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My new GT6 engine is still having a few problems bedding in.

After 1500 miles I began to get a clashy clatter at high revs & high rpm - tappet check and change of points since I can now not really get back to testing if the clatter has gone because above 4000 rpm the engine begins to misfire and won't now hardly rev  above 4000 rpm - it becomes rough and increasing misfires.

Not sure where to start - as I'm loathed to make things worse - particularly as below 4k rpm it's very crisp.

Known issue is slight wear on the throttle spindle bushes - can any here suggest a logical sequence of checks - and whether to explore fueling or electrics first.

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Is this happening only when driving, or when stationary? Does it clear as soon as you bring the revs down? Does a bit of choke make any difference?

Could be any number of things but if changing the points caused it to get worse, I'd start by taking off the distributor cap and thoroughly examining everything nearby. Are there any fraying wires that might get earthed when the base plate moves?

If nothing obvious, then maybe swap points & condenser for a known-decent set if available.

I'd also check the manifold nuts are all tight and there aren't any other likely air leaks, apart from the worn throttle spindles. 

Pete

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Good advice from Pete.

Some of questions from me:

Did the misfire exist before the tappet check and points change?

Did the tappet check reveal any big changes needed?

Did it have the head nuts re-torqued / tappers set / oil changed somewhere in the 500 - 1000 miles range?

What cam is fitted?

I suspect that the misfire is points related. As you say it’s still crisp lower down possibly too much gap leading to insufficient dwell to charge the coil, rather than gap closed up.

 I don’t really have an opinion on the noise at this point - curious to see if the tappet adjustments have done the trick.

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tappets set to 0.014" & were all pretty good. Head re torqued & oil changed by TRE @ 500 miles - Cam - a TR Enterprise Special ??? - its a rally / sprint profile and pulls all the way up from 2000k to its now rev limited 4k! ... but was easily pulling to >5k before I meddled ( albeit with the worrying characteristic of the clashy sound so reminiscent of the head that had the springs bore themselves in )   Incidentally I needed to change points as the LT lead got wrapped around the dizzy spindle wedging between the points heel and cam lob snapping off the heel !!! 

Points set at 0.020" ... should I try 15 or 18 thou' ??

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50 minutes ago, Greta said:

ok - shame faced admission time - could the tiny teenie weenie washer beneath the points pivot securing post ... that may have dropped into the dizzy....be fouling the springs or weights???

Haha! Oops...

36 minutes ago, Greta said:

Incidentally I needed to change points as the LT lead got wrapped around the dizzy spindle wedging between the points heel and cam lob snapping off the heel !!! 

Points set at 0.020" ... should I try 15 or 18 thou' ??

Was that the lead from the condenser, or the coil? Was any other damage done in the process, which you might have missed at first?

If it's a Delco dissy make sure the U-shaped LT terminals are making good contact where they slot behind the points spring (if that makes sense!). The fit is usually piss-poor, although less bad with NOS points.

 

 

Edited by PeteStupps
to remove misleading statement about points gap! 
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I think The Golden Spanner award goes to Nick. 

 0.020" if set not quite on the crest of the lobe can easily be 0.025"+  - More accurate setting ... ( must refit one of those solenoids with a button ) with a smaller gap does indeed now allow it to rev to 5000.

although it's much much better it still has difficulty holding 5000 rpm .... Dropping back periodically.

so now that's been understood  perhaps I'll start again & try to refit my luminition ignition kit that TRE disconnected. See if that will facilitate good ignition at even higher revs .....To be continued.

Thanks -  as always to all that offer help.

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