One for the VERY mechanically minded

[EFE 1230]

Anyone know if it's possible to run a "reversed" head on a jap 4cyl motor??

i.e. carbs forward facing

seen it done on old pushrod limey motors but never on a "street" ridden jap motor just supercharged drag bikes.


any pics of one done would be nice.

[yoda]

Wouldnt you end up with clearance probs? Seen it on singles and it looks cool..

[ozzy1100]

i might be very very wrong but arnt a lot of air cooled jap stuff prety simetical on things like studs etc
might be something not that hard mate but like i said i might be very wrong lol

[BANDITROD]

I really don't see a way of getting that to work you would have to get the timing chain spinning the opposite way aswell ...my head hurts

[Large]

quote:Originally posted by BANDITROD

I really don't see a way of getting that to work you would have to get the timing chain spinning the opposite way aswell ...my head hurts


Unless you can reverse the cams.

There was something in the latest 2wheels about a 500cc V8 from two fzr250s (or some other small jap 4 cylinders). The guy had to reverse one set of heads to keep the carbs in the v. Might have been as simple as a gear added somewhere.

[xa-mont]

you wouldn't need anything to spin the opposite way would you... you would just need the front valves to open when the rear ones normally would have, so its all just cam timing right?

apart from that you would just need to work out some way to get the carb/TBs in the restricted space in front of the engine and then all would be fine right?

It's not like they have a different material for the exhaust side and the intake side, it's all the same head. Maybe slightly different designs on each side for better flow, but basicly the same right?

[EFE 1230]

quote:Originally posted by yoda

Wouldnt you end up with clearance probs? Seen it on singles and it looks cool..


no clearance probs if the frame is stretched out 70's showbike style and yeah just for the looks!



quote:Originally posted by ozzy1100

i might be very very wrong but arnt a lot of air cooled jap stuff prety simetical on things like studs etc
might be something not that hard mate but like i said i might be very wrong lol



haven't got as far as trying to bolt things up as all my parts aren't in one place atm.



quote:Originally posted by BANDITROD

I really don't see a way of getting that to work you would have to get the timing chain spinning the opposite way aswell ...my head hurts



but if the cams are "backwards" wouldn't turning them "around" as well mean they then spin the same way as original?

[Hillsy]

First of all you need a motor with a central cam chain. As for the cams I'm pretty sure you just need to swap them over as they are (no need to spin them left to right).

It's been done on drag bikes before - more for convenience of carb / blower tuning than anything else.

This guy's doing one here:

http://www.dotheton.com/forum/index.php?topic=19961.0

[sharky]

Twizzle from the NCC did it on, I think, a GSX...15+ yrs go..

[EFE 1230]

http://forums.dragbike.com/forum_posts.asp?TID=7176

gooogle!

how hard can it be..............lol!

[ALBI]

^^^^ as he said lol seen it done on a efe actually ,ex drag bike from castleregh ,it was running methanol via twin 1 3/4 strombergs and 4 x pipes out under his butt ,looked wicked " the bike that is " and i was going to do it to my gsthou but never did ,if memory serves me the cams were new billet items and the firing order was swaped over to follow the head "ie from l/h to r/h and i think it was in "dragster magazine" from the early days of the mag !!

[sharky]

My mishtake...it was 1983 he did it...

http://a4.ec-images.myspacecdn.com/images01/110/e22f4ee6daaff992e26e9e55b9879e20/l.jpg

http://www.myspace.com/twizzlecustoms/photos/31035#%7B%22ImageId%22%3A31079%7D

[EFE 1230]

fuck yeah sharky that's the go!

the motor more so than the bike though..........

[RevHead]

i saw a z900 in the late seventies with the head on backwards it also ran a 4,71 blower and the exhaust came out were the air box was ,this was at Castlereagh drags

[hyofighter]

quote:Originally posted by xa-mont

you wouldn't need anything to spin the opposite way would you... you would just need the front valves to open when the rear ones normally would have, so its all just cam timing right?

apart from that you would just need to work out some way to get the carb/TBs in the restricted space in front of the engine and then all would be fine right?

It's not like they have a different material for the exhaust side and the intake side, it's all the same head. Maybe slightly different designs on each side for better flow, but basicly the same right?


im with xa on this one if you left the engine in its natural configuration and just for the sake of this theory the engine is twin cam 16 valve and all valve sizes are the same , (im seeing what i want to say in my head but am finding this hard to explain without getting confused) so twin cam motor with engine not running but number 1 piston is on the intake stroke the valve at the rear of the head is open and exhaust (front) is closed right , so take off rocker cover remove cams and swap front to rear this makes front valve open and rear closed right thus only then the path taken for fuel/air mix has been changed and timing would remain the same , the only things that pose the problems would be port sizes and flow path , am i right in thinking that ??

[Hillsy]

quote:Originally posted by hyofighter


quote:Originally posted by xa-mont

you wouldn't need anything to spin the opposite way would you... you would just need the front valves to open when the rear ones normally would have, so its all just cam timing right?

apart from that you would just need to work out some way to get the carb/TBs in the restricted space in front of the engine and then all would be fine right?

It's not like they have a different material for the exhaust side and the intake side, it's all the same head. Maybe slightly different designs on each side for better flow, but basicly the same right?


im with xa on this one if you left the engine in its natural configuration and just for the sake of this theory the engine is twin cam 16 valve and all valve sizes are the same , (im seeing what i want to say in my head but am finding this hard to explain without getting confused) so twin cam motor with engine not running but number 1 piston is on the intake stroke the valve at the rear of the head is open and exhaust (front) is closed right , so take off rocker cover remove cams and swap front to rear this makes front valve open and rear closed right thus only then the path taken for fuel/air mix has been changed and timing would remain the same , the only things that pose the problems would be port sizes and flow path , am i right in thinking that ??


You're almost right - but the valves are angled, so the putting the exhaust cam at the rear of the head means it will open the valve earlier than if it was at the front of the head due to the angle of the valve being in the opposite direction.
So, you have to change the cam timing to account for this (not a huge problem, but it means you can't use the existing timing marks on the cam sprockets).

[Shadowzone]

I've got a headache.

But I've also got a hard on thinking about this and the fact it's doable.

[hyofighter]

quote:Originally posted by Hillsy


quote:Originally posted by hyofighter


quote:Originally posted by xa-mont

you wouldn't need anything to spin the opposite way would you... you would just need the front valves to open when the rear ones normally would have, so its all just cam timing right?

apart from that you would just need to work out some way to get the carb/TBs in the restricted space in front of the engine and then all would be fine right?

It's not like they have a different material for the exhaust side and the intake side, it's all the same head. Maybe slightly different designs on each side for better flow, but basicly the same right?


im with xa on this one if you left the engine in its natural configuration and just for the sake of this theory the engine is twin cam 16 valve and all valve sizes are the same , (im seeing what i want to say in my head but am finding this hard to explain without getting confused) so twin cam motor with engine not running but number 1 piston is on the intake stroke the valve at the rear of the head is open and exhaust (front) is closed right , so take off rocker cover remove cams and swap front to rear this makes front valve open and rear closed right thus only then the path taken for fuel/air mix has been changed and timing would remain the same , the only things that pose the problems would be port sizes and flow path , am i right in thinking that ??


You're almost right - but the valves are angled, so the putting the exhaust cam at the rear of the head means it will open the valve earlier than if it was at the front of the head due to the angle of the valve being in the opposite direction.
So, you have to change the cam timing to account for this (not a huge problem, but it means you can't use the existing timing marks on the cam sprockets).


yes you are right , but i was thinking of a basic straight up and down config cam lobe to valve but i understand what you mean but if it was a rocker setup this prob wouldnt matter then maybe , is food for thought but makes me wanna just try it now for the sake of it

Four-cylinder top fuel bikes have been running this way for well over 20 years.

Have a chat to Scott Lynch at Rapid Motion in Brisbane. He'll set you straight and tell you what works and what doesn't.
There are other people around but he's the best I can think of off the top of my head.

[Dynomutt]

It is possible and some of the top fuel 4 cylinder dragbikes have used this method. The motor continues to run the same direction as normal, but the cams need to be reverse profiled, as the opening ramp would become the closing ramp and vice versa. Once the cams are sorted then it is just a case of timing the cams correctly in order to run. some aircooled lumps like the Z/GPZ and GS/X motors with a central camchain tunnel and symetrical stud patterns are easier then others. Generally extranal oilways are used to feed the head rather than running up the side of the block as per usual, but this is beneficial anyway. Look at some pics of the topfuel/funnybike type 4 cylinder dragbikes and you will see the exhausts coming straight out of the head backwards and exiting above the rear wheel. Often a bloody great supercharger is slapped on the front to feed the monsters as well.