Originally Posted by SLOW SEDAN

My questions would be what's the power goal, do either CA625 or 1/2" noticeably increase clamp, and what heads are required to actually get useful deck thickness to make it all worth it. Spending $800+ on studs and $2000+ on heads seem like a boondoggle for meager power goals.

I remember a film paper test showing clamping load between stock, typical studs, and either CA 625 or 1/2" studs but not sure where it ended up. I think this was also brought up along lines of the ching chong studs vs ARP, and then multiple chimed in with chinese stuff going 8's so why spend 2-3x as more for ARP when its not the weak point unless investing in other hard parts. Then you have sloppy guys running 8's with stock bolts

Originally Posted by Mavn

I just did 1/2 studs on my 5.3 Block. When I get home from work ill post the pictures. cant wait to run 40# On a stock 4 bolt block

Originally Posted by stilealive

I decided on the T6 93/102 BW in the S400 chassis. I want well over 1,000 RWHP. So I need to use whatever head studs are going to give me the best result in clamping force.....without swapping over to a 6-bolt block. Heads will be thick deck heads of course.

Engine is fully forged and ready, the rest of the car is ready.

Originally Posted by Floorman279

I can't see u being able to drill for studs with motor in car in a 4th gen....how u getting the drill to the bottom holes

Originally Posted by SLOW SEDAN

Solid turbo, for sure makes 1200+, some have knocked on 1400.

Originally Posted by stilealive

Bottom holes...? I thought the holes were all on the top of the block......


My engine is coming out of the car so they can install my BMR Turbo-member. So this Tick 1/2" stud kit will work fine.

But then the heads need to be drilled also...... If I just use the CA 625 stud kit, the job is very simple.....so that may be best. Only if they give me the same clamping force as 1/2" studs do......

Originally Posted by ddnspider

He's talking about the bottom row of bolt holes in the block that fasten the head to the block. That row is closest to the body of the car giving less room for a drill. It doesn't matter if you're pulling the motor, but a right angle drill might fit if it was in the car.

Originally Posted by stilealive

Gotcha.

I was reading about 1/2" studs and some were saying that by taking out that much material in so many places around the deck area....it weakens the block surface and could create issues in deck movement. I never heard of that happening. I guess with an iron block I'll be better off than an aluminum block regarding that.......

I still can't get anyone to confirm if the CA625 studs have the same clamping force (ft. lbs) as the 1/2" studs......if they do, then the 625's are the obvious better way to go. And no drilling out all that material from the deck. And not having to have the holes in the new heads drilled to 1/2".....

Originally Posted by stevieturbo

Complete and utter nonsense, and as LS threads go down into the block, they dont actually pull on the deck hard like some other engines might. And I think even the new Dart blocks thread directly into the deck...which seems a negative point for them
Fitting 1/2" studs to the LS doesnt weaken anything

Originally Posted by Floorman279

honestly just do the 625s and be done. if u were that concerned u would be buying a 6 bolt block. gasket choice is important here too.....look into cometic MLX, I like how those look and would have used them in my NA build had I not needed a .040

Originally Posted by stilealive

Yea, sounded odd.

ARP just replied to me, said the CA625's have almost the same torque specs as the 1/2" studs.

CA625's go 100 ft. lbs.

1/2" studs (8740 chromoly) go 100-110 ft. lbs.

But they said they can make a set of 1/2" studs with better material that can be torqued to 150 ft. lbs.

So, is more always better? Or can you have too much clamping force that can hurt anything?

Or....are the 100 ft. lbs. plenty for 21-22psi boost on a 4-bolt/cyl set up with a thick deck head?

Originally Posted by tblentrprz

You might be overthinking this. Reused stock 11mm head bolts have been 1000whp with stock 317 heads (IIRC ~.4" deck). If you plan to go 35+psi with 4 bolt, get a pre 2004 block with the long head bolts down into the main webbing, do 1/2" head stud mod, thick deck heads, SCE Athena SS fire ring gaskets and good to go. If you really want to get crazy, get the heads cut and have top fuel hoops installed, block setup with receiver groove and Clark copper gaskets. Now your ready for 50+ psi and you can see what it takes to split a 5.3 block in half. Just make sure your rotating assembly can handle 2000hp.

Originally Posted by stilealive

21-22 psi is what I want to make. So I’ll probably go CA625 and be done.

Originally Posted by stilealive

Or....are the 100 ft. lbs. plenty for 21-22psi boost on a 4-bolt/cyl set up with a thick deck head?