How do Techs?
Hey guys, I'm taking my 99 LS1 block to the Machine shop. I had visited there last week to discuss about some things I was looking to do to the engine because I was looking to acheive 450rwhp. It has been explained to me by others on here that switching out to stock LS6 heads would be a great idea. I'm venturing to rebuild for the first time ever. I was told the cylinders were bored too large by GM originally and which made the pistons too small and caused a ticking noise and so on. To correct the issue I should go one step up in size on the pistons which means I will need to bore the engine out to match the new larger size pistons.

Does this sound about right?

I didn't want to change the crank assembly really but If I need to then so be it. I explained that I was looking to get close to 450rwhp to which they explained I should get 228r cam with a set of springs as well. The shop told me swapping out into LS6 heads wasn't necessary if I was willing to get machining work done to the LS1 heads.

Does that sound accurate or should I stick with buying the LS6 heads? If I do that, are the stock springs good enough to achieve that power or will I still need to change the springs as well?

If I should replace the springs what ones should I get? I'm just so freaking confused on what direction to go. I will be using and LS6 intake as well too.

Please help!!

 

First off does this shop do LS motor work? Do they have a LS aluminum hone plate? It looks something like this.



The reason I ask a shop that knows how to do a SBC or a BBC may not know too much about a LS motor. Especially the small details like the oil barbell.

https://ls1tech.com/forums/generatio...lley-plug.html
Might not seem like much, but on startup when there is no oil pressure you'll learn about them quite fast.

Also when a shop says that the bores were too large by GM that makes me start to wonder, the stock Hypereutectic Aluminum pistons have a high silicon content that makes them not expand nearly as bad as forged aluminum pistons, thus they can run a REALLY tight piston to bore clearance.

Now your LS1 has a bore of 99.0-99.018mm (3.897-3.898") from the factory With an allowable taper thrust side of .018mm (.0007")
Now the piston diameter from the factory is 98.964-98.982mm (3.8962-3.8969"), with a limit of Piston to Bore Clearance from the factory of .018-.054mm (.0007-.00212")

You have the potential of an engine that still has less than 2 thousands Piston to Bore clearance, that is less than if you install some forged aftermarket pistons at (each piston manufacturer will spec what the clearance should be in a sheet with their pistons). Also if these guys are boring the engine before they have the pistons then stay away.

I don't claim to know too terribly much about LS motor valvetrains, but if you are upgrading a camshaft in terms of lift, you'll have to do the springs as well. The proper way to tell is put it on a spring testing machine and test the spring at installed height and just shy of coil bind, make sure to record what the pressure is at coil bind and what that compressed height is. Then when you pick your camshaft, you can safely say that you have enough lift availiable in your valve springs, they'll probably tell you that you don't have enough open pressure however. I just tested a set of stock 05 LQ4 springs and believe I hit about 280lb just shy of coilbind, I can't remember exactly though.

Short story is, the camshaft will dictate what springs you need.

Stock specs of your valvetrain.
Valve Spring Installed Height Intake 45.75mm (1.8")
Valve Spring Installed Height Exhaust 45.75mm (1.8")
Valve Lift Intake 11.99mm (.472")
Valve Lift Exhaust 12.15mm (.479")
Valve Spring Pressure Closed 76lb @ 1.8"
Valve Spring Pressure Open 220lb @ 1.32"

I don't know your machine shop and don't take it personal, but be wary. I've dealt with a few shops and there is more bad ones than good ones. Just watching out for you man.

 

Shimming springs to proper height should be common practice on any motor, regardless. Heads is where you make power, and that's where I would invest most of my money. You can go with 243 heads if you want, but you'd be better off buying a set of pre-ported heads (assuming you're going with stock castings) or purchase aftermarket (AFR, ETP, Mast, etc) castings.

Noice is right as far as finding a shop that has experience with LS engines. Never a good idea to have someone hit one of these blind. Funny thing is, the same guy(s) building Noice's motor are building mine, and I have NO worry about my motor coming out with sub-quality work.

Hi Matt/Mark LOLOLOL

 

Damn, I got spotted. Headed back to the garage now.

 

Get out.