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No Vacuum at lower RPM (RB25DET NEO)

DTT_Eruc
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DTT_Eruc Enthusiast

DTT_Eruc

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And the battle continues........

Timed the engine on points,ran a compression test again still did the slow build up starting to think that compression tester is maybe defective or ill need to try another one or try that same one on another engine to confirm... havent start the engine to see if its still doing the low vac issue... 

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DTT_Eruc Enthusiast

DTT_Eruc

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5 hours ago, NEO25T said:

Well fire that puppy up, you might have fixed it lol

Is your idle control plugged in properly, if thats not opening to keep the motor running, rpm will be down as well as vacuum  

illl start sometime this week.. just need time to finish mount up other components.....am running no IAC/Idle control.....

  

DTT_Eruc Enthusiast

DTT_Eruc

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5 hours ago, NEO25T said:

Well fire that puppy up, you might have fixed it lol

Is your idle control plugged in properly, if thats not opening to keep the motor running, rpm will be down as well as vacuum  

This is the slow compression build up i was referring to 

Ben C34 Grand Master

Ben C34

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How did you lap the valves, and why?

Do a leak down test or at least out air into the cylinders, I reckon you have valves not Sealing correctly. That's my current guess anyway

DTT_Eruc Enthusiast

DTT_Eruc

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7 hours ago, Ben C34 said:

How did you lap the valves, and why?

Do a leak down test or at least out air into the cylinders, I reckon you have valves not Sealing correctly. That's my current guess anyway

when i pulled down the head while communicating with you guys i did a kerosene leak down to see if any vales were leaking and if there was any only one or two which was slight on the exhaust side. Intake had no sign of leakage and i did all valves with the head turn over and the kerosene settle on the valve based..... so am trying to get another compression tester dont have access to a leak down tool..... 

 

Reason why i lapp the valves well more fine on intake and coarse and fine on the exhaust is cause the last two valves of the exhaust had a slight bend so all 12 valves were lapp over on the exhaust which change the clearance i believe....and after that is when this issue was shown..... I already change the clearance to tomei spec of 0.018 thou on the intake... i may/might start the engine and see if what i did made any difference...Engine time on points am only left to believe either the vct might have a play in this but i doubt 

 

 

all that was done to the head when taken off was - Replace exhaust #11 and #12, Tomei 1.2 head gasket,stock head bolts torque to nissan specs,changed valve seals ,lapp intake with fine and exhaust with fine and coarse...Thats about it....

Edited by DTT_Eruc
  • 2 weeks later...
tridentt150v Grand Master

tridentt150v

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Have you done a wet compression test at all?  I'd like to see a dry then a wet test and see if there is much difference.  I realise that the focus is on the head and valves being the issue [and I tend to agree], but a wet comp test would confirm this.

 

 

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