can i swap the exhaust port with the intake port?

[Bluethunder3320]

i am halfway through a vertical to horisontal conversion.

already made the dipper.


i was wondering if i could swap the exhaust port w/ intake to allow me to use the existing manifold.

it would be alot easier.

just like this pic, but the carb has to be flipped over.

what if i advanced the camshaft halfway?

 

[B man]

something tells me you shouldn't.

 

[jrmints1415]

i dont know, but if you flipped the cam it should "technically speaking" work right?? There is no difference between the intake and exhaust valve except the fact they are on different sides of the head so i dont know... give it a shot!!

 

[Bluethunder3320]

i dont know if flipping the cam will do anything but *** things up.... however the intake and exhaust are EXACTLY the same.

on my tecumseh H60, the intake is on the right side,
on my tecumseh HM80, the intake is on the left side.

i guess ^^^ the only difference is the camshafts are advanced half turn?

 

[jrmints1415]

true, but i think if you are going to do it then the cam must be flipped...

 

[Bluethunder3320]

lets hope that the camshaft has an even # of teeth.

i will let you guys know how it worked.

its 1:30 am time for bed. thanks for your opinions!

 

[jrmints1415]

haha same... np hope it works out!!

 

[Russ2251]

Will never, EVER work for many reasons. Would require a major re-engineering effort and far beyond the scope of what anybody knows on this website.

 

[fowler]

just for eductional sakes please explain

 

[Russ2251]

Porting for starters.

 

[fowler]

arrr right

somethings that look too easy usually are

 

[sideways]

Will never, EVER work for many reasons. Would require a major re-engineering effort and far beyond the scope of what anybody knows on this website.

I really need to get a list of things you've said aren't possible and prove you wrong about so many things. This might be one of them.

Blue, it can work but you'd get crap performance. You've probably noticed that on all engines the inlet valve is a bit bigger than the exhaust valve. This is because the atmosphere pushes (engines don't technically suck in air, the atmosphere pushes air into the cylinder) air into the cylinder at 14.7 PSI, the gasses are pushed out of the cylinder at serveral times that. Thus you have a larger inlet valve so it can flow enough air at the lower pressures it is subjected to.

By making the air flow through the tiny valve and less than optimal port (not that the inlet would be much better, Briggs have horrible port design) you're going to drastically decrease your volumetric efficiency (from the all ready crap standard) and thus your power. Couple that with undoubtedly unidyllic cam timing and you'l have an engine that'd be lucky to run, if it did it'd be gutless.

However, if you were to get a cam made (or make one your self) and sort out the valves ect it'd work quite well. You'd need to relocate the spark plug (and a few other things) to get it to work just as well as standard.

Basically, it's not worth the effort.

Just make a new inlet "manifold". Simply 2 flanges and a bit of pipe welded together. Much easier than getting the engine to breath through the "wrong" ports.

Thanks

Hayden

 

[Bluethunder3320]

thats not what i was hoping for.... lol....

well thanks guys.

can the carb be tilted 45 degrees if i just mount it right onto the engine (no manifold?)

 

[Bluethunder3320]

im off to get some valve lapping compound, and gasket material,,,,, so here i go.... gotta find a way to hook up the carb.

at first i was thinking the dipper would be the insanely hard part. it was a breeze!

 

[Russ2251]

This might be one of them.

That gospel you wrote just backs up what I stated.
What else am I wrong about?

 

[Bluethunder3320]

good news. the exhaust and intake are the EXACT same size. i used a valve lifter to check the size, and it fit the same way in either port.

they are totally symmetrical.

the spark plug hole is dead center between the valves as well.


im just gonna go for it. camshaft has 44 teeth so i made a mark on the 22nd tooth.

 

[Bluethunder3320]

heres an idea of what it will look like. im off to NAPA.

 

[oldbikerarlo]

Rotating the cam 180* does nothing, the piston goes up and down twice every time the cam goes around once, so it will still suck through the same valve as before, so reversing your carb and exhaust will just make it blow out the carb and suck in the exhaust. you need a compleatly differant cam. The thing about a small engine is the spark plug fires on the exhaust stroke also. The timing mark on crank and cam are so the spark is fired at correct time in the compression phase of the cycle.

 

[Doc Sprocket]

I really need to get a list of things you've said aren't possible and prove you wrong about so many things. This might be one of them.

Blue, it can work but you'd get crap performance. You've probably noticed that on all engines the inlet valve is a bit bigger than the exhaust valve. This is because the atmosphere pushes (engines don't technically suck in air, the atmosphere pushes air into the cylinder) air into the cylinder at 14.7 PSI, the gasses are pushed out of the cylinder at serveral times that. Thus you have a larger inlet valve so it can flow enough air at the lower pressures it is subjected to.

By making the air flow through the tiny valve and less than optimal port (not that the inlet would be much better, Briggs have horrible port design) you're going to drastically decrease your volumetric efficiency (from the all ready crap standard) and thus your power. Couple that with undoubtedly unidyllic cam timing and you'l have an engine that'd be lucky to run, if it did it'd be gutless.

However, if you were to get a cam made (or make one your self) and sort out the valves ect it'd work quite well. You'd need to relocate the spark plug (and a few other things) to get it to work just as well as standard.

Basically, it's not worth the effort.

Just make a new inlet "manifold". Simply 2 flanges and a bit of pipe welded together. Much easier than getting the engine to breath through the "wrong" ports.

Thanks

Hayden

Not for anything, but you just finished telling Russ that he was offside, and then you proved his point for him. Or did I miss something?

 

[devino246]

Rotating the cam 180* does nothing, the piston goes up and down twice every time the cam goes around once, so it will still suck through the same valve as before, so reversing your carb and exhaust will just make it blow out the carb and suck in the exhaust. you need a compleatly differant cam. The thing about a small engine is the spark plug fires on the exhaust stroke also. The timing mark on crank and cam are so the spark is fired at correct time in the compression phase of the cycle.

yep

Not for anything, but you just finished telling Russ that he was offside, and then you proved his point for him. Or did I miss something?

I think hes just saying its not beyond the scope of anyone on this site but that it is infact over complicated and useless.