Why?

-
straightlinespeed

straightlinespeed

Sometimes I pretend to be normal
Joined
Oct 21, 2012
Messages
10,630
Reaction score
4,399
Location
Uvita, Costa Rica
So, as I cruise this forum. I get to thinking, and usually confuse the hell out of myself. So today Im wondering and thinking. Why do you guys swap to the newer Hemi engines and not keep the LA or Magnum engines? What are the benefits? I just think of all the work that goes into swapping in a new computer controlled engine.

Now dont get me wrong after looking at some of the posts in this section of the forum, it gets me thinking of if my Durango ever gets totaled out. I may keep the running gear for future en devour. So please enlighten me and tell me why you choose this specific swap.
 
200+ additional HP?
 
the LA motor is a good motor, but its old tech. I was looking to build a EFI motor anyway, and when push came to shove, I was starting from scratch so the HEMI was a simple decision.

New hemi is 100lbs lighter than a LA motor,

The factory HP is 345-425 depending, add headers, and a tune and you are into decent #'s real easy. A camshaft and the motors run like scalded cat.

Hemi heads actually have really good flow numbers, the compression is decent, and the motors are known to go 200K pretty easy.

Parts are readily avail at the dealer, there is great aftermarker support, and the guys running these motors have great MPG's to go with the power.

JOE
 
Joe, Thanks for the explanation!

So curious, not getting carried away with insane parts but what does the average swap cost?
 
straightlinespeed said:
Are you guys hoping these up? My 360 is probably the same HP as the Hemi in my Durango.
Click to expand...

There is a car craft article about cam swaps in the HEMI that was amazing, just the TTI headers netted like 50 HP or something crazy, cam and the motors made a ton of power. Its worth a read. Some guys are stroking them and adding boost, some guys run a factory tune.

JOE
 
Depends,

I got my motor, brand new, for 1800, you can run a factory ECU for another 1200ish, manifolds/headers and exhaust cost anywhere from 250-700 depending. Fuel system is a big piece, you need a in tank pump, so that can get spendy, I thing I have 500ish in a new tank, pump and lines. I will run a 727, so you just need a flexplate for it 125 I think, motor mounts for the swap are 150 maybe...

It adds up fast, but for me I had nothing left from my last drive train, so I would have spent the same $ on LA stuff basically.
 
That is pretty reasonable! Ya maybe I will have to consider something like this someday. Right now I have a brand new rebuilt LA360 to have some fun with.

Thanks again Joe!
 
straightlinespeed said:
That is pretty reasonable! Ya maybe I will have to consider something like this someday. Right now I have a brand new rebuilt LA360 to have some fun with.

Thanks again Joe!
Click to expand...

No worries, Have fun with that 360! I cant wait til mine runs... either way I figure the outcome is the same, gas pedal=tire smoke...
 
YY1 said:
200+ additional HP?
Click to expand...

rofl. tell the guys running twin turbo 426 hemis that. 2000+ hp\

that being said... the new gen hemis are great for street cars.

for racing purposes (over on moparts.org you can find lots of info) they are very high maintenance...

the valve train needs constant inspection and adjusting. if you race them and don't take care of the top end, and something breaks, guess what? you have stuff dropping into the cylinders and then you will really have a problem. they are doable for racing but you want 2 things in a race engine: power and durability
so you can make one of them durable with proper valve train maintenance. it's expensive though.
 
What are the valve train issues you speak of? I've been spinning mine to over 7,000 rpm (stock valve train, PAC 1518, forged bottom end). I've had a couple discussions with Hemi builders about safe rpm. I'm definitely not pushing that limit. The drag pak guys push that limit at 8400, and do it with a single beehive.
 
Did anyone else here ASSume we were talking about max stroked twin turbo smallblocks?

318 LA- 150 NET HP

5.9 Mag- 245 NET HP

5.7 Hemi- 345 NET HP
 
YY1 said:
Did anyone else here ASSume we were talking about max stroked twin turbo smallblocks?

318 LA- 150 NET HP

5.9 Mag- 245 NET HP

5.7 Hemi- 345 NET HP
Click to expand...

now granted I understand those are stocks factory horsepowers. I was just curious as to why you would install a hemi, only assuming they were stock built with minor upgrades such as headers, cam etc... My rebuilt 360 is around the 350hp range. Which I'm saying is equivalent to the 5.7 in my Durango

Don't get me wrong I would consider doing it. I just wanted to know why you guys choose to go this route and why.
 
I pulled a w2 headed 408 to put in a forged 5.7. Similar output from the two motors with 60 less cubes.

I made the swap for a few reasons-
-I wanted a forged short block with shorter stroke I could road race and not worry about
-I wanted a manual, an overdrive, and A/C (obviously that works with either)
-I wanted a roller lifter cam
-I wanted to be different
-I wanted efi and to tune it myself

Problem with the swap:
- couldn't use factory power brake booster
- had to weld my own headers to use the factory PS box
- had to fab brackets for the AC compressor and buy an aftermarket AC compressor
-had to clearance the passenger inner fender

Personally, I'm glad I did the swap, for the 'different' aspect of the build. A lot of what I wanted to do would have fit better with an LA or R3 block, though. Not much room in these A bodies for the wide hemi.
 
You have 350 NET HP on a rebuilt 360?

Where did you get those numbers.

I'd LOVE to see that build. It would be around 420 gross.

I'm not saying I don't believe you, Just that you may be on the top end of what most people's budget will allow and may be into the diminishing returns area, not to mention the questionable streetablility area.

I have a 5.9 that I would love to get 420 gross out of, but I don't want a 12:1 monster that needs 100 octane and idles at 2500.

EDIT- been there, done that, though :)
 
Thanks Uhcoog for your input. As for the pass. side inner fender how much did you have to take out of it? Im assuming that this was because of the headers?

I do have to agree with the OD. I wish mine had that, I dont like turning 3k going down the road.

Are you using the drive by wire gas pedal? Or did you carb yours?
 
Nobody said they put a Hemi in so they could say they have a Hemi?
Come on, I know they are out there.
 
YY1, Im just going off of rough numbers the engine builder said I should be making. Im guessing that is engine HP not rear wheel. I have yet to get it into a dyno to get actual HP.

Yes granted Im taking there word for it, which probably shouldnt be taken LOL.
 
I can only say why I would do it. And if I ever did go through that swap it would keep the efi.

Main reason is performance,reliability,drivability and economy.

Look at the cars those motors come in. Awesome drivability because of the efi. They get what mid 20's when it comes to mpg and at well over 4000 pounds they can turn low 13's pretty easily with a coue little things like a cai and cat back exhause. Best of all worlds man.

Problem is it isn't a cheap swap. Then if you want to add od your looking at a lot more money.

Now a ls motor us where it's at. Probably do it for half the price including the od trans and you have a ton more aftermarket support.
 
abodyjoe said:
I can only say why I would do it. And if I ever did go through that swap it would keep the efi.

Main reason is performance,reliability,drivability and economy.

Look at the cars those motors come in. Awesome drivability because of the efi. They get what mid 20's when it comes to mpg and at well over 4000 pounds they can turn low 13's pretty easily with a coue little things like a cai and cat back exhause. Best of all worlds man.

Problem is it isn't a cheap swap. Then if you want to add od your looking at a lot more money.

Now a ls motor us where it's at. Probably do it for half the price including the od trans and you have a ton more aftermarket support.
Click to expand...

Joe,

You are right for sure, first about the benefits of EFI, and also about those LS motors. They are not only really nice, the aftermarket support, and knowledge avail you could swap one for literally half the cost of the hemi... I just may do one in my old TBI chevy truck when it dies.

JOE
 
abodyjoe said:
Now a ls motor us where it's at. Probably do it for half the price including the od trans and you have a ton more aftermarket support.
Click to expand...

I agree, to some extent. The cheap and plentiful LSx motors are the 4.8 & 5.3. Very nice motors that are quite capable as they sit (specifically when it comes to boost). There are similar $$ deals to be had on 5.7 hemi's as well, though they are just harder to find, and there is a limit you don't want to cross power-wise on a stock motor. The cheap 5.7 hemi does have a superior head to the GM counterpart.

As far as EFI goes - the LSx is cheaper for a factory computer swap no doubt. If you go with an aftermarket computer, it's a wash.

However if you build a forged iron block motor, they cost about the same. If you want an aluminum block, the hemi aluminum block is more expensive than the LSx aluminum block.

I honestly think it would have cost me the same or more to put an LS motor in my duster. However I have no doubt putting an LSx in a chevy is cheaper than putting a hemi in a mopar. No doubt they have cheaper swap parts.

That being said, I don't see any reason to put an LSx in a mopar. Save yourself some money and put the LSx in a chevy where you might actually be able to do the swap for 1/2 of a mopar hemi swap, or nut up and put a hemi in your mopar.

Disclaimer: I'm not someone who would boost a stock short block 4.8 or 5.3 (with opened up ring gaps and rod bolts). I would forged it from the get go. That is the advantage of the LSx - boosting a stock bottom end, and just swapping it when it blows. Yes? That's at least the argument that keeps coming up time and time again (read: hot rod magazine: Big Bang Theory)
 
YY1 said:
You have 350 NET HP on a rebuilt 360?

Where did you get those numbers.

I'd LOVE to see that build. It would be around 420 gross.

I'm not saying I don't believe you, Just that you may be on the top end of what most people's budget will allow and may be into the diminishing returns area, not to mention the questionable streetablility area.

I have a 5.9 that I would love to get 420 gross out of, but I don't want a 12:1 monster that needs 100 octane and idles at 2500.

EDIT- been there, done that, though :)
Click to expand...

if a 360 needs 12:1compression to make 420hp and you cant get it to idle under 2500rpm you might need to find a different enginebuilder and someone to tune it. i got more power than that in a stockstroke340 and it will idle at 800rpm all day long on pumpfuel. however its not cheap.

yes im looking into a gen3 swap,for a quick abody its the only way to go that realy makes any sence.
 
Just wondering,has anyone put a fuel injection set up on their late sixties 340?
If so, was the cost worth the benefits? and does it add significantly to the performance?
 
I honestly think it would have cost me the same or more to put an LS motor in my duster.
Click to expand...

not sure about a stock k-frame car. but in my dart a LS motor would be probably half the price.

can get an alumn LS with OD trans for around $3K. just have to get the proper mounts (and weld on brackets) from rms to be able to bolt the LS on to my alter-k. a $400 set of camaro headers will fit with the alter-k instead of a $1000 set of tti headers. computer set is about $1800 and i know a guy that will plug a tune into it.. up to this point yes its about 6-700 dollars cheaper for the LS. where the big money is saved is the OD trans i got with the motor. in a mopar you are looking at $3K on top of the engine swap to do a OD trans..


the after market for a LS motor is just an added bonus...
 
You must log in or register to reply here.
-

Back
Top