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Doug St. Clair
07-25-2006, 06:56 PM
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Well, I'm going on just over a year with my newly rebuilt '68 Ford 427. It's still not running "just right". Two things I've noticed - when I get in the upper RPMs (3000 - 3500), the rpms tend to bounce up and down. I'm thinking this may be related to the new carb I'm using (autolite 2100), which has a vacuum secondary (instead of my old 4300 that had a mechanical). Is is possible the secondaries are opening at the low range (3000 RPMs) then closing back down at the higher ranger (3500 RPMs)? I also suspect a "clicking" sound when running at the high RPM - but can't pinpoint it.

The other thing... if I run the engine at high RPMs for a few secs (10 or so), I can't get the thing to behave back at idle (650 RPM). I typically have to hold the throttle open a bit while I disengage the transmission. If I try to re-engage the engine at the idle speed, the engine coughs out. This usually lasts 5 minutes or so, then everything seems normal again. It wouldn't appear the temp is the issue, as I can get it to the same temp at lower RPMS without the same situation occuring.

FYI - I also switched to an MSD ignition setup.

I'm just trying to get this thing to run *right* so I can forget about it for awhile. It doesn't run as well as it did before the rebuild, but I figure it's just a "tuning" issue. Is it timing? Should I try a different carb?


Any help is appreciated!!
Doug"

jimn
07-25-2006, 07:40 PM
"What are you doing for fuel delivery to the carb- mechanical pump or electric? How did you arrive at the carb settings- trial and error or a more scientific method? Is the cam to OEM spec or does it have advance built in? If it has more advance, you need to make sure the timing is adjusted to compensate. The RPM jumping around (does it sound like that too or is it just the tach that jumps around? There may be some electrical reason for the reading to jump- is the wire on the tach input post loose? If it comes in contact with a ground, it'll kill the spark."

Doug St. Clair
07-25-2006, 07:47 PM
"I have a mechanical fuel pump (replaced during rebuild). The carb settings were "fooled around with" by someone in the busisness, but not when the "problems" appeared. The RPMs are definately jumping up and down... not just the tach gauge."

jimn
07-25-2006, 08:11 PM
"I would check to make sure the fuel pump can keep up with the engine's demand at high RPM. My guess is no but it depends on how well the motor breathes and how the carb is set. If the problem occurs when under way and stops when the boat is in neutral, it may be a fuel sloshing issue, either in the tank or in the carb itself.

"Fooling around" with a carb on this motor will really not do the job, whether he's "in the business" or not.. You need to get it set up properly and that means proper jetting, and primary/secondary flow corrction.

Personally, I would take it to a speed shop."

Doug St. Clair
08-08-2006, 10:57 PM
"Well, call me a complete fool (or at least a complete novice). I made a major leap forward tonight. I found and closed a wide-open vacuum port on my carb. I have an SD ignition, so no vacuum advance. Took the boat out after closing the "minor" vacuum leak. Holy freakin crap! The ol' 427 in the 18' flat bottom ski boat is alive and kickin! I still need to do some fine tuning, mostly with the warm idle adjustments, but she's a purring pretty. 18 months of frustration, fixed by a $2 part. All's well that end's well, I suppose.

So - any advice to a novice on how to adjust the warm idle? It's an Autolite 4100 on a Ford 427."