those big heads will have about 7.5 compression. I think the idea here, was to use "the most" of 'what he has'
Click to expand...
Ummm..... ever price up a rebuild on a frozen motor???? I mean, buying a new cam is cheaper than fixing one that has 5 lobes flattened out. Or buying another crank is cheaper than having one fixed that has been destroyed. Get the point??? Nope, not to you. Put 2000.00 bucks into a 340 because you already have it..... and by George, that makes more sense than buying a 150 dollar 318..... sigh. And here we go again, another 318 with 7.5 compression.... funny how we have put 340/360 heads on 318's and run like a mad dog (beating 340's/360's) but yet, the same ole story.... I'm tired of explaining it.
 
If it was me I'd sell the 340, sell the Milodon pan, sell the magnum heads but keep the rocker setup, and sell the Performer. Build the 360 with hyper pistons and plan to run a set of EQ Magnums with your rockers. Internally balance it, buy a stock pan. Stick the XE268 in it, an RPM Air Gap on it, and the tri Ys. You will have enough steam to put a full street A into the 12s with the right suspension, gearing, and driver and you won't have to contribute much $$ to the cause.
 
LOL @ 318willrun. True, been down that road for years here and at other places.

With his parts on hand, the 360 will do the job well. All the pRts are there for what he wants to do. He should be able to get good mileage from that cam in the 360. I see no problem at all.
 
318willrun said:
Ummm..... ever price up a rebuild on a frozen motor???? I mean, buying a new cam is cheaper than fixing one that has 5 lobes flattened out. Or buying another crank is cheaper than having one fixed that has been destroyed. Get the point??? Nope, not to you. Put 2000.00 bucks into a 340 because you already have it..... and by George, that makes more sense than buying a 150 dollar 318..... sigh. And here we go again, another 318 with 7.5 compression.... funny how we have put 340/360 heads on 318's and run like a mad dog (beating 340's/360's) but yet, the same ole story.... I'm tired of explaining it.
Click to expand...

No you missed the point entirely, and that makes you the jackass. REBUILD THE 360 is what I said earlier, but you missed that. So now I'M tired of explaining it

So let's not bullshit each other. A 7.5:1 318 is not gonna beat any decent running 340, either. Not.......going.....to......happen

Oh, n, yeah, fer yer edification, I just yanked a running 318 out of mine. So, been there done that.
 
You need to calm down and relax. No more coffee for you!
 
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