I rebuilt my engine two years before. Sealed up the china walls with black RTV and also the coolant ports. Now it's leaking a bit coolant on the front and rear of the block and coolant also comes out in the middle of the manifold. I am really pissed that I have to do it again, but what side gaskets should I buy? I've used Fel-Pro for years and never had a problem. Are there better side gaskets? Or is the RTV the culprit?

 

The only place you'll have coolant are the front and rear ports on the heads. If you've got water leaking everywhere, something strange is going on.

The gaskets and seals are part of it. The other is the threads on the 8 corner bolts need teflon thread sealer, or water will weep past the threads. The 4 center bolts likewise need thread sealer, or eventually oil will seep between the threads the same way.

 

I found that this was a result of pitting and corrosion around the ports in the aluminium TPI base. I had to media blast out all the aluminium oxide from the pitted surfaces, fill the pits with epoxy, and block sand the mating surfaces back to flat and square. I then used quality gaskets and RTV on both sides around the coolant ports. No problems and that was ~4 years ago on my daily driven LB9. I recently pulled the engine out for an upgrade and no coolant leaks.

GD

 

I disassembled the intake today and guess what I've found? Nothing. At least nothing what could have caused the problem. I am starting to think that the RTV silicone was bad or bad quality. I've done a dozen intakes on V6 and V8 3rd gen engines in the last 15 years, but this never happened to me before. I took an eight-minute video where I tried to speak english and describe what I see but my spoken english is a bit rusty 13 years after I left german high school. I will upload on youtube in the evening and share the link here.

Good point... I had a very little bit corrosion on the coolant ports IIRC... but the pits were very small. I will check the intake and the heads on monday again for them and take a few photos. You say "quality gaskets". What is quality? I've used Fel-Pro since 2005 and never had a problem. I see Mahle "nitro seal" on rockauto and also Enginetech "heavy duty" seals. What's the difference between them and the Fel-Pro metal gaskets? Any advice?

 

Which Fel-Pro gaskets (P/N) are you using?

 

I've used these ever since: https://www.rockauto.com/de/moreinfo...251830&jsn=260

 

Use Permatex Ultra Gray.

 

I refer to them as Felt Pro. I mean, when I held them in my hands, they felt professional, but after installation, not so much.

I've used Mahle and Victor Reinz with better luck lately.

 

At the shop we now call them Fail Pro. Quality seems to have dropped.

Mahle seems decent lately. Cometic is typically excellent. Remflex for exhaust.

GD

 

A short question: I have 12 hex intake manifold bolts (obviously), they are the stock GM bolts. But 4 of them are slightly longer than the other 8. Does anyone know where the longer bolts belong? I've put them on the 4 outward holes. Maybe that was wrong and caused my leaks because they where bottomed out?

 

You called it right. The 4 corners bolt holes in the heads are blind-tapped - they don't go all the way through. There is a bottom. The longer bolts are for places where the additional thickness of a bracket was. You also have to be careful not to put too long of a bolt in certain places that will go far enough through into the lifter area and contact and bind a pushrod. Since you know the longer bolts are at the corners, you can either shorten them a little bit, or replace them with a slightly shorter bolt that won't bottom out.

 

So the four longer ones don't go in the corners, but where do they go? Is there a specific spot for them to go or is it just anywhere that isn't the corners?

 

After a brief search of the entire Internet, I encountered this information.

As he said, putting the long bolts in any of the 8 holes adjacent to the water jackets, may result in them bottoming out, and not fully tightening against the intake. You could put your 8 short ones there and the 4 long ones in the center adjacent to the exhaust crossover passage, but there are push rods DIGHT DIRECTLY IN FRONT OF those, so if they're TOO long, they'll hit the push rods. Also not good.

Best to assemble them properly.

With regard to the gaskets, I've typically used the FelPro MS90314, with good results, NOT the 12xx type. I usually use whatever color of "ultra" RTV, usually in the form of The Right Stuff when possible (in a can that comes out of a nozzle under pressure) for the end seals. A light smear of it around the water jackets, and a bit extra in the corners where the heads and block meet.