just need some ideas where to start? my spark plugs look like all cylinders are burning good and even, i had the timing done not too long ago but this problem only started maybe a week ago

any help is appreciated

Valve bouncing is caused by weak valve springs, not by timing or carburetion. What indication do you have that the valves are bouncing -- could it be some other rev-limiting problem? I would start with a no-load rev test. With the car in neutral, can you rev it past 4500? If so, the 4500 limit under load is caused by something other than valve bounce

thanks ddgonzal, ill have a go after work and let you know, i have to double check but the guy i brought it off told me that it had titanium valve springs, all i know about titanium is that it weighs nothing and it cracks easy... could i have cracked springs?

Titanium springs are rare. They are lighter, but far less strong than steel

Is there a miss or does it just fall on its face? If miss pop the cap on the dizzy and see if the shaft has a lot of play in it. One of the telltale signs is the tips on trigger will be shinny because the are contacting the outer ring do to shaft slop. I've had a matchbox style distributor go bad this way, the miss started right around 4500.

I've never had a motor float the valves below 7500, I would think titanium springs would be race parts and the rate be high enough that even going south would still hit 6k.

My .02

that sounds like it hey, it misses and carries on like a pig, no power, everyone looks at you, total embarrassment haha ill have a look tonight and take some photos and hopefully post them tomorrow, thanks for the advice man

OK so i think i know what it is, i changed the clutch not long ago (the clutch shop didn't have an alignment tool so i did the best i could in the dirt) and we had a bit of a hard time putting the gearbox back in, i have a feeling that the gearbox isn't perfectly square to the motor, I'm not sure why it only happens above 4500 rpm but i did the out of gear clutch out rev and it revved to 7 grand no worries.

plus there is a heap of new symptoms today that are giving me the #OOPS#s that also point to the gearbox not being straight and the clutch needs to be looked at again

Alignment tool is only for the clutch disc, it doesn't align the gearbox, say if the engine went up the to gearbox face it is aligned no problem. The gearbox is straight when the bolts holding it to the engine are tight

what are the symptoms you are experiencing?

we had a lot of trouble getting the gearbox in, we ended up having to pull it in with the bolts as it wasnt sliding the whole way on.. the guy at the clutch shop later told me i should have just left it because forcing it on is just bad news.

so just today.. i cant keep it running when i pull up, when i press the clutch in there is a crazy whering noise that sounds like a bearing, as i go to take off it runs like a dog then when cruising at 60 in 4th (5speed 60a box) its like shakes the whole car at the end of each cycle of the motor if that makes sense

im going to drop it down to the clutch shop this arvo, ill post what was wrong with it when i get it back, taking bets on it was something stupid that i did haha

ahh that feeling when you put your car back together and its worse than before