Rebuilt 289 engine, stalls out if rpm is normal for engine, erradic engine with the slightest thrott

5

Asked by Jul 16, 2009 at 02:10 PM about the 1966 Ford Mustang Base

Question type: Maintenance & Repair

I just rebuilt my 289. stock crank, mild comp cam, 10:1 pistons, edlebrock perf289 manifold, 600 holley 4bbl, stock distributor.  In order to get it running reasonable, the timing had to be set at 30deg off TDC.  Now, in order to put it in drive without stalling (c4 tranny), the RPM has to be much higher than normal.  The idle is rough (cam is supposed to be a smooth idle), and when it's in drive, without touching the throttle, the engine occillates it's RPM--sometimes significantly.  When I apply a little throttle, the engine is very quick to respond, and maintaining very little throttle causes the engine to ocsillate it's RPM--more throttle eliminates this.  Carb has been rebuilt and tuned (so they say).  They also say that the vacuum is lower than normal, but they expected that with a performance engine.
Any ideas?

3 Answers

7,985

timing and carb are off. why did the timing need to be 30 degrees of TDC? was it required with the cam? im guessing something is up with the carb. whomever rebuilt and tuned it needs to redo it. sounds like it was done wrong.

185

This is just a guess but is it possible that when they reaasembled your engine they didn't align the timing marks on the crank and the cam properly. Unless it's a radical cam, the vacuum shouldn't drop very much and the idle shouldn't suffer either. I have a mild cam in my '67 289 and it has a smooth idle at 600rpm in drive, about 850-900 when in park.

5

The timing of the Camshaft is my first thought. We're going to look into the timing of #1 valves with respect to TDC. I'll re-check the vacuum and see where the needle dances.

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