| ||||
| ||||
| Moderated by: Greg Fletcher |
|
||||||||||||||
| 907 engine tappets | Rate Topic |
| Author | Post |
|---|
| Posted: 09-18-2024 08:40 pm |
|
1st Post |
|
Jeff Kouski Member
|
It’s obvious that my 907 J-H engine has been opened up before. Does anyone know how to tell if the valve tappets have been upgraded to the better steel tappets instead of the old cast ones? Are there any identifying markings on them?
|
||||||||||||||
| |||||||||||||||
| Posted: 05-09-2025 08:27 pm |
|
2nd Post |
|
Esprit2 Member
|
Lotus OEM Tappet Thickness (Keep tolerances in mind and measure each one individually with a micrometer... just as you would a valve shim). LOTUS Chilled Cast Iron: (A or X)026E0024Z 0.218" thick crown / 22mm skirt Pre-1988, Twin Cam, 907, 911, 912 and early 910. LOTUS Steel: B920E0017Z 0.224" thick crown / 21mm skirt 1988 on, 912 HC Exhaust only, and 910 Intake & Exhaust. 1988-92 Esprit Service Notes (ie, Lotus Workshop Manual), Section EB Engine, Addendum 1: Two Liter '920' Turbo Engine, page 58: "Tappets: "Steel tappet buckets are used (previously cast iron), and will be communized on all 910 engines. Because the steel tappets have a 1mm shorter skirt (21mm Vs 22mm), they must "NOT" be used on engines with the high lift '104' cam (912HC), where the greater skirt length is needed to resist tappet rocking." Similarly, they must "NOT" be used with 107 cams that have the VERY AGGRESSIVE opening and closing ramps. *~*~*~*~*~*~* JAE aftermarket STEEL tappets: Hi-performance/ race upgrade tappets for the Lotus Twin Cam and 9XX Series engines. Available in 0.216", 0.200", 0.180" and 0.1401" thick crowns. All skirts are 23mm skirt. Garry Kemp Hi-Performance Engines (UK), aftermarket STEEL tappets: 0.220" thick crown / 23mm skirt = Near stock. 0.240" thick crown / 25mm skirt = Thick Crown for re-ground cams (smaller base circle requires thicker shims, crowns, or both). The above aftermarket tappets are both steel for strength and long-skirt for stability in the bore with more aggressive cams. Also, re-ground cams have a smaller base circle diameter, which requires the tappet to ride higher up out of it's bore. A longer skirt preserves the required bore engagement. Tappets have unique crown thicknesses, like valve shims. If you change tappets, then measure and consider each tappet's crown thickness just like you would the thickness of a valve shim. Include it in the "valve clearance" math. Regards, Tim Engel
|
|||||||||||||
| ||||||||||||||
| Current time is 07:50 pm | |
| > Jensen Healey & Jensen GT Tech > Engine & Transmission > 907 engine tappets | Top |
