Manufactured rebuilt long block

rebuilt carb- found rubber lodged inside secondary float needle

timing confirmed at 10 degrees

new plugs, rotor, cap, wires

unplugged each spark plug while running and made engine run worse.

engine cranks right up. Idles for a sec then engine starts shaking then smooths out. 10 sec later starts shaking again. When I give it gas fuel will sneeze out of carb the same time the engine seems to stumble/misfire.

can drive vehicle but engine chokes with added fuel.

Any thoughts would be greatly appreciated on what the issue might be.

 

Check the float level.

Which carb?

FWIW: Many off-the-shelf rebuilt carbs are junk.

 

If fuel is coming back out of the carb then you have an open intake valve on a compression stroke.
You need to check the valve lash/clearance and adjust to the correct setting.
If too tight the problem will get worse as the engine heats up.
It's ok if I'm wrong someone may say so here. I'm not a professional mechanic. I have adjusted valves and know that I would do this first.
Just my .02
Bruce

 

It’s a Holley 600cfm. I rebuilt the carb and made sure the floats were right.


Looking more into it, the burst of air is coming from the drivers side bank.i Pulled the plugs and all look fine.

i was checking compression in each cylinder and the starter went out. So far cylinders 5-6-7-8 all have equal 100 psi.
Going to get new starter. 😮‍💨

 

100 PSI that is terrible! Check those valves and retest.
BTW I had a Holley on a 360 and it never ran good. I was able to get a Motorcraft and then it ran great!

 

That is a good start
Check the compression on all the cylinders
They all need to be within 85 percent of the spec
An old Ford 100 is not great but is okay
A BMW 540 needs to be 140
You should check for a broken valve spring
Pull both valve covers and see how hard it is to turn the valve springs around by hand
If any are broken, you will find then either that way or by a good visual inspection, and by watching then as you crank the engine over
Pull the drivers side bank first
Check the pushrods for being bent as well
Have fun with it
Good luck

 

So after replacing the starter I found #2 cylinder would not build pressure as fast as all the other cylinders. Pulled the valve cover. Cranked engine over and found #1-3-4 cylinder rocker arms were soo loose the barely opened the exhaust valve.

These rocker arms are not adjustable. The engine has flat tapper hydraulic lifters.

Then on the #2 cylinder that would not build pressure i could not fit any shim between the rocker and valve. Set the piston to TDC and backed off the rocker arm bolt and noticed the valves lifted just slightly.

Since the rockers do not adjust, and #1-3-4 exhaust valves would barely open, I pulled the #1-3-4 push rods out to check all the lengths. All the same length.

Back to #2 cylinder. I tapped the valves with a hammer slightly to seat them and reinstalled the rocker arms. The cylinder builds pressure to 100 psi now. Strange I don’t trust it considering the other problems I found with the valves.

I pulled the driver side valve cover ans well just to check and found all the exhaust rocker arms loose. There should be zero lash. All the intakes are tight.

All rocker arm bolts were tight. Why would just all the exhaust valves be soo loose. It’s like they need longer push rods.

I have to call ATS engines to see what to do since I bought the engine from them.

 

When did you buy the reman engine?
Damn the bad luck, that sounds like a flat cam
Find oil change receipts and or receipts from buying oil and filters then call them
They will ask for those, if there is a warranty concern on their engine

 

Thanks for the info! I just installed the engine a week ago. Hasn't left the driveway. Fingers crossed with the warranty!

 

You had better do some base timing checks etc.
Unlikely that the cam went flat in a weel or so
Who installed the engine?
Was it a long block? and the valves adjusted when it came to you?

 

UPDATE: cam got wiped during break in. Manufacture is sending a new engine. I’ll have to wait like 4 months but it is what it is. Sad day….

 

Aluminum cam?

Sixto
07 E350 5.4 198K miles