I have heard of problems with the summit carb if the summit gasket is not used. But who am I to talk? I use a 1/2" wood spacer with normal carb gaskets on mine and have no problems (I think).
Is the shudder at part throttle while driving or sitting in the driveway?
Have you done any adjustments/tuning of the carb?
PCV system?
Power brakes?
Tell us about your ignition system.
Have you done a compression check?
 

Ignition system is MSD 6AL. MSD Distributor

9.5:1 compression

Shuddering at part throttle

Summit gasket is all open , I have a dual plane manifold . So I got a similar material edelbrock gasket with divided plenums , which is a 1/4” instead of 1/2. I do have a wooden 1/2” spacer too if I need to replace the gasket I have to a 1/2” one. But at 1/2” the solid throttle link doesn’t work with my lokar AOD TV bracket

Idle isn’t the smoothest.

Brake booster yes

PCV yes (and checked )

No major asjustments yet , just leveled the front bowl float.

If I pass the part throttle point I can tell there might be a miss , but the engine just powers through it . At part throttle it shudders , and makes that phssst noice and engine smoothens for a second

Ideling it is shaky a bit .. I know this full roller motor should be smoother with my cam choice.

Last edited by Gaba (3/27/2021 10:38 AM)

I will check , but I built them with tags and built to length.. I will check on the distributor again though.

I didn’t use the open gasket

I did use a two hole edelbrock.. is 4 hole even different in “performance” on a dual plane?

The 4 hole gasket/spacer just acts to increase runner length if the intake doesn't have an open plenum.  If it does I doubt it does anything.  Honestly, at 1/4" think you're not going to notice anything IMO.  From what I've seen on dynos you have to get into 1" or taller for a spacer to really make a difference. 

Now, for sealing purposes a 4 hole gasket may work better, especially with some carb designs. 

My question would be, does the shuddering start immediately at throttle tip in?  Because if the answer is yes I would suspect a vacuum leak once the throttle blades open, which could very well be the carb gasket.

Intake gaskets are another possibility.  Fords love to create an internal vacuum leak that is hard to diagnose because its leaking from the valley to the port. 

Nos681 wrote:

Have you isolated all vacuum lines to see if still does it?

Brake booster and distributor & PCV valve is all you have?

6s6
PS Get's you a bump!
 

Nos 681

Booster checked

PCV valve checked

No other vaccum connections

While spark plugs will be removed

Yes coolant leak was the heater hose that had folded into itself on the lip, and the big radiator hose being loose at Tstat neck. That’s fixed now fully

But REBUKE THAT SPIRIT FROM HERE OF COOLANT OR OIL IN PISTON
HOLES!!! Lol ;D