BlueStreak362

iTrader: (8)

been looking around and cant exactly find the anwser, wanting to keep a streetable setup but want some cubes. looking for numbers in the upper 400's, TSP has rotating assemblies to create both a 402 and 408 from a iron block, however both are the same price, I have the LQ waiting already. I want to make the CR around 11:0.1 to still be able to run pump gas. The motor will be NA and i have no plans for spray or FI in the future. Any input on benefits of a 402 over a 408 or vice versa? any input is greatly appreciated. Thanks.

Texas_WS6

iTrader: (9)

If they are iron blocks then the only difference is one is bored 0.030" over and the other has the standard bore. There would be no noticable power difference just from the 0.030" overbore, but with the slightly larger bore you can run the newer L92/LS3 cylinder heads which require a minimal bore of 4.030" I believe, but those heads also require different intakes so if you wanted to run your intake there would be a problem. That is actualy what I am doing if you read my sign.

MelScrilla

iTrader: (2)

I always wanted to know the difference too. I wonder what the difference would be at the machine shop between keeping the stock bore or getting the block bored?

Texas_WS6

iTrader: (9)

Sorry, I just re read what you posted, you have the block and are looking at rotating assemblies. The 402 is for the standard bore which normaly is used only in a new block. If your iron block is a used block then you will need the 408 kit as it is for a 0.030" over bored block. You realy will not know for sure if you need to bore it until you take it to the machine shop. DO NOT let them bore your block until after they have the pistons in hand! But they can mic the bores and tell you if your block will run with the bore it has or if the bores need to be reworked. Most used blocks end up needing to be reworked.

Again, you will not be able to tell the difference in power from a 0.030" bigger bore if all the rest of the parts are the same.

Texas_WS6

iTrader: (9)

If the block is used most of the time they will bore it over, because thats how they make a living, and also because that way they can fit the new forged pistons to the bores properly. Also they can control the finish of the bore for the type of rings you are using and for the expected use of the engine.

I do not think the new iron blocks come with finished bores. I know the iron LSX's are not finished.

BlueStreak362

iTrader: (8)

The Iron block i was going to use was a 07 LQ4 with 10k on the clock, so fairly new. so the 402 is the same bore as the 6.0L just stroked? and a 408 is the same stroke as a 402 with .030 over on the bore? also how much power could be picked up running stock L92s over stock 317s? on a 408.

Texas_WS6

iTrader: (9)

It will depend on the intake cam setup you choose, also the chamber volume of the to heads are different. This will influence the piston dome shape to achieve your desired compression ratio, which will effect the quinch area. The question you ask is too vage to give a definet answer. I would decide first what your goal is for the engine, decide if it will be NA, FI or if it will see Nitrous. Then decide what kind of intake setup you want to run and those things will help you decide which heads to run. I personaly like the L92/LS3 heads. To give you and example of power between the two, the stock Corvette 6.0L LS2 is what 400hpwere as the stock Corvette LS3 is 435 hp.

Blkdoutbird

iTrader: (5)

Personally I would probably have the machine shop machine the block first and order the pistons accordingly. If you order pistons 4.005 and then have the machine work done and find out that they had to bore it out more than you hoped they would then you have to ship the pistons back and pay more money for shipping, and wait longer to have the motor together.

ssZL402

i just built a 402 in a 2000 ss that makes 480rwhp its all in how you build it

Texas_WS6

iTrader: (9)

Thats why you have the shop inspect it first, then order the parts. The point is to fit the bore to the piston, wich can not be done if the bores are completed before the pistons arrive.

Martin718

iTrader: (14)

so whats a 402 .10 over and stock crank cut .10?
not trying to thread jack just trying to figure out this motor i have

sroach20

iTrader: (31)

the 6.0 iron blocks are not a true 4.0 so wait to order the pistons or just do the 408. as for the ls3/l92 heads, they fit my lq4 without any machine work.

MelScrilla

iTrader: (2)

whats you top end combo

Texas_WS6

iTrader: (9)

No, a 402 is the stock bore (4.00" for 6.0L iron blocks) and an crank that has a 4.00" stroke. The stock stroke is 3.622".

the 408 is a stock bore that has been cut oversized by 0.030" to make it 4.030" bore with the 4.00" stroke.

Lots of people have to oversize the stock bore in order to clean it up due to the fact they are using a used block. If you start with a new block you can finish it to the original bore (4.000") and you have a 402. The advantage to this is thicker cylinder walls and you can bore it over in the future if need be. I think the iron block 6.0L is not recomended to go any more then 4.030" on the bore. The LSX iron block can go much bigger then that, I think its 4.250" max bore.

99Ls1fever

iTrader: (3)

I loved my 408 and if I was to give you advice go with 11.5 to 12.2 compression which I wish I would have done. I went 11.3 and through my 408 I put down 531 480 trq engine build in sig. Other numbers were with a nitrous setup. Plus a 408 is very affordable compared to a 402 IMO. Short block 408 are 3800.

Also how is your build going?