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BRITISH AUTOMOTIVE |
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www.mgbmga.com MGTD Articles |
Technical Information (MGB 20A)
ELGIN CAMSHAFT INFORMATION
Last Modified - 05/10/01
The following information is presented to you by British Automotive courtesy of Dema Elgin. (www.elgincams.com).
We highly recommend having the following camshafts nitrided (heat-treated) after grinding. It is also very important that the lifter hardness (Rockwell RC scale) be matched with your particular camshaft choice.
Old lifters are made out of very soft chilled iron and should be radiused ground, plus hardness tested, before being returned to service. New lifters should always be checked for the proper radius profile as well as hardness tested. I can not over stress how important the foregoing is.
The lift specifications listed are at the camshaft. If you want to calculate the net valve lift, you need to multiply camshaft lift times the rocker arm ratio you are using. (See technical article MGB16). From this number subtract the valve lash you adjusted the valves at, then subtract another .005" for valve train flexibility, expansion, etc.
All MGA & MGB engines:
OEM Rocker Arm Ratio = 1.5:1 Blue Printed. (Use 1.426:1 or 1.45:1)
Roller Rockers use actual ratio. 1.5:1 1,55:1 or 1.625:1
| Grind | [Seat] | [050"] | Cam | Valve | Valve | Lifter | |
| No. | Duration | Lift | Lash | Spring | RC | Application | |
| 6625075-15 | 264 | 217 | .265" | .013" | 423-435 | 50+ | MGA & MGB Street |
| CAM1156 | 244 | 198 | .265" I | .013" | 423-445 | 50+ | 1975 -1980 SMOG MGB |
| 257 | 214 | .265" E | .013" | ||||
| 6708-18 (671018X289) | 268 | 222 | .289" I | .017" | 423-435 | 50+ | MGA & MGB Street |
| E | .019" | ||||||
| 685-16 (68508-16) | 274 | 230 | .297" I | .017" | 423-435 | 50+ | MGA & MGB Street |
| E | .019" | ||||||
| 70-9 (7007-9) | 280 | 228 | .262" I | .010" | 423-435 | 50+ | MGA & MGB Street Headers 1500-5500 RPM |
| .012" | |||||||
| 70-10 (7008-10) | 280 | 228 | .278" I | .012" | 423-455 | 50+ | MGA & MGB Street 9.5:1 Headwork 2000-6000 RPM |
| E | .014" | ||||||
| 71-15 (7107-15) | 284 | 235 | .290" I | .015" | 423-455 | 50+ | MGB Hot Street |
| E | .017" | ||||||
| 72-10 (7207-10) | 288 | 235 | .290" I | .012" | 423-455 | 50+ | MGB Hot Street 2500-6500 RPM |
| E | .014" | ||||||
| 75-12 (7506-12) | 300 | 250 | .320" I | .014" | 55+ | MGB Autocross 3000-7000 RPM | |
| E | .016" | ||||||
| 76504-14 | 300 | 262 | .344" I | .015" | 55+ | MGB "E" Production | |
| E | .017" | ||||||
| (M7705-13) M77-13 | 308 | 255 | .320" I | .016" | 55+ | MGA & MGB Race | |
| E | .018" | ||||||
| 77-12 (7706-12) | 308 | 262 | .349" I | .014" | 55+ | MGA & MGB Race | |
| E | .016" | ||||||
| 78-14 (7806-14) | 312 | 266 | .328" I | .015" | 55+ | MGA & MGB Race | |
| E | .017" | ||||||
Higher lift cams are available but welding build up of all 8-cam lobes is required as well as complete motor specifications.
All Valve clearances should be set "HOT"
Send your camshaft core direct to ELGIN RACING CAMS 53 Perry Street Redwood City CA. 94063. Tel. 650 364 2187 Fax. 650 364 2268.
Valve Spring sets are provided by British Automotive through part # 72-10 only.
NOTE: Part # 423-445 is single valve spring set only. We highly recommend that dual valve spring sets be used for all camshaft applications.
We have found that the stock 1.5" HS4 & HIF4 SU carburetors to more than adequate through part # 70-10. Metering needle, damper spring and air filter changes may be required. See technical article MGB19 for further information.