SOHC 3/8" Model 30\40 (and 30M/40m Manx Type) Exhaust Guide - Each

Product no.: 0303 A11/138B

In stock

£23.00
Recommended Retail Price, plus delivery


These high quality SOHC Exhaust valve guides are made to the original dimensions of SOHC Norton valve guides - with the exhaust guide on SOHC engines a bigger outer diameter, bored to take a 3/8" exhaust valve (the inlet guide on SOHC heads are to take  11/32" valves - see Item 0301).

The guide includes the important oilway from the cambox feed, which has a small countersunk face to allow for a better tolerence when fitting them. 

The exhaust guide design shown here employs the same style of collare as our iinlet guides - which are designed to take the standard Norton International 30\/30M (and 40\/40M) inlet valve spring hairpin valve spring holder collar, which we also sell - item 0318. This slides over the top face of the guide and provides a mount for Hairpin Valve Springs (which we also offer). 

Background Information: It should be noted that the original Norton Internationsl Exhaust Guide/Spring Holder design was to cast in bronze a single large casting - where the guide also included the top piece to hold the springs.  It is not entirely clear why Norton employed this design (although maybe it was to give slightly better heat dissipation) - but these have not been available since Norton last cast them - and to make this design nowdays would be commercially unviable, hence - using this guide design, and fitting one of our Hairpin valve sping collars (Item 0318) is a more practical solution - particularly as most original SOHC single piece exhaust guide/spring holder castings are completely worn out!.

This type of Valve guide should fit all SOHC models where a 3/8" valve stem valve was employed - with both Cast Iron, Bi-metal (bronze skull and alloy fins), and fully alloy heads.  It should fit both round fin and square fin heads (i.e. early Manx).

These guides are CNC machined with the original dimensions - includig the original interference fit tolerance on the outer diameter.  As per normal practice - cylinder heads should be warmed to allow for easier removal of old guides and fitting of new (and we recommend putting guides in a freezer for at least 10 mins before fitting, to help with this).

Price is per single guide. 

Update April 2023:  A new batch of these now in stock.  Please note - the price of Phospher Bronze has risen hugely in the last 3 years since our last batch - but we have tried to stay close to the previous price.

Please note: The original Norton International exhaust valve guide and top collar was a single piece casting, as shown in the 2nd photgraph. The reason for this is unclear, although it seems most likely that it was to increase heat dissipation from the hot valve guide. The cost for making this type of guide today would make it prohibitively expensive - and frankly, unnescessary. Therefore these guides are made as per the inlet guide, to take a seperate valve spring collar (which I can also supply - Item 0318). Price is per single guide.

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