[Pci_RAID]

I finally fired up my new 400 , but it has a massive vacuum leak,won’t keep a low RPM etc. It is definitely a leak, closing the choke some (actually a lot) help it run much better.
I couldn’t find where it was getting a leaking, tried spraying with carb cleaner, nothing changed.
So I tore the intake off, it turns out the intake is sitting on the lip for the valley pan, because the Edelbrock manifold is thicker than the OEM manifold. This also caused a valve cover leak as the valve cover lip contacted the manifold as it was higher than the original.
I ground down some of the excess metal on the bottom of the manifold, but can I install the valley pan with just RTV? This would help drop the pan enough to clear the manifold better. I just don’t want an oil leak.

Any suggestions ? I may go back to the cast iron manifold.
Thanks ,
Bob

[steve25]

Yes, just let the sealer skin over really well before you place it on the motor and tighten it up.
May be 15 to 20 minutes of skin over time dependant on the air temp and humidity conditions you are working in.
Once it all together and cures for 4 hours you can trim of the flowed out excess with a rasor blade and drop the intake on.

[HWYSTR455]

You can also use like a screw driver along the lip and the stamped bead and beat down, making the lip lower. It should effect the seal if you take your time. I had to trim the bottom of the gasket too, so it sat over the ports properly.

.

[PONTIAC DUDE]

Choking the carb and the rpms pick doesn't mean the intake is necessarrily leaking. Carb issues will do the same thing.

I don't know how many carbs i have changed out on my fire up stand breaking in engines with customers carbs with my good ole test carb and ran great.

I have also put a healthy bevel in the lower lip of intakes too. Not an issues. Plenty of room to seal.

[Pci_RAID]

i pulled the intake yesterday , i could clearly see the lower section of the intake gasket wasn't as compressed as the rest.
Ground down "bevelled" the lower section of the intake runner so i should be Ok there now.

[67cruiser]

Raid i believe you but you never stated what carb. your running, if its a q-jet make sure your not leaking at hot idle compensator on back of carb. seen more than my share of this.

[Firebob]

67cruiser, got pic of that compensator? Not sure what it is.

Robert

["QUICK-SILVER"]

Originally Posted by Firebob

67cruiser, got pic of that compensator? Not sure what it is.

Robert

All Q-jets dont have them. If yours does, it's covered by a kind of rectangle shaped metal plate, screwed on right in the middle on back of carb main body. Later model carbs have the place for them but the holes aren't drilled.
Under the metal plate is the bi-metal spring compensator piece.
If you have one and think it's not working, bad cork gasket or stuck open, cover the hole on top of the carbretor, in the middle right behind air valves/flaps. You'll feel vacuum sucking on your finger.

If you dont have one, never mind.

[Indian Uprising]

Try not running a valley pan gasket (just sealant) this will help you gain additional clearance.

[Pci_RAID]

It’s a Qjet,My compensator is plugged with epoxy.

I ground enough off the lower section of the manifold to clear the pan . Now i'm waiting for the thicker valve cover gaskets from summit, they should be here tomorrow. I didn't want to grind away at the chrome covers.

Bob

[Pci_RAID]

It started right up after fixing the leak. Albeit a rough idle (shakes the car) so I probably have a carb issue on top of the vacuum leak. But now it does idle around 800 to 900 rpm. So now i need to straighten out that issue. At least the vacuum leak is fixed! Now I’m waiting for a replacement radiator from summit to replace the new one came that arrived with a bad twist.
Should I be able to get a fairly smooth idle with a summit 2802 cam in a 400 .030 over?

Built it with balanced rotating assembly using TRW forged pistons dished to get around 9.5:1 compression ratio with #16 heads, headman headers, performer RPM intake and a quadrajet.



Part Number: SUM-2802
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 2,500-5,000
Intake Duration at 050 inch Lift: 224
Exhaust Duration at 050 inch Lift: 234
Duration at 050 inch Lift: 224 int./234 exh.
Advertised Intake Duration: 282
Advertised Exhaust Duration: 292
Advertised Duration: 282 int./292 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.465 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.488 in.
Valve Lift with Factory Rocker Arm Ratio: 0.465 int./0.488 exh. lift
Lobe Separation (degrees): 114



Thanks for the suggestions

Bob