340 question

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zigs

zigs

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Looking at a 1972 340. I'm told its a solid engine. I will find out more as I go along but first
what are your thoughts on the 72 engine being from the gas crunch era. Did Mopar scrimp on the engine or is it as good as the fore runners, in other words if it proves out , is it a good block.
 
Any 340 is worth saving. Being 72 it will more than likely have a cast crank and the compression will be lower than the early years.
 
Sure it is. You can locate a steel crank and replace the pistons but at that point you might want to look at a rotating assem. Make it more gooder! 4" stroke .30 over and you have a 416. Like my 68 Barracuda.
 
Unless it's a late 72 it will have a steel crank. You can tell by looking at the damper. The other thing that was changed are lower compression Pistons and 1.88 intake valves. All that is easily remedied.
 
SGBARRACUDA said:
Sure it is. You can locate a steel crank and replace the pistons but at that point you might want to look at a rotating assem. Make it more gooder! 4" stroke .30 over and you have a 416. Like my 68 Barracuda.
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I like more gooder. There is nothing around me and most the stuff I see is high + shipping , even short blocks are$$$$$$$$$$$.
 
zigs said:
I like more gooder. There is nothing around me and most the stuff I see is high + shipping , even short blocks are$$$$$$$$$$$.
Click to expand...


What? There's all kinds of crap around here. You just gotta know where to look. I'm picking up my R block, gear drive and 3.79 crank this weekend. That's going to be the foundation for my W2 deal. Then I'm fully retired from porting cast iron anything. Plus I'm not sure what else is there I want. Maybe the rods but I doubt it. I know there is at least one set of W2 heads there. And a Fluidamper. Definitely getting that.
 
zigs said:
Looking at a 1972 340. I'm told its a solid engine. I will find out more as I go along but first
what are your thoughts on the 72 engine being from the gas crunch era. Did Mopar scrimp on the engine or is it as good as the fore runners, in other words if it proves out , is it a good block.
Click to expand...
Yes and no. While a cast crank is a down grade, there still plenty strong. The low compression pistons are as you say, easily changed out. Even so, a set of closed chambered heads will raise the ratio to a reasonable level. You'll need to know exactly where the piston sits, the head gasket dimensions, valve relief amount and head chamber cc amount for the calculators. Getting to a 9.0-1 should be easy enough. More is better. But lets see where you end up first. At 9.0-1, thats enough for most street cams to perform vcery well.

Who was the guy with an OE 360 short block & W2 heads? Running low 12's IIRC? It is a great and cheap combo. He invested in heads, cam and valve train. BAMM baby!
 
yellow rose said:
What? There's all kinds of crap around here. You just gotta know where to look. I'm picking up my R block, gear drive and 3.79 crank this weekend. That's going to be the foundation for my W2 deal. Then I'm fully retired from porting cast iron anything. Plus I'm not sure what else is there I want. Maybe the rods but I doubt it. I know there is at least one set of W2 heads there. And a Fluidamper. Definitely getting that.
Click to expand...
Where are you located.
 
I would not sweat a cast crank
and would change to cast stroker for anything short of a trailered build
small valve head is good as you can go to chevy 1.94 or 2.02 and get a new valve seat or magnum valves, anything with better shapes and lighter- lots of interchanges including +100 long for more choices in springs if you are going to run a high lift cam
(which does not work with stock heads BTW- they get turbulent)
problem is if you need ex seats and guides and valves the extra flow benefits of new heads becomes more than enticing
so let the heads be the decision maker unless you have the funds to do both the short block and the heads
heads make more difference than a small increase in compression
if you do do pistons with stock heads get the KB's that are designed for that application
skip roller rockers and other money wasters
 
IMO, roller rockers just insure the ratio is right and your getting all of your lift. There stronger than stock.
OE rockers are fine for low spring pressure cams.
 
72 block probably as good as any block but i did hear the '70 blocks had the highest nickel content.
you can build it any way you want but street and race are very different builds.
 
zigs said:
Looking at a 1972 340. I'm told its a solid engine. I will find out more as I go along but first
what are your thoughts on the 72 engine being from the gas crunch era. Did Mopar scrimp on the engine or is it as good as the fore runners, in other words if it proves out , is it a good block.
Click to expand...


It's as good as any other "good used engine". Put it on the stand, pull the intake and the pan, give it a good look, if nothing else looks looks out of place, put the pan and intake back on, drop it into a car and drive it, OR, you can throw money at it and build a stroker motor.
Have fun.
 
To answer the original question it is the same block. You just need to examine/measure the individual block. Measure if it is overbored and by how much. If rusty inside, be careful, but if assembled, hopefully that's not any issue.

The late '72 and '73 340 cast cranks have special imbalances in both ends, put into the damper and in the torque converter area. (Called 'external balance'.) So not all aftermarket dampers are available with that feature and you have to make sure the extra torque converter weight it there, or change to an imbalanced flexplate like from B&M. So just be aware of that; I just bring it up as any original damper is suspect with the rubber ring probably being rotted out by now so you may be needing a new damper for sure.

Cast cranks are pretty good; we're running somewhere around 375 HP with a 273 cast crank in a 340 (street use only). You could put a 318 crank in there, cast or forged, and using KB243 pistons, would have a good street compression number with the stock heads, and the rotating assembly would be within factory range for balance with the lighter pistons and no balance work, and NOT need the external imbalanced damper and TC/flexplate.
 
ir3333 said:
72 block probably as good as any block but i did hear the '70 blocks had the highest nickel content.
you can build it any way you want but street and race are very different builds.
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I think Mopar blocks were all high nickel blocks especially compared to Chevy and Ford.
 
ir3333 said:
72 block probably as good as any block but i did hear the '70 blocks had the highest nickel content.
you can build it any way you want but street and race are very different builds.
Click to expand...
That info on the 70 blocks was probably put out by the 70 block resellers guild to pump up prices! Kinda like the "thinwall 440" rumors that circulated for years...:rolleyes:
 
rumblefish360 said:
IMO, roller rockers just insure the ratio is right and your getting all of your lift. There stronger than stock.
OE rockers are fine for low spring pressure cams.
Click to expand...
ir3333 said:
72 block probably as good as any block but i did hear the '70 blocks had the highest nickel content.
you can build it any way you want but street and race are very different builds.
Click to expand...
I don't want a combo build . I should have made myself more clear. A good street engine . A 340 with some pop but I can run it on the freeway. I have a 68 dart 470 stroker . Not freeway friendly.
 
Well the search goes on. We were too fare apart and then shipping. I'll wait and keep my eyes open , but thank you to all for your input its all good info. The block was a good block , clean inside none molested
stock.
 
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