8 Questions On Rb26dett Rebuild ?

[Sinista32]

Hopefully some quick n Easy Questions for the techo's on the site. I have searched the site topics for answers but with no luck. I drive and learn bits n peices as I go along so If my questions are simple it indicates my knowledge

My RB26 engine has just been rebuilt with JE forged Pistons, Eagle rods and Tomei Pon Cams (260 degrees/9.15 lift) in/ex.

Q1. I'd like to know what the cylinder compression should be?

The reason being I have had two readings from different garages 85psi (all 6) and 120psi accross all 6.

Prior to the rebuild, with the stock internals, 155 accross all 6. Could my bad battery cause the inconsitency's. I am advised the Pon Cams do make a difference - what should the readings be?

Q2. Spark Plug in cylinder 1 had oil on it. 2-6 are fould. Is this part n parcel in the first few hundred Km's? Could it be from the front turbo if it has been stuffed or the run in tune?

My engine has about 450kms on it now.

Q3. My R34 N1 Turbs (3 months old) were fine prior to the rebuild. After the R&R now #1 (one) makes noises when it was first fired up and ongoing, What could be the cause or issue? Stored for 15 months while the rebuild was happening. (whinning zzzzzzzzzzzzz sound).

Q4. Should there be lots of blow bye and smoke occuring when it was initially started/ongoing? If not what is the possible cause/issue. The oil catch can was left in place during the R/R and was fairly full, but has since been emptied. Smoke has reduced somewhat but what/how do you test or rectify blow bye? What does it indicate?

Q5. I have heaps of black spots showing on the rear of the car, and black dust all over my garage floor, out the exhaust ? Part of the bedding in or is it just tuning ? Heaps of fuely smells while driving!

Q6. The AF mixture was initially set to 14.7:1 (lean?). on the PFC, Is this OK? Z32 AFM's.

It has been changed by a different tuner but apparently is now pinging (knock). Now being re-tuned to suit the AFM's.

Q7. The Aux air valve is blocked somehow, what is the effect ? Can it be clearaed or is a new one required?

Q8. Finally, Is it common to have noticable traces of fuel in your oil at the first oil change ?

Thanks in advance for your experiences/knowledge.

[paulr33]

6. AFR is not related to ecu type or model, its related to the tune and how the tuner has tuned it. pinging is usually related to much advanced ignition, but can be affected by running too lean also. 14.7 is ok for cruise and ideal but for max load and during boost build its too lean

[GTR1993]

In regard to your compression test, i am unsure if it is normal but i bought my car that already was built with forged pistons and a 1.2mm head gasket, it also has tomei cams that are around 260 degree (i dont know till i pull covers off exact specs arnt written on the recipts) but i also comp tested at 120psi.

[Sinista32]

In regard to your compression test, i am unsure if it is normal but i bought my car that already was built with forged pistons and a 1.2mm head gasket, it also has tomei cams that are around 260 degree (i dont know till i pull covers off exact specs arnt written on the recipts) but i also comp tested at 120psi.

thanks Alex - *breaths easy* thats good news to me.

[Cubes]

Q2. Spark Plug in cylinder 1 had oil on it. 2-6 are fould. Is this part n parcel in the first few hundred Km's? Could it be from the front turbo if it has been stuffed or the run in tune?

My engine has about 450kms on it now.

Q4. Should there be lots of blow bye and smoke occuring when it was initially started/ongoing? If not what is the possible cause/issue. The oil catch can was left in place during the R/R and was fairly full, but has since been emptied. Smoke has reduced somewhat but what/how do you test or rectify blow bye? What does it indicate?

Q5. I have heaps of black spots showing on the rear of the car, and black dust all over my garage floor, out the exhaust ? Part of the bedding in or is it just tuning ? Heaps of fuely smells while driving!

Q8. Finally, Is it common to have noticable traces of fuel in your oil at the first oil change ?

Thanks in advance for your experiences/knowledge.

If its blowing oil smoke *not condensation* when starting or after sitting idling and giving it a quick rev its a sign of valve stem seals, it is very possible and has been known for them to be damaged when during a head reco process.

My plugs were clean and the oil never smelt like fuel. I did multiple oil/filter changes within the first 1000kms.

It did use a little oil until around 4,000km's after that it hasn't used a drop, I've now done 40,000km's.

[rev210]

1) and most of the others....

If this motor is not run in properly and it sounds like it isn't yet. That would explain alot.

The piston rings need to bed in to 'seal'. If they haven't the compression will be crappy like yours is.

[Sinista32]

I understand the Pon Cams hadnt been adjusted. They were installed at the same settings as the standard so this had an impact.

[CruiseLiner]

the fuel in the oil might be from running excessively rich or one cylinder not firing and the fuel is washing bores and going past the rings into the sump oil.

my comp test after only 500km with 272/11.35mm cams was 155psi so that under 100psi readings sound wayyy off.

oil on one plug shows its not firing from memory

thats my opinion, what do others think of those ideas?

[Blitz]

I have done around 7000km's on my newly built engine, using 87mm CP Pistons and Tomei cams, and a recent compression test showed ~180psi across all 6 cylinders and a leakdown figure of 6-7% across all 6.

Can I ask who built and tuned your engine?

Have you done a leak down test?

[DVS JEZ]

hey sinista32,

i rebuilt my engine not long ago pretty well the same. je pistons 260 poncams etc. because piston 5 and 6 ring lands decided to melt. bad blow by before rebuild

i had a really bad problem after the rebuild of blowing blue smoke when idling, cruising but not boosting.

after about 1000kms i finally worked out that in the cam covers there are filters before the pcv outlets. mine were blocked and because the pressure couldnt go anywhere it made its way into the combustion chamber, hence the blue smoke,

i removed the cam covers and soaked the filters in kero,

havent had a problem since.

it was heaps embarrasing when you have just rebuilt your motor and its blowing smoke all over the place...

let me know if this helps

cheers

Jeremy

Edited June 27, 2006 by DVS32R

[Sinista32]

Thanks for replying guys

Cruise and Blitz - Thats what worried me on #1 cylinder, possible fuel washing the bore/s. It's highly unlikely but it wasnt worth risking.

I think a leak down test is in order.

180 PSI That's good - I'm not certain what it should be but I note one post quoting 120 from GTR1993. I expect it should increase over the run in process. However, Who would be the authority on whats the norm?

DVS - I'll get the filters out of the cam covers and cleaned. I might have the same issue. Good advice. BTW as your build is very similar Jerry whats your compression readings ? (few cars up here with the Hektic stickers on)

Cheers

Richard

[GTR1993]

This is totally hypothetical so i dont know if this it true:

When you go to a larger duration camshaft low end performance suffer because of the increased overlap (i know this doesnt have to be true but generally increased duration has increased overlap) Anyway, with increased duration low rpm performance suffers, now cranking a cut is very low rpm only few 100 rpm, does this mean that there will be a lower PSI reading as increased overlap is bleeding off cylinder compression??

[DVS JEZ]

when i had the blue smoke issue, i carried out a compression test with stock cams. it was 155psi on all 6.

only recently put in the poncams. havent done a comp test yet. has had a few hard dyno sessions. i will do a comp test this weekend if you would like.

are your Je pistons 40 thou oversize?

did the person that built your motor know that je pistons use smaller clearances then most forged pistons.

cheers

ps i dont know what hektic stickers are. i just put hektic on my profile thingy cause i like it.