Our resident guru Keith looks at the procedure for sorting your cam timing with the engine still in the car.
If there is one question that always causes a good deal of questions and answers, it’s ‘what needle do I need for my carb to start with?’ The crucial information needed to make an educated guess at the needle spec required is the type of carb or carbs, cylinder head modifications if any, engine capacity and camshaft spec. The first three are often met and answered with certainty; though the head question often leads to an ‘it’s been modified but I don’t know how extensively’ follow up. The cams question is frequently answered with an ‘ it’s not standard, that’s all I know’. And of course, that almost inevitably means they have no idea if the camshaft was timed in correctly.
The carb is easy to identity from a picture. And a modified head can be identified by removing the carb and inlet should there be no give-away stampings on the head top face – at least you can see if the ports have been messed with using a mirror and a light. Capacity is impossible, but in itself is no big deal if not known. Not knowing the cam spec is a bind, though can be reasonably identified enough to give some working idea from the way the engine runs at idle. But, and a big but, is – if the cam has not been timed in correctly, even that can be misleading. It is therefore essential to find out, and sort it if not. At least then you stand a chance of getting an appropriate carb needle spec.
This is a first for me, explaining the procedure of checking cam timing while the engine is in the car. In over 20 years scribing for the magazine, I have no idea why it has taken me this long to get around to describing how it’s done, especially considering the volume of questions that require it being done in order to advise some essential information. It may have been because of the instruments and tools required. But with DTI (dial test indicator) gauges and stands now available for £20, the only other essential piece of equipment is a top dead centre (TDC) indicator. They have been hard to get a hold of, but I have managed to find a supply and am now selling them on my website (www.calverst.com). At £8 plus VAT it’s a cheap and very useful tool to have in your arsenal. And with last issue’s coverage of cam timing with no gauges, this seemed the opportune moment to get this out there.
It is possible to check cam timing even if your engine is still in place!