MGA Elva [MGA 1600] high-speed miss

[Michael Oritt]

At high rpm's (5900 or so) the engine develops a fine miss and will not accelerate past 6200 with the pedal pressed to the floor. However if I let up the gas just the least bit the miss goes away and then I can accelerate up to about 6400. If I floor it the miss comes back.

Plugs look about right or if anything a bit on the gray side as opposed to tan--I'm thinking that perhaps I am running a bit lean at WOT.

Any suggestions, opinions appreciated.

Best--Michael Oritt (Elva Courier racer)

 

[jlaird]

Me too. I would assume fuel delivery at some point.
Step right up experts.

 

[kennypinkerton]

I was thinking lean at WOT too. That could certainly cause a throttle related miss. If it was ignition related (dizzy advance?) I'd think it would miss regardless of the throttle position at those rpms.

 

[LLAngus]

I had that with a newer head on my motor. Single spring compared to duals. The valves floated and limited RPM. This is really far out there but you never know.

/ubbthreads/images/graemlins/driving.gif

 

[kennypinkerton]

that makes sense too. Is that engine designed to rev that high?

 

[jlaird]

5900-6200 high? Shucks high is 7300.

 

[aeronca65t]

Try dropping the main jets.
Normally they should be two turns out from "full-in". (or,a s they say, "12 flats out").
Unscrew them another half turn or even more and see if this helps.
If this helps, you may have the wrong needles.
Remember, it's always safer for these engines to be a bit on the rich side. Too lean is a no-no.