Jump to content
SAU Community

Guru Needed, New 25/30 Engine Startup Problems!

Black_R33

By Black_R33,
in Engines & Forced Induction

 Share

Recommended Posts

Black_R33 Enthusiast

Black_R33

Posted
Posted

Brand new RB25/30 long motor built by RB specialist, installed it last night and it has no comp on cycl 5! Holy shite. Very confident nothing got in it during installation and don't doubt the builders skills but what could it be? If I had to guess I assume it must be stuck valve but how? How does the hydraulic set-up work? Could they be not yet pumped up? After getting oil pressure up (took the inj fuse out and cranked) I started it for about 1-2 mins thinking the plugs where fouled and it would fire up on all 6 after a bit but no good... I don't want to run it anymore as all the fuel in the cylinder will be washing the bores clean and that would be bad.....Any ideas before I have to pull the rocker covers off and start to investigatagtion the top end first?

:)

Mesmer Enthusiast

Mesmer

Posted
Posted

This happened to my 25 when i rebuilt it. We got a little careless at the end of the rebuild and didn't check the lifters as they where fine when i pulled the engine down.

At least 5 or so where locked up and not letting the valve close all the way. Replaced them and its been running fine until now.

So that may be your problem too.

John

  • 2 weeks later...
Black_R33 Enthusiast

Black_R33

Posted
  • Author
Posted

Important Update!!!!!

Did a leak down test and found exhaust valves open on cyl 5 ! AHA! Pulled the cams out and wacked 2 new lifters in it (OW!$100 each from nissan). Put it back together and cranked it.........Beautiful-No 5 no probs.... but now no comp in 1 and 4.....WHAT THE? We chopped one of the old lifters in half and found some carbon in it so we think that the lifters must be sucking that crap into them when they pump up and can't bleed down thus holding the valves open. Looks like I need to replace them all!! We have been bleeding them down before assembling the head, this is the right procedure yeah? If we have to replace the lifters does anyone know of a cheaper supplier than oem? Anyone rebuilt heads with similar probs got any stories or techniques to share? Would love to hear your thoughts!

Cheers

P.S Still pretty happy its not terminal though....phew! :)

Cubes Grand Master

Cubes

Posted
Posted

It has been suggested to me that this 'may' be the cause of my valve float, as occasionally on startup i get the lifter pump up miss. :)

I'd be interested if there is a cheaper than nissan way out of it.

Similiar year VG30 lifters are the same part number so that may be a start, well for myself with the R32 head anyway, possibly the US may have something aftermarket.

Cubes Grand Master

Cubes

Posted
Posted

No idea...

Black_R33 has experienced a bad lifter holding valves open and now I'm being told that my problem may be partially my lifters due to a couple of symptoms; the all of a sudden valve float and lifter pump up i'm experiencing and the occasional same valve float lifter pump up miss.

No idea.. Will find out when the head comes off. I had planned to pull it off this mid term break, it won't be happeneing as I'd prefer to have a little extra money stashed away just incase it gets expensive. :S

Lifter pump up miss cannot be mistaken, its a different sound to an ignition or fuel miss.

I'm sure black_r33 agrees. :domokun:

Mc. Stocky... believe me I have fantasized about a nice solid lifter conversion + a set of gtr high lift cams... high lift = lots and lots of mid range. >_<:ph34r::)

darkstar Contributor

darkstar

Posted
Posted

Try a Wrecker.....

Could also be something trival like swarf (tiny filings) either on the valve seat or in the valve guide causing them to stay slightly open.

The head should have been pressure/vaccum tested before assembly - this would have detected it before you installed.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • The Bogan
      NC MX5

      By The Bogan · Posted

      Yeah, it's getting like that, my daughter is coming over on Thursday to help me remove the bonnet so I can install the Carbuilders underbonnet stuff,  I might get her to give me a hand and remove the hardtop, maybe, because on really hot days the detachable hardtop helps the aircon keep the interior cool, the heat just punches straight through to rag top I also don't have enough hair for the "wind in the hair" experience, so there is that....LOL
    • joshuaho96
      Cas issue

      By joshuaho96 · Posted

      Could be falling edge/rising edge is set wrong. Are you getting sync errors?
    • joshuaho96
      Jacks that fit under GTR lips that can reach the subframe?

      By joshuaho96 · Posted

      On BMWs what I do because I'm more confident that I can't instantly crush the pinch welds and do thousands of USD in chassis damage is use a set of rubber jacking pads designed to protect the chassis/plastic adapter and raise a corner of the car, place the aforementioned 2x12 inch wooden planks under a tire, drop the car, then this normally gives me enough clearance to get to the front central jack point. If you don't need it to be a ramp it only needs to be 1-1.5 feet long. On my R33 I do not trust the pinch welds to tolerate any of this so I drive up on the ramps. Before then when I had to get a new floor jack that no longer cleared the front lip I removed it to get enough clearance to put the jack under it. Once you're on the ramps once you simply never let the car down to the ground. It lives on the ramps or on jack stands.
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      Nah. You need 2x taps for anything that you cannot pass the tap all the way through. And even then, there's a point in response to the above which I will come back to. The 2x taps are 1x tapered for starting, and 1x plug tap for working to the bottom of blind holes. That block's port is effectively a blind hole from the perspective of the tap. The tapered tap/tapered thread response. You don't ever leave a female hole tapered. They are supposed to be parallel, hence the wide section of a tapered tap being parallel, the existince of plug taps, etc. The male is tapered so that it will eventually get too fat for the female thread, and yes, there is some risk if the tapped length of the female hole doesn't offer enough threads, that it will not lock up very nicely. But you can always buzz off the extra length on the male thread, and the tape is very good at adding bulk to the joint.
    • Duncan
      Mistakes were made, my R34 Story

      By Duncan · Posted

      Nice....looking forward to that update
×
×
  • Create New...