Head gasget I think. 11mm block maybe?

[Mark(The Miser)UK]

521 478...  Is there a CK in front of that number? If so, then it is a 1.5 block built in October  1979

[RabbitJockey]

Awesome. 20-25 was a lot of fun in that thing, like I said I did it only a couple times to see what it would do. Your suggestions are indeed regarding a 12mm engine with ARP studs correct? Sorry there is so much information and misinformation out there it's difficult to find specifics for my situation.

Regarding exhaust manifold pressure I'm sure it's pretty high when I open the veins (open being pointed toward the wheel / the more boost setting / lever on exhaust housing toward the ground). Someone correct me please if I'm explaining it backwards. I guess that's just something that comes with running a VNT15. My only option for correcting this would be a different charger.

My EGT has stayed rather low throughout my trials. Hasn't seen over 850 and that was running it pretty much flat out from a dead stop and my fuel screw is nearly maxxed. I'm sure it will get hotter when trying to pull hills and such but I'm very comfortable with the EGT situation. I do have a little bit on my side to keep things cool though. 2.5" exhaust from the turbo back, extra oil cooler, intercooler mounted on top sticking through the hood catching plenty of cold Pennsylvania November air, and a modified gasser intake manifold. So I think it's doing very well on the intake side. But the most important part between the head and the exhaust wheel is likely a different situation.  

Thanks again for the input. Really having fun with this project.

either engine, if you can get an 11mm engine put together with studs and hylomar spray with out the block being cracked then i'd say your safe, but i'd definitely try to keep egts lower with the 11mm engine.

[matt-stunt]

So I replaced the belt and coolant hose that blew apart and everything seems to be okay. Still seeping just a little right below the #3 injector but I can live with it for now. No water in the oil, temps are normal, coolant pressure doesn't seem to be excessive judging by squeezing the rad hoses and opening the cap, I put about 40 miles on it yesterday kept the boost no more than 15 and everything looks good.

The part number on the head looks a little off...for a stock 1.6l block with 11mm head bolts it will mostly have a letter, usually a "B" or sometimes a "F" after the 373.  But there is some inconsistency to the letter coding.

There are some 373 heads without a letter trailing on 1.6 motors that have had the oil return boss built up on the outer lip to match the boss on the blocks oil return but they will still have the smaller inner diameter to the oil return (about the size of a nickel instead of the proper quarter size for the 1.6 head).  If there is a ledge showing on top of the block between the oil returns the head is built for a 1.5 l motor and that is a point of leakage.

If the block has a 16 cast into the the back side (not a 1.6) but a 1.5 liter head you are possibly running at a 25+ compression ratio before adding boost.  i had a 1.5 liter head on a 1.6 liter block for about 30000 miles and it ran good (it started really easy) but the pistons showed signs of melting below the pre-cup...the injectors (rebuilds from a local Bosch shop with France nozzles) might not have been dealing with the higher compression very well.

Thanks for the info next time I pull the valve cover ill be sure to look into this, I did glance at both oil return passages when I was re-torqueing and from what I remember they were about nickel sized. Quarter sized is much bigger than the holes I saw because I remember noting that my 1/2" drive socket would be safe from falling in the passage.

The first thing that crosses my mind or EGT not  reaching 900 is you have the probe downstream from the turbo?

I put my probe in the manifold as close to the head as I could get it. I did have it a little hotter yesterday pulling a long hill in 5th gear, lugging the engine for quite a while until the turbo spooled. By the time I was building boost the EGT was around 1050. Still very satisfied with these results.

521 478...  Is there a CK in front of that number? If so, then it is a 1.5 block built in October  1979

I didn't realize their were letters in front of the numbers when I cleaned them off ill have to look and see.

either engine, if you can get an 11mm engine put together with studs and hylomar spray with out the block being cracked then i'd say your safe, but i'd definitely try to keep egts lower with the 11mm engine.

Ill see what the block looks like when I decide to pull the head. I'm still going to keep my eyes open for a good deal on a 12mm block but for now I'm gonna get as much use out of it as I can. 

Thanks again everybody!