Intake leak ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

boundstaffpress · 04-09-2008, 06:18 AM

I have a motor that was rebuilt by a reputable shop 6 years ago. AFR heads, and AFR al intake. I put less than 2000 miles on it and had an intake leak. I replaced the gaskets and drove it very little, then pulled the engine and sold the car. This year, I dropped it in my 72, and it seems to have an intake leak again. I can get it to run smooth if I give it some gas, but it won't idle. I replaced the cap and rotor, replaced the wires and cleaned and gapped the plugs as part of the engine replacement.

When I spray carb cleaner around the intake I get no change until I get back to the space above #5 and #7. Then it stumbles.

Is there a fix for leaking intake other than remove and replacing the gaskets? Does anyone have any ideas other than intake leak? I've checked other vacuum sources.

thanks in advance

HoupPhotography · 04-09-2008, 08:11 AM

Have you checked the timing or re-timed the motor since you've re-installed it? Also, make sure the #5 & #7 wires are not touching, since they fire one after the other, you can have some issue's if the plug wires are touching.

As for the intake, I don't know of any "quick fixes"... your best bet is to take the intake off and replace the gaskets. If you deceide to go that route, don't use the intake gaskets that go on the front and back on the block, instead use some RTV silicone and put about a 1\4 inch bead on those ends AND a decent amount in the corners, let it set a minute or so, (until it skins over, do not let it dry), then put your intake on and torque the bolts.
The problem with those end gaskets is they move around when you put the intake on and more times than not they leak.

I hope it helps a little and I didn't miss anything....

Good luck man!

boundstaffpress · 04-09-2008, 04:54 PM

I timed it once, and it wouldn't run well, I have since gotten it close, but it may not be spot on.
I've done the silicone thing before. What gasket sealer do you use? I read about copper spray this week. Who makes this?

Bus Ted Knuckle · 04-09-2008, 05:23 PM

It shouldn't stumble when you spray the leak, it should run better. For copper spray, use a name brand copper spray paint. I would re-seal the intake with quality gaskets, and tighten in sequence. Unless there is a crack, that should knock out a leak for sure.

airdale94 · 04-09-2008, 06:24 PM

When you use an alum. intake you need to use a Mr. Gasket HiPerf. or Edelbrock intake gasket. Not the standard FelPro. And always use that red tack around the intake ports. Sometimes alum. manifolds need to be surfaced on the runners. I've seen them .060" out.

Fred T · 04-09-2008, 06:38 PM

For sealing the ends use ultra-black, ultra-blue or ultra-grey. Do not use the orange or copper, they are not as oil-resistant.

One thing that I have been doing when installing an intake with the engine in the vehicle is to check the rear seal before the sealant cures. After you have the manifold in place and the bolts in finger tight, use a mirror and light to inspect the sealant between the rear intake and the lip on the block. If there are any gaps you can remove the manifold and redo the sealant. Far better than finding the oil leak after it's all together.

And be sure to tighten the manifold bolts from the center out. There is a pattern like the head bolts. When you torque the bolts, do it in two steps. You will need all the advantage you can get to avoid another leak.

boundstaffpress · 04-09-2008, 06:44 PM

airdale94 - what red tack? Who makes it?
I've used Mr. Gasket 101B gaskets would you suggest a different gasket?

Fred T · 04-09-2008, 07:06 PM

He's talking about a high tack gasket sealant. It will hold the gasket in place until you get the manifold positioned. Some guys use a very thin coat of rtv on the head side. I've done both. Here's a pic.

boundstaffpress · 04-09-2008, 07:14 PM

Thanks guys.

Fred T · 04-09-2008, 07:14 PM

I've not used the Mr Gasket intake. Looking in their catalog, I would probably get one of the ultra seal sets. And at the end of the gasket section there are installation instructions.

*Billla* · 04-09-2008, 07:36 PM

Quote:

Originally Posted by boundstaffpress

I timed it once, and it wouldn't run well, I have since gotten it close, but it may not be spot on.

Not sure I understand this comment - what timing are you using?

I suspect a vacuum leak somewhere, but if the engine stumbled when you sprayed carb cleaner then something's wrong - it should have speeded up!

I'd be looking at all of the vacuum ports and lines - vacuum advance, brake booster, vacuum modulator, etc. before chasing off doing an intake R&R.

I also generally ask "what's changed" - it sounds like this was running well when pulled, then you replaced the cap, rotor, wires, plugs and now it doesn't run well. I'd look there, too...

Maybe a little OT - but anything other than a FelPro gasket is a complete waste of time IMHO

boundstaffpress · 04-09-2008, 08:22 PM

This is one of those projects with a couple of long vacations in the middle. I timed it at 8-10 degrees. I've since adjusted the timing by without a light, to try to find a better idle. No dice.

The HEI was from the last engine in the truck and worked fine. The engine is coming out of a 2+ year hibernation in storage. It ran when I pulled it. It has gone through a couple of freeze thaw cycles though since. I just replaced the cap and rotor to try and solve my woes, but the wires changed with the engine.

I'll check my ohms and see if that is an issue.
thanks again.

HoupPhotography · 04-09-2008, 08:52 PM

Quote:

Originally Posted by boundstaffpress

. It has gone through a couple of freeze thaw cycles though since. I just replaced the cap and rotor to try and solve my woes, but the wires changed with the engine.

I'll check my ohms and see if that is an issue.
thanks again.

Did you have all of the fluids drained out of the motor?

70rs/ss · 04-09-2008, 09:49 PM

Use new plags, as they fail and cleaning isn't worth the hassle of a misfiring plug.

I think you have some corrosion going on with the Alum and steel reacting. Sitting for a couple of years antifreeze becomes acidic and can eat aluminum, pull the intake and verify the heads and intake are not chewed up and use good gaskets with the proper torqu sequence and torqu specs, over tightening can cause mis-alingment and leaks, I use Ultra Copper on all my motors, paint a little around the intake passages (on the gasket) as well as the water passages, torqu it down, then let it cure over night the UC will fill in a minor imperfections and seal them.

boundstaffpress · 04-10-2008, 06:39 AM

The coolant was drained as much as I could. I don't recall if I flushed it. I left the oil in.
I'm planning a trip to Napa before the week is out gaskets, sealant, (we'll see about plugs?). I just sold a scrap 305 that will fund my little project.

Thanks again for all the help

airdale94 · 04-10-2008, 08:18 PM

That looks like the right gasket. And that is sealant. You might check the intake surfaces with a strait edge. Though the sealant usually takes care of any leaks. Also it's usually recommended not to use those little rubber end gaskets. Use a 1/4" bead of black high temp silicone. Those keep the oil in the lifter valley area.

04-09-2008, 06:18 AM	#1
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	Intake leak ? I have a motor that was rebuilt by a reputable shop 6 years ago. AFR heads, and AFR al intake. I put less than 2000 miles on it and had an intake leak. I replaced the gaskets and drove it very little, then pulled the engine and sold the car. This year, I dropped it in my 72, and it seems to have an intake leak again. I can get it to run smooth if I give it some gas, but it won't idle. I replaced the cap and rotor, replaced the wires and cleaned and gapped the plugs as part of the engine replacement. When I spray carb cleaner around the intake I get no change until I get back to the space above #5 and #7. Then it stumbles. Is there a fix for leaking intake other than remove and replacing the gaskets? Does anyone have any ideas other than intake leak? I've checked other vacuum sources. thanks in advance __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

04-09-2008, 08:11 AM	#2
HoupPhotography Registered User Join Date: Feb 2008 Location: Phoenix, Az Posts: 1,204	Re: Intake leak ? Have you checked the timing or re-timed the motor since you've re-installed it? Also, make sure the #5 & #7 wires are not touching, since they fire one after the other, you can have some issue's if the plug wires are touching. As for the intake, I don't know of any "quick fixes"... your best bet is to take the intake off and replace the gaskets. If you deceide to go that route, don't use the intake gaskets that go on the front and back on the block, instead use some RTV silicone and put about a 1\4 inch bead on those ends AND a decent amount in the corners, let it set a minute or so, (until it skins over, do not let it dry), then put your intake on and torque the bolts. The problem with those end gaskets is they move around when you put the intake on and more times than not they leak. I hope it helps a little and I didn't miss anything.... Good luck man! __________________ R.I.P. Scott Kalitta

04-09-2008, 04:54 PM	#3
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	Re: Intake leak ? I timed it once, and it wouldn't run well, I have since gotten it close, but it may not be spot on. I've done the silicone thing before. What gasket sealer do you use? I read about copper spray this week. Who makes this? __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

04-09-2008, 05:23 PM	#4
Bus Ted Knuckle Son of a gun Join Date: Jan 2007 Location: Hot Springs, Arkansas Posts: 1,636	Re: Intake leak ? It shouldn't stumble when you spray the leak, it should run better. For copper spray, use a name brand copper spray paint. I would re-seal the intake with quality gaskets, and tighten in sequence. Unless there is a crack, that should knock out a leak for sure. __________________ Bill BEATERS ARE NEATER Last edited by Bus Ted Knuckle; 04-09-2008 at 05:25 PM.

04-09-2008, 06:38 PM	#6
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: Intake leak ? For sealing the ends use ultra-black, ultra-blue or ultra-grey. Do not use the orange or copper, they are not as oil-resistant. One thing that I have been doing when installing an intake with the engine in the vehicle is to check the rear seal before the sealant cures. After you have the manifold in place and the bolts in finger tight, use a mirror and light to inspect the sealant between the rear intake and the lip on the block. If there are any gaps you can remove the manifold and redo the sealant. Far better than finding the oil leak after it's all together. And be sure to tighten the manifold bolts from the center out. There is a pattern like the head bolts. When you torque the bolts, do it in two steps. You will need all the advantage you can get to avoid another leak. __________________ Fred There is no such thing as too much cam...just not enough engine.

04-09-2008, 06:24 PM	#5
airdale94 Registered User Join Date: Jan 2007 Location: Topeka,KS Posts: 778	Re: Intake leak ? When you use an alum. intake you need to use a Mr. Gasket HiPerf. or Edelbrock intake gasket. Not the standard FelPro. And always use that red tack around the intake ports. Sometimes alum. manifolds need to be surfaced on the runners. I've seen them .060" out.

04-09-2008, 06:44 PM	#7
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	Re: Intake leak ? airdale94 - what red tack? Who makes it? I've used Mr. Gasket 101B gaskets would you suggest a different gasket? __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

04-09-2008, 07:06 PM	#8
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: Intake leak ? He's talking about a high tack gasket sealant. It will hold the gasket in place until you get the manifold positioned. Some guys use a very thin coat of rtv on the head side. I've done both. Here's a pic. Attached Images __________________ Fred There is no such thing as too much cam...just not enough engine.

04-09-2008, 07:14 PM	#9
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	Re: Intake leak ? Thanks guys. __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

04-09-2008, 07:14 PM	#10
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: Intake leak ? I've not used the Mr Gasket intake. Looking in their catalog, I would probably get one of the ultra seal sets. And at the end of the gasket section there are installation instructions. __________________ Fred There is no such thing as too much cam...just not enough engine.

04-09-2008, 08:22 PM	#12
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	Re: Intake leak ? This is one of those projects with a couple of long vacations in the middle. I timed it at 8-10 degrees. I've since adjusted the timing by without a light, to try to find a better idle. No dice. The HEI was from the last engine in the truck and worked fine. The engine is coming out of a 2+ year hibernation in storage. It ran when I pulled it. It has gone through a couple of freeze thaw cycles though since. I just replaced the cap and rotor to try and solve my woes, but the wires changed with the engine. I'll check my ohms and see if that is an issue. thanks again. __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

04-09-2008, 09:49 PM	#14
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: Intake leak ? Use new plags, as they fail and cleaning isn't worth the hassle of a misfiring plug. I think you have some corrosion going on with the Alum and steel reacting. Sitting for a couple of years antifreeze becomes acidic and can eat aluminum, pull the intake and verify the heads and intake are not chewed up and use good gaskets with the proper torqu sequence and torqu specs, over tightening can cause mis-alingment and leaks, I use Ultra Copper on all my motors, paint a little around the intake passages (on the gasket) as well as the water passages, torqu it down, then let it cure over night the UC will fill in a minor imperfections and seal them. Last edited by 70rs/ss; 04-09-2008 at 09:58 PM.

04-10-2008, 06:39 AM	#15
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	Re: Intake leak ? The coolant was drained as much as I could. I don't recall if I flushed it. I left the oil in. I'm planning a trip to Napa before the week is out gaskets, sealant, (we'll see about plugs?). I just sold a scrap 305 that will fund my little project. Thanks again for all the help __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

04-10-2008, 08:18 PM	#16
airdale94 Registered User Join Date: Jan 2007 Location: Topeka,KS Posts: 778	Re: Intake leak ? That looks like the right gasket. And that is sealant. You might check the intake surfaces with a strait edge. Though the sealant usually takes care of any leaks. Also it's usually recommended not to use those little rubber end gaskets. Use a 1/4" bead of black high temp silicone. Those keep the oil in the lifter valley area.



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