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Discussion Starter · #1 ·
I've been looking into a big valve head for my grudge busa. I've also had multiple ppl tell me it's a waste of time because they tend to drop valves like hot cakes. On the flip side, also heard that a big valve head is the way to go. Any insight on this will be greatly appreciated!
 

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Never heard of any done right that drop valves. They usually don't make more power unless you are over 1550cc.
 

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Discussion Starter · #3 ·
I know a guy that had two done by bob and both dropped a valve. I feel what u saying tho, preesh8 the info man
 

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Head work will almost always make a difference. But I've never heard of anyone hurt valves from a oversize. I would trust bills heads from port tech 100%. If they were using shitty valves that could have been the issue. Or bad craftsmanship could b the cause. But u don't know how much abuse the owner of that head was inflicting on it either so u can't blame the head when it was probably the the person kicking the mule.
 

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every engine builder that ports their own heads,,,,,,,,,,
have found what works for them from their R&D
as jay stated larger cubes or large input meaning nitrous/forced
plays a factor to what that porter has found worked for them,,,,,
some like large ports ,,,smaller id in the seat with smaller valves,,,,,,
some like the larger id with smaller runners,,,,unschrouding and reshaping combustion chamber,,,,
theres lots of ways to make flow and keep the air speed up for atomization with any of these or mixture of,,,,
as far as dropping valves,,,,oem or enlarged all drop,,,
if valve is defective,bad clearances,bad tune,wrong fuel,,pre ignition,,,coil binding,bad cut seats,ect
 

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have seen big valve heads bolted onto an already built bottom end, pistons hadn't been cut for more clearance, ended up a real mess !
 

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The worst i've heard is that oversized valves aren't worth doing if you're not going in the motor regularly for maintenance because they require relatively constant valve adjustment.
 

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I was at Bobs today and saw a head that he has done for the big boy stuff, it was for a 1630 that he did and had big valves new bronze seats and a really cool intake port, he machined off the port, then added a billet block of Aluminum, re ported the intake port he claimes smaller in diameter than oe but the intake runner is made shorter than OEM. that helps with Port velocity, through the bigger valves and with his cam profile.
now on a 1630 race only with this head he said 300rwhp is capable.
i know he did say the new valves are big bucks as they were titanium, and all kinds of goodies.
this was a Gen 2 head
it reminded me of a GS1150 pro stock head with intake all epoxied and huge, but without the huge
OH also he said the head needs his huge exhaust port and pipe, pretty wild stuff.
Bob seems to have it figured out, Brett
 

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The worst i've heard is that oversized valves aren't worth doing if you're not going in the motor regularly for maintenance because they require relatively constant valve adjustment.
And why would that be?
 
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