531 Bigger valves?

[rockheadrumble]

Hiya all,

I have a 531 head that is in need of a few valves guides so im considering putting bigger valves in seen as the seats may need cutting to match the new guides.

Can somebody please tell me what bigger valves are suitable for the 531 head using the original seat? And also if the biggervalves can use the original collets, retainers, springs, guides etc?

And what is a good size to put in keeping the flow on both sides close to an optimum % level. which i belive is around 80%.

Im fitting a stage 2 rsi cam that its said to rev reliable to 6800 using the original valve train on the 530 head. As i have the 531 head the springs are all ready bigger than the 530 head springs so I was also wondering if i fit bigger valves will the bigger 531 springs be suffice or shpould i double up?

Im not wanting to go crazy on the head, and not wanting to spend mega bucks, just help it flow a bit better as im wanting big power (350 ish). I have already ported the exhaust side although i realise itl need doing again if bigger valves are fitted.

thanks in advance.

Joe

[barkster1971]

You can get 38mm exhaust and 46mm inlet without too much faff. All the bigger ones I've seen are stainless steel so don't have the sodium in them to cool down the exhuast valves. Mr Smith has them in his head, ask him!
I was taking to a bloke who can do them for a decent price who said that you'll have to make sure everything it's 100%. I'd be tempted to run a bit of meth/ water injection to cool things off at high boost.

[crogthomas]

Originally Posted by rockheadrumble

Im fitting a stage 2 rsi cam that its said to rev reliable to 6800 using the original valve train on the 530 head. As i have the 531 head the springs are all ready bigger than the 530 head springs so I was also wondering if i fit bigger valves will the bigger 531 springs be suffice or shpould i double up?

The 530 springs are actually slightly stiffer than the 531 ones (~6%), they are also a little lighter (47g v 58g), so if you're staying with standard springs use the 530 ones would be my advice. And the matching retainers and seats of course.

[rockheadrumble]

hiya,

thanks for the info guys. iv sent smithy a pm on vpcuk but im still waiting for a reply.

im glad you've told me that about the springs, thanks mate.

anyone else out there have info on this?

joe

[rockheadrumble]

Hiya,

Iv found out i can use stainless steel exhaust valves for a pint engine, they are 38.1mm.

Im going to keep the inlet the same size as the 531 head flows a lot more on the inlet side already. Hopefully this set up will tighten the flow ratio between the inlet and exhaust.

Im just in need of uprated valve springs now.

Please can somebody please advise me where to get them.?

I have emailed RSI but they are absolutely useless in replying, I don't think they can be arsed with over seas orders. At check out they want $60 to ship a set of valve springs!

[crogthomas]

Might be worth looking at Pinto valve springs? I've no idea if they fit, but they look very close....

[barkster1971]

Kyrkmotorsport.se. has 46/38 mm race ventils ( bigger valves ) and the springs I think.

[rockheadrumble]

Hiya mate,

I think the diameter is slightly different, I did think about going down this route and buying the valve retainers as well but the cost is adding up.

Im going ring burton power tomorrow and and the spec of the springs.

thanks mate

joe