650 head or 750 head?

yeah! wireman is semi retired now and he needs more holes in his head,i mean more projects :woohoo:as long as it keeps me out of the bedroom the wife is all for it!:whistle:

Post edited by: wireman, at: 2006/03/03 23:08

Hey dnestell-Check your u2u messages.
Cheers-Colin Firth-Ontario Canada

Help me here ? a 810 kit will give what compression ratio ? 10-1 ? I am guessing here .. So what will the 650 head on the 750 bring ? Also why would you need to slot the cam gears ? .060 off a head ? Is your bike for racing ? as you can not get pump gas atleast not here any higher 94 octane .. Racing gas is 100 ? I think ??:whistle:

it depends on what pistons you use and cc's of chambers ,what headgasket you use etc.the smaller ports tend to be more responsive for streetbike motor,dont start carving on them too much.

The 810cc kit from wiseco (k810) will give a compresion ratio of 10.25-1 using a stock 750 head, if you use a 650 head with smaller combustion chambers, it will be higher (I'm not sure on the exact number, maybe 10.5-1 or even as high as 11-1, but it can be calculated) if the 650 head is used on the 810 kit without being milled, it should be fine running on supreme/premium (highest form of pump gas you get) You need to slot cam gears if you mill the head down to increase compression(on any head). Why? Because it affects the timing of the valves opening and closing, and that needs to be adjusted to make the bike work properly. It seems pretty complex to me, and I would want an expirienced engine builder to do it.
My bike will be mainly for street use, and every other weekend in summer I'll be drag racing at a local track (bracket racing just for fun)
Race gas comes in many levels of octane, My uncles 1982 drag corvette with a 548ci big block runs on 114 and has to run 116 when he uses NOS:evil: (just over 900 HP with the motor, and add 500 more HP with NOS) (anyone want me to post some more specs of the vette in chit chat?)
Scott

77KZ650 wrote:
(anyone want me to post some more specs of the vette in chit chat?)
Scott[/quote]

Please do! Insane HP bottle fed Corvettes are great :laugh:

yes bring on the pictures we like poked and stroked big fat rat motors!

A few thousands off a head will change the timing chain that much ?? Wireman you want to hop in here ?

if you take just enough to clean up the head it shouldnt be a problem,start taking big cuts then you have problems because the links on the timing chain are a certain length rather than making a differant chain and crank and cam gears its standard practice to cheat by slotting holes in cam gear with a rat tail file and rotating cam gear to bring things back into whack.this can also be used to advance or retard camshafts in motors without milled heads,which really gets complicated i think ill let APE JAY or one of the technical types explain how to do the cam degreeing process.

so how high can you go on compression before 87 starts to detonate?

Daily drivers want to know!

start gettind much over 10.25:1 you start needing good gas or you need to pull way back on ignition which causes overheating:whistle: good luck happy wrenching

If you want to install 750 valves on a 650 head then you are going to have to grind the valves seats larger as the 750 valves have a larger head. If you don't make the parts larger to match the larger valves then you are just wasting your time and money installing the larger valves.
.030-.035 is about the maximum that can be cut off the 750 head, any more than that and you are cutting into the valve seats.

The GPz750 motor I am assembling right now has had the head cut .025, if I remember I'll install the cam sprockets in the stock position and see how much the cam timing is advanced, or if I get bored I might measure the diameter of the cam sprocket and calculate the degrees of advance caused by .025 movement at the circumerence.