Building a 340 engine

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Magnus707

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Hi,
I need some help. I am not an expert on Mopar small block so I need some advice.
I have some parts, not sure what to use and in what combination. This is what I have.
  • 340 block Standard from 1971
  • Two alternatives when it comes into heads;
    • x-heads with 2.02 and 1.6 valves. Fully restored with Manley stainless steel valves. Manley Severe Duty Series Stainless Steel Valves 11782-8 2.02 and
      Manley 11781-8 - Manley Severe Duty Series Stainless Steel Valves 1.6
    • Heads Edelbrock #61779 Performer RPM
  • Rocker Arms CCA-1622-16
  • Two alternatives when it comes into manifolds
    • Edelbrock Part # 2176 Performer intake
    • Edelbrock Part # 7576 RPM Air-Gap intake
  • Mopar Performance Forged Crankshaft - P5007253 with 3.58 stroke
  • Eagle Connecting Rod Set SIR6123
  • CompCam Xtreme Energy 212/218 Hydraulic Flat Cam XE256H
  • Ignition
    • Ignition, MSD Ignition Box 6AL, PN 6426
    • Distributor MSD
    • Coil MSD
  • Carbs, Edelbrock 1405 and 1407
  • Mopar Small Block Camshaft Thrust Plate
  • Dura bond Block Hardware & Head Dowel Kit 1964-2003
  • ARP Head Stud Kit144-4001 sb Chrysler 273 318 340 360 WEDGE Hex nuts
  • New Cam Bearings & Brass Freeze Plug Set 1957-1978 Chrysler 273 318 340 360
  • Clevite CB481HN Engine Connecting Rod Bearing Mopar 318 340 360 408
  • Mopar Performance P5153513, 318-340 Main Bearings, Standard, H-Style
  • Oil pump Melling volume High, M72HV
  • Fuel Pump, Edelbrock EDL-1720
  • Summit Racing Harmonic Balancer, SFI SUM-C4277
  • Major part missing is pistons
The engine shall go be used in a Dodge Business Coupe from 1936. I have also a 727 and 83/4 rear axle with 3.73 gear. I will use 16" rims.
I will use it in the street almost as a daily driver. I would like to have as high power and torque as possible. It would be great if I could get close to 500 hp. I prefer to use what I have as long it makes sense.
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Welcome! I’m going to follow along as i also have a 340 which I’m planning on using in a 47 Dodge sedan with an A500 and 71 B body 8.75 with 3.55 gears.
 
Magnus707 said:
Hi,
I need some help. I am not an expert on Mopar small block so I need some advice.
I have some parts, not sure what to use and in what combination. This is what I have.
  • 340 block Standard from 1971
  • Two alternatives when it comes into heads;
    • x-heads with 2.02 and 1.6 valves. Fully restored with Manley stainless steel valves. Manley Severe Duty Series Stainless Steel Valves 11782-8 2.02 and
      Manley 11781-8 - Manley Severe Duty Series Stainless Steel Valves 1.6
    • Heads Edelbrock #61779 Performer RPM
  • Rocker Arms CCA-1622-16
  • Two alternatives when it comes into manifolds
    • Edelbrock Part # 2176 Performer intake
    • Edelbrock Part # 7576 RPM Air-Gap intake
  • Mopar Performance Forged Crankshaft - P5007253 with 3.58 stroke
  • Eagle Connecting Rod Set SIR6123
  • CompCam Xtreme Energy 212/218 Hydraulic Flat Cam XE256H
  • Ignition
    • Ignition, MSD Ignition Box 6AL, PN 6426
    • Distributor MSD
    • Coil MSD
  • Carbs, Edelbrock 1405 and 1407
  • Mopar Small Block Camshaft Thrust Plate
  • Dura bond Block Hardware & Head Dowel Kit 1964-2003
  • ARP Head Stud Kit144-4001 sb Chrysler 273 318 340 360 WEDGE Hex nuts
  • New Cam Bearings & Brass Freeze Plug Set 1957-1978 Chrysler 273 318 340 360
  • Clevite CB481HN Engine Connecting Rod Bearing Mopar 318 340 360 408
  • Mopar Performance P5153513, 318-340 Main Bearings, Standard, H-Style
  • Oil pump Melling volume High, M72HV
  • Fuel Pump, Edelbrock EDL-1720
  • Summit Racing Harmonic Balancer, SFI SUM-C4277
  • Major part missing is pistons
The engine shall go be used in a Dodge Business Coupe from 1936. I have also a 727 and 83/4 rear axle with 3.73 gear. I will use 16" rims.
I will use it in the street almost as a daily driver. I would like to have as high power and torque as possible. It would be great if I could get close to 500 hp. I prefer to use what I have as long it makes sense.
1





















1
Click to expand...
Lots of good parts. 350-400 horse maybe
 
Welcome! Sounds like fun and we love pictures here!
How about some flat top Icon forged pistons?
Cam seems very mild. Look up a stock 340 cam and jump one level of duration higher.
I used a Crane 427/454 cam in a truck with 4.10 gears and 28" tires. Did not notice it at idle,vacuum was good and pulled well.
But I'm sure your car does not weigh 4500 lbs!
Good luck with the project!
 
From what I know (or think I know!), neither head is going to get you to 500 HP as described. And certainly not with that cam. The cam is good for low compression engines on the street but is unecessarily limited for the engine parts you have, and the piston options that you will likely be able to use.

We need to be sure on one piece of data on your block to look into pistons: What is the block bored to? Standard 4.040" bore size or some oversize? 360 pistons are what come to mind but they are not available in infinitely large oversizes to fit into the larger bore 340 block.
 
OK, thanks. Which head do you prefer to use? The chambers are very different between the 2 heads, and so the best piston selection will be very different.
 
OK. Next question: Do you want to keep that cam? It is really very small for what you have, unless you want to emphasize fuel mileage. Being in Sweden with the higher fuel prices, we need to understand how important fuel mileage is to you.

The objective is to determine the cam for what how you want to use the car, and select the piston to optimize dynamic compression ratio with the selected cam, to keep your low to mid RPM torque high for daily driving and street use.
 
I've been looking at these.
ICON Premium Forged Pistons IC741-080
They would also be going into a 340 that is already .040 over with a 340 crank. There are also 9.6 and 20.5 cc dish tops anddifferent bore sizes available.
https://www.summitracing.com/search...gine-family/mopar-small-block-la?PageSize=100
What's the highest available octane fuel you have? Based on a 9.6 inch deck height, these pistons come out .012 under deck. A little milling would get you to zero deck and then you could select from several different head gaskets to get something that resembles quench.
 
you can't really use 360 pistons in a 340 unless you use a 360 crank and make a stroker which is what you are doing
so you need to run 360 +.060 pistons 4.060 or 0.20 over 340 bore so forget it's a 340- it's now a big bore 360 as far as pistons go
with the x heads use the kb quench dome pistons
with the closed chamber heads you need to run a dished piston to give you a true 9 to 9.5 to one with that cam
that's with running a 0 or close to 0 deck clearance with either piston to give you some quench
if the piston is say .010 down then use the Mr gsket .028 gasket
if 0 then you can use the thinner fel pro (not the 050 thick one)
there are ballance issues with either combination
I've been to Sweeden in December- i would not run an air gap
so what compression height piston for 0.0 deck you need to know this
then how much dish to give you the compression you want for the rev range of that cam
what exhaust?
who is CCA on the rocker arms?
 
nm9stheham said:
OK. Next question: Do you want to keep that cam? It is really very small for what you have, unless you want to emphasize fuel mileage. Being in Sweden with the higher fuel prices, we need to understand how important fuel mileage is to you.

The objective is to determine the cam for what how you want to use the car, and select the piston to optimize dynamic compression ratio with the selected cam, to keep your low to mid RPM torque high for daily driving and street use.
Click to expand...

I think I should use another cam
 
Wyrmrider said:
you can't really use 360 pistons in a 340 unless you use a 360 crank and make a stroker which is what you are doing
so you need to run 360 +.060 pistons 4.060 or 0.20 over 340 bore so forget it's a 340- it's now a big bore 360 as far as pistons go
with the x heads use the kb quench dome pistons
with the closed chamber heads you need to run a dished piston to give you a true 9 to 9.5 to one with that cam
that's with running a 0 or close to 0 deck clearance with either piston to give you some quench
if the piston is say .010 down then use the Mr gsket .028 gasket
if 0 then you can use the thinner fel pro (not the 050 thick one)
there are ballance issues with either combination
I've been to Sweeden in December- i would not run an air gap
so what compression height piston for 0.0 deck you need to know this
then how much dish to give you the compression you want for the rev range of that cam
what exhaust?
who is CCA on the rocker arms?
Click to expand...

Sorry, CCA is just part of Summits part number.
 
Garrett Ellison said:
I've been looking at these.
ICON Premium Forged Pistons IC741-080
They would also be going into a 340 that is already .040 over with a 340 crank. There are also 9.6 and 20.5 cc dish tops anddifferent bore sizes available.
CHRYSLER 5.9L/360 Mopar small block LA ICON Premium Forged Pistons
What's the highest available octane fuel you have? Based on a 9.6 inch deck height, these pistons come out .012 under deck. A little milling would get you to zero deck and then you could select from several different head gaskets to get something that resembles quench.
Click to expand...

I have read that you should not go more than 0.030 with a 340 block
We got gas with 98 octane
 
To really know what you can safely overbore, to, you really need to sonic test. Some 340 blocks are on the thick size and will easily go .060 over, or 4.1 inch bore size and have metal left (340 T/A blocks in particular). How much is 98 octane gasoline a liter there in Sweden? Here in the U.S., our pump octane rating is an average of research octane numbers and motor octane numbers. Are your octane numbers RON, MON, or R+M/2 ratings? More than likely, it is RON and in reality equal to 93-94 octane at the pump. If you have a MON rating of 98, you are probably going to be very close to R+N/2 of 104 rating.
I also notice you listed the Edelbrock magnum type head with the 58 cc chamber. An example for you if you leave the Edelbrocks at 65cc's and use the following Cometic gasket.
Cometic MLS Head Gaskets C5917-036
If you leave the piston .002 below deck to have .038 piston to head and use the 4.06 bore piston with 5 cc valve notches you come up with 12.3:1 final compression. That's okay if you have an actual R+M/2 octane rating of 104, and might give you a pretty fair shot at 500hp with the right cam.
 
he's only going .020 over 340
He'll be fine
.010 down with the .028 gasket works are there any pistons in .020 0ver?
cam will be fine since he owns it
you do not need expensive rockers with that cam
stock will work fine
 
Magnus707 said:
I have read that you should not go more than 0.030 with a 340 block
We got gas with 98 octane
Click to expand...
Doubt its the same as what we commonly call 98.
If that's the reasearch octane, might be similar to our 92 or 93. Just guessing.
In US & Canada, maybe Mexico, Octane is the average of Motor Octane and Research Octane. Also called the Anti-Knock Index (AKI)
 
Last edited:
Could he not run .060 KB 107’s with his 3.58 crank in the 340 bored .020? Would the KB 107’s work with his Edelbrock heads. He just needs to make sure the crank has the correct main size for the 340 block.
 
Yes, still could use the KB hypers available for less with 4.06 bores, and there are three separate dish sizes, too. Basically a hyper version of the Icon pistons, both are manufactured by UEM. The one with an 11.2 cc dish at zero deck ( Cometic MLS Head Gaskets C5917-036 ) would yield a 10.85-10.9:1 compression ratio. The tighter piston to wall tolerance with hypereutectics will have a little less rock in the bores and give a little more tolerance for a .036 piston to head clearance.
 
Last edited:
Mopar Performance Forged Crankshaft - P5007253 with 3.58 stroke ....that is what he has listed...so the 360 piston is good to go
 
Magnus707 said:
Hi,
I need some help. I am not an expert on Mopar small block so I need some advice.
I have some parts, not sure what to use and in what combination. This is what I have.
  • 340 block Standard from 1971
  • Two alternatives when it comes into heads;
    • x-heads with 2.02 and 1.6 valves. Fully restored with Manley stainless steel valves. Manley Severe Duty Series Stainless Steel Valves 11782-8 2.02 and
      Manley 11781-8 - Manley Severe Duty Series Stainless Steel Valves 1.6
    • Heads Edelbrock #61779 Performer RPM
  • Rocker Arms CCA-1622-16
  • Two alternatives when it comes into manifolds
    • Edelbrock Part # 2176 Performer intake
    • Edelbrock Part # 7576 RPM Air-Gap intake
  • Mopar Performance Forged Crankshaft - P5007253 with 3.58 stroke
  • Eagle Connecting Rod Set SIR6123
  • CompCam Xtreme Energy 212/218 Hydraulic Flat Cam XE256H
  • Ignition
    • Ignition, MSD Ignition Box 6AL, PN 6426
    • Distributor MSD
    • Coil MSD
  • Carbs, Edelbrock 1405 and 1407
  • Mopar Small Block Camshaft Thrust Plate
  • Dura bond Block Hardware & Head Dowel Kit 1964-2003
  • ARP Head Stud Kit144-4001 sb Chrysler 273 318 340 360 WEDGE Hex nuts
  • New Cam Bearings & Brass Freeze Plug Set 1957-1978 Chrysler 273 318 340 360
  • Clevite CB481HN Engine Connecting Rod Bearing Mopar 318 340 360 408
  • Mopar Performance P5153513, 318-340 Main Bearings, Standard, H-Style
  • Oil pump Melling volume High, M72HV
  • Fuel Pump, Edelbrock EDL-1720
  • Summit Racing Harmonic Balancer, SFI SUM-C4277
  • Major part missing is pistons
The engine shall go be used in a Dodge Business Coupe from 1936. I have also a 727 and 83/4 rear axle with 3.73 gear. I will use 16" rims.
I will use it in the street almost as a daily driver. I would like to have as high power and torque as possible. It would be great if I could get close to 500 hp. I prefer to use what I have as long it makes sense.
Click to expand...
1





500 hp is pretty high hp per cid especially for a daily driver. Plus the X heads are good for about 400 hp and eddies 450 hp unported, It takes a 360 ish size engine make peak hp about 500 hp @ 6500 rpm, 450 hp @ 5900 rpm, 400 hp @ 5200 rpm, 350 @ 4600 rpm.

Around 1 Hp per cid for most is about the best compromise for street friendly performance, for some 1.1 hp per cid, Above that your more into street strip territory.

I'd go with with Eddies and a high lift short duration hydraulic roller, kind of how new Hemi and LS make power all head flow with moderate cam.















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[/QUOTE]
 
B3422w5 said:
Eagle SIR rods are complete junk. I wouldnt run them lawn mower
Use anything else. Anything
Click to expand...
Please elaborate!
273 said:
1

500 hp is pretty high hp per cid especially for a daily driver. Plus the X heads are good for about 400 hp and eddies 450 hp unported, It takes a 360 ish size engine make peak hp about 500 hp @ 6500 rpm, 450 hp @ 5900 rpm, 400 hp @ 5200 rpm, 350 @ 4600 rpm.

Around 1 Hp per cid for most is about the best compromise for street friendly performance, for some 1.1 hp per cid, Above that your more into street strip territory.

I'd go with with Eddies and a high lift short duration hydraulic roller, kind of how new Hemi and LS make power all head flow with moderate cam.
Click to expand...
I think 273 nailed this. I myself would opt for ether a solid flat tappet or roller. But it is hard to get a small roller and out perform a good solid lifter cam.

At 370 cubic inches, you’ll need 1.35 HP per cubic inch to make 500 HP. We are getting a little stout here.

The only thing I can suggest s to save up for the best cylinder head you can purchase. A serious full porting of the Edelbrock heads will be in order. You’ll need to work on the RPM-AG a bit as well (IMO) with gasket/port matching it and going as deep as possible. The capability of the intake really comes through with this work and (again, IMO) with 370 cubic inches, it will be a good pay off.

How heavy is the Dodge business coupe?
 
Mattax said:
Doubt its the same as what we commonly call 98.
If that's the reasearch octane, might be similar to our 92 or 93. Just guessing.
In US & Canada, maybe Mexico, Octane is the average of Motor Octane and Research Octane. Also called the Anti-Knock Index (AKI)
Click to expand...

In the US you use another way of measure octane than we do. I believe you use two different systems, MON (Motor Octane Number) and PON (Pump Octane Number). In Europe, we use RON (Research Octane Number).

I think it is like this 98 Oktan RON is almost the same as 93 Octan PON and 95 RON is close to 91 PON. 95 RON is 87 MOM.
 
Lot's of good advice above...

I think you should determine what you want to use the car for... I assume the 36 Coupe isn't exactly on the light side.
As said you will never get 500-ish HP with that cam... and it also appears to me you want a decent driver and not a race car.

So either adjust your perspective of horsepower and keep it at the 425-450 HP level (which is definitely doable with your parts, except the camshaft),
or step up the game with even more camshaft, a decent converter and a steeper rear end.
 
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