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Author Topic: 7mm valves  (Read 2591 times)

Offline gazareth

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7mm valves
« on: 25 August 2013, 15:13 »
hey guys. does anyone know if there is any gains to be had by fitting the agg 7mm valves into the pb cylinder head?
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Offline gazareth

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Re: 7mm valves
« Reply #1 on: 26 August 2013, 18:41 »
anyone??? :undecided:
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Offline Gambit

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Re: 7mm valves
« Reply #2 on: 26 August 2013, 22:46 »
Waste of time
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Offline danny_p

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Re: 7mm valves
« Reply #3 on: 27 August 2013, 00:11 »
smaller stem size will increase port area avalible to flow

some minor gain,  worth it probaly not, used to just machene back the stem a bit.

valve head itself is the problem when it comes to airflow 
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Offline gazareth

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Re: 7mm valves
« Reply #4 on: 27 August 2013, 00:13 »
I don't suppose it would be worth stripping down just to convert it. but if it was needing guides done anyway it would be same amount off work to change to 7mm stems. and both types of guides cost the same.
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Offline danny_p

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Re: 7mm valves
« Reply #5 on: 01 September 2013, 13:02 »
looked at the price of valves yet ?

the cheepest, quickest and singel biggest power gain you will get from that cylinder head is to have the valves and seats tri cut.   end off

all the flow problems are where the air has to turn the corner then get between the valve seat and valve head, i would proably be modifying the sd valves rather than replaceing them but more likly to be changes to the back of te valve rather than stem to start with

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Offline gazareth

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Re: 7mm valves
« Reply #6 on: 01 September 2013, 13:32 »
I have a set of low mileage 7mm valves already. also have the springs/collets and retainers which need to be changed to. yeah I might just get some head work priced up. got 2 spare heads anyway so car wont be disabled for any length of time.
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Offline danny_p

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Re: 7mm valves
« Reply #7 on: 01 September 2013, 13:41 »
well if thevalves are there it would be rude not to,      still get them and the seats tri cut   it would be rude not to
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Offline gazareth

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Re: 7mm valves
« Reply #8 on: 01 September 2013, 16:47 »
very true. only problem is the 7mm inlet valves are .5mm longer than the 8mm pb 1s so when the seats are cut it could be pretty close to binding up the hydraulic tappets. I will have to do some careful measuring first or just get the valve tip ground down a touch.
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VW BUSH

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Re: 7mm valves
« Reply #9 on: 01 September 2013, 20:33 »
Quote from: gazareth on 01 September 2013, 16:47
very true. only problem is the 7mm inlet valves are .5mm longer than the 8mm pb 1s so when the seats are cut it could be pretty close to binding up the hydraulic tappets. I will have to do some careful measuring first or just get the valve tip ground down a touch.
Careful they are not case hardened could leave the tops a bit soft if you take too much off. Suggest you get them all done on a cylindrical grinder to the same length over the set +0 - 0.005 on the correct items
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