340 Vs 360

[Dartswinger70]

Some like the small engine challenge, others are simply working with what they got as well as a possible limited spending amount.
The adage of bigger is better is what you present but I wonder why if such is the case, why didn’t you recommend a stroker at maximum CID?

A stroker? lets do it... actually right as we speak I have a 340 stock bore going together, no race stuff just in street form close to how it may have been in 1970. I am contemplating a single plane intake with a 750 Holley. Just to floor it and see what happens, then play around from there with dual planes and edelbrocks I also have a 600 Holley somewhere, its nice when you have the "right junk" laying around...

 

[rumblefish360]

Nice! I have to get on my 340/904 equipped Duster soon. It’s been sitting too long. Wiring/ignition issues plus other cars and garbage.

 

[rumblefish360]

When it was still up north….

 

[273]

360 LA had those dished pistons get rid of them, up compression and...voila! however, this is what I don't like about the 70s 318 and 360 (low compression) but at least the 360 has the heads.

Dark ages for engines 70s-80s

318 you re always going to throw 360 heads on one so why not just get a 360 start with the low compression and the heads, throw some pistons in it and be done...

Makes sense but everyone has different wants, but really compared to either end of our v8 spectrum bore wise 273-440\400 the 318,360,340 sit close together in the middle but obviously 318 3rd best out of the 3.

I never get the guys spending hours porting 318 heads thinking something will come of it.

I could see for a 273 since valve size is limited

 

[PROSTOCKTOM]

@PROSTOCKTOM

What length rods are available for the 340?
Does Molnar offer cranks greater than 4.00 for the small block?

If you're using a stock Mopar rod journal size crankshaft the 6.123" length rod is all that's offered.

If you're using a crankshaft that's made to use a 2.100" Chevy rod journal you can get them in the following lengths.

6.125" In Stock
6.250" Back Ordered
6.300" In Stock
6.400" In Stock
6.500" In Stock

Price is the same for any length rod listed.


Molnar does not offer any crankshafts with more than 4.00" stroke for a SBM.

Tom

 

[Mean416]

I think the differences are very minute and secondary to the important stuff.

If you are stroking it the 340 has a little bit of advantage just because of bigger bore size gives you more cubes. Also probably better flow characteristics.

Stock stroke, but otherwise properly built engines, the 360 will make a better package in most situations. Longer stroke, more torque, more area under the power curve. Emphasis on "most cases".

 

[Brian Hafliger]

If you're using a stock Mopar rod journal size crankshaft the 6.123" length rod is all that's offered.

If you're using a crankshaft that's made to use a 2.100" Chevy rod journal you can get them in the following lengths.

6.125" In Stock
6.250" Back Ordered
6.300" In Stock
6.400" In Stock
6.500" In Stock

Price is the same for any length rod listed.


Molnar does not offer any crankshafts with more than 4.00" stroke for a SBM.

Tom

 

[33IMP]

Ain't Germaine to the discussion (the damn Germans got nothing to do with it! Buford T Justice) but I love the Bahama yellow, Rumble. Hope you keep it. Don't see that color much.

 

[273]

RPM = Displacement over Time = CFM, CFM = Potential HP.

Since RPM is somewhat fixed for what most guys will accept in a street car engines say idle to 5500 rpm. Since we won't just keep spinning higher that leaves more torque though efficiency and or CID the only other NA way to increase power. But for those willing to spin it can add displacement through RPM.

 

[fishmens67]

2" bore x 4" stroke or 4" bore x 2" stroke. lol

 

[rumblefish360]

RPM = Displacement over Time = CFM, CFM = Potential HP.

Displacement is fixed & not changed through rpm.
CFM is not potential because of limitations of what’s consuming it.

But for those willing to spin it can add displacement through RPM.

You can’t increase the size of an engine through rpm.

I see where you’re going with this but this is ill spoken and needs to be combined with an explanation of to what’s going on. The statements by themselves are false & can be misleading.

 

[273]

Displacement is fixed & not changed through rpm.

Static displacement is, but were dealing with a running engines so I'm talking Dynamic displacement, what an engine displaces every minute.

CFM is not potential because of limitations of what’s consuming it.

Fuel and it's volume of air has a potential energy an engine only gonna use a % of that potential energy to make hp.

You can’t increase the size of an engine through rpm.

What is displacement in our case, but volume/weight of air, the engine measure displacement x ve% moves that much air per revolution, more revolution more air being displaced eg.. A 360 moves 0.104 cfm (cfm = volume of air per minute or a displacement of air per minute) per revolution more revolutions more displacement. A 360 @ 5000 rpm = 521 cfm a 360 @ 6000 rpm = 625 cfm at 100% VE. A 340 @ 5316 rpm = 521 cfm a 340 @ 6378 rpm = 625 cfm same dynamic displacement and yes sure you also spin the 360 more to.

I see where you’re going with this but this is ill spoken and needs to be combined with an explanation of to what’s going on. The statements by themselves are false & can be misleading.

I guess, makes perfect sense to me

 

[fishmens67]

My 2" bore has a 1/2" int valve 3/8" exh and the 4'" by a 1'' int valve 5/8 exh. lol

 

[Jadaharabi]

Hey Abodyjoe..not meaning to divert from thread topic but what size pistons is that girl holding in your avatar...can we get a closeup maybe so we can see the numbers,overbore etc...jus wonderin

That is just wrong to be asking a guy about his wife.

 

[rumblefish360]

Static displacement is, but were dealing with a running engines so I'm talking Dynamic displacement, what an engine displaces every minute.

Fuel and it's volume of air has a potential energy an engine only gonna use a % of that potential energy to make hp.

What is displacement in our case, but volume/weight of air, the engine measure displacement x ve% moves that much air per revolution, more revolution more air being displaced eg.. A 360 moves 0.104 cfm (cfm = volume of air per minute or a displacement of air per minute) per revolution more revolutions more displacement. A 360 @ 5000 rpm = 521 cfm a 360 @ 6000 rpm = 625 cfm at 100% VE. A 340 @ 5316 rpm = 521 cfm a 340 @ 6378 rpm = 625 cfm same dynamic displacement and yes sure you also spin the 360 more to.


I guess, makes perfect sense to me

Soooooooo much better. Now if everyone reading the prior post understood the basic idea of the second post it would make so much more sense than it does over the first post.

Now as long as the engine(s) are as efficient (VE) as hoped for…..

 

[Dartswinger70]

Soooooooo much better. Now if everyone reading the prior post understood the basic idea of the second post it would make so much more sense than it does over the first post.

Now as long as the engine(s) are as efficient (VE) as hoped for…..

^^^ You have more patience than I do LOL! But back on topic, I would take a LA 360 if I could get rid of those dished pistons and stuff zero deck or positive deck a la 340 pistons in it ...true story I once scrapped a 360 short block because at the time they were about as plentiful as 318s (boat anchors) I wish I'd have kept it but I had 340s and needed room in the garage...does anyone else remember when Mopar guys were running at minimum 383 big blocks and small blocks were undesirable unless they were 340s? I had guys giving me small blocks because hey pulled them and replaced them with big blocks and wanted the "scrap metal" out of their garage. This was pre magnum days. Ive had 318s given to me free attached to 904 transmissions and 360s 50 bucks LOL!

 

[rumblefish360]

@Dartswinger70 I try and sometimes people get pissed off at me. It is what it is….
You still can not increase C.I.D. through RPM!
You CAN cycle through it more per second. Making use of all 8 cylinders faster in this way is how he is saying “Increased CID” which is IMO, not the way to say it.

This is where people like the 340 better. The shorter stroke can rotate or/or cycle through all of its cylinders quicker. If you reduce the engine size via stroke, the engine will keep doing what the example is above quicker and so on and so on….

An excellent example of this is the older super stock racers running tiny displays hind screaming 5K+ off the line and buzzing 9K on the big end. Wait…. They do that now!
LMAO!!!!

Back in my youth, the 318 paper weight was for people moving and the 360 “DOG” motor was for big car people moving.
383’s (A big block that thinks it’s a small block) was the poor man’s big block and somewhat disrespected because the 440 rules the day.

 

[Dartswinger70]

@Dartswinger70 I try and sometimes people get pissed off at me. It is what it is….
You still can not increase C.I.D. through RPM!
You CAN cycle through it more per second. Making use of all 8 cylinders faster in this way is how he is saying “Increased CID” which is IMO, not the way to say it.

This is where people like the 340 better. The shorter stroke can rotate or/or cycle through all of its cylinders quicker. If you reduce the engine size via stroke, the engine will keep doing what the example is above quicker and so on and so on….

An excellent example of this is the older super stock racers running tiny displays hind screaming 5K+ off the line and buzzing 9K on the big end. Wait…. They do that now!
LMAO!!!!

Back in my youth, the 318 paper weight was for people moving and the 360 “DOG” motor was for big car people moving.
383’s (A big block that thinks it’s a small block) was the poor man’s big block and somewhat disrespected because the 440 rules the day.

yeah I cant get into the arguments with the book readers here IMO nothing has changed with 318s the LA ones, no one suddenly discovered something that makes the facts about these from the mid 80s suddenly untrue. Magnums I have no experience with but I would think they are the way to go in true low buck build scenarios. man its funny to think that 35 years ago 383 was the way to go like you said. I always played around with small blocks because like said they were free or just about free, but a first car of mine was a 318 B body then I found a 340 A body, and got rid of the "bigger car" LOL! But at the time I remember saying my B body "needed a 383..." this was 1988 or 1990 a guy I knew was into the big blocks would sell me stuff cheap even for back then, I bought a 360 cast intake with a carb adapter and 600 Holley for 40 or 60 bucks LOL! threw it on a 318 ...it was just too easy he'd call me a couple times a year "hey you want a 360...?" even when I bought my 70 Swinger 340 with all the spare parts in 1993, it was a steal...I wont say what I paid LOL!

 

[ir3333]

i don't remember 383's getting any respect back in the 60's but they may have been desirable in your area?

 

[Dartswinger70]

i don't remember 383's getting any respect back in the 60's but they may have been desirable in your area?

i don't remember 383's getting any respect back in the 60's but they may have been desirable in your area?

Possibly, yes or it could be the time I am talking mid 80s. i also remember Mopars in general didnt get any love. there were a few nice ones, but mostly they were primered running works in progress... while other guys had cars with paint LOL! Mopar was the low buck car when I was in High school. the auto shop vo tech guy had a Mopar LOL!

 

[ir3333]

If you build them to an equal standard the 340 will always outperform the 360.

 

[273]

@Dartswinger70 I try and sometimes people get pissed off at me. It is what it is….
You still can not increase C.I.D. through RPM!

Never said you can increase CID through rpm, just what an engine actually displaces the displacement/volume of air per minute, CFM which is cid x rpm / 3456 = ve% which Cid is part of that process. I see CFM as a measure of displacement.

This is where people like the 340 better. The shorter stroke can rotate or/or cycle through all of its cylinders quicker. If you reduce the engine size via stroke, the engine will keep doing what the example is above quicker and so on and so on….

Agreed, a 340 basically always be made to be spun slightly higher to displace the same cfm as a 360 and a 318 can't cause a 318 & 340 always can be made to spin the same rpm. But for the average 300-450 hp build there all capable.

Back in my youth, the 318 paper weight was for people moving and the 360 “DOG” motor was for big car people moving.
383’s (A big block that thinks it’s a small block) was the poor man’s big block and somewhat disrespected because the 440 rules the day.

I know people who still feel that way

 

[Mean416]

If you build them to an equal standard the 340 will always outperform the 360.

Can you qualify this statement? Given a good equivalent standard of build, i.e. same cam heads, intake, compression, quench, similar reciprocating assembly etc, how is the 340 gonna out gun the 360?

 

[273]

I'd give 340 slight advantages cause or bore size, bore stroke and rod ratios but in an average build your not gonna see a huge power difference if at all. There no reason both from stall speed to shift points can't have very similar power curves. Streetability the 360 gets the slight advantage and need less gear. So really it's down to personal preferences.

 

[Dartswinger70]

Like said Id take a 360 LA minus those dished pistons and I think it would run good...put a hi compression piston in it.