liftin'em on nittos

iTrader: (2)

i am having a 408" nitrous motor built for my new setup. but was just sitting around wondering how much a similarly setup 348" would make. the motor is solid roller, high rpm, ~400 worth of spray. i would assume the 408" will make more power due to larger CI, and it wont have to be pushed as hard to make more power than the 348" motor. i could be wrong. anyone have experience with both. if i run the 408 for a while or hurt it and i have feedback and info from those with experience i might go with a 348 for a backup motor. thanks for any info guys.

JZ'sTA

iTrader: (23)

I would do a 370 for a nice solid back up motor.
If you do have a problem the 370 can go in without changing a thing.
the 370 costs almost exactly the same as a 347 anyway so you would be much better of doing the 370 then the 347 IMO.
As far as power between the 2. Spraying a 400 shot is no easy task on any LS style motor. I believe with the extra cubes the 408 will handle the nitrous better and produce better gains on the juice when spraying that much.
If you were running a 200 or maybe even a 250 I would thing the gains would be similar but with the 400 shot extra cubes should be your friend.
The 370 is defentially your answer for a back up motor. The only other combo I would consider would be a 380 using a stock off set crank and the 6.0 block bored 4.030.
Right in the 379 cubic inch area. The offset crank will add a hair of compression to get the backup motor very similar to the 408.

guinness2

Do you have some specs and sources on doing the 370??

JZ'sTA

iTrader: (23)

Sure it is a very common build.
4.030 bore and stock 3.622 stroke.
It is the same exact build as the 408 but uses a stock crank instead of the 4" crank.

guinness2

Are people doing alot of offset ground cranks on stock ls1 bores??

JZ'sTA

iTrader: (23)

No most either go stock or aftermarket.
A offset ground crank costs a couple hundred bucks at the machine shop and therefore most just do a larger aftermarket crank.
It isn't that popular in comparision but works great for those trying to get some extra cubes cheep.
you can get 385 cubic inches with a offset crank and a 4.060 bore.
I would probally just stick with the 370 as it is still a damn good setup.

2000_LS1

Good thread because I am debating on something similar. I am debating on building the 347 for a turbo then playing catch-up with the 408 so i won't have any down time with the car. I cracked 2 pistons (#7 & #8) while stock with a 150 shot n2o trying to beat a car like a dumb-*** but he did the same thing on the next guy he raced, lmao, and went to the 408 for n2o purposes. I am running a TNT 200 for now, have a NX 300 DP and progressive controller but I am not sure I want to use it. I am leaning heavily towards slapping some -28cc pistons in, 76cc AFR 225cc Heads, a thick gasket, and a 116lsa cam in the 347 to see what it will do. Also thought about slapping a 75-125 shot on it to cool the intake air down a little. Who knows??? I have the extra AFR 225's, will probably send them to TEA to get the intake side ported to 227cc, and maybe a 230~/.580~/116 cam. I am still doing research but it will probably happen before next year's racing season. Wish me luck!!!

2000_LS1

Also, JZ, can you tell me more abut this 385/379? What would an offset crank do to a 347? 362 or so? You said 379 with a 6.0 block. Can you post a link or something to get more info...I haven't heard or read of anyone doing this so it may be right up my alley. How much Compression jump? Recommended for FI? Sorry for the q's but you got my attention.

JZ'sTA

iTrader: (23)

I will look at this post first and do my best to help out.
I dont mind helping with the info I know and have but I am not the smartest guy on here so if other members would like to chime in feel free.

I will start here.

[QUOTE=2000_LS1] I am leaning heavily towards slapping some -28cc pistons in, 76cc AFR 225cc Heads, a thick gasket, and a 116lsa cam in the 347 to see what it will do.QUOTE]

Lets ditch the thick head gaskets, as the thinner gaskets are better in almost every combo a LS1 can think of.
Even with a smaller gasket say .040 with the combo listed about your gonna be at 7.26:1 CR. I dint think that is to good.
With the 347 I would do somewhere in the area of a 72cc head with a -8/-9cc piston for between 8.85 and 8.95 to 1 compression.
In a 408 to get this compression using a .040 gasket still and lets keep the 72cc head for now you would need somewhere in the area of a -24 piston.
In a 370 a -14cc piston would get you in the same compression area.

Let me try and explain more of why I like the 370 combo as a back up motor.
Lets say you blow a piston and Diamond/JE is on back order. To throw the 370 in is very easy. Everything that bolts on the 408 bolts right up to the 370. The heads are already on a 4.030 bore and can stay that way. You will need new head gaskets, and a cam gasket kit but thats about it. Even the cam should be okay unless your runing like a 260+ degree cam or something outragious. Also the 370 WILL make more power then the 347 given the same setup. You get extra cubic inches and you get to have a larger bore. On a larger bore the heads flow better air and the motor makes more power.
The only thing you loose vs the 408 is the torque, and you will also loose some compression due to the stock size crank being used.

I know your friend pulls on you with the same combo, however I dont think sending the AFR heads to TEA is worth it. BTW I use TEA heads so dont think I am trying to bash them. The 225's are really a 229cc head and thay are probally opened closer to a 237 then a 227 like you think. Maybe you just got the wrong info from your friend. now way would TEA take a 229cc port and make it a 227cc. AFR says 225 but when they are finished it came to 229cc.

I could go on all day debateing the nitrous vs turbo stuff but that will always end up with preference. You can make anything fast just depends on your budget and how you want to get there.
BTW are you sure your heads are 76cc? They aren't 72?

JZ'sTA

iTrader: (23)

off set crank.
I am not the brightest guy in this subject but will do my best.

It is a easy process done at the machine shop.
Basicially a 346 (stock cubic inches) can get a 3.905 bore which is now a 347.
A 6.0 motor and stock crank can go 4.030 bore easily. Some sonic check their block and go 4.060.
The 385 combo is based on a offset crank I believe offset to make it a 3.72 instead of a stock size being 3.622.
What happens is you get just a tad bit more compression as well.
Lets say your running a 66cc head and .040 gasket and flat tops for this comparision.
A 370 with stock crank gets you right at 11:1CR
A 375 with is a stock crank and 4.060 bore gets you around 11.1:1CR
Now you have the same bores with offset cranks.
A 4.030 bore and 3.72 crank gets you 379.6 cubes and 11.25:1 CR
A 4.060 bore and 3.72 offset crank gets you 385 cubes and 11.4 CR.
To many every bit helps.
Now we will look at the 347 combo.
You can bore the LS1/LS6 block much more so we gonna use the 3.905 bore only here.
Lets keep the 66cc head for now even though compression will be much different.
347 with flat tops, .040 gasket, and 66cc heads
347 cubes and 10.45:1 CR
Now we offset the crank to a 3.72 and we get 356.4 cubes and 10.7 CR.
You still have more bore then stroke which is good and your motor is closer to square with many people like.

SLowETz

iTrader: (12)

JZ- I agree w/almost everything you've stated, although one fact that should be noted for the NA guys who are looking at a 370" build..... while the 370" motor will(should)always make more power than the 346" given all else is equal, the power made above the 346" can be a wash when factoring in the additional 100lbs. of the iron block. IMHO, the power gains are there, but because of the additional weight, you're not "necessarily" going any quicker vs. a forged(IE: bullet proof)346"... (*edit*... in a NA application).

If one wanted to throw a huge hit at it(in excess of 250+), then by all means the iron block will always be the way to go, but for those who choose to stay all motor, I'd lean toward the forged 346" as being the better choice.

Sorry for bending the topic, just thought it a valid consideration....

2000_LS1

Thanks for the advice, I am still looking into the TT set-up. The thing I like about about going that way is then I would have an n2o set-up (currently using), and also a TT set-up. The only one I would lack then would be a S/C. I doubt I ever have 3 of them though.

Yes I am sure about the 76cc chambers, we ordered them not too long ago. As far as the 225's, cool didn't know that. Maybe he does a ~240cc intake port, but like I said, it's not really worth if when removing ~50 lbs can produce the same outcome.

JZ'sTA, Thanks for all of your input, I said it in another thread and I'll say it again, you seem to know your ****. I am going to finish researching this and then decide which way to go.

JZ'sTA

iTrader: (23)

Your are exactly correct and I agree.
You will gain around 85lbs when going iron.
Which one is better? Again its personal perference.
I have a 408 in 1 car and a built 347 in another, so I am a fan of both.

My best friend did a 370 also and made just under 500 in a M6 through a 12 bolt, and had a set of 1000 dollars on top of the car with a T Rex, Hooker's, fast 90/90. I was very impressed making that power with a "cheeper" set of heads. He made almost 40 more horse then I did in my 347 but got the extra weight. I still beat him but I run a 4400 stall compaired to his 3800 nitrous stall.
To me it isn't worth changing over unless I was gonna try and run a bunch of boost or a bunch of nitrous.
Both setup's work, however for a BACKUP build when running a 408 the 370 would be my choice.

2000_LS1

I have read that the 346/347 work better with boost vs. a bigger cube, would agree or still do a 370? I know they are WAAAY different in one going to be a 347/370 TT and the other being a 408 300 n2o. But I hinestly don't know **** about FI, never have messed with it. I am doing all the reading I can stand, also thanks for posting in the other thread.

JZ'sTA

iTrader: (23)

I am gonna save the Nitrous vs Boost for a bit later.
However a 347 vs a 370 I dont mind.
What you have to understand is a 347 is easier to boost then a 370.
If it takes a Twin 37 to boost a 347 with 20PSI correctly it will take maybe twin 44's or bigger to make the same boost in a 370.
Also the intercooler will need to be bigger, the piping larger, etc.
Therefore it is better sometimes to boost a 347.
Now if you were making 700 with a 347 and changed everything to work just as efficient with a 370 with the same boost you would more then likely make more power.
Cost goes up as you need upgraded parts.
Now when doing a 408 things get very expensive to do correctly.
The bigger stroke eats up air and as a example I had a incon TT stage 2 kit a few years ago. It was on my 408 setup for boost with just under 9:1 CR, turbo cam, etc.
I couldn't get more then 9PSI out of my setup without the boost being Extreemly Hot even intercooled. I took the kit of and went nitrous. I sold the kit to someone doing a forged 347. He made more power then I did with my 408 and with similar boost.
The setup runs great on his car.

JZ'sTA

iTrader: (23)

Dude I am gonna have you reading until your eyes fall out.
here is a good turbo FAQ page.
https://ls1tech.com/forums/forced-induction/208864-turbo-faq.html

2000_LS1

damnit boy...I ain't even done with the first one. between you and jrp...****. I'mma just have to print them off and put them in bathroom i guess. That way i know Ill read them lmao.

Solid346

i already have a 347ci solid roller with high Cr and i am thinking increasing the size and reducing the cr. so 414ci soild roller is my objective. do you think it is worth the money on the 370ci solid roller

JZ'sTA

iTrader: (23)

If you mean is it worth it to have a 370 as a backup I would say that depends on how rich you are. For me, I would keep the 346 as a backup since you already have it.
A 408 solid roller can make some huge power if done correctly.

2000_LS1

I'm so rich I have to swim through my money like Uncle Scrooge...until I wake up!!!