351C Intake Valley Pan

[Stan R 10]

Question - Is the valley pan required?

 

Background:  

351C in 69 Mustang

C6 Auto

3.89 gears

Trick Flow 195 Heads

RPM Air Gap Manifold

Lunati about 235 degree at 050 intake duration

Holley 650 vac secondaries, currently 74 pri and 78 sec jets, 6.5pv

3500 stall converter  (its mostly a mild track car but on the street some)

 

Engine makes 7 to 8" of vac at idle (750).  Under light throttle, mixture @ 12.5 to 13 on wideband. On full throttle mixture goes to 15 and beyond a little. !!!!  yikes.

 

Engine runs ok. Little stumble from dead idle.

 

I did not put a valley pan in when built. Got mixed answers whether to use. Could the lack of the pan make the manifold not sit correctly on the heads. Would/could this be causing the low manifold/super lean via a large vac leak in the valley. I can not hear anything leaking but cant find anything else either and want to ask before just taking apart and re-installing with pan.

 

Any help and ideas would be greatly appreciated.

[SA69mach 39]

An easy check for manifold leaks is by spraying some short shots of carburetor cleaner (flammable type) along the manifold edges, and then around the base of the carburetor, at idle, and then at about 2500 revs.

 

If you have a leak, the engine will rev up as the carburetor cleaner spray gets in, for a short time.

 

Don't forget to spray at any vacuum taps in your manifold,( for brakes or transmission lines.)  For that matter, check all the lines too. 

[Wycked69 20]

The pan simply kept hot oil from splashing on the bottom of the stock intake. (remember the 351C intake is a dry intake) Some use it but many of the 351C engine builders do not. You are using an RPM airgap intake so oil splash is of no concern. I typically do not use it and I built a few 351C's with both stock heads and intake as well as after market intakes like Blue Thunder which I currently have on my 68. I've not had a problem not using the turkey pan.

 

Before taking anything apart, make sure you've torqued the intake bolts to proper spec. Also, keep in mind that an intake leak can occur from the bottom side of the intake as well as the top.

[Rsanter 152]

No it's not. But I always run one because as said it keeps the hot,oil off the bottom of the intake.

Also I think that a pressed metal gasket is far better than any of the composit gaskets made

 

Bob

[3pedal 95]

I am running the same heads on my 4-bolt 408 Cleveland Scat stroker...I used Trick Flows intake gaskets, they are too hard and do not seal correctly...I swapped them for Fel Pros and used sealer on the head side  and gasket...14 inches of vacuum at idle...duration 224/230....set your initial timing to 17/18 adv...with 7/8 inches of vacuum.... your  PV is too big, try a 4.5 ....Try a 35 squirter to get rid of stumble....don't need a metal valley gasket...I think your carb is too small for racing, need a 750 DP.....joe 

[Stan R 10]

Thanks for the replies guys

 

Really do not think I have a big leak underneath valley. But can't figure out why so low vacuum at idle. Will keep playing. Got the WOT mixture close last night with secondary jets.   PV change does not seam to do anything for mixture at WOT, whether the 6.5 or 4.5 (have used both). Maybe a drill to the PVCR's!

 

3 Pedal - yes the carb is too small - but it is keeping my right foot honest with a stock bottom end. Acquired top end for engine, then lost job and decided to put it together anyway with stock bottom. Didn't like the trick flow gaskets either when I put them on - but heads are awesome.   Hopefully soon it will be a 393 or 402, maybe bored for the 408 - but I hate say "i'm gonna do it"  everyone says that.

 

Stan