Others Rotating Assemblies
HRC Extreme Billet Main Caps
 Precision CNC machined from superior quality low carbon 1020 billet material. Available as stock replacement (straight bolt) or with splayed outer bolt holes. The splayed caps feature 10 degree angled outer holes to positively reinforce and tie the block together. Main cap set consists of the center 3 caps. Front and rear caps are also available. Use together for ultimate in bottom end stress and flex management. Drill bushings included with caps requiring them. Side notches for easy removal. Proudly 100% manufactured in the U.S.A. Line boring required after installation.
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| Chev 350 Main (2.450” Journal) |
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| H350R |
4-Bolt Replacement, 3 pcs. |
| H350C |
Converts 2-Bolt to 4-Bolt, 3 pcs. |
| H350S |
Converts 2-Bolt to 4-Bolt, Splayed Outer Bolts, 3 pcs. |
| H350E |
Flat Bottom, Splayed Outer Bolts, 3 pcs. |
| H350F |
Front Cap (2-Bolt), 1 pc. |
| H350RDS |
Rear Cap, Dry-Sump (2-Bolt), 1 pc. |
| H350RWS |
Rear Cap, Wet-Sump (2-Bolt), 1 pc. |
| Chev 400 Main (2.650” Journal) |
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| 454365TS2 |
454 Main, 4.375” Stroke, 6.535” Rod |
| Chev SB, 2-Pc Seal, 2.100” (LJ) Rod Pin |
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| H400 |
Converts 2-Bolt to 4-Bolt, Splayed Outer Bolts, 3 pcs. |
| H400E |
Flat Bottom, Splayed Outer Bolts, 3 pcs. |
| H400F |
Front Cap (2-Bolt), 1 pc. |
| H400RWS |
Rear Cap, Wet-Sump (2-Bolt), 1 pc. |
| Chev 454 Main (2.750” Journal) |
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| H454 |
Converts 2-Bolt to 4-Bolt, 3 pcs. |
| H454RWS |
Rear Cap, Wet-Sump (4-Bolt), 1 pc. |
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Main Cap Support Straps
 Designed to support the front and rear OE?style main caps for higher horsepower applications. The best thing to use next to billet replacement caps (see above). Milling top of the caps is necessary, but line bore is usually not affected.
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| H350FS |
Front main cap strap, Chev. 350 |
| H400FS |
Front main cap strap, Chev. 400 |
| H350RSDS |
Rear main cap strap, dry sump, Chev. 350 |
| H350RSWS |
Rear main cap strap, wet sump, Chev 350 |
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Suggested Main Cap Fasteners
Using Howards Billet Main caps will strengthen your block extremely. However, good quality fasteners must be used for full effect. We highly recommend the use of high quality bolt or stud kits with a rating of 180,000psi or higher. ARP’s Pro Series fasteners (200,000psi) are a good match with our main cap kits. The following recommended part numbers are for use as a guide only. Certain applications may require different lengths, check with the manufacturer if you are not certain.
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| H350R or H350C Main Caps |
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| Bolt Kits |
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| 134-5202 |
Hex Head (180,000) |
| 234-5201 |
12 pt. Pro Series (200,000) |
| Stud Kits (200,000psi) |
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| 134-5601 |
Hex Head w/o windage tray |
| 234-5601 |
Hex Head w/windage tray |
| H350S Main Caps |
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| Stud Kits (200,000psi) |
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| 234-5602 |
Hex Head w/splayed bolts |
| H400 Main Caps |
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| Stud Kits (200,000psi) |
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| 234-5605 |
Hex Head w/windage tray |
| Main Cap Support Straps(w/HRC billet or OE center 3 straps) |
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| Bolt Kits |
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| 234-5203 |
12 pt. Pro Series (200,000) |
| Stud Kits (200,000psi) |
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| 234-5603 |
Hex Head w/straight bolt caps |
| 234-5604 |
Hex Head w/splayed caps |
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