I have a stock lq4 and I'm thinking of making a 402 or a 408. Is there a advantage to have one or the other? Other than the ci of course.

 

The 408 would have super clean bores, nicely hatched to accept and seat the fresh rings.
The 402 is probably used and needs honing which would make it bigger than 402 after all is done.

 

Used? I'm going to bore my lq4 to a 402 or 408. I'm assuming that I can make ether or.

 

usually the question between 402, and 408 is LS2 block or Iron block. with 6 cubic inches it really wont make that much difference, but if you have an iron block, then i would go 408 cause it is available.

 

You don't bore to a 402, a 402 can be made with the stock bore size and 4" stroke.

There is no advantage, but if you stick with the right bore you can get cheaper off the shelf pistons as opposed to custom ones.

There are many 4.000, 4.005 and 4.003 pistons readily available, so a 402, 403 and 408 are easily made. Tho I would at least do a light hone of the bore to a 4.006 just to clean it up.

 

My LQ9 block was clean enough that all it needed was a hone to 4.005", which provided me with a 402 inch motor with the stroker crank. I saw no reason to bore it to 4.030 when a simple hone would suffice. This left room for next time, though obviously I hope there doesn't need to be a next time! It also saved me a few bucks at the machine shop.

 

so 408 I would bore .030
over with a stock crank ?

 

Don't bore it to make power. The gains are minimal and you'll want to have some room left in there for the next rebuild.

 

no a 408 is a .030 bore on a 6.0 iron block with a stroked crank.

 

and btw you are not really going to notice much difference if any on 6 cubes so its really what you want to go with.

 

ok this is a real newbie question. can you make a stock lq4 crank a stroked crank

 

Do an .005 cleanup hone if that is all it needs and you will be at 403ci There are a ton of shelf pistons available for the 4.005 bore and as stated you can get another rebuild out of it....


Edit: No combs.

 

the 403 is that with a stock crank?

 

The 402-408 require the use of a 4" stroked crank.

Stock crank will yield you between 364 and 372.

 

ok thank you.

 

No , the stock crank has a stroke of 3.622" so with the hone to clean it up You'll have a 366 or pretty close

 

That provided you with a 403 CID

 

Do people really refer to these as a 403? I realize that technically it is a 403, but my SDPC 402 is based on a new GM Performance 6.0, 4.005" bore, LS2 block with an Eagle 4.000" stroke crank. All references to this motor are just that, an SDPC 402. Maybe this is like the late-1969 thru 1972 396's .... a .030" bore by GM yielded 402's, but, they were still 396's. I don't remember a single SS402. Although, some GM brands like the Impala were marketed as 402's with 402 air cleaner emblems.

By the way "combs_425", everyone did a great job setting you straight on a 402/408 stroker 6.0. For the most part, most build a 402 out of the aluminum block LS2 (4.020" max recommended bore) and a 408 out of the iron block Lq4/LQ9's.

 

403.13074032 inch^3

Right you are sir.

 

All this info did help.thanks guys