I read what I could and decided to port a spare set of aluminum heads from 95 z28. Everything worked out well even thou I almost screwed up few times.
It was time to do the valve job and resurface the heads, so I decided it would be a good idea to pressure test them. Guy at the machine shop tested one head and found a leak in the intake bowl. Here are the pictures (big):

In this picture, to the left of the valve guide there are some scratches, that is where the leak is. It is not visible, but I was told that is where it is.
whole chamber

Same thing twisted 90 deg cw (the crack is above the valve guide)
bowl zoom in

from intake side

I tried matching up the crack location with a picture of cut away LT1 head (area marked red)
cut away picture marked with a suspected trouble area

The guy down at the shop who pressure tested this head said that these heads are probably no good since I took off too much material from those areas. I didn’t think I took off that much to cause a leak, I am thinking maybe this is just an imperfection in the casting that surfaced after porting.
I need opinions here.
The head was tested at 30 psi. I was told by the same guy that these heads are probably not salvageable, but I was hoping to get it welded, and I do know a very good local welding shop.
I can feel the area (part of the area) between the valve seat and valve guide with my fingers and there is still a lot of material there, feels like 4-5mm or so, but I can reach down to the damaged area.
The guy also said that even if I weld this crack up, other similar areas may crack later due to expansion /contraction.

So like I said I need opinions from experienced porters, please look at other pictures to check out the porting work

here is a link to the complete web page about this project

Thanks

 

Im not an experienced porter but from the knowledge I do have I think they should be able to be welded up and fixed. Doesn't look that serious to me...

Aaron

 

Ive seen top fuel motors with weld beads all over the blocks dont see that that cant be welded. Good luck because it looks like you put some time into that.

 

ok, The reason that the guy said that the head was not able to be repaired is not because of the crack, but rather the lack of material all around that area. From what the machinists said, I think that all of the bowls are similar in dimension so he is worried that they are all thin, and will crack with the expansion and contraction

But, it can be fixed,

Find a good welder, have him weld the entire back of the bowls up (most likley, all of them if they are all close to the same dimension), then smooth them back up, make sure that you leave AT LEAST .100 thick of material (anything less will crack when heated up and cooled down repeatedly), Now, the heat put in it may move the valve guides so you need to have them checked for clearance and out of round, If they are, have them fixed. Now, put a valve in the guide and lap it in, make sure that there is constant contact between the seat and the valve, if not, time for a valve job. Something else I would do, is have the head sealed, There is a chemical that when you put it into the water jacket, will seal all porosity from the welding and the porting from the inside out.

If you have any more questions, email me
also, if you want some feedback about the portwork, email me

Nick

PS- I am a professional head porter and machinist

 

Nick obviously knows more about this than I do. So I'm sure what he describes can be done. But you can get a set of LT1 heads for $200-250. I see them FS all the time. If it were me, I'd start over.

Just my $0.02.

Rich Krause

 

Neat info. BTW, it is nice to have certain specialists/experts on this board in addition to most of the rest of us who are hobbyists/amateurs

 

But you can get a set of LT1 heads for $200-250. I see them FS all the time. If it were me, I'd start over.

Just my $0.02



I agree, that is probably what I would do too.

 

I just got a set for $230 shipped. If you have calipers you can measure some parts of the head as you go, FWIW my head got about as thin as .035" (like a spark plug gap).

It looks like you really put some effort into those heads though, so congrats on that mark!

 

yeah if you have them too thin not only will the expansion/contraction be bad but also the fact that coolant is under pressure when hot, I dunno but have them flowed & pressure tested again, they look very good though

 

Thanks you guys for all the replies.
I will try to have them fixed.

Something interesting found out yesterday. Guy at the shop said that if I push on the crack I will probably make a hole (since it is so thin) well I figured, what do I have to loose, so I tried making a hole but couldn't which tells me that material is still thick enough. I used screw driver and both hands (decent pressure).

That is exatly what the machinist said.
What surprizes me is that I didn't really take off that much material, that is why I am leaning toward the "casting imperfection" problem, or maybe I am just in denial

I will e-mail you

Yep, that is where I got these heads. I bought a set of heads and intake for 300 shipped.

not yet, I wanted everything done first.

Thanks, I did spent about 50 hours on them.