340+ for the STREET

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hemisedan

hemisedan

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Trying to get my head together on a good high performance LA motor for an A body. Yes, I will use this for a daily driver, even in snow. What I'm asking, and I've been out of the game for many years is:

Thoughts on a stroker 340?
Gas mileage (yes I know that we aren't suppose to be concerned about gas, but I am)
(plus I still want to have power) That's called having your cake and eating it too

What I'm looking at are 67-69 Valiant 2-door sedan, or 68-69 Dart GTS

Just in the planning stage now, trying to get in my head what I want to do, power wise as well as in the transmission department. I prefer manual transmission, but most of what I have been finding are torque flights. They're good, this I know, but I like to crash gears.
 
If you want mileage, build a stock stroke 340 with a spread bore carburetor like a Thermoquad.
 
Sounds pretty good, I had considered FiTech, or FAST EFI too. More expensive, but very nice to have.
 
I'm convinced an OD trans is the best thing you can do for mileage. With all due respect, a 416 is going in the opposite direction And dont forget the extra $ for higher octane. I have a small block 68 cuda that gets 13-14 mpg w/ 3.23 gears.
My /6 64 Val got 23.8 driving to Carlisle, also with 3.23 and no OD.
 
I would not recommend the FAST EFI.

I have installed the FiTEch with good luck, but would lean towards the Holley Sniper just for the customer support aspect. The big win of the Fitech is the fuel command center. It is a simple solution for a simple problem that trips up a lot of people.

Last, do you have the 340? The more I read these posts, I recommend the modern Magnum family over paying $3-4000 for an ok 340 that will still need something. I think the common 360 380hp crate engine is about $5000.
 
I haven't thought much about the Magnum family, but with the roller cam, or going the 3rd Generation hemi could be an option too. However getting into the engine bay is not exactly easy. Thankfully, mother mopar does offer a wiring setup for the late 5.7.
 
Ok, 3 questions we always need to know and have to ask: how much money are you looking to spend? What mpg are you hoping for? How much performance are you needing to be satisfied (E.T. expected is much better than sayin' "400 horse")? And NO, saying "as fast as I can for as little money as I can spend with the best mpg possible" isn't the answer. Give us hard core numbers. Numbers set goals.
 
Gearing and cam will be the major deciding factors for your mileage.
 
Buy a cheap 4 banner Subaru for winter and mileage, build the 340 for summer and who gives a crap mileage and fun.
 
A 416 can get decent fuel economy. It's all in the build, tune up and overall gearing. A 416 can pull a 3.23 gear and taller tire without issue.
 
318willrun said:
Ok, 3 questions we always need to know and have to ask: how much money are you looking to spend?
Upwards to $10k.
What mpg are you hoping for?
15 mpg in town, around 20 mpg on the highway.
How much performance are you needing to be satisfied (E.T. expected is much better than sayin' "400 horse")?
In the 400 range, or more, power, I"d just say sufficient, to put a number for ET, in the low 13's I guess.

And NO, saying "as fast as I can for as little money as I can spend with the best mpg possible" isn't the answer. Give us hard core numbers. Numbers set goals.
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Those are as close as I can come to numbers. I've seen crate 402 or 408 motors with 420 hp, which would probably work. But, I still don't like cast cranks and that is what they usually use with the lower power motors.
 
dano said:
Buy a cheap 4 banner Subaru for winter and mileage, build the 340 for summer and who gives a crap mileage and fun.
Click to expand...
Not interested in a Winter car. These cars were meant to be driven, not just stored in a garage. Just my opinion, of course.
 
crackedback said:
A 416 can get decent fuel economy. It's all in the build, tune up and overall gearing. A 416 can pull a 3.23 gear and taller tire without issue.
Click to expand...

This is pretty much my thoughts and I just asked to see if there are any other odd ball type guys out there that have done this, like I am. But, I've been called worse too.
 
hemisedan said:
Not interested in a Winter car. These cars were meant to be driven, not just stored in a garage. Just my opinion, of course.
Click to expand...

I guess its all perspective, after 20+ years and over $30k into my car I don't want some yokel tee boning my GTS.

What are we all considering "good fuel economy"?
 
Google Hot Rod Dave Super Duper mileage.He did an extensive sm blk. mopar build documenting results for each change.I think he ended up at 30 plus mpg!
No..an overdrive is not always the answer.I have a friend that installed an overdrive and his mileage went down.I think it was mentioned but your cam and gears play a big part in your mileage.Hi lift,short duration usually is best.Your cruise rpm must be at the rpm your max or most efficient lo speed torque is produced.
The easy way is to follow Rusty's post and use a modern grind stock style cam.
 
hemisedan said:
Those are as close as I can come to numbers. I've seen crate 402 or 408 motors with 420 hp, which would probably work. But, I still don't like cast cranks and that is what they usually use with the lower power motors.
Click to expand...
Ok, this is why we ask. To go low 13's in a A-body doesn't take near 400 ponies, even with highway gears. The number 1 horsepower number thrown out there, be it a chivy, ferd or mopar guy, it's always 400 hp. It is very easy to get one horsepower per cubic inch in a mild built street motor. I think 340 horsepower would be more than sufficient to achieve low 13's, keeping highway gears and spread bore for the mpg, and be very reliable.
  • Start with a good exhaust (Doug headers, backed by a good system)
  • Followed by good heads-factory 340 heads will fill the bill if you do the following: hardened seats, good valve job, mildly ported. HEADS are KEY.
  • You could find a better cam, but the factory one works well with the two mods listed above.
  • IF automatic, get a good converter.
Your well on your way (not sure much more is needed).... and I'll let others chime in. Options are plentiful, such as overdrive tranny, FI, and a big list that will follow I'm sure.
 
replicaracer43 said:
You couldn't be more wrong sir...
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I thought the magnum was better as well until i had two long time custom cam grinders tell me that the LA is a better choice and despite all the hoopla...the the LA heads are better as well.Let the argument begin!
 
ir3333 said:
I thought the magnum was better as well until i had two long time custom cam grinders tell me that the LA is a better choice and despite all the hoopla...the the LA heads are better as well.Let the argument begin!
Click to expand...
There is no argument
 
toolmanmike said:
The stock Magnums don't put out any more ponies or torque than LA engines do.
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Allpar must be wrong or the horsepower was rated different between the 68 318 and the Magnum 5.2.
318 spec.PNG
318mag.PNG
 
I don't need a chart, horsepower was rated different in 1968 than it was in like 72 up....do some research yourself.
 
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