Flat top pistons

[jay28]

Hi all,

I have a 260z with a worn out l26 motor, I got my hands on a l28 motor (f54 block p90a head solid lifters)

Im going to use an E88 head that I have instead of the p90a,

I have the motor stripped down, The block doesn't need to be rebored just honed and would like to keep it that why if possible.

I was wondering is it possible to get standard size 86mm flat top pistons to increase my CR.

This is my first rebuild so if anyone has anyother sugestions please feel free to advise me,

Thanks,

Jay.

[Jeff G 78]

It should already have flat tops if it's a F54 block unless it is a turbo motor. If it doesn't already have them, then yes, simply buy pistons for an '81 - '83 NA motor. If your E88 head has not been milled and doesn't need to be (block as well), then you should yield around 9.8:1 CR. Most heads have been or need to be milled flat, so that will bump the CR a bit, so be sure to measure the head thickness before you begin. It should be 108mm thick from the valve cover surface to the bottom surface. You will need to run premium fuel with flat tops.

[beandip]

Well a F-54 with that head should be a Turbo engine with dished pistons. I thought a P-90a was a hydraulic lifter head. If the P-90a you have is in fact equipped with solid lifters , what is the reason NOT to use this head. Flows better has the right shaped combustion chamber and big valves . Just curious. Gary

[jay28]

thanks for the replys guys,

My p90a head has solid lifters, think its a UK spec motor, also has the dished pistons...........I was going to use the E88 head as I was told that the CR would be too low using the p90a head on an NA motor.

Can anyone recomend anywhere to get flat tops?

Ill measure the head tomorrow to see what thickness is it.

Ive a stage 4 cam set on the way for the E88 head so hope I chose the right one to use!!

Thanks,

Jay

[sblake01]

From what I understand, a P-90a head has hydraulic lifters. Perhaps you mean a P-90? Back in the day, we used to put P-90 lifters in P-90a heads but it required an adapter that screwed over the base of the solid lifter.

[sblake01]

Read this from the Datsun Z Garage:

The P90 is the turbo head from the '81-82 ZX. It has the same combustion chambers as the P79, but has square exhaust ports like the N42. The P90 and P90a are said to be the best flowing heads due to their turbo origins. They both use an internally oiled cam.

The P90a is an interesting turbo head which I believe came out in 1983 only. It has hydraulic valve lifters instead of standard rocker arms, which make the engine almost silent. It has identical chambers and ports to the P90 and uses an internally oiled cam. I think with a low lift, higher duration cam this head would be a hot setup. But the manuals say nothing about servicing it and replacement lifters do not exist anymore

.

[jay28]

No its a p90a head with solid lifters, I understand the UK spec p90a heads came with solid lifters, it definetly has solid lifters and say's p90a on the head........

Im from Ireland , so thats how I cam to have the Uk spec motor..

Jay

[jay28]

http://www.bandmzcars.com/headinfopage.html

It say's on the bottom that there were 2 versions of the p90a head.

Can anyone recomend a place to get 86mm flat tops from?

Thanks,

Jay

[Go240Zags]

I've heard of several P90As with solid lifters, see them on eBay every once in awhile. In the U.S. I think they are the exception, not the rule -- but they do exist.

[sblake01]

My friend just reminded me that the US got the hydraulic and the rest of the world got both versions of the P90a.

[jay28]

so which head do you recomend using? E88 or p90a with the solid lifters?

Also cam anyone recomend somewhere to get a set of 86mm flat tops?

Thanks for the help,

Jay

[Jeff G 78]

I got mine about 10 years ago from Victoria British (now called Black Dragon), but I wasn't very happy with the rings they came with. I have heard that they now use different rings, but I can't confirm. The rings that came with mine were all thrown in a box together with no markings or directions as to which way they should be oriented. I had never seen notches before like the ones on these rings. I asked several engine builders and they had never seen such a pattern either. Of course VB couldn't give me any tech advise as to which order they went in or whether the notches faced up or down, so I had to take an educated guess at it. I still don't know if they are in right. Someone posted a few years back that the ones they bought from VB came in typical ring sleeves that were well marked. Hopefully this in still the case. As far as I know, they are still available in 86mm, but you might have to call them to find out for sure. I tried to look at their online catalog, but the pages are too small to read and it gives an error message when I try to zoom in on the page. Here is the link http://www.blackdragonauto.com/icatalog/z/t.asp?page=54

I think I paid $240 USD for the set of six with rings and pins back when I got mine. That was considerably cheaper than anywhere else I could find at the time.