428 Police Interceptor carb plate

[mjhcobra]

I am using the 428 Police Interceptor engine and read that a wedge plate can be used under the carb to level out the carb since the PI intake has a pretty good angle on the carb mounting surface. I calc'd it to be about 5 to 6 degrees and did find a 5 degree plate that is one big plenum, not 4 individual holes.
Would using this plate cause any performance issues?

Is there a particular plate that was used by Shelby?

Thanks,

Martin

[DanEC]

Reportedly the dual quad cars used wedge plates under the carb. Not sure about the single quad cars but they may have also. I've found the wedge plates at Summit and Jegs by Moroso and others. I thought I remembered the Moroso one to be a 4 degree wedge but maybe they are 5 deg. They are fairly thick - 3/4 inch at the large end, again from memory. So you need some hood clearance. I thought the Moroso plate was 4 holes but maybe my memory is faulty. In theory the spacers should boost torque very slightly and will help keep the carb a little cooler - Shouldn't hurt performance.

[mjhcobra]

Below is the one that seems to be most available-Moroso 65030 5 degree wedge plate.



Hood clearance is a good thing to check once the plate is on and before I get the air filter.

[DanEC]

I checked back and it looks like the 4 holer I was thinking about was the TransAdapt model with 8 deg angle. If you have a four hole, dual plane intake, I would be hesitant to use an open spacer on it - probably no major issue would result but it would affect the fuel/air distribution in some fashion. Could be for the better but might be for the worse. Your best bet may be to get a half inch phenolic insulator spacer and see if a machine shop could mill it to a 3 or 4 degree angle.

When I inquired about a smiliar subject a couple of years ago, several pointed out that a carb sloping down towards the front a couple of degrees was actually preferred to being dead level. Under acceleration the car will level up as the nose of the car rises.

[mjhcobra]

Below is a PI intake and it does not have the 4 separate holes.




I would guess that the open wedge plate would not affect performance with the intake.

[DanEC]

[quote=mjhcobra;1288734]Below is a PI intake and it does not have the 4 separate holes.




I would guess that the open wedge plate would not affect performance with the intake.[/QUOTE

On Chevrolet BB motors it's an old L88 Chevrolet Power Book trick to mill out the center divider on the plenum of the factory aluminum dual plane intake. Doing so sacrifices some low speed torque and response but typically boosts upper range HP. On the BB Chevrolet the carb usually has to be rejetted in a staggered pattern - each bore a different jet size - to optimize it.

Using on open spacer on that manifold will be essentially the same thing as milling down the divider part way - it will allow the two separate plenums to act somewhat as one larger plenum. The above is the type of effect you can expect from doing so. The odds are you may suffer a slight loss of low speed performance/response but in a light car like the Cobra, you probably won't even notice it.

[frdfver]

If EM had set the eng at the right angle for your chassis and rear axle combination you wouldn't have the driveshaft or carb angle-spacer problems. I have also had to work thru some design quirks on my NAF to get it how I want it so I understand your frustrations and can only say that you will work it out and end up with a car you can enjoy.....

Paul T.