View single post by stevegarnjobst
 Posted: 11-27-2015 11:19 pm
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Joined: 10-22-2015
Location: Maplewood, Minnesota USA
Posts: 35
Esprit2 wrote:
...The early JH Mk I 907 did have the small ports, however, the later Mk II did get larger ports... the ones I believe are 1mm taller. Lotus produced the 907 through 1980, and late 907/ early 912 heads had ports that were larger yet. That may (??) be what Mike Taylor showed to you. The big port head will bolt right on.

I don't know enough about JH to know how far their 907's ports went down that evolutionary path. But the last of the JH engines were pretty much the same spec as the Lotus 907s of the day, with the exception of carbs and distributor advance curves. JH & Lotus Strombergs used different needles and tuning. JH used DHLA 40 Dellortos, while Lotus used the larger 45s.

Do you have pictures you can post of the two heads with small and large ports?

Tim Engel

I didn't take a photo of the J-H and Lotus heads side by side, but I can probably ask Mike for a shot or two. Mike says the larger port heads were the only ones used on Lotus cars, some of which were produced at the same time as later Mk II J-H's, so it's quite possible some of the Lotus-spec heads were used on the last J-H's. I'm not quite ready to buy a big port head yet, but the possibility is definitely intriguing.


Last edited on 11-27-2015 11:20 pm by stevegarnjobst