400 problems
Thread Starter
|
Freshman User
Joined: Apr 2012
Posts: 36
Likes: 0
400 problems
I rebuilt a 400 and it would start right up every time you hit the key it was awesome. But now i cant even get the damn thing to start. All new plugs and wires dist. cap and rotor. has good spark. i drained the oil and found alot of gas in the oil.Could this be a valve issue? It has a eddy 750 on it that was a little out of tune but it would always fire right up. Roller rockers are all good and tight. if you crank it for awhile gas will just run out of the headers. I need some help here. This issue brought my whole project to a stop. Any ideas?
Cargo Master
Joined: Nov 2009
Posts: 2,364
Likes: 118
From: starship enterprise
Sounds like a fuel issue to me. I think it could be intake valve related but you should hear that. When you crank it it will come up on compression on one cylinder that will not sound right, like the starter will speed up and then slow down when that one is over, it will happen the cylinder(s) come up on compression, and if it is intake it will push air (the compression) out the intake. I doubt this is the problem since if it was then you would have more fuel in that one cylinder, not all of them.
I am leaning towards a stuck float in that carb. I have had this happen before. Look down the carb with the air cleaner off and see if any fuel is puking out anywhere while you crank it or while the pump runs if electric. If you see anything coming out, then you need to remove the top of the carb and fix the floats. It sounds like it has developed the "edelbrock Mystery Leak" that arises periodically without warning and usually needs some Attention on the floats, needle & seat, and maybe accelerator pump. Mine has done this 2 times, runs flawless then one day quits and will not run till you fix it. Good luck.
I am leaning towards a stuck float in that carb. I have had this happen before. Look down the carb with the air cleaner off and see if any fuel is puking out anywhere while you crank it or while the pump runs if electric. If you see anything coming out, then you need to remove the top of the carb and fix the floats. It sounds like it has developed the "edelbrock Mystery Leak" that arises periodically without warning and usually needs some Attention on the floats, needle & seat, and maybe accelerator pump. Mine has done this 2 times, runs flawless then one day quits and will not run till you fix it. Good luck.
Hotshot
Joined: Feb 2004
Posts: 10,842
Likes: 2,612
From: The Shenandoah Valley
Edelbrock carbs like a MAXIMUM of 6 psi, they recommend 5.5 psi max fuel pressure. A good operable 351m or 400 mechanical fuel pump just like what come on the truck will put out 7 psi steady. Holley and MC carbs will handle 7 psi easy, it's all due to float displacement and float arm length and leverage against the inlet beedles. The Carter (what the Edelbrock is a copy of) was used back in the day with 3-5 psi .... even on those Mopar muscle cars. 7 psi will push the fuel past the needles.
You may need to install and set a fuel pressure regulator ahead of that carb, like the Holley 12-803. Set it at 5.5 psi.
The other thing that comes to mind is .... you may have a bad fuel pump with a ruptured diaphragm and it may be how gas is getting in the oil .... it maybe ran OK with a small tear and limited pumping ability limiting psi and all the while it may have been pumping fuel through into timing chain area as well.
If you do replace the pump and oil and filter and the truck starts, check the fuel pressure. Read the Edelbrock instructions and get the Holley FPR.
You may need to install and set a fuel pressure regulator ahead of that carb, like the Holley 12-803. Set it at 5.5 psi.
The other thing that comes to mind is .... you may have a bad fuel pump with a ruptured diaphragm and it may be how gas is getting in the oil .... it maybe ran OK with a small tear and limited pumping ability limiting psi and all the while it may have been pumping fuel through into timing chain area as well.
If you do replace the pump and oil and filter and the truck starts, check the fuel pressure. Read the Edelbrock instructions and get the Holley FPR.
Thread
Thread Starter
Forum
Replies
Last Post
CelticOne
1973 - 1979 F-100 & Larger F-Series Trucks
19
Jul 9, 2016 06:55 AM
carbpower1978
1973 - 1979 F-100 & Larger F-Series Trucks
4
Feb 21, 2012 01:07 PM
