Nismospek Posted August 29, 2017 Share Posted August 29, 2017 (edited) With all the recent postings I was hoping to get some help trying to read out my Flow sheet. I picked off this head from Yahoo Auctions Japan. It was completely bare missing cam towers and about everything else. All I could tell from the photos was that it had been ported and that it had welded chambers. I decided to risk it and put a bid in knowing full well I might have just bought a new paperweight. I finally got it back from a reputable builder with new seats, Datsun Spirit Big valves and some unfurling of the valve area. I was told that different flow benches are like dynos. It seems that the flow bench used for this head maxes out at 160 cfm at 10 inches of water. Not sure how this coverts to newer type flow benches that read at 20 inches etc. Also not sure how this relates to max lift on the cams? Edited August 29, 2017 by Nismospek Quote Link to comment Share on other sites More sharing options...
turbogrill Posted August 29, 2017 Share Posted August 29, 2017 Seems like it's been ported for high lift aggressive cam. The flow numbers at low lifts looks small compared to high lift. Good if you have a high lift cam, bad if you have mild lift cam. But I am no expert. Quote Link to comment Share on other sites More sharing options...
ryant67 Posted August 30, 2017 Share Posted August 30, 2017 I'd get it flowed somewhere locally at 25 or 28 inches. If you have a stock head, get them to do that as well for a baseline. Then at least you can have numbers on a comparable scale to what others do. I'd expect the head to perform well though, fingers crossed for you! Quote Link to comment Share on other sites More sharing options...
Nismospek Posted August 30, 2017 Author Share Posted August 30, 2017 Cam is 483 lift and 276 duration. Does that mean the max cfm is equal to the max lift on the cam? Quote Link to comment Share on other sites More sharing options...
turbogrill Posted August 30, 2017 Share Posted August 30, 2017 It's probably mucj much better than stock but I would think that head would perform best at a crazy 600 lift or something. But again, no expert. I wouldn't worry too much. What compression do you get? Quote Link to comment Share on other sites More sharing options...
Nismospek Posted August 30, 2017 Author Share Posted August 30, 2017 (edited) Going to use a thicker headgasket to lower cr. This head has been shaved a couple times over its life. Hopefully 10.5 or 11 to 1. Hope to run 91 octane. Edited August 30, 2017 by Nismospek Quote Link to comment Share on other sites More sharing options...
turbogrill Posted August 30, 2017 Share Posted August 30, 2017 What cam is that btw? Quote Link to comment Share on other sites More sharing options...
Nismospek Posted August 30, 2017 Author Share Posted August 30, 2017 A special grind recommended by the builder. My Z spends its life on streets or Canyons. Quote Link to comment Share on other sites More sharing options...
Nismospek Posted January 11, 2018 Author Share Posted January 11, 2018 Found a nifty calculator. Decided to convert everything to 25 inches which is what I believe Rebello uses. 100 lift 58 cfm 200 lift 117 cfm 300 lift 158 cfm 350 lift 178 cfm 400 lift 189 cfm 450 lift 192 cfm 500 lift 200 cfm 550 lift 205 cfm 600 lift 213 cfm 650 lift 219 cfm Quote Link to comment Share on other sites More sharing options...
Gollum Posted January 11, 2018 Share Posted January 11, 2018 On 8/30/2017 at 7:26 AM, Nismospek said: Going to use a thicker headgasket to lower cr. This head has been shaved a couple times over its life. Hopefully 10.5 or 11 to 1. Hope to run 91 octane. You mention that the chambers were welded, how much quench pad is there? If a lot, then a thicker gasket might be hindering more than helping. Google quench pad and quench distance to learn more. Also, pics are always nice. Quote Link to comment Share on other sites More sharing options...
rossman Posted January 11, 2018 Share Posted January 11, 2018 (edited) The converted numbers are similar to my Rebello ported p90a head. The port is what Rebello called a "mild port." Custom Isky Turbo cam Intake: .535 lift, 278 duration, 114 lobe center Exhaust: .535 lift, 278 duration, 114 lobe center Ported head with 1 mm over sized stainless intake valves Intake: 201 @ 25" water Exhaust: 151 @ 25" water Edited January 11, 2018 by rossman Quote Link to comment Share on other sites More sharing options...
turbogrill Posted January 11, 2018 Share Posted January 11, 2018 4 hours ago, rossman said: The converted numbers are similar to my Rebello ported p90a head. The port is what Rebello called a "mild port." Custom Isky Turbo cam Intake: .535 lift, 278 duration, 114 lobe center Exhaust: .535 lift, 278 duration, 114 lobe center Ported head with 1 mm over sized stainless intake valves Intake: 201 @ 25" water Exhaust: 151 @ 25" water .535 is a lot of lift! For NA cams it's typically only seen on racy cams. (Maybe because it requires some skill to get right? Notched pistons valve train stability?) Quote Link to comment Share on other sites More sharing options...
Leon Posted January 11, 2018 Share Posted January 11, 2018 (edited) 3 hours ago, turbogrill said: .535 is a lot of lift! For NA cams it's typically only seen on racy cams. (Maybe because it requires some skill to get right? Notched pistons valve train stability?) Not really. I'm running an Isky L6 grind (.540" lift, 270 duration) with flat-top pistons and a Rebello "street ported" P90 on an OEM HG. From memory, my measured piston-head clearance is 0.023", piston-valve is ~0.080", and compression is 11:1. Runs great on 91, even with MBT timing @ 35* all in if I remember right. Edited January 11, 2018 by Leon Quote Link to comment Share on other sites More sharing options...
turbogrill Posted January 11, 2018 Share Posted January 11, 2018 (edited) 7 minutes ago, Leon said: Not really. I'm running an Isky L6 grind (.540" lift, 270 duration) with flat-top pistons and a Rebello "street ported" P90 on an OEM HG. From memory, my measured piston-head clearance is 0.023", piston-valve is ~0.080", and compression is 11:1. Runs great on 91, even with MBT timing @ 35* all in if I remember right. Interesting, so how come a lot of the other 260-290 duration NA cams have such moderate lift? Edited January 11, 2018 by turbogrill Quote Link to comment Share on other sites More sharing options...
Leon Posted January 11, 2018 Share Posted January 11, 2018 2 minutes ago, turbogrill said: Interesting, so how come a lot of the other 260-290 duration NA cams have such moderate lift? There's no point in running high lift when the rest of your system can't make use of it, you have to see the big picture. I'm also running triple 45s with a ported intake and a 6-1 header into a 2.5" exhaust. I sized my cam based on a conversation with Ron Iskenderian about my use case. Most cams you see advertised online are the tip of the iceberg, just bulk items sold to people that want to say they have a "Stage III cam". Talk to a cam grinder and expand your horizons. I will say with the .540 lift cam, there was little room for error during setup due to it using a lot of the lash pad. Quote Link to comment Share on other sites More sharing options...
rossman Posted January 11, 2018 Share Posted January 11, 2018 Rebello built my entire long block. He used notched flat top pistons with a metal head gasket. Compression is 8.5:1 according to him. The cam is a regrind but all the lash pads are stock height. I guess he compensated for the difference in cam base circle by adjusting the valve heights. Quote Link to comment Share on other sites More sharing options...
TimZ Posted January 22, 2018 Share Posted January 22, 2018 On 1/11/2018 at 2:18 PM, Leon said: Not really. I'm running an Isky L6 grind (.540" lift, 270 duration) with flat-top pistons and a Rebello "street ported" P90 on an OEM HG. From memory, my measured piston-head clearance is 0.023", piston-valve is ~0.080", and compression is 11:1. Runs great on 91, even with MBT timing @ 35* all in if I remember right. I run that cam too - no piston clearance issues, but I did have to be very careful to maintain adequate clearance between the stem seals and the bottom of the valve spring retainers at max lift. Regarding the flow numbers, at .485 lift you are into the flatter part of the flow curve, so it should work just fine for you. A higher lift cam would net you a bit more flow, but mostly by spending more time in the "flat" portion of the flow curve. I believe that the more "mainstream" cams have lower lift because that leaves more margin for error for less experienced builders. They will work with stock valve springs and there is still ample clearance between the retainer and the stem seal, for instance. They will generally just "bolt in" and work. Quote Link to comment Share on other sites More sharing options...
madkaw Posted January 22, 2018 Share Posted January 22, 2018 Damn- I thought my ISKY 490 was big league need to up my game ! Quote Link to comment Share on other sites More sharing options...
Chickenman Posted January 22, 2018 Share Posted January 22, 2018 (edited) On 1/11/2018 at 11:25 AM, turbogrill said: Interesting, so how come a lot of the other 260-290 duration NA cams have such moderate lift? Biggest issue is with a reground Cam, you are " lift limited " by the duration profile. To get more duration at the Nose, you have to grind the Peak or Toe of the Cam. That means you've now reduced the effective " Lift " of the Cam. To get the Lift back, you have to reduce the Base-Circle Diameter or Heel of the cam. You can only go so small with a Base Circle, before you start running into geometry and Valve acceleration issues. Make the Acceleration and Deceleration ramps too aggressive, and you end up with Valve Train instability and short component life. On some re-grinds, they have to " undercut " the core diameter of the Camshaft. That means that they actually reduce the diameter of the Camshaft BETWEEN the Lobes in an effort to get the Base Circle diameter smaller. Of course that can weaken the camshaft core as well. Now, if you start off with an unground new " Billet " camshaft you can get a LOT more lift and duration than a regrinds. Because you have all that extra metal to use on the Profile. It's not unusual to see Datsun L series Race cams ground on a fresh cam Billet having .600" + Valve lift ( 1.54 Rocker ratio ) . That would be impossible on a reground Camshaft. Edited January 22, 2018 by Chickenman Quote Link to comment Share on other sites More sharing options...
Chickenman Posted January 22, 2018 Share Posted January 22, 2018 2012 Nissan Motorsports manual: Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.