redaces

What is the max displacement you can get from boring and stroking an LQ4 block? and what would the compression be ?

..... normal flat pistons, not domed, forged crank.... and, a cam designed for low to mid range power not top end.....

i.e. a street car... not a quarter mile dragster or a top speed record contender.

though...... i would like to put a turbo on it eventually too lol.

and.. of course, it may be limited to parts availability too...

If i recall, you can make these things something like 7.7L or something crazy.... "?"?"?"

SS10Tech

I did a search on this because it would save alot of typing - it can be done but not easily, and there are complications with short deck long stroke combinations - particularly with piston ring seal design and top-loading. You should read this carefully and understand these are max effort NA builds. If you want to build a turbo motor i would look at other rod/stroke combinations.

https://ls1tech.com/forums/generatio...lq9-block.html

willyfastz

You can do 4.065/4.070 bore and a 4.100 stroke in the LQ4 block and have a pretty good street engine.

If I had plans of a turbo I wouldn't go much more than the trusty ol 408ci set up. Than way you could have a strong na engine until you get the turbo and a really strong FI engine.

If you really plan to do a turbo I would go ahead and build it as a FI engine. You can do 9:1 compression with a nice turbo cam. A setup like that will run real good na but will be ready for the turbo when you are.

KCS

iTrader: (20)

I couldn't agree more. The compromises you make to get those last few cubic inches just wouldn't be worth it on a turbo motor. A 408 is probably about as big as you want to go.

batboy

iTrader: (6)

I've never heard of a 7.7L LQ4/LQ9. You must be thinking of the LSX iron block.

The biggest safe overbore for the LQ4 is 4.030", but if the block is sonic tested some (not all) can be bored out to the LS3 size of 4.065". For FI or nitrous I'd keep some meat in the cylinder walls and stay at .030" over. For stroke the main choices are 4.000", 4.100, and 4.125". Again, for FI stay with the 4" stroke due to stronger piston crown.

bore X stroke = displacement
4.000 X 3.622 = 364 / 6.0
4.000 X 4.000 = 402 / 6.6
4.030 X 4.000 = 408 / 6.7
4.065 X 4.000 = 415 / 6.8
4.030 X 4.125 = 421 / 6.9
4.065 X 4.125 = 428 / 7.0

Can't calculate the compression ratio without knowing the compression chambers of the heads you plan to use. If you are staying with the 317 heads (71cc) that came stock on the motor, then you'll probably be about 11:1 with -3cc flattop pistons and GM gaskets (assuming 408 CID). That's too high for FI but fine for N/A. You'll probably want to use somewhere in the range of -12cc dished pistons for around 10:1 CR.

willyfastz

I would sonic check your block to make sure, but most have at least .300" cylinder walls. .070 over would hurt nothing.
'

willyfastz

I would do a 4.065" bore X 4.100 stroke" If I wanted a little more cubes. But for what he wants just do a 4.030" x 4" or even a 4.030" bore x 3.622" stroke. With a turbo you wont need a lot of stroke.

midevil1

iTrader: (17)

I have done over a dozen LQ4's to 4.065. Might as well throw the block away if it could only be safely bored to 4.030. You must be thinking of the SBC.

bww3588

iTrader: (49)

4.030 is safe without sonic testing. I don't think he said anything about the block being junk.

Turbo 370's and 408's are tried and true. Chasing a few extra cubes in a turbo engine is a waste of time and money when you stack it all together on paper. You might get that warm and fuzzy feeling when you build a 416 or larger, but you'll feel like you swallowed a bag of nails if it let's loose because of the longer stroke.

midevil1

iTrader: (17)

He said .030 is the safest you can bore a LQ block. If you sonic test it, only some can go .065. Mis-info.. This isn't a SBC. Don't compare the LS engine to that Dinosaur and the technology that was used to cast it's blocks. EVERY LQ block that I have gone .065 has sonic tested .300 or more.

bww3588

iTrader: (49)

So we should take this for gospel because you said so? I think not. That information has been said from many shops that are sponsors here.

Regardless of how many thousands of 6.0's you have built, .030 is safe without testing. More than that, it is a good idea to have it tested, esp if your building a boost or nitrous engine.

Sales4@Texas-Speed

iTrader: (4)

If its going to see a turbo later just do a 408(4.030 bore, 4.00 stroke) and be done with it. The 408 can make great power on motor and will handle boost with out worry. Like previously stated the last few cubic inches aren't really going to help that much N/A and will only limit you when you put the turbo on.

midevil1

iTrader: (17)

I never said not to test it. I never said you have to go .065. GO BACK TO DRIVING THAT 12 SECOND BMW.

bww3588

iTrader: (49)

Eat a dick. Obviously you can't read either.

You said every block ever cast can go past .030 over...period. that right there means you don't have to sonic test it.

Your an idiot, because this is not true. Spend more time reading and less time making yourself look like an *** by getting peoples names wrong.

SVTconfused

im personally more interested in the big bore shorter stroke idea...

4.050 bore or so and a shorter stroke so you can rev the **** out of it and quickly at that but still have the air flow room of the big bore...

but im different than most... i tried to make a ford fast