Timing Belt Dramas... Car Wont Start :(

[Big Fella]

As someone esle stated, pop the sparkplugs back out and turn the engine over with the belt on. it should be easy enough to turn with a normal ratchet(ie not a huge breaker bar) if you are still having issues, then i'd be looking at bent vlaves.

It's at about this point that i'd be calling a mechanic mate. we always get cars thru work that are hard to diagnose over the phone(or forum in this case) but turns out to be something easy.

as a side note, Astra engines which are notorious for bending valves when the cam belt snaps(interference engine)- the crank can be turned over by hand independent of the cams. with a 4 valve per cylinder type engine you normally have enough clearance

[JAV360]

Not sure if anyone has suggested it but have you done a compression test?

In my experiences working on holdens, if a belt isn't lined up, breaks or comes off, its most likely all the valves will be bent to some extent.

Its unfortunate that its happened but I guarantee you aren't the first and won't be the last preson that goes through this.

[JAV360]

just remembered it doesn't start. my bad.

[-RBD2-]

You can borrow my car for the cruise Adam,as I'll be in Sydney

if you don't sort yours out that is mate

it's there if you want to enjoy straight pipes for a day...

[chef_stagea]

Thanx rod but I'm not a fan of driving others cars! Couldn't bring myself to take the car back with a sticker lol

makes sence now that I should have turned the wheels with the belt on! Not sure how I'll attack it!

You can borrow my car for the cruise Adam,as I'll be in Sydney

if you don't sort yours out that is mate

it's there if you want to enjoy straight pipes for a day...

[GRIM_R32]

Hey Adam,

Reading through the thread on what you did, i would have to agree with Roo, to me it sounds like you have bent valves, as others have said with plugs out you should be able to turn the motor over with minimal force. By the time you try fault finding it would be quicker to just pull the head off.

Edited August 1, 2010 by GRIM_R32

[chef_stagea]

So say the valves are bent.. I'm up for all 24 valves?? Or just the ruined ones? Or do they all go?... New sleeves for the gone valves.. And springs should be ok??

[heslo]

I'll put another vote in for bent valves. If you take the head off, you're gonna need to machine the face before you slap it back together too. Depends how many valves are bent as to what you will need to replace but no, you won't need to replace ALL of them, just the bent ones.

Best bet, rip it off, send it off to somewhere like Rhemac, get them to give it a once over and go from there. Turn a negative into a positive even. Do a bit of porting while it's off maybe?

[-RBD2-]

Haha,that's cool Adam

you can just swap all my parts out for the inspection

it's there if you want to take it,talk soon

[Daleo]

So say the valves are bent.. I'm up for all 24 valves?? Or just the ruined ones? Or do they all go?... New sleeves for the gone valves.. And springs should be ok??

Unlikely to be all 24 valves, replace bent valves , re-cut seats, valve grind, maybe guides, and new stem seals. If it's apart, you might as well do it right. A reputable head specialist would look at what you have damaged and recommend the best course of action.

[GoldZilla]

Vote 11ty for bent valves - like others have stated, if you've turned the crank with the belt off, then because the valves stay in position, then it's a fair chance that there was contact between the moving piston and the valve which is still in it's original spot.

Also, while the head is off, check the pistons in the affected cylinder to make sure there's no damage from contact with the valves. It's not likely, but it's better to check and know for sure than put it all back together and still have issues.

[RubyRS4]

So say the valves are bent.. I'm up for all 24 valves?? Or just the ruined ones? Or do they all go?... New sleeves for the gone valves.. And springs should be ok??

No not 24 of them. More than likely the most will be 2 inlet valves on one cylinder and 2 exhaust valves on another cylinder. Try measuring the valve clearances to see if that gives an indication of which set of inlet and exhaust valves are bent. If thats too hard, then remove the head, remove the cams (so all valves should be closed), tip the head onto its exhaust side outside and pour kero/fuel down each inlet port, if there is a leak then there's your bent valves ... then do it again to the exhaust side.

Mark the bent valves and note which cylinder they're from. While you're there, might as well remove the valves and see about cleaning any carbon build up from them. Round wire brush on a drill does the trick nicely. But probably let the head specialist do the work. Just make it easier for him by identifying the bent valves (following the steps above).

BTW, I gave you my advice yesterday while lying in hospital waiting for xrays ... don't say I'm not dedicated

[32TAXI]

Compression test all cylinders before removing head!

[Tangles]

to save you $100 Ive got a full set of Intake & exhaust valve seats. RB25 Neo

they sent me the wrong set when I did my head work

come and grab them if you wish

http://cgi.ebay.com/ebaymotors/EPP-Intake-...sQ5fAccessories

[rb30dett]

Sorry mate you have bent valves for sure, don't cause more damage by doing a compression test it will only increase your repair bill. What is your location if in Brisbane I can help with a head swap. You won't know the extent of the damage till you pop the head off. If you want to test before you remove the head then pop cams off so valves are shut then remove spark plugs and fill chambers with compressed air, IMO the head needs to come off anyway cause I am positive the valves are bent so this is just to satisfy your doubts.

[BensDR30]

I concur. DO NOT do a compression test, this will cause more damage even if it's just the value seats. You should do a proper leak-down test with the cams out - you will soon see which cylinders have damage. If that's too much trouble, them just start stripping it down, because that is certainly the next step...

[chef_stagea]

ben i was thinking the same thing... continuing to turn them over is going to keep smashing them... its allready been ran twice for a second and it didnt sound good... how do i do a leak-down test? engine internals arent my strong point...

i think i may just go with roo's way... rip it off see forsure whats happened... will it be SERIOUSLY obviouse to the eye whats bent? like is it going to be smashed up super bad.... or just the tinyest of gap leaking air?

i know with jetskis... out of time bits can smash up sparkplug tops with ease...

roo thanx very much for helping me out

and ben i might have to speak with you once the heads off... for some seriouse questions! lol

does anyone know whats most likely going to be broken? ATLEAST one pair of exhaust and one pair of intake valves?...seats? springs?

im going to port and polish the head while shes out too positive thinking will help alot!

also whats the story with head gaskets? ive looked and theres diff size,price etc etc what do i look for here? is there power to be had?

[Tangles]

mmmm highflow head, go poncam on exhaust side for sure!!

[GoldZilla]

i think i may just go with roo's way... rip it off see forsure whats happened... will it be SERIOUSLY obviouse to the eye whats bent? like is it going to be smashed up super bad.... or just the tinyest of gap leaking air?

i know with jetskis... out of time bits can smash up sparkplug tops with ease...

also whats the story with head gaskets? ive looked and theres diff size,price etc etc what do i look for here? is there power to be had?

It *should* be quite clear what's damaged, depending on how bad the damage is. It's at least semi-likely that the valve won't be sitting on the seat properly if the shaft is bent.

And the extent of the damage varies with each different engine - in some cars the valves protrude A LOT into the combustion chamber, and in some cars they don't. Some heads have a clearly visible "dip" in the head for the combustion chamber, and others have an almost flat surface across the head along the CC. Sometimes the valves are at massive angles to each other, sometimes not. As you can probably figure out, it really depends on an engine-to-engine basis, taking into account how the engine was designed in the first place.

Head gaskets? You'll have heaps of choices. Some are thicker (meaning you'll lose compression, and therefore torque down low), some are thinner (meaning the opposite effect - more compression, meaning more torque, and quicker to come onto boost). You don't have to spend a ridiculous amount, just make sure you're buying quality.

[Stinky Rooster]

Basically, you wont be able to tell anything with the head on.

Take the head off and remove the cams. As Nick said, any valves that dont sit all the way closed are going to be bent at the very least. Another good diagnosis trick would be to mount the head on a stable flat surface and fill the combustion chambers with water, leave for 20 minutes and then see which ones drop in level - these are the ones with suspect valves, although the RB engine does have a pretty high level of interference and I think most damage is going to be rather self evident.

Also take a really long hard look at the piston crowns and bore condition around the tops of the cylinders. The piston crowns are what will actually do the valve bending, and this usually dislodges any carbon build up in the area - especially if an exhaust valve has copped a hit. Carbon deposits floating around a combustion chamber cause hotspots, preignition (pinging) and generally score the hell out of anything they touch, but damage caused by this is usually quite easy to miss to the untrained eye, so take your time, and try and get a mate or two to go over everything a second time, just in case.

Head gaskets - unless you are running uber high boost, have a massively ported head or huge cams, I would stick pretty strictly to the std head gasket. Felpro and the like do good quality aftermarket ones that wont break the bank, but raising or lowering the compression ratio on a turbo engine can lead to some pretty significant changes in your engine, and most of them arent good. Raising your compression will get you on boost quicker, but the increase in running temp, combined with the need to pull timing out to stop pinging will see any gains eaten up pretty quick, and lowering your compression ratio will allow you to crank up the boost at the turbo (if you have a hi-flow or big aftermarket jobbie) but the increase in lag, and drop off in low end torque, will kill the joy of driving.