Howdy ya'll. I have a 1984 K5 blazer with a 305, but the blazer boys dont seem to know HALF as much about heads and 305s as yall, so I hope this isnt a problem for me to post on this forum and ask about something other than a third gen.

Let me beat you all to it, I cant just swap in a 350. This is the only car I have, and I need to deliver pizza in it. I dont have the money for a 350, nor do I have a cherry picker or any other required tools.

I blew out the head gasket on my K5, I think. All i know is a small amount of mosture is getting into the oil, and alot is going right into the cumbustion chamber and being burned. I plan to pull the intake off, and see if I can find evidence of a leak. Assuming I can not, I will throw away the stock one and install a used performer. I have heard of 305 intakes cracking, which would cause my problem.

Assuming I do all this and the problem continues, I will be pulling the heads off and replacing the head gaskets. Since the heads will be off, and I suspect the valve guids are shot, will these heads work well on a 305?

Casting number:
3932441....69-70...350..........76cc chambers

Just would love some opinions and input. Im dirt poor right now, so I have no money to spend on anything Even the 110 for the head gasket kit is a hard hit

 

Stay away from those heads with a 305, they have 76cc chambers instead of the small 58cc chambers a 305 needs, you will lose compression, power and mileage.

 

Exactly what DartbyU said, those heads are way too big for a 305.

You can get decent gains by porting and polishing the 305 heads if you want to go that route or, if you have the money, check out a set of World "Torqurer S/R" heads with the 58cc combustion chambers for 305 motors. They claim 30+hp just by swapping them in.

 

Your 84 Blazer should have 14022601 casting heads on it, if it is still stock. They are one one the BEST 305 castings you can run. They have a tiny 53cc combustion chamber, 1.84/1.50 valves, and 160ish cc intake ports. They work very well on a 305. Do yourself a favor while the engine is apart. Change the timing chain to a double roller and swap the factory camshaft out for a factory 350 cam. The stock timing chains had composite plastic teeth and were prone to failure. Thats the reason mine had to come apart and have the heads re-worked at 175,000 miles. The chain left while the engine was idling and I bent several valves. The cam also had a couple of lobes that were on their way out. The factory 305 cams of that era were very soft.