Help Needed To Diagnose Problem

[=premo=]

I've just finished rebuilding an engine for track use after it had spun a bearing. Started it up and it sounds rough, shakes a bit (although it was on car stands so might not be an issue when its on wheels) and start's popping out the exhaust at 2000rpm so I turned it off straight away and went shopping for explosives to blow it up (getting sick of it).

I used a backing plate to setup the timing belt but its not actually on the engine. When I used the backing plate I held it up to the cam gears so I could see the marks from the back of the engine and lined up the tooth on the cam gear to the mark then looked from the front of the engine to make sure it was the right tooth that I had just lined up. I checked it at least three times to make sure the marked tooth was at the right spot. The only thing I can think of is that the marks on the backing plate are not symmetrical so when I've flipped the plate horizontally so I could see the marks against the cam gears its given a different result... Although the backing plate does look symmetrical.

Any suggestions on how I can diagnose the problem or work out which gear needs to go which way?

I still have 10 degrees of adjustment either direction on the cam gears that I haven't used so I might not need to pull it apart to fix the problem if I can work out exactly what the problem is. Its also possible that timing isn't the problem at all but its the only thing I can think of that could have stuffed up. If it wasn't for the popping I'd think there was nothing wrong and its just a bit rough.

Any good help is much appreciated.

[Nathan76]

sounds to me like it has jumped a tooth, i would be redoing the engine timing properly not just from the cam gear adjuster

[blind_elk]

Why aren't you running the backing plate? What could be so important that you would risk the valve timing being off and a valve punching a hole through your brand new pistons?

Use the backing plate - it's there for a reason.

[=premo=]

Put the backing plate on and realized that the cam timing is out a tooth on both gears because of the tensioner's. Because its an RB30 I have two tensioner's and when I've done them up its pulled the cam's around almost a full tooth. The down side is that wasn't the problem. I checked the compression to make sure no bent valves and all is good but when I started it up again it was doing the same thing. Pulled off coil pack plugs 1,2 and 4 and no difference, the fkn thing is running on 3 cylinders. All the spark plugs are black as fk and its blowing heaps of fuel and black smoke out the exhaust. The popping at 2000rpm is still there.

I'm currently running RB20det coil packs even though its a RB26 head and engine loom, are RB20 coil packs different to RB26 coil pack's and could this be causing the problem or is it more likely to be a tuning problem?

Thanks,

Daniel

[blind_elk]

First thing to do is move coils in 1, 2 & 4 to 3, 5 & 6, see how it runs. If the coils in 1/2/4 aren't firing, then it's the igniter or loom, or maybe spark plugs; if 3/5/6, then it's the coils.