Vortec Head Troubles

[rn2fine]

As part of my resto on a 72 Suburban I built up a brand new 350 with mainly GM and Edekbrock parts including Edelbrock E-Tec 170 heads and an Edelbrock Vortec Performer manifold. Performance and mileage is great with this Vortec style system. However, two months into driving I experienced a mystery coolant leak. Was losing approximately 12 to 20 ounces of coolant every time I drove the vehicle. No signs of coolant in oil or anywhere visible in the engine compartment. It turned out that coolant was escaping from intake gasket at the rear coolant passage and running down the back of the block. A quick check of the internet, a conversation with a mechanic at a GM dealer, and a conversation with a private mechanic revealed that coolant leaks on the rear of the 350 Vortec intake gasket are very common. The private mechanic advised that I add some extra silicone sealant between the head and the gasket around the coolant passage. The gaskets are really different than anything I have used in the past. Both the GM and the Fel Pro gaskets are hard plastic with silicone rubber impregnated around the ports and passages. Again, the Vortec setup is awesome, just prone to leaks from what I have heard and now experienced. Anyone dealt with this before?

[Rooster's 67]

yup as a n automobile Technician I replace 1-3 a week on the late vortec intake gaskets, a little extra RTV at the ends of the gaskets and follow the torque sequence to a T and it lessens the possibility of a "come-back"

[rn2fine]

When adding extra RTV should I put it on both sides of the gasket around the rear collant passages or just the engine side of the gasket as the private mechanic recommended to me?

[Rooster's 67]

I put a THIN LAYER on all four coolant passages

[Rooster's 67]

both sides sorry

[Mudder]

My gaskets that Scoggin Dicky sold me with my vortecs came apart and began sucking oil. Neighbor that works for GM told me the same about the water ports and silicone. The gaskets they sold me were a paper type gasket that had been pressed together.

[Rooster's 67]

I always use the GM gaskets on these....And I trust Fel-Pro 99% of the time.

[Mudder]

Neighbor said the fel-pros and GM's seemed to be the same but just a different color.

[Project1970]

I don't remember exactly what gaskets are on mine...FelPros, IIRC...but a thin coating of RTV, and the standard toss-the-rubber-end-seals-over-your-shoulder bit (mmm, The Right Stuff...) and 20,000mi later, at least THAT part of my engine is still leak free!

Never had that problem on my mom's '97 Suburban...though it did get other cooling problems, thanks to that crappy 5-year coolant that likes to clog your entire cooling system up...

[jmanz69]

I had the same problem on my 98 Silverado. I didn't notice it til I went to turn my heat on and the heater core made a gurgling sound. And no heat. Then my temp gauge went way high. After it passed the air bubble it was normal again. Took it to the dealer (still under warranty), and they told me a lower intake gasket leak. They of course fixed it for free and I was on my way. Seems they make comprimises, you get better performance, but the design of the rest of the head leaves a little to be desired. Hope the cost savings of not using those 4 center bolts and having crappy gaskets made up for the warranty repair costs for GM.