ok i own a 90 nissan 300zx N/A with approx. 150k miles, i'm in the middle of a fuel injector swap due to clogged fuel inectors. when i had the intake plenum removed i noticed a huge build up of carbon in the intake chamers, you cant even see bare metal. is there a suggested method of removal for this carbon build up?
geeting all that out is gonna be a b**** i can already tell.
with this many miles how dose everone feel about me having my motor rebuilt? would i get noticable performance along with the benifit of haveing a near new motor again??

 

if you have good compression and oil pressure, don't worry about a new motor. spray carb cleaner all around the manifold while it's out and clean what you can. especially the butterflies. then once it's back on the car find a write up on manifold cleaning and do that. sea foam or some other stuff will take it all out pretty well usually

 

i had actually perormed a sea foam injection about 300 miles ago.. and a tun of carbon ended up comming ou the tail pipe... but the only place i could get the seafoam to get sucked in back one of the houses off of the balance tube so i''m not sure how much of the plenum got cleaned or how good, but from what i see in the plenum.. it makes me think that the sea foam didn't domuch of anything.. unless it was allot worse.. then that makes me wounder about inside the block... thats y i ask if it would even be worth it to have my motor rebuilt...

 

if you have the money to rebuild your engine, and at that many miles....id say do it.

btw, when doing seafoam, there are two hoses right underneath the throttle bodies that you can use. or use the hoses on the intake pipes themselves

 

you can surely get it clean without a rebuild if it is dirty. but yes i agree, if you have the money, a rebuild will never hurt. haha when i changed my heads, the pistons had so much build up on them that i scraped it off with some wood. i think it was about a normal amount though

 

If it ain't broke, don't fix it.

Removing the engine and stripping it down to refresh it and put it back together WILL break things in the process (wires, connectors, sensors, bolts, etc. I've seen 300ZX's with over 200k miles on the engine, and 1 with over 300k miles, so I'm not going to recommend rebuilding an NA if the compression and oil pressure are fine (I only say NA because if you were shooting for a 700rwhp TT, that's a different story). Keep up on the scheduled maintenance and use carb cleaner on the intake.

 

I'm closing in on 190,000 miles. Runs strong and beats all my friend's NA's