z_cars_rule Posted June 20, 2005 Share Posted June 20, 2005 For the past 2 months my '81 has been smoking quite badly, the problem being shagged rings. Now being a "while I'm at it" sort of person i have decided to give the whole motor a freshen up. I am going 0.040 over bore with a 10:1 CR light port and polish with reseated valves new cam and full exauhst. and of course new bearing/gaskets Now to my question, when i get a new cam, do i need to replace my lash pads/rockers? do you think 150 rwhp is acheivable with this? Thanks for your time. Quote Link to comment Share on other sites More sharing options...
Here comes trouble Posted June 20, 2005 Share Posted June 20, 2005 What you want is the nose of the cam lobe on first contact within .010 to .015 of the rocker arm pad and this can be remedied with different thickness of lash pads. This is the last job you can do and by visual inspection.. You do not want the side of the cam lobe prematurely contacting the end of rocker pad. Quote Link to comment Share on other sites More sharing options...
Thumper Posted June 20, 2005 Share Posted June 20, 2005 150hp should be no problem. You should be able to get 160-170 rwhp. What head do you plan to run. And from what I've read you have to replace lash pads and rockers when you put a new cam in. Quote Link to comment Share on other sites More sharing options...
Clifton Posted June 20, 2005 Share Posted June 20, 2005 If your pads are smooth and don't have a divet then they are fine. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted June 21, 2005 Share Posted June 21, 2005 I am going 0.040 over bore with a 10:1 CR light port and polish with reseated valves new cam and full exauhst. and of course new bearing/gaskets do you think 150 rwhp is acheivable with this? Thanks for your time. Well, for comparison, before my turbo swap I had done a mildly rebuilt L28 similiar to what you are going to do, including: - L28 block fully rebuilt, bored .060 over, flat top pistons - N42 head, light port and polish, stainless steel valves - 10.3:1 compression - Mild cam, 480 lift 270 duration - Rebuilt SU's from Z therapy - 3-2-1 header into 2.5" non mandrel exhuast, thru resonator and muffler, no cat that combo put down almost 170rwhp and 170ft lbs of torque. Before that, I had the same motor in my 280zx, the only differences were that I had just the stock cam, and of course, running EFI instead of the SU's. I had installed an adjustable fuel pressure regulator to richen it up a bit as it ran way lean after the build and would detonate pretty bad. With the fuel pressure up, I dynoed that setup and got 145rwhp and 165ftlbs of torque. needless to say the SU's and cam really livened up the top end a bit at the cost of some low down grunt. So yeah, 150rwhp should be no problem for ya Quote Link to comment Share on other sites More sharing options...
z_cars_rule Posted June 21, 2005 Author Share Posted June 21, 2005 Thanks for all the replys guys. I am going to be running a mildly ported N42 head and the exhaust i cant decide to go for a 2.25 or 2.5" mandrel system. So bastaad525, do you recommend that i get an adjustable fuel pressure regualtor too? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted June 21, 2005 Share Posted June 21, 2005 z cars rule - since you're asking that question I'm assuming you're running EFI? Then yeah, if you're build ends up like mine, you will probably need more fuel. Oh, I dunno how much difference it makes but I forgot to mention when the motor was in my ZX I also had a 60mm throttle body as well. With 100% bone stock EFI in my '80 ZX, at WOT my car would start to ping bad at around 4500rpm all the way to redline. One thing though... again, when it was in the ZX and had the detonation problems, I was running the stock cam. A hotter cam will lower dynamic compression, and may be enough on it's own to keep detonation from occuring. So, you may not need any more fuel. The FPR was a good solution for me. I ended up turning the fuel pressure up to either 42 or 45 psi at idle with the vacuum line connected, so like 7-10psi increase if I'm not mistaken? And the slight richening didn't hurt 'normal' driveability. I also had to retard timing a bit... I had been running 12* BTDC, stock is 10* BTDC, but had to drop it to 8* BTDC after the rebuild. There are of course, other methods of getting extra fuel, like larger injectors, which would give you much the same results, but minus the adjustability, which along with ease of install and tuning, were the main reasons I chose the FPR. Quote Link to comment Share on other sites More sharing options...
z_cars_rule Posted June 21, 2005 Author Share Posted June 21, 2005 Yes i am running EFI, i dont know how our aussie fuel comapres to yours so i might just be able to get away with just a FPR and stock timing. I will be getting it dynoed before and after at the same place to see the difference and how it is running so i could probly tune it all there to eliminate detonation. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted June 22, 2005 Share Posted June 22, 2005 yeah this was on crappy California 91 octane fuel, I'm pretty sure you guys in Aus... and everywhere else for that matter, have better Quote Link to comment Share on other sites More sharing options...
z_cars_rule Posted June 23, 2005 Author Share Posted June 23, 2005 haha yer your probly right, too bad we only get our octane ratings in RON, so it is hard to compare the two, BTW our RON is 98 for premium Quote Link to comment Share on other sites More sharing options...
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