thoughts on my build

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mopar marc

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Hey everybody, Just like to get some input on my 340 build have not assembled yet so not to late to change
70 340 block 40 over
stock forged crank 10/10
arp rod bolts
cast (stock) pistons earlier compression 10.2:1 (so i am told by machinists)
moly rings
j heads 2.02 valves hardened seats comp srings and retainers (901-16 single with damper)
comp xe-268 cam
double roller chain
windage tray
hv oil pump
perfomer rpm intake (not air gap)
holley 650 double
car (67 dart) will have 727 i am thinking 2500 stall input here would be appreciated. with 8 3/4 391 sure grip. Thanks in advance looking for between 350-400 hp
 
the stall is near perpect for that setup.
your going to have one stout street car.
what exhaust system will you use?
 
2 1/2 and more than likely cheapy headers until I can afford some tti headers thanks for the input I almost went with the xe 274 cam but am always hearing dont go to boig on the cam or carb I have done some mild builds but am still learning (does it ever stop)
 
Sounds like a nice street mill. Just be carefull of the 10:1 compression, iron heads and small cam may not like pump gas.
 
Sounds good, but to get 10.2 from that shortblock setup, you better have it all blueprinted. I'll put money it's not very close to that as it stands. Also, the cam is mild, but if in the future you see yourself wanting more cam, you should replace the pistons with something better, with some valve reliefs. Also, I wouldnt run the 650 dp, I'd run a std 3310 vaccum secondary.
 
I think the comp. ratio is a tad high. But hey, if it measures out and specs up at that......Pump gas would be a concern. I'd rather run a tad under on the ratio than have to much and have to retard the timing in order to make it run without pinging.
You lose more power from retarded timing than low comp. ratio.
Cometic gaskets, though expensive, can provided a thicker gasket to drop the ratio a tad in the exact bore size you need.

The carb is a give and take. Though I'm with a vaccum secondary carb for auto on a mild build, if you can run the DP and set it up right, you'll enjoy it more than a VC Carb.
Also the total HP output of the carbs CFM difference isn't that much.
You'll enjoy the smaller carbs streetablity over the larger one.
The higher velocity through the carb offers better throttle response and potential gas mileage.

IMO, I think it's a good build.
 
Thanks for the input, I have other carb options to go with (carter afb) so I will see wich one does better once I get it together. I plan on using the fel pro head gaskets ( came in the kit) again I am new at this and learning as I go I dont think it will end up at 10.2 but i would be happy with 9:1 neighborhood as I think that would work well with the gearing and cam how can i be sure about the end result? (Before hand)
 
Comp ratio end result or combo output?
 
comp ratio more than anything end result of the combo will be what it will be. I know there are desktop dynos but have never used one. I have done compression checks on engines but that doesent tell you the ratio. I would like to know where I end up with my comp ratio. thanks rumble fish you and others have helped me out in the past and I appreciate it. Sorry for the delayed response as I am working in france right now and am keeping different hours. Marc
 
Well that sounds like a two for. Out in another country (?) and at work while gathering car smarts. I guess so long as she runs on pump gas, your good to go.
 
yeah its a rough life I will be back home soon and plan to start assembly, I am a helicopter mechanic and we have many contracts in europe this summer thanks again for your help. marc
 
I dynoed an almost exact copy of your build - 387hp @ 5750rpm
differences - 700cfmdp holley and Isky 230*/480 lift cam.
You will have a very fun streetable kick some A$$ car.
Don't go cheap on the convertor - Dynamic 9 1/2" with 3200 stall will give you the best of both street and strip.
Get an FBO ignition kit - ECU, coil, cap and rotor - best bang for the buck web:4secondsflat.com
 
sounds good to me just enough to scare the wife around town. thanks for the input. marc
 
Marc, I missed this before... Nice hood ornament on the Charger in your sig... ;)
 
Mopar marc will have to do the math to get his desired comp ratio, but if it turns up to high he can always advance the cam 2/4 degress to drop the DCR, it will not affect cam performance, cam timming will come in sooner.
 
Thanks Rick. Thats my lady on the hood she is one of a kind and is very supportive of the hobby, Thanks for all the input guys. Marc
 
mopar marc you end up with the compression ration by this formula (swept volume + combustion chamber volume)/combustion chamber volume. Swept volume is easy enough to calculate. Just calculate the volume of one cylindar. Yours comes out about 43.3 cubic inches with the added volume from the overbore added in. Its easier if you then convert this to cubic centimeters. Theres 16.39ccs in one cubic inch. So you end up with 709.69cc for the swept volume. The combustion chamber volume is way more complicated to calculate. You need to determine cylinder head chamber volume, volume of the piston top (adds ccs for reliefs, subtracts from ccs for domed pistons), volume because of deck clearance (zero deck=0, below deck adds volume, above deck subtracts volume), and the clearance because of the head gasket. Add all these numbers together and plug into the formula above and you'll get your compression ratio. Hope this helps.
 
Marc, does she know shes a Avatar on here? Hummmmmm, I wonder if mine will fall for it.......naaaaaaaaa
 
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