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1956 - 1968 Corvette: Service News: Connecting Rod Bolt Usage

Model Year: 1956-1968
Subject: Connecting Rod Bolt Usage
Source: Chevrolet Service News
Date: August, 1968

A new connecting rod assembly incorporating a 7/16" diameter connecting rod bolt is being used in late built Corvette R.P.O. L-88 (427 cu. in., 430 H.P.) engines and heavy duty M4 service engines. Early built R.P.O. L-88 engines and all other 427 cu. in. engines incorporate the 3/8" diameter bolt. The connecting rod nut used on the 7/16" diameter bolt should be torqued to 70 ft-lbs.; the 3/8" diameter bolt nut should be torqued to 45 ft.-lbs.


Due to considerable variance between connecting rod bolt usages, a chart has been included in this article giving a listing of connecting rod applications by model year and by part number.

Connecting Rod Bolt Usage Chart
Year Application Part No.
1968
Corvair 6255636
4 & 6 cylinder engines (except 292) 3892670
292 cu. in. engine 3789421
307, 327 & 350 cu. in. engine 3916399
366, 396, & 427 (except Corvette RPO L-88 2nd Design) cu. in. engine 3862720
Corvette RPO L-88 2nd Design (427 cu. in., 430 H.P)1 3942409
1967
Corvair 6255636
4 & 6 cylinder engines (except 292) 3892670
292 cu. in. engine 3789421
283, 327 & 350 cu. in engine 3892670
366, 396 & 427 cu. in. engine 3862720
1963-1966
Corvair 6255636
4 & 6 cylinder (except 292 engine & 1963 L-6 engine used in K Series Trucks) 3892670
292 cu. in. engine 3789421
L6 engine used in 1963 K Series Trucks 3916399
V-8 engines (except 348, 409, 366, 396 & 427) 3892670
348 & 409 (except Special High Performance RPO Z-11) 3732718
Special High Performance 409 engine (RPO Z-11) offered in 1963 3837689
366, 396 & 427 cu. in. engine 3862720
1962
Corvair 6255636
6 cylinder engines (except Chevy II) 3836670
Chevy II 4 & 6 cylinder engine 3892670
V-8 engines (except 348 & 409 engines) 3892670
348 & 409 cu. in. engine 3732718
19562-1961
Corvair 6255636
6 cylinder engines 3836670
V-8 engines (except 348 & 409 engines) 3892670
348 & 409 cu. in engine 3732718
1: Also used in Heavy Duty M4 service engines.
2: For model years prior to 1956 reference Parts Catalog under group 0.623.

 

Connecting Rod Bolt Configuration
Part No. Thread Torque.
3732718 3/8-24 x 2 45 FT. LBS.
3789421 3/8-24 x 1 29/32 45 FT. LBS.
3836670 3/8-24 x 2 1/4 45 FT. LBS.
3837689 3/8-24 x 2 25/64 45 FT. LBS.
38623720 3/8-24 x 2 1/8 45 FT. LBS.
38923670 11/32-24 x 1 7/8 35 FT. LBS.
3916399 3/8-24 x 1 39/64 45 FT. LBS.
3942409 7/16-24 x 2 1/8 70 FT. LBS.
6255636 5/16-24 x 1 57/64 25 FT. LBS.
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