772 vortec heads cracked.....

[Typhoonracer]

is this an on going issue with 772s? I have heard that they crack even if not ported, but if ported too much snap crackle, pop they go.....

I have cracks between the valves in ALL comb chambers..... (pictures to follow.....)

I am looking for the correct casting number for the L35s that work on our trucks....

I have GM #10238181 & GM #10240209 either of these better than the other or no difference?

Thanks for the help... Trying to get her back on the road!!

 

[Maxtor]

Re: 772 vortec heads cracked.....

Hi Steve. I have posted regarding this subject before....unfortunately this can be an issue with the vortec heads especially as HP increases. Bottom line, you need hardened exhaust valve seats or aluminum heads. Some (or maybe all?) marine vortec heads have them already pressed in, but I have never been successful in finding a good list of marine casting numbers. The ring is easy to see around the exhaust seat.

No reason though a shop can't press in seats though in any casting.

Hope this helps.

Mark

 

[Logan]

Re: 772 vortec heads cracked.....

I have a good 181 casting number L35 that was magnafluxed and passed. If you want it, pay shipping and it's yours.

 

[Typhoonracer]

Re: 772 vortec heads cracked.....

Thanks guys!
Mark I may have seen your Sy way back in the day.... Meet Jim when he was tuning one at US41... 90* temps, 90% humidity..... the truck Jim was tuning was still running VERY deep 11s.....

Logan,
Check your PM.

 

[dgoodhue]

Re: 772 vortec heads cracked.....

What size valves does the 772 Vortec have in them. I have heard and read that 2.02/1.60 tend to crack. I went with 2.00 & 1.56 valves for that reason.

 

[Maxtor]

Re: 772 vortec heads cracked.....

What size valves does the 772 Vortec have in them. I have heard and read that 2.02/1.60 tend to crack. I went with 2.00 & 1.56 valves for that reason.

Smaller valves would definitely help Dave, but that is obviously a high heat/high stress area that GM never intended for this application. I do run the 2.02/1.60 valves. The guy from Lingenfelter that did the set I am running now said the hardened exhaust valve seats were a must-have. I found a new set of marine castings and they used those for the build. They have been on for about four years now, no issues yet.

 

[Fairclough]

Re: 772 vortec heads cracked.....

If you don't have a cat, you could run leaded fuel.

 

[Quickstop [UK]]

Re: 772 vortec heads cracked.....

And kill your O2 sensor...

 

[0966Sy]

I've seen and heard of several cracked vortec cylinder heads, all where big valve heads. I think the most overlooked thing when modifying a cylinder head is spring pressures. When adding aftermarket springs to compensate for a higher load on the spring for use with aftermarket cams. Seat pressure and open pressure should be checked with any performance built head. My brand new casting cylinder heads with stock size valves required the exhaust spring seats to be milled. The aftermarket springs, without being milled likely would have caused coil bind and to much seat pressure causing excessive force applied to the valve seat. Combine these problems with a head not set up correctly with big valves and porting, I wouldn't be surprised to see cracks in the seats. Just my .02 cents, many machinists shortcut this check when modifying springs for a cam. There are many other valve train related checks as well, but spring pressures ultimately effect the force applied to the valve.

 

[12secondSY]

Re: 772 vortec heads cracked.....

The vortecs on my old Ty cracked. Back then I hadn't seen all this and thought I was the only one. It had either 2.02 or 2.05 valves and they were ported. I knew I messed up soon as I saw that it cracked between the valves. Part of that was my lack of tuning knowledge too. That cylinder got hot.

 

[Fairclough]

Re: 772 vortec heads cracked.....

Talking about spring pressure, I have some ported 772's at Fastlane (Chapman Racing) and I'm going bigger on intake and exhaust, I will be using beehive springs, with titanium retainers, and aluminum roller rockers. I plan on running around 20 psi on a 6th turbo. They are recommending leaded race fuel for lubricity, and to help with the heat.

 

[Teahead]

is this an on going issue with 772s? I have heard that they crack even if not ported, but if ported too much snap crackle, pop they go.....

I have cracks between the valves in ALL comb chambers..... (pictures to follow.....)

I am looking for the correct casting number for the L35s that work on our trucks....

I have GM #10238181 & GM #10240209 either of these better than the other or no difference?

Thanks for the help... Trying to get her back on the road!!

Necro post.

What's the diff between GM #10238181 & GM #10240209?

Does one have screw in studs and the other press-in?