Issues with newly built 427May 18 2017 at 10:46 AM
|Greg (Login gaaj427)|
Hello all, I want to pose this question to the amazing knowledge base on this forum. I have recently built a 427 dual quad for my Fairlane. The engine is 4.24 bore, cammed and runs great when cold. When the engine runs for about 10min and gets warm about 220deg the engine starts to load up. It also seems to stumble some at idle.
It is running about 6" vacuum, 14deg initial timing, I had the carbs rebuilt by Carls Ford and I have adjusted the float bowls to factory specs then I adjusted them low as they were "dripping" when the engine shut down as the engine would flood.
When the engine is cold, it starts first time and will do that multiple times. Once it gets hot, the carbs flood the engine and I have to hold the throttle wide open to get it restarted. I put spacers under the carbs (thinking it was heat related), lowered the power valve to 2.5, made sure the gas cap is vented but the problem is still there.
Interestingly enough if I run the engine at 3-4k it runs fine even after I get it restarted with WOT but as soon as it goes to idle it dies and will be hard to start again. I adjusted the point gap to spec as well.
This is a head scratcher and I am back to it being a carb issue but I wanted to see if anyone else had this issue....
Thanks for your input!
you may want to check
|May 18 2017, 11:36 AM |
your fuel pressure. what are you running for a fuel pump? with the engine shut off, look down the carb throats $ see if fuel is dripping from the nozzles or just leaking onto the blades. also from one carb or both, or from the primary or secondary.
Install a good fuel regulator and drop it down to like 4.5 psi.
|May 18 2017, 9:41 PM |
I have had similar issue. I have two carbs rebuilt by the same outfit, and had to re-rebuild both of them. I also rebuilt two more carbs, and had similar issues with them. Genuine Holley needles worked way better than the aftermarket kits. The are touchy with modern additive added gas. It will vapor lock/boil in the lines and over pressure the Holley needles and dribble into the engine. BTW, change your oil, it gets ruined from the gas running down the cylinders.
It will take about 1000 miles to loosen up the engine, and temperatures should come down. Don't run it sitting. Drive it. Then at about 1000 miles, consider dropping the thermostat down to 180 or 160 even if you have a 195* in it now. I don't mind running over 200, but 220 bothers me.
Sounds like it's vapor locking
|May 18 2017, 11:48 AM |
I've had all sorts of the troubles your describing here lately. I tried some ethanol-free gas and it helped some. I put a jumper hose between the bowl vents and cut a few slices in it near the top of the loop which helped some too. My latest trick is I've wrapped the bowls, fuel pump and fuel lines with space blanket. It looks funny as hell but seems to have worked. Up to 85 degrees ambient outside and no flooding. Todays pump gas just doesn't work well with carbs. I'm almost ready to try fuel injection. Almost.
"They can't arrest us all"
I'm no carb expert but...
|May 18 2017, 4:25 PM |
the hard hot starts are probably being caused by the carbs slightly flooding over. A cold engine will not be too bothered by the excess fuel leaking through the carbs but when hot it will flood out.
I would first check fuel pressure to make sure its not too high. If that's OK then take a look at the needle and seats. If they aren't closing properly that could cause fuel to over fill the bowls and drip out of the boosters. If they are ok then I might take a look at the main bodies. I've done 2 sets of 2x4 Ford Holley carbs lately and they all needed the main bodies machined flat. Over the years of countless rebuilds and heavy handed wrenchers they tend to distort and need to be machined flat again.
In addition to fuel issues......
|May 18 2017, 5:55 PM |
That engine shouldn't be 220° within ten minutes...... an FE should never be run at 220 in my opinion. Check that the head gaskets are turned the right way.....tab to the front, water blocked at the front. With the water pump off, you can stick your finger in the hole in the block and feel if the water is blocked off at the deck (it should be). Might save you some pain, and it is easy for seasoned veterans to slip up and put one on backwards......
Re: In addition to fuel issues......
|May 18 2017, 6:10 PM |
Agree with the esteemed Mister Patrick. 220 is a Chevy temperature (silly buggers have the sender by the exhaust port). 180 or less is what I like to see.
Also on dual quads I run the fuel pressure down to 4 or 5 psi. Any more just invites problems. Some mechanical pumps will be more like 7 psi.
Issues with newly built 427
|May 19 2017, 8:17 AM |
Here is a tip for you. Check the power valves on both carburetors. If the power valve or round gasket is broken, it may let the gas leak into main body "vacuum chamber". If this is the case, the gas will leak into the engine without you seeing it and it floods the engine. If you open up the carbs, remove the bowl and metering block carefully to see if the chamber is wet. If this is the case, you have leaking power valve(s).
Re: Issues with newly built 427
|May 21 2017, 5:48 AM |
High HP in small engine bays causes all kinds of heat related issues. I had similar issues with my mustang. Electric fans and an aluminum radiator fixed my overheating. Bypass fuel regulator with a return line solved by boiling fuel issue.
69 R code Mach 1