Lincolnman

First off, my apologies if this is the wrong area. I was unsure if internal meant short or long block.
I have not found any information on interchange of heads on blocks. I know that the LSX 6 bolt block takes either 4 bolt heads or 6 bolt heads, but is it possible to go the other way and use the 6 bolt heads on the 4 bolt block? I have looked at them and it APPEARS that they SHOULD, but I do not know, and would be very mad if I spent $2600+ on heads and then couldn't use them. So, can this be done, and if so is anything special required? Like would I have to have the fifth and sixth bolt holes on the heads milled off for any reason or anything weird?
Thanks in advance!
P.S. Don't ask why, that's not the point.

Mike454SS

iTrader: (4)

They'll bolt right on, but if they're made for a large bore, they won't work with a small bore block.

Jon@Texas-Speed

iTrader: (18)

Yes they will bolt right on. You only use the 4 bolts in the block and leave the other two out.

Jon

01ssreda4

iTrader: (96)

But why?

Sales2@Texas-speed

iTrader: (5)

Because you can buy the best heads you can afford, once! Then when you have the coin to upgrade the short-block to a 6-bolt block, you already have the heads and just need the head bolts/studs and you're ready to rock without spending another $2000+ for heads!

hirdlej

iTrader: (31)

I know which heads you're looking at. Don't do it. Trust me

Jon@Texas-Speed

iTrader: (18)

I don't... Which ones?

01ssreda4

iTrader: (96)

See it now?

Sales2@Texas-speed

iTrader: (5)

Ahh, yes. Thanks.

gpr

iTrader: (6)

Is it possible to modify a 4 bolt block to use all the 6 bolt head studs? For example, take the 4 bolt block and machine the extra 2 holes needed for the 6 bolt head. This way you don't need to buy a new block and will have the clamping force by using all 6 bolts? I'm not sure where they put the extra 2 bolts, but seems like if there is enough meet in the block it would be a feasible and cost effective way to add more clamping force.

Lincolnman

I am aware of that, I figured on a Darton sleeved block.

You do!? Okay, why not?

Let's wait and see if he is right.

Well, technically with metal ANYTHING is possible. You could even melt it and recast the block as new. Practically though -no. As far as I know it is not because the two outermost holes are in machined bosses that do not even exist on a normal 4 bolt block. The inner two bolts (valley pan side) exist on at least some blocks (maybe not all), only cover two cylinders per side instead of 4, and they appear to be too small to do anything with anyway. Regardless, without the outer ones even if you COULD use the inner bosses drilled and tapped you would wind up with a non-concentric 5 bolt pattern on the center two cylinders and only 4 on the outer cylinders, leading to incredibly improper torque loading and failure.
Nice try, though.
Take a look at these for reference.
LS3 Block - note the bosses on the intake side that are lacking on the the outer side of the block and also on the front and rear cylinders.

LSX Block - look at the location for the extra two bolts per cylinder.

Shawn @ VA Speed

iTrader: (3)

yes it is possible. The block in the picture started out as an ls2 block. we releeved it to 4.125 bore. Strengthened the deck and added provisions for 6 bolt heads

Lincolnman

I'll bite - what were the provisions? You machine bolt "tabs" and then TIG them on a heated block?
I would like to know more about how you did this and was it just for the purpose of the extra clamping force?

Mike454SS

iTrader: (4)

I'm actually curious how much it cost to modify the aluminum LS2 block (weld/heat treat/drill/tap) and then do all the other typical machine work that any high end build requires...I really haven't seen many strength related bottom end failures in the aluminum blocks, especially not when fitted with billet main caps...if it's a more attractive price than an LSx thats cool...plus it weighs less, which is the attraction of the Warhawk over the LSx...but again, that one costs a lot too...I'm guessing the procedure would be mostly the same for any other production aluminum block, maybe just slightly different prep work to the original casting if it's shaped slightly different (like the 6.2 pictured above with the 2 bosses near the lifters that'd need to be modified)...granted I'm sure there are bottom end strength benefits to the LSx and Warhawk that won't be seen in a modified production block...but for lower 4 digit power builds, they're probably not necessary for a lot of those builds.

dreamls1

iTrader: (25)

Can you add provisions to lq9 to make it 6 bolt?