Re: Downloads! Service Manuals, Parts Diagrams, Magazine Scans, etc.
This is thanks to Peter Smith, it is quoted from another site:
I've been researching different engine combos and have accumilated some info I'd thought I'd share. Here's some interesting data I got from the folks over at cycle concepts, I'll post some info I've found on the 750 in another thread:
Dwayne and I have been racing GSXRs for over 10 years now, and we have seen and tried it all. So believe me when I say that the head is the very first place you should spend money, even before pistons.
I will give you some example numbers from a personal street bike that we did a bunch of experiments with several years ago. The bike had 40mm Mikuni flatslides, a full Race-only Yosh exhaust, and a Dyna 2000 ignition
Stock 1127 engine with degreed cams, 750(oversize) carb boots, Mikunis: 130hp
Stock 1127 pistons with a full port job and 30mm intake/26mm exhaust valves, stock cams: 154hp
1216 Wiseco pistons with the same head/cam combo: 161hp
1216 Wiseco pistons, same head with .380" lift cams: 169hp
1277 JE pistons, head shaved to increase compression, same head and cams 180hp, sidewinder exhaust
1277, same engine except for .425" intake cam: 182hp
1277 same engine, except for oversize intake seats, 31mm intake valves, and the head slightly reported to take advantage of the larger valves: 190hp
As you can see, the oversized valves and port job were worth 24hp alone. It took 5mm oversize pistons, oversize sleeves, bored cases, huge cams and a sidewinder exhaust to exceed that level of power increase.
If you add in the gain from the 31mm intake valves, and you have a total power gain of 30hp from just the head!
To put it in perspective, I have seen 1340 big blocks with ported stock-valve heads that barely broke 150hp. That same engine, with a stock head, only made about 144hp.
Also, I would stay away from the slingshot head, unless you are going all-out with a serious engine. The carb boots for the Slingshot head are only made for 36mm carbs. The oversize boots from the 90-92 750s are made for factory 38mm carbs, and are way bigger, and allow for a straighter port design. The problem is, the 90-92 boots don't fit the Slingshot head. They bolt up,but they are about 3/8" too low, so they actually hurt airflow. Plus, the raised ports on the Slingshot head put the carbs so high that they hit the frame in an 1100 chassis.
Also, the Slingshot head has such a small combustion chamber that the piston domes must be hand-fitted or the engine won't even turn through. And the valve pockets must be cut deeper in the pistons to accommodate a Slingshot head as well.
The best head to use, unless you are building a high-dollar race head with weld-on spigots, is the 91-92 1100 head. It has a nice raised floor entry into the short-side radius on the intake side, and is worth 4-6hp over the 86-90 1100 head. And the big carb boots bolt up perfectly.
Now if you want a 33mm intake valved, offset-guide monster head, capable of over 210hp with a stock crank, then the Slingshot head is the way to go. That what Dwaynes brother TJ has on his Heavy Hitter bike.
ok...with you being on a budget there are a few things you could...
1. 1277 cc kit...makes great power and extremely reliable.
2. i would recommend rods but if you can't get that in your the watercool rods are the next best thing...with these rods you can spray it up to 80hp...the key to this is timing control...i recommend the prostreet 2 box...this will give you all the room for your future expansion to the engine and nitrous...
3. undercut the stock tranny
4. mtc lock up
5. start with a slingshot head...oversize intake/exhaust valves, springs/retainers and cams to accomadate the raised compression/nitrous...
'92 750 Liquid, Full Hindle Comp Plus System, Stage 2 Jets, Vortex Rear Sets, K&N Filter, Gold DID X-Ring 525, Galfer SS Front Lines, Full Custom Paint
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Mike, you will ride hard forever. RIP
RIP Rob, proud to have known you.