Expiremental OM617 build
Expiremental OM617 build
![[Image: IMG_20161208_153523_zpsu19inb2c.jpg]](http://i346.photobucket.com/albums/p435/R-3350/IMG_20161208_153523_zpsu19inb2c.jpg)
" />[img]<a href=[/img]
![[Image: IMG_20161209_141529_zpsk0xnssr1.jpg]](http://i346.photobucket.com/albums/p435/R-3350/IMG_20161209_141529_zpsk0xnssr1.jpg)
" />[img]<a href=[/img]![[Image: IMG_20161209_144741_zpsaghyqto0.jpg]](http://i346.photobucket.com/albums/p435/R-3350/IMG_20161209_144741_zpsaghyqto0.jpg)
" />as for the car now, it has made a significant difference in its personality. all of a sudden the engine likes to rev before i had to give it a good bit of pedal in neutral to get it to rev fast. now about 1/2" of pedal makes it jump right to 2000. i haven't driven it enough to make any concrete observations on spool, egt, and off boost response. however i can say all are better.
the head porting was something i did a while ago while i still had access to the NDT equipment at the airport i was working at. i used an ultrasound inspection probe to gauge the port wall thickness. in some places it was over 1/2". i started by opening the throat of the ports to the edge of the gasket hole while also reducing the center divider wall to around .125" then i raised the roof of the port as much as possible to decrease the short side angle. i also opened the valve throat to around 87% of the valve face diameter while tear drop profiling the valve guide boss (theres not much there to profile but every little bit helps). finally i increased the short side radius as much as i could. all of this was interspersed with ultrasound inspections to prevent breaking through the port walls, the thinnest i went was .125"
i also ported the manifolds and turbo housings to match the ports on the head and optimize flow. the exhaust in particular needed a lot of attention as the stock egr manifold is not good it has lots of large nodules the interrupt flow. in particular the #1 port is very bad.[img]<a href=[/img]
![[Image: IMG_20161213_210631_zpsubeakhil.jpg]](http://i346.photobucket.com/albums/p435/R-3350/IMG_20161213_210631_zpsubeakhil.jpg)
" />[img]<a href=[/img]![[Image: IMG_20161212_201956_zps7kxyk9w8.jpg]](http://i346.photobucket.com/albums/p435/R-3350/IMG_20161212_201956_zps7kxyk9w8.jpg)
" />[img]<a href=[/img]
![[Image: IMG_20161212_201928_zpsxvfya8gm.jpg]](http://i346.photobucket.com/albums/p435/R-3350/IMG_20161212_201928_zpsxvfya8gm.jpg)
" />something i did while i was waiting for the tensioner gasket was to look at the coolant flow paths and how i could optimize it to help keep the head cooler. they can crack at higher output due to the inability of cast iron to dissipate heat like aluminum can. i noticed the stock thermostat housing half that bolts to the head is the outlet from the head and there are a lot of sharp corners in the flow path and plenty of excess material to remove to help it flow better. you cant see what i did as its not easy to get a shot of the work but if you get a chance to examine the flow path it becomes obvious what to do.[img]<a href=[/img]
![[Image: IMG_20161212_204330_zpsvexqrz3p.jpg]](http://i346.photobucket.com/albums/p435/R-3350/IMG_20161212_204330_zpsvexqrz3p.jpg)
" />im also looking into removing the threaded plug at the back of the head to fit a hose to. then run a feed from that through a small aux radiator to an electric pump and back into the front most port on the side of the head. this should help keep the head cool during protracted high power output.
one final not to anyone interested in porting. its at your own risk. it would be quite easy to wreck a head by grinding too far and it's not going to get any easier to find good heads as time goes on. that being said if you are willing to take the risk and accept the responsibility go for it. it can really help these asthmatic engines behave more like a proper German engineered piece of machinery.
i just recently got the car running again. as with all projects like this it became the death of a thousand paper cuts. i kept finding i needed another part or was missing something. the real kicker was i have multiples of almost every gasket on the engine as spares but i didn't have a timing chain tensioner gasket and it took a week to get one. the new head looked great after i got the modded pre-chambers in and the valves lapped and installed (new bronze guides valve seals rotocaps ect ect).[img]<a href=[/img]" />
[img]<a href=[/img]" />[img]<a href=[/img]" />
as for the car now, it has made a significant difference in its personality. all of a sudden the engine likes to rev before i had to give it a good bit of pedal in neutral to get it to rev fast. now about 1/2" of pedal makes it jump right to 2000. i haven't driven it enough to make any concrete observations on spool, egt, and off boost response. however i can say all are better.
the head porting was something i did a while ago while i still had access to the NDT equipment at the airport i was working at. i used an ultrasound inspection probe to gauge the port wall thickness. in some places it was over 1/2". i started by opening the throat of the ports to the edge of the gasket hole while also reducing the center divider wall to around .125" then i raised the roof of the port as much as possible to decrease the short side angle. i also opened the valve throat to around 87% of the valve face diameter while tear drop profiling the valve guide boss (theres not much there to profile but every little bit helps). finally i increased the short side radius as much as i could. all of this was interspersed with ultrasound inspections to prevent breaking through the port walls, the thinnest i went was .125"
i also ported the manifolds and turbo housings to match the ports on the head and optimize flow. the exhaust in particular needed a lot of attention as the stock egr manifold is not good it has lots of large nodules the interrupt flow. in particular the #1 port is very bad.[img]<a href=[/img]" />[img]<a href=[/img]" />
[img]<a href=[/img]" />
something i did while i was waiting for the tensioner gasket was to look at the coolant flow paths and how i could optimize it to help keep the head cooler. they can crack at higher output due to the inability of cast iron to dissipate heat like aluminum can. i noticed the stock thermostat housing half that bolts to the head is the outlet from the head and there are a lot of sharp corners in the flow path and plenty of excess material to remove to help it flow better. you cant see what i did as its not easy to get a shot of the work but if you get a chance to examine the flow path it becomes obvious what to do.[img]<a href=[/img]" />
im also looking into removing the threaded plug at the back of the head to fit a hose to. then run a feed from that through a small aux radiator to an electric pump and back into the front most port on the side of the head. this should help keep the head cool during protracted high power output.
one final not to anyone interested in porting. its at your own risk. it would be quite easy to wreck a head by grinding too far and it's not going to get any easier to find good heads as time goes on. that being said if you are willing to take the risk and accept the responsibility go for it. it can really help these asthmatic engines behave more like a proper German engineered piece of machinery.
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