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Showing results for tags 'porting'.
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What you see below is a 2nd gen "F" head with 4 downward sloping intake ports. My client is planning on running about 10#s of boost though this........ More to come........ :D
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I've recently purchased a daily-able FX16 so I don't have to use Surreptitious(AE71) all the time... I named the FX "Skippy", and knew upon purchase that it didn't run. This is what was found when the head was pulled... something broke, and eventually got embedded - see arrow So.... OST-032 is Skippy's new head! stripped and ready for cleaning........ Can anyone tell me why one chamber is already clean???? More to come..... :D
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I've seen quite a few threads in Rollaclub showing SR20 swaps. As I've done some porting on the SR20, and I have a new client whose SR20VE I'll begin porting next week (if all goes well on delivery to me). Between now and then I'll drop a few photos, and some flowbench results from my "play" with a highport SR20DE Not a lot of fwd heads around so "beggars"(me) couldn't be choosey. For those who know something about SR20s... this is a 2.0 liter dohc 4 cylinder - fwd "highport" 1st gen SR20DE. It uses HLAs (hydraulic lash adjusters) as part of the valvetrain Obviously the first thing to be done - was cleaning up the mess And for easier imagination the paths through the head have been marked out in Sharpie The intake and exhaust bowls have been measured - nothing fancy so far... Intake: Exhaust: Observations Intake: the bowl and seat work allow the valve to breath to its maximum, the intake valve head is 34mm. Typically the best compromise is somewhere between 85% and 90% of the valves diameter should equal the bowl/seat. The SR20 is pretty good straight away at 86%(29.2mm). Short Radius - the short radius is the only place to easily increase the overall valves draw on the port. A un corrected short radius that interferes can have little or no air flow at lower lift points. This will hurt overall filling of the cylinder, and lower power Exhaust: The exhaust valve is 30mm, using the same formula (85%-90%) the seat/bowl should be at least 25.5mm(85%), but stock exhaust seat/bowls are only 24.7mm on average(82%). The short radius was garbage interfering far worse in the exhaust port then it does in the intake. more to come..... :D
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I recently was sent a 20V Blacktop (Noir Crowning) head...... so once unwrapped and set up on the bench.... inspection begins.... Over all the casting quality has gotten much better. Although there still is port-bowl-seat shift, the shift amount - at least in this head, is minimal. There is one REALLY, and I mean REALLY odd ball bit........ the 3 intake valve seats have NO semblance of an even 3 angle... Looking into the Blacktop service manual the 3 angles are suppose to be 30, 45, 60. Well the throat cut - 60 degree cut, in essence is the bowl angle and so the back of the port (highest pressure area) has no effective throat cut, while if you look carefully, the throat cut at the short radius is so small, it also becomes more or less insufficient... and the the throat cut between the two... is nothing short of an extreme change - from a width @ the back of the port of almost 5mm, to the width at the short radius of the port of less than 1mm. One thing is certain - the factory put a lot more effort in to making the bowls and seats as smooth a transition as the factory could do... the bowl machining marks you see are not by me... those are all factory machining Adding some more info.... The heads thickness measure..... My dial caliper is likely off by .001" and getting a chamber volume and it is very close to SamQ's 37.8cc measurement.... I'm closer to 38cc Further inspection...... shows a few issues on the exhaust side... look @ those casting marks.... as they travel from the bowl to the port. Also the small "step" in the machining/casting hurts flow, especially at lower lifts. More to come........ :D
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A delicate dance... titled as such because OST-031 and OST-030 will be built almost simultaneously. As you can see... OST-030 in the background, with 2 heads in front Clients head on the left.... anyone see an issue?? How about if we isolate the two sets of chambers.... clients head on top It's replacement on the bottom See anything now?? Closer?? I've dismantled the replacement and I've sent it on to get cleaned and pressure checked.... So with it @ the shop to get cleaned, the delicate dance proceeds as I move back to OST-030 More to come... :D
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To the Rollaclub forum... I'm a cylinder head porter. I often post examples of my work in forums around the world... why I've missed this one for so long... I have no excuse.... :oops: and now on to the topic at hand..... As I always do... my client is anonymous, unless he wants to share. This head is sold to a client in California. This is his daily driver, that gets a track beating/work out every few months or so. Retaining emissions compliance is paramount, but we can get a bit more without offending the sniffer. This is a largeport head, it is the stock thickness, having never been re-surfaced. A key for me in figuring out overall "wear" is often judged on the condition of the old valve seals. The old seals that came from this head were still "pliable" (read as didn't crumble under finger pressure) - A few intake valves did show signs of build-up, the exhaust valves were all dry. #4 exhaust port Its pretty crowded in there, but a bit of seat to bowl blending, and a re-taper of the port will allow the exhaust gasses an easier path Now that it is stripped, its off the the machine shop to get cleaned, and de-carboned. Maybe they can get rid of that horrid paint for me too More to come...... :D