Leaping Jaguar


Having read A Graham Bell and other various engine tuning books, I was gagging to have a go modifying the cylinder heads for better performance.

Excellent condition cams were kindly supplied by Chris Coleman were sent to Kent Cams to be re profiled as Race spec with 308 degrees duration, 49/79-79/49 @ 0.50", 105 degrees LBA, inlet 10.66mm lift, exhaust 10.61mm, overlapping of 98 degrees. Original figures are trademark Jaguar for its engines, with minor variations, 256 cams, 17/59-59/17.

Unfortunately, I did not notice some microscopic marks on the edge of the lobes, caused by a sharp object (grinding apparatus?) in the journal number 3, 4 and 5 as I trusted Kent Cams to do a sterling job, causing the cam to seize on start up and ruining number 4 cap.
Fortunately I had spare caps and cam carrier and was able to rebuild the head. I did contact Kent Cams, enclosing photos of the offending cam (RH) explaining the problem and to make them aware of this problem. I was not looking for a refund or compensation as I should have checked the cams with a loupe if necessary when it arrived, not a couple of year later. Still, they never dignified me with a reply.

I embarked on the long journey to gas flow the heads, using an air grinder with hardened steel die to remove the bulk of material, relying then of special flap wheels (conical and cylindrical) proper for this job, acquired from Demon Tweeks, finished off with abrasive sponge wheels to give a smooth, satin finish as polished surface causes a drop in suspension of the gas flowing, not promoting good charge velocity and turbulence. The inlet valve guided boss was completely removed as it is not detrimental to heat dissipation and gas velocity performance, on the exhaust side it was removed as much as possible without creating a too thin of a barrier with the water jacket and still providing decent support for the exhaust valve guide, promoting good heat dissipation in this critical area.

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