Oversized Valves

[cintidude04]

Anyone have any information on oversized valves.
Trying to research if they might be worthwhile on an engine over-bored, with aggressive road race cams, that's been ported with a valve job, and had an efi swap.

Just haven't found much useful information on them as of yet.

[Mojoe]

the valves in my V&H engine that I sold a while back had over size valves. I can't remember how much over, though.

the only time I would consider going over is if I had extensive modding done to the engine, such as a big bore kit, race cams...and at least 38mm carbs, preferably 40mm.

larger valves aren't totally necessary, but for sure they will help the engine breathe better.

[cintidude04]

So for the engine I was speaking of it is not a necessary thing obviously, but could be a good idea. I was thinking either .5mm or 1mm oversized valves.

Thankyou for the input Mojoe. Also do you know what type of intake boots I could use to fit a 38 or 40mm throttlebody. I dont know of any oil boilers that used carbs that large.

[arsenic]

A lot of oil cooled GSXR 750's used 38mm carbs. When you say 40mm carbs, you know that's the ID right? I have RS40's on a GSXR 1127 engine and the stock intake boots work fine.

[cintidude04]

Yes I am aware it is the ID. We've had enough conversations about RS carbs that it was a given in my mind.
Cool, thankyou Arsenic. Somehow I was under the impression the 1127 used 36mm because a friend is using 750 carbs on an 1127, but that could be because it was a GSXF instead of a GSXR I suppose.

[arsenic]

Are you talking about Cheriff (Tom)? Cause I sold him those 36mm carbs. Thay also have a Factory Pro jet kit and I included 37.5 pilot jets. The 90-92 GSXR 750 used 38mm carbs. The GSXR 1127 DOES use 36mm carbs, but that a 36mm ID. The OD is 42mm. When you use a bigger ID carb, the OD is the same. Example, the pre 98 Katana. The 600 uses 33mm carbs, the 750 uses 36mm carbs. But the OD on both is 42mm.

[cintidude04]

I was referring to MD86.
So if say I were to use a set of 01-03 GSXR 600 throttle bodies with an OD of 38mm, the GSXR 750 90-92 intake boots would be a good fit.
Edit. My appologies, just double checked, the OD is 44mm.

[arsenic]

The 1mm in diameter bigger than 42mm. Just use WD-40.

[cintidude04]

Works for me.
Now back to valves, any views on those Chris? If I don't respond right away it is because Im heading into work now.

[arsenic]

I didn't use oversized valves on either engine. The dream engine is over bored to 813 and the 1127 is over bored to 1216. I did use a 750 head on the dream engine and valves are back cut with a 30 degree angle. I haven't done any work to the 1127 yet. I'm just gonna send that to Sin and let him do his thing. I don't have any idea if he's planning to use oversized valves.

[scottynoface]

Talk to kibblewhite and see what they say.

[cintidude04]

Scotty. Who is kibblewhite? And what would be the best way to contact them, ie. Webite with contact info. I was planning on having ape racing take care of the valve and porting work and web cams hardweld the cams. Unless y'all can suggest better (less expensive but as good quality) company's or persons to get in contact with about it.

[arsenic]

APE will recommend over sized valve for sure.

[scottynoface]

http://www.kpmivalvetrain.com/

They specialize in ultra high performance valvetrains...

650-359-4704

[arsenic]

I can tell you, no matter how much you mod a Katana motor. It's never going to be "ultra high performance".