Major service coming up: advice sought

Owner of a 152k '91 with 7psi CTSC and intercooler, AEM series 1. Car has some track history prior to 120k, when the CTSC was installed by the next owner. Seeing around 400rwhp. I don't see myself really needing more power i.e. going turbo at this point. I am not currently planning on tracking the car other than maybe the odd track day, but car is driven fairly hard on the street with frequent trips to the redline.

TB/WP/clutch were done at 120k, 9 years ago by Mark Basch along with motor mounts and a lot of other bits and pieces.

Hot oil pressure at the gauge is between 0 and 1 bar at idle and 4 bar at WOT (using a new SOS sender to repalce the factory), and using a new AEM sensor Teed off the “zero pressure” light sensor, I see ~18-22psi at hot idle and about 80psi under WOT, 60psi at 3500rpm, 75psi at 4000rpm

I had a compression test done when I bought the car a year ago:
front L-R 176-168-175
rear L-R: 172-165-150.

I just had a leak down test done in cylinder order: 3%-6%-2%-3%-1%-2%. Possibly transposed #2 and #3 though...does anyone have a diagram of which cylinders are which numbers?

So, I have a local specialist lined up to do the work and prefers engine out if possible. Cost to me is the same. He does all manner of imports, has a nitrous NSX and did his TB/WP engine out and a lot of other work including a tranny rebuild.

So, planning on the obvious minimum of:

- TB/WP
- SoS LMAs (never been done AFAIK)
- Valve adjustment
- Replace all coolant hoses
- Replace coolant and oil obviously
- Inspect clutch, replace if necessary – SOS 275? 350?
- Change Whipple oil
- Replace intercooler coolant
- Powder coat the spare set of valve covers
- replace coil pack cover seals and mounting bolts

Considering replacing/doing the following:
- Oil pump – how do my AEM sensor numbers look at the pump? Or should I do this anyway? Use the SoS new billet gears?
- Thermostat
- Motor mounts – typically necessary?
- Cam seals?
- Add an oil temp sensor?
- Inspect tranny and diff (I have a spare diff)
- Reduce exhaust noise: wrap headers and swap out cats for low mileage ones
- Sending off injectors to be cleaned/tested or upgrade to ID1000s

No need to do the following:
- clutch and brake master cylinders (done in 2013)
- replace SC belt and plugs (all done in last 4 months)

FWIW I have a spare block, crank and heads, all tested and blessed by a local well respected machine shop. Oh and a set of brand new CP pistons. Emergency backup...

I guess the real question is, given the compression test, leakdown and oil pressure, should I do a tear down and rebuild, full rebuild for power or leave as-is? I am all for saving money by combining jobs and preventive maintenance, but only if a big dollar job is really necessary.

Given engine already out of the car, what are approx $ figures for a stock motor rebuild, or a mild build with ARP, head gasket, piston upgrades plus machining? What would YOU do and why?

Thoughts on what I should also be looking at for my list, and on the (re)build question.

And if anyone has any parts I need, shoot me a PM with a price!

Thanks!

Page 7-5 of the Service Manual is cylinder numbering.

But it's rear right to left and then front right to left.

Page 3-2 has the compression specs, list 142 as a minimum at open throttle.


Manual is here.

http://www.nsxprime.com/FAQ/Reference/1991_svcman/1991servman.pdf


Compression test was a year ago and then you had one cylinder almost out of tolerance, something some where will also say they have to be a certain percentage within each other but can't find it, chances are your out of tolerance.

if it's coming apart a bare minimum would be forged pistons, metal gaskets, ARP head bolts would be nice and consider a billet oil pump gear while it's apart. This is considering as mentioned it's for FI.

- - - Updated - - -

I'll try answer few more when i get time.

i did a big mechanical refresh last year,and had a few suggestions-
have injectors cleaned/calibrated at RC Engineering, if that wasn't addressed when your car was supercharged.the car pulls much harder and stronger after doing mine
on the LMA's, consider the SOS upgrade kit
clutch master/slave,especially if getting a new clutch. if they're original,they're pretty old

If I were you, I would discuss it with your mechanic. Since you obviously trust him to do the work, he should be able to advise you of the pluses and minuses and cost estimates for all the various options. I'm not saying it's a bad idea to ask here - I hope you get a lot of replies with knowledgeable opinions that help you with your decision - but your mechanic is the one who will be taking responsibility for the work, and can for sure tell you approximately how much any particular option is going to cost.

FWIW, a while ago I had a rebuild-vs-replace decision to make regarding my NSX engine, and my mechanic was able to give me really good advice on it.

HTH

Thanks for all the feedback and the links. Clutch and brake masters were done a couple of years ago. For the LMAs, yes I planned on the SoS kit, and had also planned on sending off the injectors or maybe upgrading them to ID1000s. Good reminders though. I'll update my initial list for new readers

Keep it coming!

Cheers

Anyone else have any thoughts on this? I am going to be at S0S on Friday so will pick up the LMAs then. Based on solid leak down numbers my main concern is the oil pressure, so wondering if a new oil pump or the SoS pump gears will help.

Good list. I'm looking at my third major service in the next year so this is topical discussion. One thing you didn't mention that I've been thinking about lately is replacing the fuel pump, resistor, FPR, and filter. Mine is giving that funny hesitation below 3k RPM that is a sign that it's time. I would have thought that a higher flow rate pump might have been needed for your FI setup but I didn't see any mention. Due to age/mileage and maybe larger injectors, you might want to consider. I know SOS sells different pumps and also makes an upgraded wiring harness.

I should have mentioned fuel pump replaced a year ago with a Walbro 255. Resistor is bypassed. I need to look into the fuel filter though. Thx!

NSX2398 said:

Good list. I'm looking at my third major service in the next year so this is topical discussion. One thing you didn't mention that I've been thinking about lately is replacing the fuel pump, resistor, FPR, and filter. Mine is giving that funny hesitation below 3k RPM that is a sign that it's time. I would have thought that a higher flow rate pump might have been needed for your FI setup but I didn't see any mention. Due to age/mileage and maybe larger injectors, you might want to consider. I know SOS sells different pumps and also makes an upgraded wiring harness.

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