Guest vodkaboy Posted May 15, 2003 Share Posted May 15, 2003 i have heard that in a few Zs nissan put a head on with a hydraulic valvetrain... i was wondering what advantages/disadvantages this head might have, and how hard it would be to find one, or find parts for one... Quote Link to comment Share on other sites More sharing options...
DatsunBoy77 Posted May 15, 2003 Share Posted May 15, 2003 I happen to have one. There are some advantages as quieter valvetrain and no need to adjust them. But there are many other disadvantages. For one parts are hard and expensive to come by. Nissan doesnt even carry them. They also dont like high lift cams because they cant bleed down fast enough. There are others, but it is getting late and i have an exam at 9 am. Quote Link to comment Share on other sites More sharing options...
Guest vodkaboy Posted May 15, 2003 Share Posted May 15, 2003 I happen to have one. There are some advantages as quieter valvetrain and no need to adjust them. But there are many other disadvantages. For one parts are hard and expensive to come by. Nissan doesnt even carry them. They also dont like high lift cams because they cant bleed down fast enough. There are others, but it is getting late and i have an exam at 9 am. would it be worth geting one for the sake of having a nice quiet valvetrain, considering i dont have plans for a larger cam anytime soon, and i also need to rebuild the head i have sooner or later, and wouldn't mind another head while i do that... Quote Link to comment Share on other sites More sharing options...
DatsunBoy77 Posted May 15, 2003 Share Posted May 15, 2003 If it is just a cruiser and not a race car then maybe. This way you can just take it out withought really worrying to have to constantly adjust the valves. Not a bad option if you use it just for some summer cruises and weekends and like hassle free low maintainecne. I am debating switching over to a non hydrolic so i can get a high end cam. The head only cm on the 83 turbo's and flowed very good. Basically the same as the regular P90, but hydrolic and labeled P90A. Not all P90A's were hydro, but i bet most of those were converted and actully were hydro. Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 15, 2003 Share Posted May 15, 2003 You need to pick the right head for the application. If you are going non-turbo, then for you to use the P90A head (which is the only hydralic head that I know of), you will need flat top pistions in your block (F54), or your CR will be too low (7.4:1). With the flat tops the CR will be around 8.5:1. Not great, but better. If you are going turbo, just bolt it on to a turbo block (F54, dished pistons). That's what I'm running. Pete Quote Link to comment Share on other sites More sharing options...
Guest vodkaboy Posted May 16, 2003 Share Posted May 16, 2003 actually, i was planning on building myself a homebrew supercharger (T-bird SC Eaton M90, i can give you some details if your interested). 8.5:1 comp ratio is also a hair higher than what i have now... IIRC, the '77 L28 had 8.3:1... anyway, I am assuming that its not really a race head, and although im not doing much racing yet, i would like to get into it as soon as i have some other things taken care of (specifically rust, and EFI problems). How poor of a race head is it, side be side, with say, my stock '77 L28 head Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 16, 2003 Share Posted May 16, 2003 I think the P90A sucks. The hydraulic lifters bleed down and when the start to fail, you are SOL since Nissan doesn't carry replacements anymore. Even when they did, they were expensive. I swapped to a P90 and made power actually. I would never ever us a P90A, I would run a P79 instead. Quote Link to comment Share on other sites More sharing options...
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