john kosmatka Posted May 30, 2003 Author Share Posted May 30, 2003 I have the 83l28et which from what I read has a p90a, which according to you guys is not good for performance. I plan on using the stock t3 turbo with a intercooler and 10-12psi of boost and a bov. Would it be better to change to a p79 or a p90 than to keep the stock p90a. Thanks John Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 30, 2003 Share Posted May 30, 2003 I think you need to determine if it has hydraulic lifters or not. If you take the valve cover off, you should be able to tell if it is a solid or hydraulic. Look at the rocker arm, and the back side of it should have a spring on it that attached at the base of the pedastal that the rocker arm sits on. If it has a spring its a solid, no spring, hydraulic. Also solid lifter heads have a 17mm and 14mm bolt that you adjust the pedestal the rocker arm sits on. If the lifters are working properly I would leave it for now, but find a solid lifter P90. You won't know if they are working until you crank the engine up and listen. If you hear a bunch of clattering from the head, lifters are bad. Quote Link to comment Share on other sites More sharing options...
Guest thepenguin99 Posted May 30, 2003 Share Posted May 30, 2003 john kosmatka if your p90a head is in good shape dont worry about changing it. It really isnt worth the effort unless your p90a is in bad shape. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 22, 2003 Share Posted June 22, 2003 I just noticed something really wierd about my P90 head. The two exhaust ports in the centre are wider than the ones on the outside of them. Does anyone know why that is? Quote Link to comment Share on other sites More sharing options...
Guest cw280z Posted July 7, 2003 Share Posted July 7, 2003 yet it has square exhaust ports. it came from an 82 2+2, i have read an article on the p-79 stamping issue and apparently the p-90 was made with a p-79 casting mold. has any one else ran across a square exhaust port head on an n/a car? i'm assuming that it will flow like a turbo head and that it only has a different cam in it than the turbo head. the head was on a car i bought for parts and i have pulled the motor, but i have not torn the engine down yet. i have not looked over a turbo head and was wondering if anyone else has compared the two? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 7, 2003 Share Posted July 7, 2003 Yes, cw280z, the square ports on the P90 are high flow ports for turbo applications, and are very popular heads for N/A build-ups as well. I'm wondering, though, why ports 3 & 4 are larger than 1, 2 , 5, and 6. Can someone shed some light on this? Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted July 7, 2003 Share Posted July 7, 2003 I was talking with Jim Thompson about the P90A solid lifter heads, and he said that the japanese version P90A heads came with the solid lifters. So I think the best way to check this is to do exactly that, pull the valve cover and check to see if their solid lifters. As for why hydrolic lifters are less preferable than solids, with a hydrolic lifter system the valves have been reported to float at high RPMs sometimes, and this is not a good thing at high RPM. Chase Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 7, 2003 Share Posted July 7, 2003 Yes' date=' cw280z, the square ports on the P90 are high flow ports for turbo applications, and are very popular heads for N/A build-ups as well. I'm wondering, though, why ports 3 & 4 are larger than 1, 2 , 5, and 6. Can someone shed some light on this?[/quote'] All the heads without liners in the exhaust are like this. Beats me why, but they are. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 7, 2003 Share Posted July 7, 2003 Maybe I'm cluching at straws here, but do you think it could have anything to do with thermal efficiency--what with exhaust ports 3 & 4 being next to each other? Quote Link to comment Share on other sites More sharing options...
David K Posted July 7, 2003 Share Posted July 7, 2003 Does anyone else have or seen one of these? And yes' date=' I'm sure. Joe[/quote'] I have a p90a hydraulic head. Im re furbishing the lifters by soaking them in deisel fuel and then boiling them in hot water on the stove. That should remove all deposits, and make them like new. Do not buy them new, since they are hard to find and very expensive. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 7, 2003 Share Posted July 7, 2003 Maybe I'm cluching at straws here, but do you think it could have anything to do with thermal efficiency--what with exhaust ports 3 & 4 being next to each other? Nothing to do with anything other then manufacturing cost savings. One of the tricks to get power out of the L6 head is to do a lot of work on 3 & 4 exhuast ports to get them to flow the same as the others. The ones on my N42 head built by Sunbelt are raised and reshaped. The header and exhaust gasket needed some work to get them to line up with the new ports. Quote Link to comment Share on other sites More sharing options...
Guest cw280z Posted July 8, 2003 Share Posted July 8, 2003 Yes, cw280z, the square ports on the P90 are high flow ports for turbo applications, and are very popular heads for N/A build-ups as well. what is the poss. that this head is stock on an n/a car, i am not sure that it did, i was assuming that it did however. i guess someone could have put it on there. the car was not a super high mileage car is why i assumed it came on the car. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 8, 2003 Share Posted July 8, 2003 The P90(A)'s never came on N/A cars from the factory. Quote Link to comment Share on other sites More sharing options...
DAW Posted July 9, 2003 Share Posted July 9, 2003 JDM n/a L28 with P90(a) heads. DAW Quote Link to comment Share on other sites More sharing options...
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