SpeedFactory Extreme Pro Duty CA625+ Head Stud Kit for B/K Series

SpeedFactory Extreme Pro Duty CA625+ Head Stud Kit - B & K Series VTEC

When you're boosting a B or K series past 30 psi, the head studs are what stand between combustion pressure and a lifted head. This is the strongest kit SpeedFactory offers, built from ARP's Custom Age 625+ material, 37 to 40% stronger than standard off-the-shelf studs. It's for hardcore drag builds where clamping force matters more than cost.

It Needs A VTEC Head, Not A VTEC Engine

Read this carefully, because it's the fitment gate and it catches people out on hybrid builds.

This kit fits VTEC heads. What matters is the head, not the block, and that distinction is everything on a swapped or hybrid engine.

So it fits a genuine VTEC engine like a B16A, B18C, K20, or K24. It also fits an LS-VTEC or B20-VTEC build, where a VTEC head sits on a B18A, B18B, B20B, or B20Z block, because the head is the VTEC part.

What it does not fit is a complete non-VTEC B-series, meaning a B18A or B18B with its original non-VTEC head. No VTEC head, no fit.

If you're running a hybrid, go by your head. If you've put a VTEC head on a non-VTEC block, this is your kit. If your engine is non-VTEC top to bottom, it isn't.

Why CA625+ Over Standard Studs

The material is the entire product, so it's worth understanding what you're paying for.

Most head studs, including ARP's own standard kits, use 8740 chromoly. That's good material and it's fine for most builds. CA625+ is a different tier entirely.

It's 37 to 40% stronger than standard studs, with 260,000 to 280,000 psi tensile strength. That translates directly into more clamping force, which is what keeps the head sealed against the block when cylinder pressure is trying to lift it.

It also has roughly 17% higher yield strength than ARP L19, which means it takes a higher initial torque and higher cyclical loading before it starts to stretch. On a drag engine seeing repeated extreme boost, that fatigue resistance is what keeps the clamp load consistent over time.

No Special Handling

This is a practical advantage over the other high-strength option.

L19 is strong but fussy. It's susceptible to stress corrosion and hydrogen embrittlement, which means it needs careful handling, oiling, and storage or it can fail from corrosion rather than load.

CA625+ is immune to both. It needs no special handling, doesn't require you to keep it oiled on the shelf, and won't quietly degrade from corrosion. You get L19-and-beyond strength without the babysitting.

Built For Easier Installation

Two details that make the job less painful.

The studs have a 3/16" hex broach on top, which lets you thread them in with an Allen key and, importantly, install them with the cylinder head on the car if you need to. That's a real convenience on an engine that's already in the bay.

The kit uses oversized forged 9/16" 12-point nuts and hardened parallel-ground washers rather than the smaller 1/2" hardware most kits ship. The larger contact area distributes clamp load better across the head, which is part of getting even sealing at high pressure.

Direct Replacement, No Machining

These drop in where the factory head bolts came out. No modification to the head or block, no machining, nothing to adapt.

Each kit includes 10 CA625+ studs, the nuts and washers, ARP Ultra-Torque assembly lubricant, and instructions. Use the supplied lubricant, since torque specs are calculated around it and substituting something else changes the clamp load you actually get.

Fitment

1994-2001 Acura Integra GS, LS, RS, and GS-R
1997-2001 Acura Integra Type R
2002-2006 Acura RSX
2004-2008 Acura TSX
1999-2000 Honda Civic Si
2002-2005 Honda Civic Si
2006-2011 Honda Civic Si
2002-2006 Honda CR-V
1994-2001 Honda Del Sol VTEC
2003-2011 Honda Element

Covers B16A, B18C1, B18C5, B20-VTEC, LS-VTEC, K20A, K20Z, and K24A. Requires a VTEC head. Does not fit complete non-VTEC B18A/B18B engines or the K24Z7.

Who Should Run These

This is for the drag or high-boost builder who's decided the head studs aren't the place to compromise. Past 30 psi, the strongest material available, no special handling, and clamping force that holds the head down when everything else is trying to lift it. Confirm you're running a VTEC head, use the supplied lubricant, and torque them properly.

Fits: Honda and Acura B and K series with a VTEC head, see the application list above. Material: ARP Custom Age 625+, 260,000-280,000 psi tensile. Strength: 37-40% over standard studs, ~17% higher yield than L19. Hardware: oversized 9/16" 12-point nuts and parallel-ground washers, 3/16" hex broach. Includes: 10 studs, nuts, washers, ARP Ultra-Torque lubricant, instructions. Recommended for: boost above 30 psi. Requires: VTEC head. Does not fit: complete non-VTEC B18A/B18B, or K24Z7.