Strange Looking Oil After Rebuild
 

Last year I had the 350 in my 72 C20 rebuilt by a coworker who also has an engine shop as a side business. I’ve had a few minor problems with the rebuild including a leaking oil pan and the incorrect timing cover put on (that ones mostly my fault). After the 30 min cam break in and oil change it has only ran at most another hour in my garage/driveway.

I’ve started taking the front of the engine apart to replace the timing cover and also pull the oil pan so I drained the oil today. Again only 1hr of run time on the oil. Well it has a pretty strange look to it, I can’t tell if it is “milky” or what is going on.

Thoughts? Send for black stone oil analysis? Or is it obvious I have some sort of coolant/oil mixing issue?

Re: Strange Looking Oil After Rebuild
 

Water or coolant mix.

Re: Strange Looking Oil After Rebuild
 

Yeah, that’s coolant. Park it until you find the source of the leak.

Most common points on a rebuild are the intake manifold coolant passages (most likely) and cylinder head gaskets. Look for seepage around the intake corners first…but you likely need to pull the intake. No smoke out the exhaust when it’s running?

What was the oversize on the bore and how much was the block decked? If there was a hefty cut on the deck and new heads, there’s probably an angle mis-match on the intake unless it was cut to match.

Goes without saying that you shouldn’t be having any of these issues with a fresh rebuild…

And honestly, kinda surprised for the $$$ for AFR for a mild build...

Re: Strange Looking Oil After Rebuild
 

Sadly that’s what I figured. I haven’t noticed any smoke when running or strange smells either. It did run a little off but that could be the fact it wasn’t timed perfect and I also didn’t get to tuning the new edelbrock carb. The first time or two I ran it in the truck it did puke some coolant out the outflow, at the time I figured it was because I filled the radiator full and I don’t have an overflow bottle but I never had that happen before the rebuild.

The block wasn’t bored, he said the cylinders were still in spec. I believe no decking either. Technically the heads are summit racing rebadged AFR heads so they were on the cheaper side. The original heads were in rough shape so the builder recommended just getting new ones as price wouldn’t be that much more compared to rebuilding.

Thanks for the comment on the intake, I’ll get check that out before I go down the path of pulling the motor.

Re: Strange Looking Oil After Rebuild
 

You used composition, not stainless steel head gaskets?

Re: Strange Looking Oil After Rebuild
 

The rebuilder put the heads on so I’m not sure what style he used.

Re: Strange Looking Oil After Rebuild
 

Who put the intake on?
Could be leaking there too

Re: Strange Looking Oil After Rebuild
 

Just got the intake off. Here are some pics. Definitely see some oil that has coagulated from the coolant. But there doesn’t appear to be any signs of intake gasket leak.

I guess it must be a head gasket issue.

Re: Strange Looking Oil After Rebuild
 

So, a couple of hard messages.

There’s no way a used GEN I block bore was “in spec”, especially if cast pistons were installed. Also a bad idea not to at least take a clean-up cut on the deck.

There’s no Summit rebadged AFR heads, and Summit-branded parts are often garbage in my experience.

Every overhaul should come with a “build book” with measurements and part numbers - otherwise, maintenance/upgrades are a nightmare.

I guess…I’m unhappily letting you know that I would have concerns about the overhaul.

I hope this is something simple and easy to fix.

Re: Strange Looking Oil After Rebuild
 

That intake install looks horrible :(

I don’t trust the FelPro gaskets at the water passages and always put a thin bead of RTV black.

I’d see the water in the valley as an indication it’s leaking from the intake.

Worth for sure pulling the heads.

Re: Strange Looking Oil After Rebuild
 

By cast pistons do you mean the original ones? This was my grandfathers truck, he had the engine rebuilt once before and he told me it didn’t need boring then either. There was only maybe 10k on the motor between then and now but it sat 30+ years so every gasket/seal leaked, hence the 2nd rebuild. I can’t confirm one way or another if it actually needed boring but it was honed and the original pistons were put back in with new rings.

I bought the heads myself and they had an AFR casting, along with the summit etching on the front. I’ll try and get a pic once it is apart.

Not arguing at all it was a ****ty build, he does 10-15 engines a year for racing so I didn’t expect to have so many issues.

Re: Strange Looking Oil After Rebuild
 

Definitely sloppy. Would you recommend a different intake manifold gasket? Or just always use rtv on the intake side of the gasket as well? He had sealer on the head side but that’s it.

Even though you think it’s leaking from the intake I still should pull the heads and redo just to confirm?

Re: Strange Looking Oil After Rebuild
 

While you've got the pan off, since you've been using water as a lubricant, I would recommend pulling the main and rod caps and taking a look at your bearings.

Re: Strange Looking Oil After Rebuild
 

Having sat that long, is it possible the engine was exposed to freezing temperatures and a cracked block was the result.. Was the block tested for this before the rebuild??

Re: Strange Looking Oil After Rebuild
 

So there's kind of a lot to unpack where we're at, so I'll try to get through it.

Stock pistons are cast and they're fit VERY tight - .001 +0/-.0005. Without knowing what specifically was done it's hard to say how much the bottle brush hone took off - but probably a couple of thou - which will open up that clearance up to an unacceptable level. So reusing cast pistons at a standard size isn't an overhaul by any means and produces unacceptable piston-to-wall clearance and so blowby and the risk of rocking pistons.

If you've got the P/N for the Summit AFR heads, I'm all ears.

I can't speak to a guy that builds "racing" engines - but if he can't even install an intake then he's not much of a mechanic, no less an engine builder. Sorry, but there it is. Anybody can bolt an engine together, but that's not overhauling.

I'm honestly not sure what to offer as advice from here. Before we talk about gaskets, recognize that the intake manifold needs to be cut to match the angle of the heads. If that's not done, then it's really hard to say if any gasket and sealant combination is going to seal at all - not just the water ports but all the intake ports could be open at the bottom as well creating a vacuum leak. Setting the intake in with no gaskets and no front/rear valley sealant in and taking a head-on pic would help evaluate the situation, maybe.

I'd pull the heads regardless just to see what's in there. Just me. Would be interesting to know the bore size. And it'll tell you pretty quickly if there's a leak there.

So...I don't know what to tell you on where to go from here. It's a crappy not-overhaul, so it's hard to tell what was actually done and if the thing is even runnable. That much water is incredibly destructive and basically makes the oil useless. I'm sorry, I just don't have good advice here. If it was me, I'd tear it down and figure I was starting over, but that's not a cheap choice by any means. Otherwise, just put it back together as best you can and takes your chances.

Or go back to the guy and ask some hard questions.

I really am sorry; I hate giving this kind of message.

Re: Strange Looking Oil After Rebuild
 

...and what the Hell are those tall valve covers over?

Re: Strange Looking Oil After Rebuild
 

I may be too late, but if you haven't removed the heads yet, I would take the time to retorque the heads. It may reveal the cause of the leak. You never mentioned if the heads were retorqued after the break in period.

Re: Strange Looking Oil After Rebuild
 

I drove the truck for 2 years prior to this engine rebuild with no issues so the block should be fine from that at least.

Re: Strange Looking Oil After Rebuild
 

Yep understood, I appreciate the advice.

Once i get the engine pulled I'll measure the bore and see what it is at. I never got around to driving the truck since this rebuild, just ran a few times in the garage so hopefully the damage isn't bad. But I will find out once I tear down to investigate. I would assume if the block wasn't decked (for right or wrong) the intake angle should still be correct. But who knows, I'll try to get a head on pic like you mentioned as well.

The heads are SUM-162SBCSTRFT. Maybe they're just AFR castings, machining/finishing could be someone else.

Those valve covers were put on many years ago. I guess the exhaust manifolds being close to the old stamped covers caused them to leak so my grandfather put these on in the early 80s. I believe I need tall valve covers with the head/rocker arm setup.

Re: Strange Looking Oil After Rebuild
 

I will give it a shot before I pull the heads. He broke the engine in at his shop so right now I cant say one way or another if the heads were retorqued.

Re: Strange Looking Oil After Rebuild
 

I think the teardown is the best path forward. A basic rebuild won't be crazy money, and ensures you have a solid engine.

If the manifold was cut before, and then new heads...then the angle can still be wrong. But thicker gaskets can cover this up if the clearances just don't stack up. A lot of shops miss this.

I don't see anything at all in that P/N noting anything AFR. So...I dunno, but I guess take the price and go. 195 heads are a horrible choice for a mild engine - there will be no intake velocity and the engine will have very poor low- and mid-range performance and throttle response. Those need a high CR and a pretty big cam to work. And...I have seen some true garbage in the Summit-branded stuff. I like Summit and spend a lot of money with them, but I don't buy their brand in anything important :)

Valve covers make sense if you've got a full roller rocker setup. Again - super overkill and $$$ for a mild engine, but if you've already got them...

Happy to help once you know what you have to set a path forward. Interested in a morbid way to see what the bearings and cam look like :( But hoping for the best!

Re: Strange Looking Oil After Rebuild
 

Could the ends of the manifold and the block be curving/angled away from each other on the ends where that RTV has crept in between them?

Re: Strange Looking Oil After Rebuild
 

Testing for cracks and other flaws is a common procedure for any rebuild, no matter the history of the "candidate"... Every "race engine builder" should know this...

Re: Strange Looking Oil After Rebuild
 

I noticed these spots in the valley by cylinders 5 and 6. Going to have to get some magnaflux, hard to tell if it is just leaking down from the head gasket or block is cracked. After cleaning it I can’t see any cracks but I know that doesn’t mean much. I was a 6.2/6.5 diesel owner in the past ��

Also Pulled the valve covers, no coagulation or obvious signs of problems.

EDIT site won’t let me post pics right now so I will try again later

Re: Strange Looking Oil After Rebuild
 

Pics