351W-Internal antifreeze leak

Was told this 74 mudding bronc (my new rock crawler project) I picked up had a pretty healthy 351W in it. Was supposedly 11:1 and ran real strong. Was also told by some friends in the jersey mudding circle that is had been overheated here and there (stock EB radiator full of mud on a high RPM truck, anyone who's mudded knows the deal).

Was pretty psyched when I pulled the valve cover off and saw this. Looks like a pretty fresh rebuild.

http://luxjo.supermotors.net/74 ROCK CRAWLER/351W/DCP03604.JPG

My enthusiasm was squashed when I drained the oil and got a very small amount of fresh antifreeze. Not good, decided to pull the intake and see what I could find.

http://luxjo.supermotors.net/74 ROCK CRAWLER/351W/DCP03605.JPG
http://luxjo.supermotors.net/74 ROCK CRAWLER/351W/DCP03606.JPG

Found 2 small antifreeze leaks, right where the head meets the block, on both ends of cyl head. First thought was head gasket (especially after the overheat rumors), but pulled the head and found no problem with head gasket or any visible cracks in head/block.

One intake bolt was missing (see second pic for bolt hole filled with grime and/or maybe even a broken bolt), making me then think maybe the leaks were intake gaskets and dribbled down the bottom of head and into the valley. Would make sense as both of those points are the water passage crossovers

I'm used to dealing mostly with M-blocks, being spoiled by the dry intake. Does a typical intake leak dribble under the head and down the valley like the first pic shows. That first leak looks a bit older as the block was rusting in that spot. Would be nice to just put in new gaskets and call it good.

Also, pistons are maked .060. Any rock crawling type usage overheating tendancies with a 60 over windsor??

I would suspect head gaskets too considering the overheat history. But that last pic look likes an intake gasket leak.

As far as overheating with a 60 over 351W during rock crawling I'd say you are likely to see some. Mine's 30 over and will run 175* all day long on the street. All it needs is some airflow to move that hot air out. But when I'm on trails after an hour or two of idling or slow going - especially if it's a crowded group - I see 210-220*. It hasn't overheated on me and all it generally takes is an opportunity to get some air flow on a straight away or to shut it off and run the e-fan in order for me to drop the temps. I'm running a triple pass, 4-core radiator, ceramic-coated headers and cut inner fenders.

rmfreeze said:

I would suspect head gaskets too considering the overheat history. But that last pic look likes an intake gasket leak.

As far as overheating with a 60 over 351W during rock crawling I'd say you are likely to see some. Mine's 30 over and will run 175* all day long on the street. All it needs is some airflow to move that hot air out. But when I'm on trails after an hour or two of idling or slow going - especially if it's a crowded group - I see 210-220*. It hasn't overheated on me and all it generally takes is an opportunity to get some air flow on a straight away or to shut it off and run the e-fan in order for me to drop the temps. I'm running a triple pass, 4-core radiator, ceramic-coated headers and cut inner fenders.

Click to expand...

Thanks for the engine bore info. Not much I can do about it, except build a complete new engine at this point. I do plan on running no core support or inner fenders and using a full width, 2 core (1 inch cores) alum radiator and Mk VIII fan. Hopefully, that will be enough.

water leaks around the intake ports and into the valley are pretty common on SBF's. Put some new gaskets and maybe a little RTV around the water ports and make sure the intake manifold surfaces havent warped and bolt it back together. I'd also fix that one missing bolt might help prevent future leaks.

While .060 over may run a little hotter as long as the cooling system is working good you shouldnt have a problem but that 11-1 comp ratio may also cause more heating and drivability issues during rockcrawling.