Guest Z Draci Posted August 5, 2005 Share Posted August 5, 2005 Ignoring the obvious "Oh, it's because the P90a has hydraulic lifter so that's why" or "Not all P90a heads are hydraulic" answers, I want to get past that and get to the point of my post. I want to know if the P90a head is inferior in any way by having the lowest lift out of all the L-series heads. Does this mean that it "flows less" or is "less efficient?" Does it limit its performance potential because of it (besides the obvious fact that aftermarket cams have to be custom ordered for the P90a)? Yes, I know I can get a good P90 and call it a day. My P90 is in need of a rebuild and I want to try out the P90a in the meantime. Any info, comments, and suggestions is appreciated! Quote Link to comment Share on other sites More sharing options...
Thumper Posted August 5, 2005 Share Posted August 5, 2005 I have never heard that the p90a with hydraulic lifters having less lift then the p90. Also you do not need a custom cam to run hydraulic lifters. Only problems with hydraulic lifters is they tend to bleed down and not hold pressure as they get older and there are no replacements for them, and once the engine needs to start spinning over 6krpms you will have lots of rocker slap because the lifters can't keep up at that pace. But as long as you have the stock t3 on the engine you do not need to shift above 6k. Quote Link to comment Share on other sites More sharing options...
Bob_H Posted August 13, 2005 Share Posted August 13, 2005 ..... and once the engine needs to start spinning over 6krpms you will have lots of rocker slap because the lifters can't keep up at that pace. .... That is not true. With a huge camshaft not designed with spring pressures in mind, yes, that can happen. Also - if your lifters are old and worn out,(or more often, clogged up with old congealed oil), they will exhibit the same even on a stock camshaft. I ran a mild aftermarket camshaft with my P-90a and had no lifter bleed-down up to 7k rpm. Many years ago I outlined my setup on my website, (the Datsun Workshop - its still there). With Sunbelt's new camshaft profiles and their corresponding lower spring pressures, (less than stock), a P-90a and an their aftermaket camshafts would be no problem with good lifters. I have not personally heard of a P-90a having less lift than the other Z heads - but that doesn't mean it isn't true. I doubt it though. Just some minor corrections. -Bob Quote Link to comment Share on other sites More sharing options...
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