EricYJ-TA

iTrader: (10)

My Stock LS1 commited suicide a couple of months ago. I have been putting together parts (Port and Polished 243 Heads, injectors, headers, cam, etc) for some time now only to discover my #3 piston and cylinder wall is toasted. Fortunately I scored a bare LQ4 iron bock yesterday. I have been looking at Texas speeds 408 rotating assemblys.

My first question is the stock rotating assembly vs the 408 assembly how much of a power diffrence am i looking at here?

I have just spend a boat load of money on a set of 243 heads getting a valve job and stage 2 porting and 650 lift dual valve springs. will these heads be compatiable with the 4.000 bore of the LQ4?

Should i go with the 408, is it feasable to shoot for a cam with more lift and duration? Currently i have two choices 236/242 comp cams, and a 233/239 TSP Cam which one can i expect to make more power with?

Thanks

EricYJ-TA

iTrader: (10)

bump anyone?

redtan

iTrader: (5)

You should see a good 10-15% more power and a lot more torque under the curve.

243s are great for a 4" bore, the come stock on LS2s and their cousin the 317s come on LQ9s.

I prefer higher lift cams to make more torque early on, but they are harder on the valvetrain. As far as those two cams we can't tell until you tell us the full specs of each. Just from the duration, the higher one will make more power given everything else is equal.

technicalninja

iTrader: (1)

You will need to provide more info for answers. What's your crank and rods out of the LS1 like? reusable? It's the same stroke as the 6.0. It might be possible to do a cheapy build with them. All you might need is pistons.

Your heads will work fine with the 4.0 bore stroked or stock. They may not make the highest HP #s but midrange should be excellent. Who ported the heads? Do you have CFM readings at different lifts? This info is necessary to make accurate predictions.

What is your use/application? be specific.

Are street manners and general fuel economy a requirement?

Do you have a target SCR/DCR?

Have to pass emissions?

What's your budget?

What's your expected power goals?

What intake do you have?

370-408 CI is approx 10% increase in size. expecting a 10% increase in power is very believable... so 30-60 hp depending on your chosen state of tune. This is a gross simplification but for the information given it'll work...

Either of the cams will function in the motor, which one is best is the question and it cannot be answered until you provide more info.

Your title said "scored an LQ block.... now the bad news," What was the bad news?
Didn't see any bad news posted, guess I missed it...

Finally HP/$ ratio will be far better if you can reuse the LS1 rotating assembly. If you're on a tight budget this is the direction I would go...

RoidedSS

I would say the 408 route would be a good route in terms of giving you the most potential. What is your budget? You might also want to look at the 402 route to cut back on machining costs...I'm looking into doing the same thing right now and you need to know what your goals are in compression. I haven't done all the math on what the compression will be with the 243's I have sitting around, but since you will be needing new pistons, this will allow you to decide your compression goals. The larger motor will also like the larger cams when compared to the ls1's stock displacement. Both cams will probably make around the same power but like everyone else has said, its mroe about the set up you end up going with. just give us an idea of your budget and ls1tech can give you some better advice then what is there so far

EricYJ-TA

iTrader: (10)

[/QUOTE]Your heads will work fine with the 4.0 bore stroked or stock. They may not make the highest HP #s but midrange should be excellent. Who ported the heads? Do you have CFM readings at different lifts? This info is necessary to make accurate predictions. [/QUOTE]

The heads were ported by Kotzur Racing located here in San Antonio. I am currently waiting on valve springs to show up for the heads to be complete. I will post the CFM readings once I get the reading sheet.

[/QUOTE]What is your use/application? be specific. [/QUOTE]

I am mainly looking for street and mile track use.

[/QUOTE]Are street manners and general fuel economy a requirement?[/QUOTE]

Not particularly. If it does it does if it does not I am not to particulary worried about it.

[/QUOTE]Do you have a target SCR/DCR? [/QUOTE]

I am looking at keeping it Mid 10’s to Mid 11’s. I basically looking to be able to use pump gas.

[/QUOTE]Have to pass emissions? [/QUOTE]

No

[/QUOTE]What's your budget? [/QUOTE]

I am willing to spend the money to do it right the first time.

[/QUOTE]What's your expected power goals? [/QUOTE]

I am interested in about 450 rear wheel horse power. If I make more I am totally fine with that.

[/QUOTE]What intake do you have? [/QUOTE]

I have the LS6 intake right now. I am looking at moving to a FAST 92 or 102. Depending on my Intake requirements for the motor.

[/QUOTE]Your title said "scored an LQ block.... now the bad news," What was the bad news?
Didn't see any bad news posted, guess I missed it... [/QUOTE]

Well I had thought I blew a head gasket. Went to pull the heads and replace it and noticed the piston was chipped and the cylinder wall is scarred very bad, I think its to the point where it will need to be re sleeved to work properly.

My desired endstate is to have build a reliable, well-planned, and fun vehicle.

wildcamaro

iTrader: (15)

well tuned 408s can make 575-600 hp at the crank with ease (as long as you have aftermarket everyhting..heads/intake/headers, etc.) that size motor is pretty potent