Any issues with a 73 head on a 72 block? I have coolant leaking to the crankcase.

I haven't pulled things apart yet and I hope it is an intake issue.

Just wondered if there is something that obviously needs to be done with a 73 head that I overlooked..

Jay

 

did you plug the extra coolent passages?(scallops)
that should be the only real difference that'd be problematic on older blocks

 

On the 455 it leaves a water passage uncovered. I'm not familiar with the 350s, but it sounds like it could be the same thing.

 

Correct, the later heads have extra coolant passages to solve the issue with the 68-72 heads being prone to cracking. You either need to block the passages in the heads or change to early heads.

BTW, if you were using a 73-80 block you could use any 68-80 heads without issue.

 

Good info I had forgotten about, Sean.

I'm hereby correctly spelling the word scallops to help this thread show up with the search function!

Devon

 

They should look like this.

 

We're on the same page, Jason!

Devon

 

Hmmmmm.. This is EXACTLY what happen to me. Original 72 block , engine ran OK with 71 intake manifold, heads and carb. But when the 73 heads were installed......coolant in the crankcase. I had a set of correct 72 heads that needed to be gone through, but it wasn't a priority. I picked up the 73s as they were a good used set that I could just clean up and bolt on. Well , needless to say the right ones are now on and we'll see what happens.

 

I keep on bringing this up but a few times a year someone has this happen... Make sure you flush the engine right away with fresh oil. I suggest at least 2 oil changes as soon as possible with about 10 minutes run time between oil changes. You need to get the coolant contaminated oil out of the engine ASAP.

 

rather than spending more money to rebuild another set of heads, why not just plug the offending holes in the '73 heads... I imagine 1/2" or 3/4" plugs would worko No:

 

Nope.. Didn't notice the extra passages.. Thanks everyone for the info.

At least In noticed it before I tried to run it.

 

Since I had them and they were date coded,I'd rather put the right ones on. Plus the fact that the old ones are plainly stamped 73 right on them, they looked way out of place when everything else was correct.

 

No problem with that here.. 71 car 72 engine 72 and 73 heads 78 tranny 70 something intake..

 

Well I removed the intake and water seems to be seeping out all over the place on the bottom of the heads on both sides.. The intake did not appear to be leaking.. Guess it's time to pull things apart and have a second look.. The gaskets were marked "up or top" and i'm relatively sure I got that right..

 

Get those heads off and look for the center coolant scallops.

 

Now I see.. What messed me up was that I was under the impression that one of these heads came off of this engine. The one marked 73 I knew did not, so I just made sure the two heads were alike.. Lesson learned..

Which brings me to the next question, how do I block these ports?? I have HOURS porting and gasket matching not to mention a fresjh valve job..

THanks for your help,
Jay

 

I have never blocked them myself however you can most likely just drill them out to a common tap size, tap threads into the passages, then add pipe plugs. You could also use frost plugs likely if you could find a size that fits snug, some epoxy to be sure it stays put and seals well.

 

But isn't that defeating the purpose, which is to prevent the head cracking problems? Or am I missing something?

BTW, I have a 71 block, and likely 71 or 72 heads. I'm going to search for a set of heads to have ported while I continue to drive my car. I'd be wise to look for 73 + heads?

 

I think you are missing something.. THere is no possible way to make a 73+ head work on a pre 73 block without blocking off the center coolant ports. The center coolant ports hang out into the lifter valley and there is nothing on the block (under them) to support them. Blocking the ports just essentially makes them into a pre 73 head..

My machine shop drilled the hole out round, taped it and installed pipe plugs and milled them back flat. They are already back on the engine and it will go back in today if I can get off the internet..