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Uncontrolled Acceleration - Scary!

April 15 2012 at 3:32 AM
Graeme Anderson  (Login rhinosoft)

Hi All,

you may recall a few months ago I had my 390 rebuilt then it blew up due to the engine builder not doing the right thing. Well I have the engine back and the car is running a treat now, get lots of compliments on it, I have not posted the full engine specification yet since I'm waiting on my rebuilder to advise me what model Lunati camshaft he put in it, but I am happy...but poorer now!

Today I had a scary moment, can anyone suggest what it might be after reading the following please?

- installed MSD 6AL with recurved Duraspark distributor
- has Holley 670cfm street avenger Carb
- replaced the vacuum secondary spring to one lighter than factory (can't remember color)

On the freeway I was travelling at a constant 60mph and gave it a few bursts up to 75mph, just for testing of course. I noticed that the engine when lifting off the accelerator would not slow down, like the throttle was stuck on.

I managed to pull off the freeway safely and the car stopped with a back fire ;should have turned off engine and coasted, live and learn. Checked all the linkages and there was nothing at all snagged up, return springs good. Restarted and it ran fine, but I did not have the gonads to floor it again on the freeway since I was so far from home!

Made it home on 2 barrels and checked for sticking butterflys on the 4 barrels, looked down the carb (while engine off!) and moved linkages etc but there did not appear to be any fouling on carb mount or gaskets at all.

My only thought to this stage is the rear 2 butterfly valves have stuck open and when engine was shut down the carb mechanism pulled them shut again? Any thoughts appreciated.

thanks a lot


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