I am in the military and own a 1974 chevy blazer K-5 with a sbc 400. I rebuilt the top end back in 2008 and the lower end has TRW pistons and a RV cam. I had to pay someone else to finish the rebuild due to time constraints. I bought remaned heads and Z28 high compression springs. Everything in the upper end was replaced besides the intake. When my dad drove the truck from southern georgia it started sputtering and back firing through the carb and lost power. It would turn over but wouldnt run for long. When we got it back home the shop said that the heads were hot tanked for too long and OEM heads that are hot tanked for too long the rocker studs come lose because the sleves become brittle due to excessive heat. My question is how hard is this to fix and could the engine be seized and should I just replace heads or just buy a new engine. I need the truck running now more than ever because I am coming home and need it to drive from SC to TX. Any ideas would be appreciated.
I have never heard of a problem with hot tanking a head to long. Pull the valve covers and look to see if the studs are pulled. I do not know what sleeves they are talking about, the studs are set into the head. If you have a large cam the studs could have pulled out but I doubt you would lose more than one cylinder before the racket made you stop driving. The studs holes could be tapped and then screw in studs installed if needed. I am very sceptical of what the shop told you. Run a compression check if all cylinders are low check the cam timing. This could be something simple like a distributor.
In reply to dmyntti:
I agree. First thing, pull the valve covers and check the studs. Then go from there, but I never heard of hot tanking causing that either, and how would the shop know that anyway versus the studs just coming out due to excessive spring pressure or a radical cam?
In reply to bravenrace:
Or rockers too tight. Ask me how I know. Also, if you break even one rocker arm, it sounds like all hell is breaking loose (done that too).
+1 to pulling the valve covers, the lower part of the studs will be cleaner/shiny if they've pulled out of the head. I'm doubtful. If they'd pulled, the valves wouldn't be opening enough, so it would be down on power or running rough, but not spitting back through the carb.
+1 to cam timing, and ignition timing in general. This is my bet. When I read your description the first time, I assumed the engine ran okay for the start of your dad's trip, but I'm not so sure having reread. If symptoms were there from the first time he tried to start it, check both, but cam timing seems likely. If symptoms started after it ran okay for a while, check ignition timing.
I'm going to move this thread to the main forum so you get even more help.
run a compression check.. crank over the engine with the valve covers off an watch to see if all the rockers move..
if i had to bet, i'd bet that it's a flat cam..
Hot tanking gets heads hotter than a running engine? 
Our hot tank ran at 210 degrees. Hotter than that and the water boils off.
Maybe they use a pressure cooker?
Is this a 4 year old rebuild then with lots of miles? If so it could be any number of things. And a mechanic making guesses based on a telephone description of the symptoms would almost certainly be wildly inaccurate.
Nicest model year of Blazer though besides of course the 72....
OK, my bad, it was in a shop for the diagnosis. So its a head problem of some kind which seems a lot cheaper to fix than a new motor.
Knurled wrote:
Hot tanking gets heads hotter than a running engine?
Our hot tank ran at 210 degrees. Hotter than that and the water boils off.
Maybe they use a pressure cooker?
yea, hot tank sounds like a lame excuse 
The hot tank excuse is BS. I have assembled so many SBC's and of those a bunch of 400's and that was never an issue.
What could be an issue is that they installed the cam bearings wrong or used the wrong head gaskets. This screws up oiling and or causes over heating.
Pull the valve covers and see what is up. You do know about the need to add steam vents to heads that are not 400 specific?
You said you got reman heads. They could have been over heated and sent in as cores and now that they are back in service they failed due to overheating previously. However I have never heard of this happening and I have got some SBC's really really hot and it never happened to me.
i still say flat cam- the "Z28 high compression springs" might be putting too much pressure on the "RV cam", which is a problem with the new oils that don't have all the phosphorous and zinc goodness that is needed to keep a flat tappet cam alive.
Flat cam or a distributor that has moved. Backfiring through carb says timing related.
The rocker studs can actually pull out if they're press in style, ESPECIALLY with the heavier springs. If you pull the valve covers, lay a straight edge across the studs and make sure they all appear even. If some are pulling out, the fix is having the heads machined for screw in studs, or pinning the press ins, but IMO that's a crappy way of doing it.
the Z/28 springs aren't all that stiff- they were designed for the relatively tame cam that was installed in the 69 Z/28.. they have been run in probably hundreds of thousands of small blocks over the years and pulling studs really isn't an issue with them... but it doesn't take much to kill a cam these days, that's why i said to remove the valve covers and see how much rocker arm movement there is and see if the rockers are looser than they should be.
SBCnoob, find another shop. Where abouts in S.C.? Someone here may be able to recommend a reputable mechanic.
The backfiring through the carb has me thinking flat cam lob as well
