p90 vs. p79 in a boosted application.

[m1ghtymaxXx]

Well the Z is going under the knife this winter. I have a 83 turbo parts car, and a 83 N/A. Both motors are in decent shape, with 152 XXX kms.

 

My plan for winter is to turbo charge with a z31 ecu, injectors, intercooler, exhaust and ka throttlebody.

 

I plan to use the N/A shortblock, using the turbo oil pan, but i'm not sure if its worth swapping heads too.

 

Being a 83, i assume the p90 has hydraulic lifters if that changes anyone's opinion.

 

Do you think i should keep the N/A motor sealed up with the p79 head and just swap manifolds, or use the p90 as well?

 

Keep in mind, i've never come close to swapping a motor, so everything i do will be a learning experience.

 

Also, the N/A motor has a good exhaust like at the manifold at the 6th cylinder, which i imagine is the typical snapped stud. If its broken off in the head, i guess i'd have to pull the head anyways.

 

Edit: Forgot to mention, the car will be my summer daily driver, built for weekend auto-x duty, thus the reason for higher compression and quicker throttle response. Alcohol injection is a consideration, but not until i have the suspension addressed.

 

As for power goals, whatever the block will take safely, but i have piece of mind know I always have the turbo shortblock on standby.

 

Please feel free to critique any other elements of my build too.

[m1ghtymaxXx]

Forgot to mention as well, my concern is in the exhaust port liners. I've heard conflicting reports on here as to weather or not they will hold up to the added exhaust temps generated by boost.

[Thumper]

I believe there has been quite a few threads about this over years. Try a searching some more and you should find all the info you need.

[spork]

Either head will work fine for a mild turbo build. When starting to look for the bigger hp numbers, then a different head could help along the way. Several guys on here have gotten past the 400hp mark on a stock head and cam. To get to the 400hp mark with less boost, some headowrk and cam will do wonders. (but you're also spending more money. Do some searching and I'm sure you'll find the info you are looking for. Try re phrasing your search and it's amazing the information you can find if you use just the right search terms.

[m1ghtymaxXx]

I did search but i came up somewhat inconclusive. This was the post got me a little worried though:

The P-90 has the SAME chambers and valves as the P-79. The difference between the two are the exhaust ports. The exhaust ports on the P-90 are square like the N-42 head where as the P-79‘s exhaust ports are the Round exhaust ports with liners like the N-47. For a turbo engine, the liners are NOT desirable as they will come apart in short order and as those small parts of broken metal try to pass through the exhaust turbine it will cause problems, at best those broken chunks of exhaust liner will just block the turbo from spinning, or they could end up damaging the turbine… Either way, not good.

For a Turbo application, use the P-90.

 

This is the only mention i could find of this problem. I'm not doubting braap's knowledge, he pretty clearly knows his stuff. I'm just wondering if theres something missing hear, like at what power levels or exhaust temps this problem starts to occur.

 

Keep in mind i plan on using flattop pistons, so that will likely be a limiting factor in how much power i can make.

 

 

Edit: It just hit me now, yeah, that p90's got a turbo cam. And being a hydraulic lifter head the cam won't work in the p79. I guess i'm leaning towards the p90 again. My biggest worry is dropping the timing chain down into the into the front cover.

 

I guess with the motor out this shouldn't be a hard job.

[BRAAP]

There are other threads on this forum regarding the exhaust liners and Turbo charged engines. I’ve seen a few liners “burn out" on N/A engines, yet there are others on this forum that are running Turbochargers on their round exhaust ports, liners still in-tact.

 

In short, I prefer not to use the liners on Turbocharged L-6, on the flip side, it has been done and done successfully by members here.

 

 

Keep searching. Search for Turbocharged N-47, exhaust liners, turbo, etc, and you'll find those threads.

[ckelly78z]

If you have both the N/A shortblock, and the turbo shortblock along with both heads in similar condition, why wouldn't you just use the combination that Nissan put together for optimum performance....the F-54 block with turbo pistons, along ith the P-90 head ???

[m1ghtymaxXx]

If you have both the N/A shortblock, and the turbo shortblock along with both heads in similar condition, why wouldn't you just use the combination that Nissan put together for optimum performance....the F-54 block with turbo pistons, along ith the P-90 head ???

 

Since i'm not looking for huge power figures (yet), i figured i'd build the motor for response.

 

I figure (correct me if I'm wrong), with the same compression, better flowing exhaust, replacing the afm with a maf, deleting all the emissions garbage, and bigger tb, i'd have the same, of not more power off boost then i running the motor NA in stock form. That should make for a pretty responsive feel even with a larger turbo.

[Thumper]

Since people are being nice and not making you search (I guess I can too) here is a few websites that will help you.

 

http://www.geocities.com/row4navy/p-90.html

 

http://datsunzgarage.com/heads/index.htm

 

http://datsunzgarage.com/engine/index.htm

 

http://www.atlanticz.ca/zclub/techtips/

 

http://www.msu.edu/~levesqu6/links.htm