Carb Bore VS Intake Rotor Timing.

[Joe Warren]

And the shortest path to get the fuel to the top of the piston is the best path. Ease the Flow.......... Jerry crowther years ago came up with some interesting ways of doing this on big block 90s....... but they were small bore with a thick liner. never forget he had his boost transfers cut into the chrome side of the liner. (inner side) With a loop hole cut into the piston to connect it all..

 

[stan simpson iv]

And the shortest path to get the fuel to the top of the piston is the best path. Ease the Flow.......... Jerry crowther years ago came up with some interesting ways of doing this on big block 90s....... but they were small bore with a thick liner. never forget he had his boost transfers cut into the chrome side of the liner. (inner side) With a loop hole cut into the piston to connect it all..

Been there done that...

 

[dwilfong]

I don't cut more than I have to on the case to get the flow path I want. Now the liner and piston I butcher.

Cut it so when you look in the intake window you can see the bottom side of the top of the piston. Heck you can see the glow plug thew the boost port.

So I guess there is a little taken out.

Just never gave it top priority in my thinking.

Now the 45 Mike had that Frank O did was hogged so far it had epoxy on the case to make it bigger.

Ran good till it popped off. :lol:

Saw a MAC 84 pop the top of the case at the last race. Think Tom had one do the same thing. Not bad for beating the snot out of them for 10 years.

Still think there is more in the pipe than any thing we can do to the case and sleeve.

Spent some time talking with Andy about pipes. He opened my eyes to a few thing that are not in any books or soft wear.

Will run them by Scott and see what he thinks about making some changes when he gets some time.

Here is a pic of where I am at now with the carb .520-.710

Don't think you could get much more thew the window. just need to play with the spray bar a little to see what is what.

Here are some pics of the newest 91RS P/L set. Thy opened up the ex port and changed the transfer shape.

Hope the 1.01 gets the same treatment.

 

[dwilfong]

And the shortest path to get the fuel to the top of the piston is the best path. Ease the Flow.......... Jerry crowther years ago came up with some interesting ways of doing this on big block 90s....... but they were small bore with a thick liner. never forget he had his boost transfers cut into the chrome side of the liner. (inner side) With a loop hole cut into the piston to connect it all..

Been there done that...

Yes Andy has a good example of the Question mark.

Stan why don't you jump in here and spread some of the wisdom. We won't bite.

What are you doing with Lupe's nova 45?

David

 

[Joe Warren]

dave what is your email

 

[dwilfong]

dave what is your email

PM sent

 

[stan simpson iv]

And the shortest path to get the fuel to the top of the piston is the best path. Ease the Flow.......... Jerry crowther years ago came up with some interesting ways of doing this on big block 90s....... but they were small bore with a thick liner. never forget he had his boost transfers cut into the chrome side of the liner. (inner side) With a loop hole cut into the piston to connect it all..

Been there done that...

Yes Andy has a good example of the Question mark.

Stan why don't you jump in here and spread some of the wisdom. We won't bite.

What are you doing with Lupe's nova 45?

David

Take the motor out of the box, slap it on the a$$, run it till she blows...

 

[dwilfong]

And the shortest path to get the fuel to the top of the piston is the best path. Ease the Flow.......... Jerry crowther years ago came up with some interesting ways of doing this on big block 90s....... but they were small bore with a thick liner. never forget he had his boost transfers cut into the chrome side of the liner. (inner side) With a loop hole cut into the piston to connect it all..

Been there done that...

Yes Andy has a good example of the Question mark.

Stan why don't you jump in here and spread some of the wisdom. We won't bite.

What are you doing with Lupe's nova 45?

David

Take the motor out of the box, slap it on the a$$, run it till she blows...

Dude realy just slap it on the A$$.

I will have to bust Lupe's B@!!s. All Stan said he did was slap it on the A$$.

 

[scott bouchie]

I have bin messing with the pipe Scott made for me and it will suck the guts out of the case. the needle is over two turns out from where it was with the MACS pipe.

The only problem is it is hard to tune. the volume is large with this pipe and it stows a large mixture load in the pipe then the sharp rear angle slams it all back in.It hits like a sledge hammer. I call it the piston breaker. but it drops off bad after you hit the RPM tune of the pipe.

Some more changes should make it gentle. But it did show me how the right front half will draw all the way to the carb.

David this is why your motor breaks rich so bad....the rotor and transfer ports are open too long and that three stage diffuser is pulling fuel to long,your totally over scavinging the motor....open the rotor at 25 degrees abdc and you will see a different motor!

 

[scott bouchie]

That last post didn't really make since,what I was getting at is opening the rotor at bdc is to early for that pipe with a 3 stage diffuser,that's why its pulling so much fuel.....there's to much overlap between the rotor and the transfer ports.Try opening the rotor at 25 degrees abdc.

 

[dwilfong]

I have bin messing with the pipe Scott made for me and it will suck the guts out of the case. the needle is over two turns out from where it was with the MACS pipe.

The only problem is it is hard to tune. the volume is large with this pipe and it stows a large mixture load in the pipe then the sharp rear angle slams it all back in.It hits like a sledge hammer. I call it the piston breaker. but it drops off bad after you hit the RPM tune of the pipe.

Some more changes should make it gentle. But it did show me how the right front half will draw all the way to the carb.

David this is why your motor breaks rich so bad....the rotor and transfer ports are open too long and that three stage diffuser is pulling fuel to long,your totally over scavinging the motor....open the rotor at 25 degrees abdc and you will see a different motor!

I will lower the port timings with the new piston and will cut a new rotor for the next test.

 

[scott bouchie]

Leave the sleeve where you have it and just use the stock rotor.....

 

[dwilfong]

Leave the sleeve where you have it and just use the stock rotor.....

Leave the sleeve where you have it and just use the stock rotor.....

I knew some thing was not right. This eng set up was just sucking down the fuel and hitting like a sledge hammer.

It is amazing how the things we do to make a eng run better with a mediocre pipe will be to much for a properly designed pipe.

 

[Ray Sametz]

Leave the sleeve where you have it and just use the stock rotor.....

Leave the sleeve where you have it and just use the stock rotor.....

I knew some thing was not right. This eng set up was just sucking down the fuel and hitting like a sledge hammer.

It is amazing how the things we do to make a eng run better with a mediocre pipe will be to much for a properly designed pipe.

Dave, with Scotts 3 stage diffuser I bet it also trottles like driving a car.

 

[Joe Warren]

We have been all over the place on this post but my orginial post was. that you can gain a ton of performance Changing or enhancing the intake timing number that the mfgers offer. the Stk bore carb can do much more if you widen the opening of the rotor or disk. Many engines 45 size & Up approx .004 material removed from the rotor or disk is 1 Crank degee. Many of our engines today have good opening numbers 27-37 Abdc but they close the rotor or disk very early.56 -58 Atdc... If you have a degree wheel and can move the rotor or disk to 65 ATDC this would be a great number you dont want to go much past this for a heat racing engine. Then you can back up and look at what you can do to the opening for a total of 216 218 intake duration total. For those that are Grinding Blindly?? ( I know this happens) Don`t make cuts that exceed .010 at a time before testing. the mfger has the rotor numbers very close most of the time. they are trying to limit the RPM with the Numbers they provide so you can get life out of the engine or incase you under prop the boat. After you have altered the timing numbers you will gain RPM, make sure you allow the prop to control the rpm & dont over Rev the engine and kill it.... ( we call that... turning it out of the frame) 1st thing to remember when you have your engine turning more RPM is (Choppy water and a Rich Needle sound alike in race conditions.) be careful twisting that little 3rd channel knob.......... & bolt on that new Big Bore carb after you have the Intake numbers optimized.. A Nice new aftermarket carb will compliment a Engine that has good timing numbers.