intake gasket 360 magnum

hls30 · 10-03-2009, 12:23 AM

Is there a better gasket set for the common air leak caused by the intake-valley pan gasket failing. I have had it done twice am I am at 90,000 miles. I understand you should change out the bolts when you do this and I made sure they were done the 2nd time it was done. That was about 20,000 miles ago.
It has the typical pinging at part throttle under load even when the truck is empty and a very slight hill. It has now started idling erratic like a vacuum leak. I have sprayed brake cleaner all around the intake manifold and around the vacuum lines and it does not change the erratic idle. It does it more when it is warming up but mostly will idle fine once it is fully warm. During warm up if I hold the throttle just lightly I can get into a lean surge condition as as I apply a little more throttle you can hear what appears to be another or two cylinders kicking in. During this warm up time if I put it in neutral and hold just above idle it will surge back and forth between 2500 rpm and 800 rpm. The idle speed motor seems to be operating as I shift in neutral at red lights it will try to compensate and again when I shift it back into drive. The check engine comes on sometimes but not always. I know an intake leak could cause oxygen sensor fault codes. I gues maybe I should have injector pattern checked while the intake is off. I will have the codes read as well.
Is there anything else that I may be overlooking that could cause this type of type of symptoms.
I would appreciate any help.
Allan

BernieB · 10-03-2009, 01:36 AM

Edelbrock makes a good gasket set for that intake. Much better than Fel-Pro IMHO. And I agree, it sounds like a vacuum leak you're dealing with, but before you go tearing it down and doing the gaskets you should locate the leak. Might not be the gaskets this time.

hls30 · 10-03-2009, 11:04 AM

Thanks, good idea I will start pinching some hoses including pvc valve, brake booster, evap and even the ac- heater flap diaphragms and hopefully see a leak. The reason I thought it was the gasket is the way the problem at idle goes away once the engine is fully warm but it still pings like crazy with a very slight load even when the truck is completely empty.

BernieB · 10-03-2009, 12:12 PM

Pinging can have other causes besides a vacuum leak.

hls30 · 10-03-2009, 04:10 PM

From what I understand there is no knock sensor. I have actuated the egr valve to see if if the pinging goes away under load and it won't. The timing is fixed and I understand the distributor does only spark distribution and the timing is crank sensor controlled . I did change out the cat last year but not because it was restricted. The pinging stays the same no matter if I use 91 octane or 87 octane. The pinging is even under very slight load like 1/8 throttle opening and goes away once you reach a constant speed. I would think that if the pinging was timing induced it would be better with the 91 octane versus the 87 octane specially at such small throttle openings.
I don't know maybe I am overlooking something. I am sure it is, it is always something that is being overlooked.
thanks

jimbo543 · 10-13-2009, 12:53 PM

dealer has a metal plenum gsk, try flushing/cleaning injectors and running top engine cleaner through engine. use fuel injector cleaner in the tank.

10-03-2009, 12:23 AM	#1
hls30 Junior Member Join Date: Sep 2009 Posts: 3	intake gasket 360 magnum Is there a better gasket set for the common air leak caused by the intake-valley pan gasket failing. I have had it done twice am I am at 90,000 miles. I understand you should change out the bolts when you do this and I made sure they were done the 2nd time it was done. That was about 20,000 miles ago. It has the typical pinging at part throttle under load even when the truck is empty and a very slight hill. It has now started idling erratic like a vacuum leak. I have sprayed brake cleaner all around the intake manifold and around the vacuum lines and it does not change the erratic idle. It does it more when it is warming up but mostly will idle fine once it is fully warm. During warm up if I hold the throttle just lightly I can get into a lean surge condition as as I apply a little more throttle you can hear what appears to be another or two cylinders kicking in. During this warm up time if I put it in neutral and hold just above idle it will surge back and forth between 2500 rpm and 800 rpm. The idle speed motor seems to be operating as I shift in neutral at red lights it will try to compensate and again when I shift it back into drive. The check engine comes on sometimes but not always. I know an intake leak could cause oxygen sensor fault codes. I gues maybe I should have injector pattern checked while the intake is off. I will have the codes read as well. Is there anything else that I may be overlooking that could cause this type of type of symptoms. I would appreciate any help. Allan

10-03-2009, 01:36 AM	#2
BernieB Senior Member Join Date: Jul 2009 Location: Fredericksburg, VA Posts: 1,901	Edelbrock makes a good gasket set for that intake. Much better than Fel-Pro IMHO. And I agree, it sounds like a vacuum leak you're dealing with, but before you go tearing it down and doing the gaskets you should locate the leak. Might not be the gaskets this time. __________________ If the guys who design 'em had to take one home, use it every day for 2 years, and do all the maint and repairs themselves, cars would have a button on the dash to change the oil, filters & plugs.

10-03-2009, 12:12 PM	#4
BernieB Senior Member Join Date: Jul 2009 Location: Fredericksburg, VA Posts: 1,901	Pinging can have other causes besides a vacuum leak. __________________ If the guys who design 'em had to take one home, use it every day for 2 years, and do all the maint and repairs themselves, cars would have a button on the dash to change the oil, filters & plugs.

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10-03-2009, 11:04 AM	#3
hls30 Junior Member Join Date: Sep 2009 Posts: 3	Thanks, good idea I will start pinching some hoses including pvc valve, brake booster, evap and even the ac- heater flap diaphragms and hopefully see a leak. The reason I thought it was the gasket is the way the problem at idle goes away once the engine is fully warm but it still pings like crazy with a very slight load even when the truck is completely empty.

10-03-2009, 04:10 PM	#5
hls30 Junior Member Join Date: Sep 2009 Posts: 3	From what I understand there is no knock sensor. I have actuated the egr valve to see if if the pinging goes away under load and it won't. The timing is fixed and I understand the distributor does only spark distribution and the timing is crank sensor controlled . I did change out the cat last year but not because it was restricted. The pinging stays the same no matter if I use 91 octane or 87 octane. The pinging is even under very slight load like 1/8 throttle opening and goes away once you reach a constant speed. I would think that if the pinging was timing induced it would be better with the 91 octane versus the 87 octane specially at such small throttle openings. I don't know maybe I am overlooking something. I am sure it is, it is always something that is being overlooked. thanks

10-13-2009, 12:53 PM	#6
jimbo543 Senior Member Join Date: Sep 2007 Location: MN Posts: 205	dealer has a metal plenum gsk, try flushing/cleaning injectors and running top engine cleaner through engine. use fuel injector cleaner in the tank.