Timing mark issue...

[240slidekat]

Ok this is gonna be long but please read and help....Ok heres what happened. Got the car started, did a leak check, fix all my leaks, then had the car idle for a less than a minute. I did a quick rev and when it hit about 3000rpm i heard a "Thunk" and the motor just turned off. it did not bog down or anything it just STOPPED. Cranked it a few times and does not start at all. it cranks but does not turn over. i did the whole start up list (check air, fuel, spark TIMING) and found the culprit. i think my timing belt slipped. At top dead center the crank marks lines up, intake cam gear mark and back plate mark lines up, and the exhaust cam gear mark is off by about 10-13 teeth (sorry didnt count the exact number). Ive been searching around and i know that its highly possible and most likely that my valves are bent. My question is there any way to get the mark to line back up. i tried spinning the cams and i can only go to a certain point and it doesnt wanna spin anymore . im thinking that its the valve hitting the pistons thats preventing me to spin it further. So is there any other way for me to get it to line up???Here is a picture i drew up.

Modified by 240slidekat at 10:19 PM 3/5/2008
Modified by 240slidekat at 10:38 PM 3/5/2008

[Bluefire]

Your probably SOL. Take the belt off, yank the cams and do a leak down test to check the valves...

-Bluefire

[240slidekat]

the belt is already off thats just a picture i drew up. ok i thought of something, tell me if this make sense. since the valve are driven by the lobes on the camshaft, what if i remove the camshaft and move it so that my timing mark lines up then should the valve just follow it. then hook the timing belt back up and do a compression test. you got a link or a very detailed explanation on how to do a leak down test. i mean i know the purpose but need to know what kind of tools ill need and whre to get get it. thanks

[rb25drag]

I don't understand whats so hard about lining up the cam mark with the belt? Are you trying to get the cam to stay in one position while you put the belt on, thats porb not going to work? More than Likely you will need to put a wrench on the cam and move it one way or another for it to line up and slide on.

But honestly if it popped that was porb the valves hitting your pistons and more than likely bent all the valves and could have possibly busted a piston or 6.

A leak down test is a start but more than likely your looking into a rebuild.

[Shocker]

this is the worst disaster possible... You might have missed a tooth when installing,.

heres the deal, the reason you marks didn't line up after wards is because they had been turned, then wont line up again (well maybe after a ton of cycles they will go back).

So the real way to tell if your marks were correct was to just get the motor at TDC and check over the marks, if any are off then you ****ed up....

EDIT I just looked at your picture harder yea, from your explanation you did some damage... Looks like its time to pull the head and inspect.

sorry man..

[240z4u]

If you read the FSM it says that the marks only line up on every 6th? or so rotation.

I agree about the leakdown test. bad news bears.

Sorry dude.

Evan

[mott6904]

Time to port and polish the head...bad timing... hope you get it and going again before race season

[l0nestar]

Not to be a coq, but that is why I had my engine on a stand and tested everything by hand :-\ I made quite a few 'hand cranks' and intensely monitored the marks before 'certifying it' and installing it in my chassis. I think Carl may have even been there for the first firing... maybe not.

This sucks, big-time, and I'm truly sad to hear of this unfortunate event.

[Darius]

Yep like everyone else already said, your valves are smoked. Call up ferrea. Keep us posted too.

[240slidekat]

hey darius, i havent work on my car so i dont really know how much damage but i think i might get a permanent NRRBA membership. im almost ready to call it quits.

[Sil240]

Bro don't call it quits.See if you can get another Rb25 head.Then you can work your the blown one afterwards.

[240slidekat]

im looking for a Rb head right now but no luck...

[silviasgp06]

are you sure it slipped? they do not line up on every revolution.have you ruled out everything else, maybe i missed something while readin this but ide hate for you to pull the head off and find nothing wrong internally. good luck

[240slidekat]

yea they slipped and to even make matters worst after i reseated my camshaft, reinstall the timing belt, and after i had everything lined up i spun the crankshaft via rachet to make sure nothing is binding and/or making weird noise. i noticed that only half of the camshaft is spinning...i was like ! i took off the cam bracket to see WTF and what do you know my tomei pon cams sheered in half. i dont think my RB wants to play anymore

[Darius]

are you sure it slipped? they do not line up on every revolution.have you ruled out everything else, maybe i missed something while readin this but ide hate for you to pull the head off and find nothing wrong internally. good luck

The timing marks on the actual belt do not line up on every revolution, but the marks on the cam gears and crank do.

I'm afraid you are in for a full rebuild or you could just buy another long block and part your existing one out. You could actually recoupe a lot of money from doing that. Don't quit though, just chalk this up to a learning experience and keep chuggin along. You'll get there soon enough.

[Shocker]

The timing marks on the actual belt do not line up on every revolution, but the marks on the cam gears and crank do.

Every other...

Was this the built block? Let me know how many valves you ****ed once you remove the head... I might be able to help you out...

I just did this today, and I tell you what I took my good old ****ing time. I meticulously counted the teeth even after EVERYTHING was 100% lined up lol, then cranked it buy hand about 20 times soo slow just listening and feeling for any interference...

I do know how you feel man, I was there all last year, my RB was/maybe still is cursed.

Not sure how your pon cam snapped? was it the one with the VTC cam gear? I know I get scared as hell tightening the intake cam, ****ing 12.5 kg/m's! I can just see the shaft twisting as I crank....