big block streetability,in all seriousness

nads.com wrote:

I shift my 1015cc .407lift engine down to third gear at 85 or 90 and it takes off like a rocket, just curious would your motor be past the power band if you shifted at that speed?

What gearing are you running?

My bike, @90MPH in 5th = 5790 RPM.

Downshift to 4th @90 MPH = 6550 RPM

Downshift to 3rd @90MPH = 7926 RPM

Incidentally....if the big bore motor doesn't spin up quickly, it's because the head / valves are not sufficient for the size of the motor and / or the cams are not correct.

These motors are generally not altered stroke. You're still accelerating the same mass in the bottom end. With a big block motor built with the combination of components properly setup, you have the opportunity to generate more force on the rod....

It's about volulmetric efficiency.

You have a much bigger bore to feed fuel and air to create the pressure to spin the crankshaft. Bigger valves, better flowing head and camshafts that yield the required curtain area must be part of the equation or it's going to run out of steam & it struggles to rev.

Two things I don't particularly like about big block on the street are the potential for heat problems and the potential for oil leaks.

Make that 3....The COST.

But if you want one, then by all means, build it. Just make sure you put it in a frame that's worthy of the HP potential. You can get seriously hurt in the blink of an eye when you double the HP you're used to having...

I just did an LTR450 Suzuki. It got a stroker crank, big bore cyinder and I pushed another 30CFM through the intake port. It revs faster than it did when it was stock

That looks very purdy Larr .
How about grafting 4 of them to gether for my KZ.:woohoo:

larrycavan wrote:

nads.com wrote:

I shift my 1015cc .407lift engine down to third gear at 85 or 90 and it takes off like a rocket, just curious would your motor be past the power band if you shifted at that speed?

What gearing are you running?

My bike, @90MPH in 5th = 5790 RPM.

Downshift to 4th @90 MPH = 6550 RPM

Downshift to 3rd @90MPH = 7926 RPM

Incidentally....if the big bore motor doesn't spin up quickly, it's because the head / valves are not sufficient for the size of the motor and / or the cams are not correct.

These motors are generally not altered stroke. You're still accelerating the same mass in the bottom end. With a big block motor built with the combination of components properly setup, you have the opportunity to generate more force on the rod....

It's about volulmetric efficiency.

You have a much bigger bore to feed fuel and air to create the pressure to spin the crankshaft. Bigger valves, better flowing head and camshafts that yield the required curtain area must be part of the equation or it's going to run out of steam & it struggles to rev.

Two things I don't particularly like about big block on the street are the potential for heat problems and the potential for oil leaks.

Make that 3....The COST.

But if you want one, then by all means, build it. Just make sure you put it in a frame that's worthy of the HP potential. You can get seriously hurt in the blink of an eye when you double the HP you're used to having...

I just did an LTR450 Suzuki. It got a stroker crank, big bore cyinder and I pushed another 30CFM through the intake port. It revs faster than it did when it was stock

i believe what youre referring to is called excessive hp to brain cell ratio in scientific terms! :laugh:

larrycavan wrote:

nads.com wrote:

I shift my 1015cc .407lift engine down to third gear at 85 or 90 and it takes off like a rocket, just curious would your motor be past the power band if you shifted at that speed?

What gearing are you running? Stock. Moved intake centerline valve to 112 from rec. 108. Don't know if I'm missing torque and peak hp but it goes like crazy up top with what's seems to be no end (Running on maybe?). compression is 180 and dropped to 155 with cams. If I tried to drag id probaly fall on it's face out of the hole, but every foot after the power keeps multiplying. Tack don't work but it always was 6000 at 80 in 5th. Don't mean to hijack this thread. Never ran a big block from what I see the cams are mostly ground supporting low end torque (by the open and close numbers)probly based on flow limitations in the poor little heads. If my motor realizes max flow at 9000 and a big block at 6500 I'm not betting the extra weight of larger pistons is going to equalize the weight and speed factors in force. :woohoo:

My bike, @90MPH in 5th = 5790 RPM.

Downshift to 4th @90 MPH = 6550 RPM

Downshift to 3rd @90MPH = 7926 RPM

Incidentally....if the big bore motor doesn't spin up quickly, it's because the head / valves are not sufficient for the size of the motor and / or the cams are not correct.

These motors are generally not altered stroke. You're still accelerating the same mass in the bottom end. With a big block motor built with the combination of components properly setup, you have the opportunity to generate more force on the rod....

It's about volulmetric efficiency.

You have a much bigger bore to feed fuel and air to create the pressure to spin the crankshaft. Bigger valves, better flowing head and camshafts that yield the required curtain area must be part of the equation or it's going to run out of steam & it struggles to rev.

Two things I don't particularly like about big block on the street are the potential for heat problems and the potential for oil leaks.

Make that 3....The COST.

But if you want one, then by all means, build it. Just make sure you put it in a frame that's worthy of the HP potential. You can get seriously hurt in the blink of an eye when you double the HP you're used to having...

I just did an LTR450 Suzuki. It got a stroker crank, big bore cyinder and I pushed another 30CFM through the intake port. It revs faster than it did when it was stock

Larry is the expert hear , so i would NEVER dought him. i think a kz head should be your last choice, for a few reasons.. What u need to do is find out all of the pro, and cons of each, then make an EDUCATED decision
Larry is the one to ask these question. He has ported them all.
My personal choice would be the GPZ , but I may be lacking some knowledge in that decision. I feel that it is easy to grow out of a KZ head as u demand more power, and easier to grow into a GPZ. And much cheaper to start with a mild gpz head, than a wild KZ.
The KZ has small valves, u can only go to 37.5mm(reliably), j gas 37mm to start with, and GPZ has 38. the kz also has smaller xht valves.
In order for kawi to get the bigger valves in, they moved the guides further apart.
This is the problem with the kz. To accommodate larger valves, u cannot move them apart, so u have to grind the seats and sink the valves down deeper. This itself impedes flow a bit . now when u add large cam’s , u have to sink them more, since u can easily run into valve to valve contact, specially if u install larger xht valves too..
The j solves this ,but the GPZ went 1 step further.
The j has a larger combustion chamber, so u need custom pistons to gain back the 2 points of compression that u loose would loose from 10;1 to 8;1. The GPZ looses 2.5 points , so u need custom pistons here as well. The last thing would be the GPZ’s bathtub shaped chamber. I think this is another bonus, as it will help improve combustion.
Otakar can help u here. He has custon pistons, but he has a j bottom end i think(witch would require 18mm pins).. Ask him where he bought them.

I just changed my mind about a big block.

But.... it seems like you could build a motor with an extremely good mid range just by going with the APE street kit.

My bike is almost done, I just want to have fun. I ride a Ducati monster,(still building the KZ) until the monster, had no idea how handy a good mid range "punch" is on the street and actually works well in technical parts of the track. I can keep up with the Japanese litre bikes in the tight part of the track, only loosing sight of them on the straights.

The question is .... If you keep everything practicle, can you dependably run the big block? (i.e. the APE street kits)

Good mid range comes from all the things you are talking about, high velocity is created with small valves, and heads. This is the optimal recipe for partial throttle openings, and a quick response. It just "will" run out of flow (air restricted) at higher RPMS.

larrycavan wrote:

kzz1p wrote:

You should think bigger!

You can run 10's with a 1075 with pistons, cams, 29's and a stock head (other then valve springs)

With a big motor you should be going faster, save it for the track..........

You can run mid 9's all day long with under 1015cc if the motor is done right & chassis is setup properly and it doesn't need anything larger than 31mm carbs

But it's not going to run on the street without race fuel, the valve springs will not live a long life and it would be a total pain in the arse to contend with on a daily basis.

No matter what the approach, the first consideration is how much money can be put into the project. It adds up pretty quickly, much faster than the dream to build it turns into reality.

Then let's not forget there's the small matter of the chassis that needs to be gone through :huh:

What compression is needed for race gas to work Larry? What does a mothball in your gas do to combustion? Does it oxygenate the fuel?

Depends on the engine type as to what octane it will tolerate. You can over do octane and loose power too.

You don't need to put moth balls in the tank. The oil companies are already doing that for you these days :laugh:

I'm resurrecting this from 12 yrs. ago and R.I.P. Larry C, you are missed.  I'm putting a 1428 street monster together.  MK2 Crankshaft, welded with thrust device installed, KZ bottom end, undercut trans., GPZ head with 38.6mm intake valves, 10.5 street pistons. Megacycle 470-65A. Mikuni BS34 carbs. Should be fun.  Going to run Hayabusa front end so I have great suspension and braking, and a Busa swingarm which comes out to about 3" over.  Dyna 2000 ignition so I can adjust ignition curve as well. I'll of course run an oil cooler but I will probably mount it on the rear to get extra oiling capacity.  Thoughts?
 

wrote:

I'm resurrecting this from 12 yrs. ago and R.I.P. Larry C, you are missed.  I'm putting a 1428 street monster together.  MK2 Crankshaft, welded with thrust device installed, KZ bottom end, undercut trans., GPZ head with 38.6mm intake valves, 10.5 street pistons. Megacycle 470-65A. Mikuni BS34 carbs. Should be fun.  Going to run Hayabusa front end so I have great suspension and braking, and a Busa swingarm which comes out to about 3" over.  Dyna 2000 ignition so I can adjust ignition curve as well. I'll of course run an oil cooler but I will probably mount it on the rear to get extra oiling capacity.  Thoughts?
 

If you fit a cooler with a long hose run you must fit a thermostat to ensure oil quickly circulates in the engine when cold. 
Without a thermostat the accumulated delay in oil to the top end will gradually accelerate cam train wear.
If using no thermostat you should fit the cooler in a position with the shortest hose run as possible which is either on the front down tubes or in the low pressure area behind the carbs if there is sufficient space.