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Need Advice - What Valves And Seats Are Right For Me?

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#1 BaronVonchesto

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Posted 19 April 2018 - 06:09 AM

Hi all,

 

My mini is a 1976 998cc series A engine (unmodified). If you followed my previous posts you would know that I've been having engine troubles. I've gotten that sorted but its still not running as well I think it should (though its very driveable).

 

With the engine idling I can hear hear occasional and irregular "poof" sounds coming from the exhaust. I suspect the valves are leaking a bit, and I'm considering doing a top overhaul.

 

If i have the cylinder head taken out I might as well change the valve and valve seats since this engine (to my knowledge) has never been opened.

 

I'm looking for recommendations on what valve and valve seats I should get to maximise my returns. I know that typically for road cars one just gets standard valve and seats. I also know that David Vizard recommends getting 30 degree valves and seats to improve the flow and performance of the engine.

 

Unfortunately here in Malaysia I dont think cutting or machining down valves/seats is much of an option (i dont have the knowledge & equipment, and i'm not sure anybody here really does).

 

So can I get recommendations for valves and seats to get for my Mini please?



#2 timmy850

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Posted 19 April 2018 - 06:38 AM

If your engine has never been rebuilt you won't have unleaded valve seats installed. If you want them to be fitted they'll have to cut the head and then insert the new seats. This isn't really a performance upgrade, unless you install larger vales and get some porting work done.

 

You can get a leakdown test done to test if the valves are sealing well prior to removing it 



#3 BaronVonchesto

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Posted 19 April 2018 - 07:16 AM

i've never found any literature to concretely state the need for hardened seats for unleaded petrol



#4 nicklouse

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Posted 19 April 2018 - 07:45 AM

i've never found any literature to concretely state the need for hardened seats for unleaded petrol

it is fact you need them or you will burn the exhaust valve seat out and get seat recession. the seat burning away.



#5 Spider

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Posted 19 April 2018 - 07:46 AM

Hi all,

 

My mini is a 1976 998cc series A engine (unmodified). If you followed my previous posts you would know that I've been having engine troubles. I've gotten that sorted but its still not running as well I think it should (though its very driveable).

 

With the engine idling I can hear hear occasional and irregular "poof" sounds coming from the exhaust. I suspect the valves are leaking a bit, and I'm considering doing a top overhaul.

 

If i have the cylinder head taken out I might as well change the valve and valve seats since this engine (to my knowledge) has never been opened.

 

I'm looking for recommendations on what valve and valve seats I should get to maximise my returns. I know that typically for road cars one just gets standard valve and seats. I also know that David Vizard recommends getting 30 degree valves and seats to improve the flow and performance of the engine.

 

Unfortunately here in Malaysia I dont think cutting or machining down valves/seats is much of an option (i dont have the knowledge & equipment, and i'm not sure anybody here really does).

 

So can I get recommendations for valves and seats to get for my Mini please?

 

If you have no local machining facilities, then your options really are very limited. Just about anything beyond a hand lap of the valves, you'll need machine work done.

 

A quick google for 'engine machining shops in Malaysia' brings up a few shops there and a few in Singapore.

 

Short of that, maybe an exchange head from the UK or elsewhere maybe an option.

 

Standard Valves will be fine for everything except maybe out and out racing.

 

i've never found any literature to concretely state the need for hardened seats for unleaded petrol

 

It's not a generally well understood phenomenon as to what happens and the need (or not) for them.

 

If all you'll be doing in an A Series is potter about, you'll likely not need them, however, generally, if you are going to sit on RPMs over about 3k for period, you should have them.

 

The factory fitted them in later years, and wouldn't do so if not needed.

 

Here's one from someone who thought they knew otherwise,,,

tJJ3YUY.jpg

 

 

 

 

For what it takes to fit them and the consequences of not doing so, I always fit them. It's a no brainer.



#6 Turbo Phil

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Posted 19 April 2018 - 08:20 AM

If you're looking at improving performance while the heads apart deshrouding the valves by opening the chamber out will give you a decent gain in flow, this is essential if you're contemplating fitting larger valves otherwise you're unlikely to see any gain at all as the shrouding is simply made worse. Unless you're looking to use 6,000+rpm on a regular basis the road spec valves will be fine, adding a simple 30degree back cut on these also improves flow dramatically.
Phil.





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