Big Valving a GS1100 4V

[Silvermachine81]

O.k,

Who has gone 1mm oversive on an 1100 head and was it worth it?

I'm thinking of maybe going 28.5mm/24mm or 28mm/24mm soon and need to know if its worthwhile.
I have NO valves for this head so need to buy some anyway :wink:

The bike will have 36mm VM's, 348 grind web cams, wiseco 1134 kit (10.25/1), 4into1 etc, dyna ignition/coils......

Also, Will the bigger valves make it perform like an 1150 head?
I know the 1150 heads flow better.
Is it just valve sizes or are the ports a better/bigger design?

Any feedback would be great

 

[rosco15]

The ports on the 1150 head are way bigger. The valves are also bigger on the 1150 head. 1150 Is the way to go.

 

[Silvermachine81]

The ports on the 1150 head are way bigger. The valves are also bigger on the 1150 head. 1150 Is the way to go.

I've been looking for an 1150 head for years and cant find one (Im not in the US).
This is my only option which is why I want to know if its worthwhile.
Ive seen some bikes with stock valves put out some good power before but I had heard that larger valves make an engine run better everywhere :?:

 

[rosco15]

I bought 2 off ebay over the winter for around $275. THere is one on ebay right now. I had an 1100 head with +1mm stainless valves in it 325 lift megacycle cams. Slight porting. Ran a best of 10.11 @129. I ran almost that fast with the stock valves. I took those valves and put then into an 1150 head. No porting, but I switched to a set of 348 lift web cams. So far I've been 9.77 @135. Big power difference.

A friend of mine had a ported 1100 head with stock valves in a dragbike. He used to run in the 8.90's with it. He switched to an 1150 head last year with slightly more cam and now he's running 8.60's.

Check ebay and see if someone you think you can trust will ship to you from canada or the us. I sent out a big block by boat about 2 years ago. Took weeks and weeks, but he finally got it.

Here is one on ebay that is missing some parts. Something about the intake doesn't look right to me.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4556326225&category=35595

Here is an entire 1150 motor for $500
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4556777149&category=35595

 

[Silvermachine81]

Thanks for your help

I'm in New Zealand so the shipping would be horendous
Ive brought some lightweight guitar stuff in before and the freight just kills it.

This head is brand new (like in the plastic and original box) so I have to do something with it which is why I though 28/24 or just max it.

I searched the archives yesterday and found the post where you said the times werent much better with the big valve job
Bet that pissed you off.

I think you mentioned though that there was more power after the first 100 feet or so? Sounds like that didnt help your times much but there definitely was a gain :?:

My other problem is that as this is a 'street bike' and also an ultra rare Wire Wheel model, I have to keep it looking original or feel the rath of those "You destroyed a classic" clowns out there

 

[rosco15]

Stock head make like 128 hp. Bigger valves was roughly 132 or so. It reved quicker and picked up a little mph. Dont get me wrong. It made a difference, but the switch to the 1150 head made a huge difference. I just wish I had put a 1260 kit in it. Maybe that would be the better route for you. Head work can be expensive. Put a low compression 1166 or 1260 kit in it. More grunt and still look stock from the outside.

 

[Silvermachine81]

Thanks again rosco

Youve basically answered my question.

Im presuming though that if I do this I will have to get the ports made bigger to accomodate the larger valves.
Ive got very little $$ right now so that may be the killer.

Maybe I should just stick to stock sizes :?:

 

[Dink]

I would stick with stock valve sizes in any street motor, careful porting is very possible at home, the heads on a GSX motor are pretty good , admittedly not as good as an 1150 one( I have both)but all it neds is a thorough decoking and tidying around the bowl area anyway.
Dink

 

[Silvermachine81]

But will I have to "Pocket Port" it if I do go larger, or just cut the valve seats bigger?

It just seems like if I have to buy 16 valves I might as well buy what's going to give me the best overall power.

I believe I read in some book ages ago that larger valves will improve power right across the board.

 

[rosco15]

You can go + 1mm by just cutting the seats. Any bigger and you have to replace the seats.

 

[Anonymous]

I have been 8.3s spraying a 28.5/24 ported 1100 head, on muscle it went 9.0s, 68" 700# package nobar street tire.

 

[Anonymous]

it can work well is my response, if that is all you have to work with. Have some one port it that knows what they are doing. I still have the head, I keep it around in the pile of parts that is gonna be a 1260 stock block katana streetfighter someday.

 

[Silvermachine81]

I have been 8.3s spraying a 28.5/24 ported 1100 head, on muscle it went 9.0s, 68" 700# package nobar street tire.

That sounds interesting, Thanks Man.

The biggest problem for me is that weve just had a Baby and suddenly all those things you'd like (like maybe an 1150 head) kinda become out of reach.

I mean this is a brand new head and ive kinda gone off the whole revvin the arse outta the thing to get any power buzz.
I kinda like how it use to be such a useable powercurve when stock.
I just want more all over than stock.

Thats why I thought just put in the bigger valves and leave it with the mods its already got.
Porting always seem to help the top end IMHO which is not what im after anymore.

I want tirespinning nasty power not wheelstands at 7000rpm.

What was your experience of how the powercurve changed after you'd done the big valve job?

 

[GER144]

If you are on a tight budget, leave the stock valves in the 1100 head, but get the ports cleaned up by someone who knows what they are doing, get a good valve job, and some small cams like G3's with good springs.

A ported/cleaned up stock-valve 1150 head will work good too, just remember you will need the cyl. studs for an 1150 also. But if you are wanting the engine to look original, leave the 1100 head on it.

I have a nice 1100 head that works real well. It is a 28.5/24 valve head, epoxy ported, I used to run G3 cams in it, now I run the G7/G9 combo. At usually around 4000 ft. altitude, I would run 9.40's/140+ with a low-compression 1133cc engine. With my big hi-compression 1428, I went 8.80's at 153+mph. This head cost me a pile of money back when I had it done in 1996, but I have always been happy with the performance.

 

[Anonymous]

It was a ground up build, 1428 cc, G7/G9, 40 mikunis, tons of torque. dont have anything to compare it to, MPHed about the same as my 180 hp "stock " busa.

 

[displaced]

what are you fellas using for rear tires/tyres????

 

[GER144]

I use Metzeler's on just about all my bikes. Metzeler's hook up good. There are many others too. If you have a wide rim (17x6) Shink 003's are great if you have power and want good hook.
On the dragstrip I was using a Mickey-Thompson 26x10-15" out back.

 

[Guest]

Both the 1100 and 1150 heads are woefully under valved.

As an example, the largest valve you can put in these heads using the stock valve location is 31mm intake. A stock hayabusa has 33 mm.

Motors are basically air pumps. The more air you can get in and out, the more power you can make. Knowing that, is is plain to see why all of the newer bikes make way more power.

At the minimum, 1.5 over intakes and 1mm over exhaust should be used for any kind of high performance street bike. This can be done without changing the seats. The 1100 can take 28.5mm intake. The 1150 29.5mm.

Jay