340 vs 360

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Moparguy45

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Just wondering where i should go next. My slant 6 finally died and was wondering which would be best to build. I have been buying some parts when I could towards a v8 swap. I have 4.04 bore 11:1 comp je pistons on 496 rods with polished tops, a mopar 280/280 adv. duration .474/.474 lift cam, a Edelbrock Torker 2 340 single plane intake, and a set of j heads with the 2.02 intake with stock ports. the trans will be a 727 with trans go shift kit and upgraded clutchs and bands. the rear end is a 8.25 3.21 sg but soon will be replaced with a 9.25 3.55 sg. any direction you guys can give me would be greatly appreciated.
 
This question comes up from time to time...

You can build a great engine from a 360 or a 340.......

From what i have learned on this forum, this is what it really comes down to......

Do you want to be able to tell people you are running a 340?

If you don't care, get a 360. A 360 block costs less and is easy to find.
 
what would be some of the pros and cons of them. Like isnt the 340 more high reving than the 360?
 
The 340 has the "Cool" factor and came with better parts in stock form.

The 360 is 20 cubes bigger.

Rev limit will mostly be set by cam/valve train.

On a custom build...... I feel (and this is just my opinion) that it really again comes down to ... Do you want to be able to tell people you have a 360 or a 340.

Seriously.... Both are great foundations for builds. If it wasn't for the fact that my car has a 340, I would build a 360.
 
Everything being equal..the 360 will have more punch. With it's longer stroke it will deliver more torque and torque is what it is all about on the street. Cheaper to build too, and I am into cheap !! 400 horses is SO easy with the 360..you would have to try to keep it inder that level. Good luck on your build up..this IS the fun part. Keep the rest of us informed.

Terry
 
OMG! This again, LOL and yikes!

Do a search on it and see what (LONG) threads come up.
They should.

It's a good question, but if this carries on....I'm gonna pull my hair out. Ha ha ha ha.

360!

Cheaper and makes peak power a few hundred RPM's sooner and more torque all over. IMO, it's a no brainer..................
 
340s are more expensive than 360's....not because they are better, but more for the reason that they are more sought after by the numbers matching crowd.

360 has 20 extra cubic inches (due to the longer stroke)

more 360's laying around

.....id go 360
 
360 for sure. I've run them in all of my a bodies and I love em'! I dig 340s and I'd run one if I found one cheap, but it was really the heads on the stock 340 that made them special.
 
360.....hands down.

Leave the 340's for numbers matching resto freaks.

340's are overrated for small block power.

Without scratching/inspecting your block surface under the drivers side head or crawling up underneath your car, no one could tell you your engine wasn't a 340, if it was a 318 with bolt ons.

This topic is really brought up way too frequently.
 
dragnknights said:
but it was really the heads on the stock 340 that made them special.
Click to expand...

oh yea, i forgot to mention that, SOME 340s, but not all, had 2.02 intake valves compared to the 1.88s. They were basically the same heads between the 340 and 360 just those few years of 340's had the bigger valves. You can get the 360 heads machined for 2.02 intake valves relatively cheap. It cost me $250.00 extra to get the 2.02's in my 360 heads I used on my 360.
 
Prine said:
360.....hands down.

Leave the 340's for numbers matching resto freaks.

340's are overrated for small block power.

Without scratching/inspecting your block surface under the drivers side head or crawling up underneath your car, no one could tell you your engine wasn't a 340, if it was a 318 with bolt ons.

This topic is really brought up way too frequently.
Click to expand...
340,s overrated??My opinion is they were underrated.Compare a 340 small block in 1970 to any other small block.And you say they,re overrated?My 2 cents.360,s are a good motor,but 340,s can be stroked bigger than a 360.
 
1968FormulaS340 said:
The 340 has the "Cool" factor and came with better parts in stock form.

On a custom build...... I feel (and this is just my opinion) that it really again comes down to ... Do you want to be able to tell people you have a 360 or a 340.

.
Click to expand...

Just build a 360 and tell anyone who wants to know that it's 340....if it matters to you at all (and it really shouldn't matter one iota, if you dont have an original numbers matching 340 car - which you don't).
 
What are the 4.04 pistons for? That diameter would be a stock bore 340 piston or a 0.040" overbore 360 piston but there is also the piston height difference. If they are 340 pistons and you hang them on a 360 crank they will stick out of the bore more than you can make up with a head gasket. If they are 360 pistons and hang them on a 340 crank they will be way down in the hole resulting in very low compression.

As far as which way to go! What ever motor you can get the cheapest is the way to go. Most likely the 360 will be cheaper but there is a deal from time to time on 340's. I just picked up a very low mileage rebuilt 340 long block for zip. Will likely use it for a stroker motor.

Another option is to pick up a late model 360 magnum from a pickup. They have better heads than the J heads you have and are a roller cam motor.
 
dgc333 said:
What are the 4.04 pistons for? That diameter would be a stock bore 340 piston or a 0.040" overbore 360 piston but there is also the piston height difference. If they are 340 pistons and you hang them on a 360 crank they will stick out of the bore more than you can make up with a head gasket. If they are 360 pistons and hang them on a 340 crank they will be way down in the hole resulting in very low compression.

As far as which way to go! What ever motor you can get the cheapest is the way to go. Most likely the 360 will be cheaper but there is a deal from time to time on 340's. I just picked up a very low mileage rebuilt 340 long block for zip. Will likely use it for a stroker motor.

Another option is to pick up a late model 360 magnum from a pickup. They have better heads than the J heads you have and are a roller cam motor.
Click to expand...

Best answer I have seen yet!

Jack
 
dgc333 said:
What are the 4.04 pistons for? That diameter would be a stock bore 340 piston or a 0.040" overbore 360 piston but there is also the piston height difference. If they are 340 pistons and you hang them on a 360 crank they will stick out of the bore more than you can make up with a head gasket. If they are 360 pistons and hang them on a 340 crank they will be way down in the hole resulting in very low compression.

As far as which way to go! What ever motor you can get the cheapest is the way to go. Most likely the 360 will be cheaper but there is a deal from time to time on 340's. I just picked up a very low mileage rebuilt 340 long block for zip. Will likely use it for a stroker motor.

Another option is to pick up a late model 360 magnum from a pickup. They have better heads than the J heads you have and are a roller cam motor.
Click to expand...

how do you tell if they are 360 or 340 pistons?
 
I have had few 340's in my car . They really run well, 3300 lb car is going 12.06 @ 112 mph with a cast iron (stock 2.02 valve) head, 30 over High compression 340 with a hydraulic camshaft. I would not consider that engine to be OVERRATED!!!

If you can get a 340 at a good price it should have a lot of things you will like to do to a 360: FORGED STEEL CRANKSHAFT, fully bushed floating piston pins, forged aluminum pistons, double roller timing chain, windage tray, 2.02 intake valves, etc. All of this was stock in 340's from 1968 to 1971, which is why they are great little race engines.

If you are going to replace the entire rotating assembly, use an early 360 block or a 340 with a bad crank.

If you want to rebuild a engine without replacing all of the internals, a forged steel crank 340 is a stronger engine than a cast crank 360. Either can be built to be a good street strip package.

Before you decide, price out what it will cost you in parts and machine work.

340's do not really rev any higher or quicker than 360's, both of them are torque engines that really get it all done by 6000 rpm.

Bob
 
pettybludart said:
My 2 cents. 360,s are a good motor,but 340,s can be stroked bigger than a 360.
Click to expand...

He wasn't askin about strokin a engine, though you are correct due to the larger bore of the 340, I just can't see such a big deal in the few cubes difference in the engines after it gets stroked.
After all, once you go there with the small block, no one is looking for mileage, LOL!
 
Moparguy45 said:
how do you tell if they are 360 or 340 pistons?
Click to expand...

A the distance from the center of the pin to the top of the piston (piston height) on a 340 will be approximately 1.84". The distance on a 360 will be approximately 1.67". This measurement is to the flat surface on the edges of a dished piston and does not include the dome on a domed piston.
 
a 340 with 3.31 crank and 6.123 rod with 1.84 ch piston has a total length of 9.618....with the LA engine deck height being around 9.60...piston has an postive deck height of .018...which is good..

360 with 340 piston of 1.84 plus 6.123 and 3.58 stroke has a total length of 9.753...and with the LA engine deck height of 9.60...pistons has a postive deck height of .153.......you will need some pretty thick head gaskets to get that to work.....

usually need to use the low compression 72-73 pistons...with 1.75 ch....and that still puts the piston out about .060...which is close to do able...

but why?....340 pistons weight alot...360 pistons lighter and cheaper....
 
ok so what about the 340 "496" rods? will they work in a 360 because the pistons i have i think are 340 pistons with those rods and have got a 360 block that i could get from a friend for cheap and i like that the pin is not pressed into the pistons so i would like to keep the rods atleast if they are 340 pistons.
 
well i just measured and the pistons are for a 340. so it looks like i need to start looking for a 340 block.
 
much as i hate to say it...there are alot of 340 blocks on the "bag"
 
Yes,....I said overrated!

Overrated, by the fact that MOST people think you have to have a 340 based small block to make the most power/torque.

This has been hashed out so much, its not worth it to go into detail about the pros/cons.

I prefer 318's and 360's because of the availability. Finding a 340 anywhere close to me is nearly impossible without some serious cash outlay....and there is really no measureable sacrifice in using a 360 over the 340....when faced with this dilemma its almost always more beneficial to start with more cubic inches.

So, say what you want about my opinions...I measure most of your comments with a grain of salt...I have another one that will hurt your feelings....300-400whp out of any engine over 5.0L is pretty pathetic with todays technology and parts availability.....and I know what you'll say or think next...."oh yeah, what do you have that makes more, that isn't pathetic".....and to that I say...nothing at the moment.....but my next small block will be 318 based and make more Wheel Horsepower than a Naturally Aspirated 426 Hemi....no hood scoop needed.
 
I thinkI saw a 340 for sale on this site for 500 bucks, that's not too bad.
FWIW
 
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