whats sort of compression psi would you get with a rebuilt engine done 350 miles just curious as to how much psi there should be before the rings are fully run in

I did a compression test and getting around 120 to 130 psi spec is 150 to 175 ish

if I put oil on bores its nearly 200 psi lol

rich

350 miles ... is a little low for comp testing on new pistons/rings/bores m8 i wouldnt worry to much about the reading right now .. long as there all with in the same spec as each other you be good to go ..

 

give it another 500>1000 miles then do comp test by then the rings and bores should be smooth to seal 100%

cheers bud just that I had a little concern over rings sealing especially when I had mi boost controller pipe come off and hit 20 psi boost for a short blast say 5 seconds which kicked a load of smoke out, and blew mi dip stick out as well , but after it cleared up not a hint of any smoke, so thought pcv passing but there not that old, anyway if I run boost at 9 psi all ok still

if I go over 15 psi it blow dipstick out and kicks smoke out I know engine has to bed in and its not good giving it a lot of boost.

any ideas?? rich

You don't run 15psi on a freshly built engine. Standard boost only.

 

Did the builder not give specific instructions for running in? If you're blowing the dipstick out, it's pressurising the crankcase. 120-130psi is way too low for a fresh engine, it shouldn't be smoking at all even at 30 psi of boost, they're all features of a very worn & tired engine I'm afraid. I'd assume that the bores were glazed when you decided to run high boost, unless it's a badly-built engine which also sounds like the case as boost pipes should not be popping off.

 

What map are you using for running in?

 

Turn the boost down to 9psi, drive it under load and snap the throttle shut. Do the same from high revs. I reckon it's too late and you're going to have to have the bores rehoned and run it in properly.

I would remove the pcv valves in case, but as Noel says, it doesn't sound good. Do you have aftermarket cams?

I shut it down as soon as it blipped above 20 psi and saw smoke at rear, as soon as I sorted boost controller its fine but i did a experiment to see why it smoked, so increased boost bit by bit and gave it a little blast only for very short duration 5 seconds and no smoke till boost gets over 15 psi, but nothing on idle or reving and if boost is low its fine

ive got jwt cams in as well

using aem ecu live mapped it no detting running with dual wide bands to monitor afr etc

rich

Which ones? You'll get lower comp readings with the 500's

 

Either way, it shouldn't pressurise the crank case. Either you're pcv's are stuck open, or rings are not sealing properly and unlikely to improve

Rereading, the fact the compression jumps up with oil I'd say your rings are not sealing and very unlikely to get better now. I doubt it's your higher boost run that's done it, most likely an issue with the build

Yeah that's my gut feeling too if the bores a glazed will honing. The bores alone be ok or new rings needed as well even though they only done 350 miles

And can the cometic headgaskets be re used ?

 

Rich

 

 

Sent from my iPhone using Tapatalk

Were the hores boned properly?

 

If it was rich on start up, then you can glaze the bores and it is back to the drawing board.

 

When I ran a brand new Cosorth YB in many moons ago, I ran it on a standard map with standard injectors and low boost. There are various ways of breaking an engine in, but your engine builder should have a preferred method.

Yeah the map was extremely rich on start up so that won't have done it any good :(

 

 

Sent from my iPhone using Tapatalk

Thought as much since it's low across the board. Glazed bores, rings will never seal properly. What you can do is follow the instructions in post 4 regarding snapping the throttle shut. But if it's very rich every time on start up, it won't matter at all. I doubt it will do much, but it's the only thing you can try to improve things.

 

Then:

1. Get it mapped properly.

2. Pull it all apart and start again.

3. Run it in properly using base boost levels.

 

Why wasn't the boost controller switched off for running in?

It was switched off but pipe came off probably by me lol

Fuel is ok now it wasn't run for 350 miles rich only for set up and moving car in out if garage

 

 

Sent from my iPhone using Tapatalk

It was switched off but pipe came off probably by me lol

Fuel is ok now it wasn't run for 350 miles rich only for set up and moving car in out if garage

 

That is likely what has caused your issues.

Yeah I guess so

Can I re use the piston rings and cometic head gaskets ?

 

 

Sent from my iPhone using Tapatalk

Gaskets, yes. I would replace rings

Yeah, you can use the Cometic head gaskets. Whether or not you should, is a matter of debate...

I've always though once they are compressed they are fukt but never tried reusing em

I guess I ought to order new it's been a long time ordering parts where is best place to get em nowadays ?

 

 

Sent from my iPhone using Tapatalk

Czp or speciality Zed in the USA

Yeah il give Greg an email ....

 

 

Sent from my iPhone using Tapatalk

I've always though once they are compressed they are fukt but never tried reusing em

I guess I ought to order new it's been a long time ordering parts where is best place to get em nowadays ?

 

 

Sent from my iPhone using Tapatalk

 

Not because of compressing them, but from a quality point of view.

 

Reusing MHGs a couple of times is not normally a problem.

mm stripped engine and bores looked good

also greg at speciality zed says don't use cometic headgaskets they use genuine Nissan ones as they have had loads of failures with cometic

so if your bores look good what was the issue mate? just rings? bad machining, too large bore for piston and ring?

Not sure yet not had time to measure bores and ring gap but will do this week end but nothing obvious xhatching still on bores