big block oilcooled gsxr750 motors

[03gixxerpilot]

DC i will try to remember to look tomorrow for you, also bear in mind that the later long stork (90-91) models had much stronger rods than the early ones, even thought they are pretty much the same rods.

there is a way to easerly tell the diffrence but i will have to look at the rods again to remember what it is.

Cheers Clive

[DCRacing]

Thanks Clive, Let me know when you get a chance.

I have decided to go bigger than when i first looked at the project. Sort of going down the path that Dynomutt has suggested. When i first looked at it I was talking to Joe Marshall and he suggested the Busa pistons and 1127 sleeves in the 750 cases and 1100 cams. He reckoned use the CRF250 valves, as they were the same size and better/lighter.

I probably would look at sorting the bottom end like Dynomutt suggests, probably not quite as far tho.

[03gixxerpilot]

ok will do,the main thing i am trying to achieve with mine is to build it with as many of the shelf parts as possible so for me the big priority is stock parts and minimise the amount of machining etc,

will proberly go for high proformance stuff a bit later but want to build it with as many stock parts as possible.

[Dynomutt]

You'll need to use a shortstroke block to resleeve as the 750 longstroke block hasn't got enough material to machine out for the larger liners, if you use the shortstroke block then you can use the shortstroke head which already has the larger valves. You will need to reduce the dish on the pistons I removed just shy of 1mm from mine, and also remove a load of the head as well, if you take another 1mm from the head then you still end up with around 9.5 to 1 compression same as a B12, which for my purposes is fine as I'm turboing it, you could get a set of 08 onwards high compression Busa pistons from JE or Wiseco, stock 81mm bore which would help get the compression up into double figures. The biggest part though is the rods, stock rods will fail as they cant handle the increased weight and stress of the larger pistons. Carrillo will make them as a special order, but they are no longer an "on the shelf" item

[03gixxerpilot]

Q. what is the weight of a standard busa piston.
Also what is the weight of a Carrillo rod.

Clive

[DCRacing]

I did have all the figures on the piston weight, i know they are somewhere safe......
I will give Joe a ring and see if i can get the specs from him, as he is the one who had a lot of this data
As far as the rod weight, i am not sure.

[Dynomutt]

Dunno I'll weigh the rods and check. One thing though the rods I have are all within 0.1g of each other. I can't remeber the piston weight, and I can't weigh them yet as they are still with the chap doing the boring work.I had 0.75mm shaved from the piston crown to reduce the dish, and raise the compression up a little. The shortstroke block that I have resleeved allows me to use the shortstroke J/K head which has larger diameter valves than the longstroke. I'm having 1mm skimmed from the head, in total this should give me a compressio ratio of about 9.5 to 1 which will be fine for a low boost set up.
I'm still thinking about piano wiring the block, but I reckon I'll only do it if it needs it, as I'm only intending to run low boost anyway, so I'll see how it goes with a sprung steel gasket first.

[03gixxerpilot]

after a long spell away form this project, i have gotten of my ass and started work on it again.

i am not sure where i left of in the story of what i am doing and what i have done so far, and to be honest i couldn't be fucked reading through all the posts form the past.

So where i am at the moment...........
today i have assembled the bottom end of the motor, and boxed up the crankcases complete with an 1100 gear box in it... just because i could, yes yes i know it is a 5 speed rather than a 6 speed, but just wanted to see if i could do it.

spacer plates will be ready on monday, so hopefully next weekend i can get the pistons and barrels etc together and check deck heights etc, through the week i will cc the three heads i have put aside for the project, all of which will have differing combustion chamber capacity, they are a standard 750 short stroke (dot) head, a standard 1127 head, and a 1127 head of a race motor, (head was preped by Stone Brothers Racing)
i will also have to work out the cc above the piston crown and below the crown so that i can get an accurate compression ration when i do all the working out.
Hope to have some more progress for you next week :-)

Cheers Clive

[Dynomutt]

The volumes of the heads differ by about 4cc, the 750 DOT head is nominally 22cc volume, and the 11/12 heads are nominally 26cc, although it needs to be measured accurately as they differ quite a lot.
On my 1003cc motor build I'm using the DOT head, with a zero decked block, 1 base gasket and one MLS head gasket gives a squish of 0.95mm.
With 30 thou' skimmed off the piston and the DOT head gives 9.0-1 C/R, with the 11 head it would drop it to around 8-1 C/R
I'm not too bothered about a high C/R as I'm using a turbo on my motor.

[03gixxerpilot]

i am very particular about getting things right, and since i am using non Suzuki pistons with a different shaped dome on the piston, i will want to get the exact measurment for each combustion chamber of the head that i use, your info on the approx volumes is greatly appricated as this will allow me to calculate at aprox CR that i will get for each different head. i still got to work out how much volume the dome is going to take out of the volume of the combustion chamber, but i will get to that later this week i hope.

[03gixxerpilot]

got the spacer plates today, but unfortuanatly wont have time this weekend to do any more work on the motor, but will be onto it again following weekend