There has not been a lot written in any detail about modifying Lotus Twincam engines since the 1970s, and even back then, information was scarce, so I decided to try to document my learnings from building and modifying many Lotus Twincams from the early 1980s to now in 2024.

The bible on twin cam engines is “Lotus Twincam Engine,” written by Miles Wilkins in 1988. It is focused on the standard engines and gives little technical detail around the many modifications done to these engines in the search for more power, but it is a crucial resource for anyone working on rebuilding these engines in standard or modified form.

Only two significant reference sources were available that dealt with engine modification in detail when I started modifying the engines.

• The Dave Bean catalog in the engine section has an extensive write-up on modifications. This is still available in hard copy form from Dave Bean Engineering
• Tuning Twincam Fords by David Vizard was published in 1969 and can generally be found online.

You could also deduce some of what people were doing from the parts catalogs of places like QED. However, most of the people selling parts for modified engines, apart from Dave Bean, did not provide much information on their use or the overall design of their modified engines.

Not much has been written since in any comprehensive, technical, or engineering way. However, there are plenty of references on the Internet if you do a Google search, and I have attached a reference list at the end of this document. However, most of these internet articles have little reliable technical information.

Modified parts availability is continually changing, so while I will discuss various parts from various suppliers based on what I have used, you always need to check if they are still being made and available. The accuracy of many replacement parts is also often variable, so they all need to be carefully checked. I always keep the original parts I am removing as it makes checking new parts easier if you have a good comparison with a part that you know fits.

I am sure people will have other approaches, and it is not possible to cover every possible modified engine variation that may have been done. I am sure that people may disagree with what I describe here. My writings are primarily based on what I do and why from what I have learned, and they may differ from other’s experiences. Every modification item needs to be considered in the context of the overall engine build and the intended engine use, the quality of the specific parts used, and the quality of the machining and assembly work. So, there are no guarantees whether the advice given here will work as intended on your specific build.

I have included a lot of history in this document, as I hope it interests you. It is a valuable source of information on what has been done in the past and why It's essential to understand precisely what you have and its suitability before you start modifying a particular engine or building an engine from a set of modified components.

The document is intended as a general guide to the range of modifications possible and some of the issues and outcomes when doing these. It is impossible to cover all possible combinations of modifications or all the potential problems and outcomes, but I have tried to cover all the common combinations.

The final chapters in part 2 on rebuilding a modified Twincam are based on a build I did in 2020 of one of my competition engines. Hopefully, this adds to some of what is described in the Wilkins book about building these engines.

Rohan Hodges

File:Lotus Twincam Modification Feb 2024.pdf