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HONDA - Reinforced Engine Parts
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HONDA - Reinforced Engine Parts
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ARP 8740 rod bolt kit with nuts for Honda and Acura 1.2 and 1.6-litre engines.
ARP lists this kit for Honda and Acura four-cylinder engines of 1.2 litres and 1.6 litres. ARP's website gives no engine code or model for this part number, so the table shows the applications exactly as ARP states them.
ARP intends kit 208-6001 for Honda and Acura 1.2 and 1.6-litre engines: it replaces the original rod bolt with an M8 bolt in 8740 steel, pressed into the rod and closed with a nut.
At every engine revolution, the rod and piston assembly pulls on the rod cap, and only its bolts hold it against these inertia loads. The original ones are intended for stock power.
The box contains the bolts that are fitted by pressing them into the rods, together with the matching nuts. ARP advises measuring the stretch of each bolt during tightening; without a gauge, the instruction sheet states 35.3 Nm. 8740 is a chrome-moly steel that ARP heat treats to 180,000 psi tensile strength, with threads rolled after heat treatment. As a reference point, standard engine fasteners mostly belong to classes 10.9 and 12.9, i.e. 150,800 to 176,900 psi minimum strength. The engine speed allowed by the 8740 bolts goes up to 8,750 rpm (calculated estimate).
| Part number | Brand | Grade / material | Nut | Thread | Under-head length |
|---|---|---|---|---|---|
| ARP-208-6001 | ARP | 8740 steel | Not published | M8 | Not published |
Before the bolts are pressed in, ARP asks for a chamfer around the top of each rod bore, large enough to clear the radius under the bolt head.
| Reference | Tightening torque | Stretch |
|---|---|---|
| ARP-208-6001 | 35.3 Nm | 0.127 - 0.140 mm |
ARP gives priority to stretch control for an accurate preload; the torque in the table is used only when no gauge is available. Torque and stretch figures in the table apply with ARP lubricant.
The values above come from the ARP 208-6001 instruction sheet applicable at the date of publication; it is authoritative in the event of any difference. Read the ARP 208-6001 instruction sheet
The ARP instruction sheet does not require a thread locker for this kit; only ARP Ultra-Torque grease is applied, on the bolt threads as well as on the bearing face of the nuts.
Once the fasteners are fitted, the ARP instructions call for the big ends to be checked and resized by a machine shop.
Tightening to stretch means setting the preload on how much the bolt actually stretches, rather than on a torque affected by friction. With the bolt fitted, the dial gauge is placed on both its ends and the bolt is tightened until the stretch given in the table is read. It is the safest method on a highly tuned engine.
Torque and stretch figures are only valid with ARP assembly grease, applied to the bolt threads and to the bearing face of the nuts.
ARP (Automotive Racing Products) came into being in the early 1970s, when Gary Holzapfel, who came from the aerospace industry, decided to tackle the engine failures caused in motorsport by inadequate fasteners. Today the brand produces thousands of part numbers in California for the cylinder head, the main bearings and the connecting rods, in materials suited to each application, with manufacturing known for its consistency.
| Brand | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| Honda | Engines 1.2 L | |||
| Honda | Engines 1.6 L | |||
| Acura | Engines 1.2 L | |||
| Acura | Engines 1.6 L |
On every revolution the rod bolts hold the cap against the inertia forces of the piston; if one lets go, the rod can go through the block. An 8740 kit costs little against the cost of rebuilding the bottom end.
