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-   -   Dauntless engine rebuild (http://www.jeepforum.com/forum/f19/dauntless-engine-rebuild-1528035/)

farmerdanny 05-25-2013 07:10 AM

Dauntless engine rebuild
 
So, I recently rebuilt a V6 dauntless odd fire engine. Had the block remachined, new littered, head job, oil pump, water pump. Put a DUI ignition, Oppy intake, headers and a holley 4 barrell carb (390 cfm). The problem? I can't get the engine to run correctly. It kinda runs, but takes a very long time to idle down after taking your foot off the pedal. Occasional back fire in the exhaust.

jeepdaddy2000 05-25-2013 12:25 PM

Quote:

It kinda runs
Could be anything. Need a better description.
I would make sure you:
have an ODDFIRE v6 distributor
Insure the #1 wire is on the correct cap tower and you have the firing order right
Check for manifold leaks



Quote:

but takes a very long time to idle down after taking your foot off the pedal
Throttle linkage binding/sloppy
Throttle spring too weak
Throttle plates hanging on carb gasket
Possible choke high idle linkage problem

farmerdanny 05-25-2013 09:22 PM

Those are all good ideas, but I have checked all those. The throttle is new and very loose. I even ran it without the throttle connected to make sure.

Question: With new headers and an almost free flow muffler, what affect does almost no backpressure have on the engine? Can a combination of the free flow exhaust with a carb that's dumping too much fuel be the problem?

jeepdaddy2000 05-26-2013 10:10 AM

Quote:

It kinda runs
Simply need a better description.

Quote:

but takes a very long time to idle down after taking your foot off the pedal
Are you saying that the idle is still high with the plates completely closed, and then drops slowly?
The only way to raise RPM's in a gas engine is to introduce air into the combustion chamber (too much fuel won't do it). this can only come from the carburetor or a leak in the intake (manifold) system. The issue with manifolds vacuum leaks, is they traditionally don't go away. This means the idle stays high. You can check using starting fluid. spray around the base of the carb and anything vacuum related. If the idle goes up, then you found a leak.
Does you carb have an idle dashpot? It would be a small round device that the throttle would contact the linkage.
http://www.allfordmustangs.com/forum...lp-dashpot.jpg
You don't usually see these on modern aftermarket carbs, but if there is one, it could be effecting the idle.

My suggestion is to start from scratch.
Dwell
timing
carb idle mixture
curb idle
This would help eliminate such odd variables as a sticky breaker plate or issues with the vac advance.

farmerdanny 05-27-2013 06:59 AM

1 Attachment(s)
When I first did have this problem, it did have a rather large vacuum leak at the back of the intake. So, I took the intake back off and reset everything and there doesn't seem to be a leak anymore. There's no dwell. The timing seems to work best at about 12-degrees Before TDC. That sounds like a lot, but I read that's typical with this distributor.

When I rev the engine and totally take my hand off the accelerator, the engine takes a long time to drop down to an idle. If your driving and take your foot off the gas and put on the brake, it seems like it's still pulling a bit before it slows down.

No dashpot on the Holley.

I have attached a picture of the engine.

When I say it kinda runs. Well, after the engine temp reaches 185 degrees, it will finally idle by itself and sounds great. A nice loud rough rumble. Until then, I need to feather the throttle. I get the occasional backfire, usually out the exhaust but occasionally back through the carb. I messed with the timing forever, but I have heard these odd fire engines are a ***** to get set up. But, once they are, they are an awesome engine.

I will check again for a vacuum leak again tonight. I will use my propane torch this time. I seem to get better luck with that than brake cleaner.

jeepdaddy2000 05-27-2013 07:01 PM

Quote:

The timing seems to work best at about 12-degrees Before TDC. That sounds like a lot, but I read that's typical with this distributor.
Sounds right, I run about 10.

Quote:

When I rev the engine and totally take my hand off the accelerator, the engine takes a long time to drop down to an idle. If your driving and take your foot off the gas and put on the brake, it seems like it's still pulling a bit before it slows down.
When you rev it by hand and drop the linkage, have you manually checked to see if it is completely closing? A weak spring may not be forcing the curb idle screw onto the body. You may also want to check it with the vac adv disconnected, and inspect the advance weights in the distributor to insure the springs are solid and the weights return freely.
225's traditionally are a bit slow spooling down due to their heavy flywheel, but you should never feel the engine is pulling coming up to a stop.

Quote:

When I say it kinda runs. Well, after the engine temp reaches 185 degrees, it will finally idle by itself and sounds great A nice loud rough rumble. Until then, I need to feather the throttle.
This sound like a lean mixture. Recheck your instructions for setting up the choke.

Quote:

I get the occasional backfire, usually out the exhaust but occasionally back through the carb.
Again, possible lean mix. Backfiring in Holley carbs is usually accompanied by a blown power valve. You need to check yours. If it is bad, you will never get the idle mixture right. If it is still backfiring after it is warmed up, you may need to:
check the accelerator pump.
Go a step larger on the mains.

Quote:

I messed with the timing forever, but I have heard these odd fire engines are a ***** to get set up
No different than any other engine.

Checklist?
1 Again, insure you have an oddfire distributor and the #1 plug is on the actual #1 terminal. This is huge, as the odd firing order will give you fits if your off.
2 Check the choke for proper adjustment. It should be closed when cold, open about 3/16" when started, and be completely open when warm. Don't forget to adjust the choke high idle screw so the engine is running in the 1K RPM range when cold (you can set this to your liking once the engine is running properly)
3 Check the power valve. If it is blown, I wouldn't replace it till you get the rest of the issues sorted out.


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