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HRC Extreme Billet Main Caps

hrc h350s-main-capsPrecision 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. 

Chev 350 Main (2.450” Journal)
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)
454365TS2 454 Main, 4.375” Stroke, 6.535” Rod
Chev SB, 2-Pc Seal, 2.100” (LJ) Rod Pin
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)
H454 Converts 2-Bolt to 4-Bolt, 3 pcs.
H454RWS Rear Cap, Wet-Sump (4-Bolt), 1 pc.
Main Cap Support Straps

main-cap-support-strapsDesigned 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. 

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

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.

H350R or H350C Main Caps  
Bolt Kits  
134-5202 Hex Head (180,000)
234-5201 12 pt. Pro Series (200,000)
Stud Kits (200,000psi)  
134-5601 Hex Head w/o windage tray
234-5601 Hex Head w/windage tray
H350S Main Caps  
Stud Kits (200,000psi)  
234-5602 Hex Head w/splayed bolts
H400 Main Caps  
Stud Kits (200,000psi)  
234-5605 Hex Head w/windage tray
Main Cap Support Straps(w/HRC billet or OE center 3 straps)  
Bolt Kits  
234-5203 12 pt. Pro Series (200,000)
Stud Kits (200,000psi)  
234-5603 Hex Head w/straight bolt caps
234-5604 Hex Head w/splayed caps
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