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Showing results for tags 'pnp'.
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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
