It will also help clog up your heater core and radiator. Stay away from that garbage. If you have electrolysis build up (like many of these do) in your head and block, pour that junk in there and youe almost guaranteed to be doing a head gasket soon.
That being said. My 80 model had a cracked block since about 83-84. The man I got it from cleaned it with a wire wheel and put some marinetex on it. Still there to this day. If I were in your shoes I'd clean it very well, mix some jb weld (the 4 minute kind) let it set over night and roll with it. I used it on a 5.9 cummins block in a pinch to get it home and as far as I know the man is still running it. Been a few years back since I talked to him.
What the redneck says it true and an excellent caution. I should have included that with my recommendations. This can happen in older vehicles that have components that are near plugged up.
I Have had success using both options (JB weld and seal tabs) for money issue customers and in a pinch situations.
I know that some people dislike them (seal tabs) due to the potentials. If used correctly (not five times, Because more will work better) and the instructions followed properly I have never had an issue Myself. I also would like to mention that Subaru and Cadillac use this same technology as part of the regular maintenance. Seal tabs and cooling system stop leak additive.
http://paceperformance.com/i-6485739-3634621-gm-cooling-system-seal-tabs-for-cadillac-aluminum-engines-other-gm-iron-aluminum-engines.htmlhttp://www.amazon.com/Subaru-SOA635071-Coolant-System-Conditioner/dp/B00IGZP2UESubaru does not call it a sealer but trust me, I have used it many times and its a sealer.
I believe there are others that use seal additives strait from the factory.
