Big Bore Engine Upgrade

[nvmike24]

I am thinking of increasing the 1100's displacement. I saw the thread on the 82mm pistons from Hank Scott Racing. I am not sure I need to go that far. That being said, Speed costs, How Fast Can You Afford To GO? To all those who have taken the plunge what if anything would you do differently? Has anyone increased valve size as well? What carbs are being used? Just how much can the crank handle and still be reliable?

[JMR]

I am thinking of increasing the 1100's displacement. I saw the thread on the 82mm pistons from Hank Scott Racing. I am not sure I need to go that far. That being said, Speed costs, How Fast Can You Afford To GO? To all those who have taken the plunge what if anything would you do differently? Has anyone increased valve size as well? What carbs are being used? Just how much can the crank handle and still be reliable?

I'd recommend 1314cc for a real difference. 1219 doesn't do much at all. 1250 requires sleeve replacement so I'd just go to 1314. You will need a 1200 cylinder. OS valves work very well. RS carbs work well if you know how to tune carbs. I'd use 40's. The crank can handle any of that and more. You will need a clutch conversion kit. With cams and port work you get easily into the mid 150 HP range which makes for a pretty fun ride.
It is to bad the valve angle stinks on the FJ head as there would much more power with the same modifications.

[racerman_27410]

one thing you have to keep in mind when doing (or not doing valves) is that you change the position of the power.

big valves are nice when riding on the track where you are constantly in the big end... for street riding low and midrange torque is king and you get more of that by staying with the stock sizes. 

IMO the 1349cc kit is the way to go... i mean why go halfway when you can go all the way! 

i also had my crank lightened and IMO that really woke the engine up as far as responsiveness goes.

roll on power wheelies are good Kookaloo!   

[Brook]

....... that is so true,.........position of the power.

[Pat Conlon]

Big valves are no big deal in a FJ head. There is only so much room for larger valves.
We are only talking about 1mm increase on the intake valve and 1.5 mm increase on the exhaust valve.

I was going to leave my valves stock with my 1349 but Randy talked me into going with the bigger valves. I did need new valves anyway.
Randy explained it this way: "Look, you are increasing your displacement by 22.6% (1349/1098= 1.226) therefore on the intake stroke with the big 82mm pistons your air velocity will increase accordingly. If you go with bigger intake valves from 25mm dia. stock to the larger 26mm intake valves, that's only a 8% increase in valve opening area which is is no big deal. Your intake air velocity with the big pistons and big valves will still be much higher than stock."
"Why build a 1349 motor only to bottle neck it at the valves?"
"Same with the exhaust valves. Stock exhaust is 29mm and the larger valve is 30.5mm which is only a 10% gain in opening size, no biggie considering you are pushing 22.5% more exhaust gas out of the motor.."

"Besides", as Randy reminded me, "You need new valves anyway...."

"Now, make the check out to......"

Seriously folks, I am very happy with Randy's work. Very happy. I would do it again in a heartbeat. I should have done it sooner.

The TORQUE...Oh my God!  Shit and Giggles.

[JMR]

Big valves are no big deal in a FJ head. There is only so much room for larger valves.
We are only talking about 1mm increase on the intake valve and 1.5 mm increase on the exhaust valve.

I was going to leave my valves stock with my 1349 but Randy talked me into going with the bigger valves. I did need new valves anyway.
Randy explained it this way: "Look, you are increasing your displacement by 22.6% (1349/1098= 1.226) therefore on the intake stroke with the big 82mm pistons your air velocity will increase accordingly. If you go with bigger intake valves from 25mm dia. stock to the larger 26mm intake valves, that's only a 8% increase in valve opening area which is is no big deal. Your intake air velocity with the big pistons and big valves will still be much higher than stock."
"Why build a 1349 motor only to bottle neck it at the valves?"
"Same with the exhaust valves. Stock exhaust is 29mm and the larger valve is 30.5mm which is only a 10% gain in opening size, no biggie considering you are pushing 22.5% more exhaust gas out of the motor.."

"Besides", as Randy reminded me, "You need new valves anyway...."

"Now, make the check out to......"

Seriously folks, I am very happy with Randy's work. Very happy. I would do it again in a heartbeat. I should have done it sooner.

The TORQUE...Oh my God!  Shit and Giggles.

I agree with that assessment Pat. The only thing I'd say is that the valves are reversed. The OEM intake is 29mm. Truth be told I'd recommenmd the larger valves even with stock cams and stock bore. Look how large valves are on new bikes with similiar displacement.

[nvmike24]

I thought the small intakes was an odd configuration. I know they have 4 not 5 valves, lol. I have the 1200 cylinders sitting in a box but still looking for another very clean set. I will talk to Randy and see how fast I can afford to go. Waiting on the remaining GSXR stuff for the 1200 so I have something to ride while the 1100 is on the Modification table. Just need the Brake bracket and torque arm. Still need to decide if I will be going with a different swing arm setup or just the GSXR wheel on the 1100 as well. Decisions Decisions. I think I can get the FZR rear setup that the Front came from but I think the whole package is a little heavy. Complete GSXR setup is hard to find. Looks like it may be an expensive winter. I will be OK as long as I keep the Wife in goodies for her Vulcan 800. Got to order a Big can of Simichrome!

[racerman_27410]

I was given two choices when i had my engine built.... torque monster (stock valve sizes) or big horse power (larger valves)    Where and how i normally ride, big end power is nowhere near as important as monster torque so i stayed with the stock valve sizes.

3rd gear out of a corner with the back tire spinning and the front wheel up in the air is great fun!  

i  also had the benefit of having been able to line up against an engine exactly like mine, same FCR's, cams, lightened crank.. the difference being his engine has bigger valves Vs. my stock size valves..... out of the hole i win every time.... roll on's.... i win.... only on the very top end does he pull me.....but i dont ever get to those speeds unless doing a track day.

top end testing of a 1349 engine on the street is a sure fire invitation to either death or the pokey.

According to the fella who built my engine the FJ has a very inefficient combustion chamber and by increasing the pump (piston size) ,in conjunction with the stock size valves, actually improves cylinder filling via the increased intake velocity..... like i said it only bottlenecks on the very top end where maximum volume/flow is required to keep accelerating.



where that stock valve size choke point happens on the speedometer in real life is way above my comfort zone on the street so i dont really feel like i'm missing anything.... even though the dyno says i am missing some HP on the top end as compared to Andy Y's engine.


 on the street.... 115 lb/ft of TORQUE ROCKS! (especially with my fully loaded saddlebags)


In life....

KOokaloo RULES!  

[rktmanfj]

It's serious Kookaloo (with a capital 'K') either way!     

[andyb]

Bigger valves will also in effect make the cams more aggressive (they'll flow more, sooner).  Stock valves and cams on a bigger motor will act smaller, choking the top end a bit but giving it a smooth idle and a fairly flat torque curve.

Personally, I'd go ahead and put the valves in it.  The extra CC's should produce big gains over stock everywhere in the range, and a massive top end punch when you want it?  Sign me up!

[JMR]

 If you use the larger valves increase the seat ID to 90% of the valve OD.

[Pat Conlon]

The big valves go on the intake???








Shit

[Pat Conlon]

 With the added displacement, I think it is important to consider, and plan on, how you are going to keep your compression ratio to ~10.5-1 so you can run pump gas. Especially folks who get the shitty 91 octane E15 pisswater.

[andyb]

Partially you can cheat with your cam timing, but that's not really the right answer  

Ideally the right piston and the right gaskets will get you there, but you may have to compromise a little on your quench height.

[JMR]

The Cometic steel .010 base gasket is a good start for getting good squish/quench. Make sure you use some 1104 (now 1194) on the oil feed side.