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MG MGA - Valve springs
|My engine is from an Austin A60, and I'm upgrading it to 1622, as far as possible. The head is 1600, casting IH967, but has single valve springs. I have 2 options -stay single or convert to double. I'd welcome any opinions on this, as well as any possible help getting the proper hardware to match the double springs if I go that way. I see that later MGB heads only have single springs. Note I'm not planning to race this engine, just normal road use, eventually.|
|Single springs were used on engines of lesser tuning level, smaller valves, smaller ports, smaller carbs, milder cam. For the higher tuned engines MGA and early MGB always had double valve springs. MGB switched to single valve springs with the 18V engine in 1972, which did have larger valves, but this was also accompanied by other changes to lighter tappets and single row timing chain.|
If you are converting this engine to MGA specification, and especially if you intend to do any spirited driving at all, I would recommend installing dual valve springs and double row timing chain.
|Barney, the engine has duplex chain. Not sure why this is relevant. The valves are standard 1600 size. The cam has a lower lift (.31" at the valve) than the A. Presumably the single springs are good for the peak rpm of the A60, but the A went a bit higher, and I will install a standard A camshaft. The carbs are from the 1600. I think the PPO blew the original engine and replaced it with a long block A60.|
|I suppose the single row timing chain in 1972 was simply a cost reduction item. It was accompanied by use of lighter tappets and single valve springs which would lighten the load on the cam drive. |
For engines with long years of use and high mileage, tooth wear on timing sprockets is "significant" (to put it mildly), and timing chains "stretch" and they wear (changing cam timing a little). You can install a new timing chain to correct most of it. When the sprocket teeth get sharp enough to cut your finger tips its time to change the sprockets as well. When I see dual row sprockets worn that bad, I can't think of any reason to use single row other than short term cost reduction for original production.
|I just figured out the conversion cost to go double springs using VB 2005 catalogue - $138, most of which is for the guide shrouds, plus I'm not sure which double springs to order - the 1500/1600 or the 1622 (my head casting is 1600). So I've decided to restore as is (clean up and lap the existing valves. If I find they float at the rpm I will be driving, I'll either convert then, or probably better still find a 1622 or early B head with the bigger valves. So I'll order the HC pistons for that eventuality (large chambers). The current piston are (or were) dished.|
Is there any critical measurement of the sprocket teeth to determine wear? Eg fitting a certain drill shaft into the teeth as a radius gauge?
This thread was discussed between 06/01/2009 and 08/01/2009
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