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1966 Mustang
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Discussion Starter #1
Hi guys, first post here but have been cruising the site for awhile now for all sorts of questions related to my mustang.

Anyways, the 289 in the car had been consuming a lot of coolant and blowing white smoke for a few minutes after first start-up. I always shut it down and refilled radiator when the engine started getting hot, so it never over heated badly. There was no oil getting into the coolant or coolant in the oil. I tore it apart to replace intake and head gaskets but neither showed any obvious signs of damage or leakage. The engine has stock heads, stock/very mild cam, performer aluminum intake, edelbrock carb, and headers.

I have a couple questions about what I found inside the engine:

First, I see what looked like oil/water milkshake mix in cylinder 2 only. I don't think this dripped out of the head as it was being lifted off, since none of the other cylinders had this. Any idea what caused this milkshake? Could it be a combination of leaky valve seals and head gasket? I did notice the umbrella seals on most valves were held up near the top of the valve at the retainer, not sitting down over the guide. I don't have much experience with this type of seal, but is that normal?
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Do you think this #2 cylinder bore is usable as is or should it be dissembled and honed? After cleaning the bore there is some discoloration but no roughness or scratches that I can feel. The compression on that bank was: #1-132psi, #2-140psi, #3-152psi, #4-143psi. Unfortunately I lost my note sheet with cylinder 5-8 compression readings, but I remember these all being 140-150psi.
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I also noticed that the valve faces in cylinder 2 looked cleaner than the others (lighter brown instead of black). I assume this is due to water leaking into this cylinder.

So, what do you think: should I tear it apart to hone cylinders and replace rings. I haven't cleaned up the block's deck or head surface yet to check for flatness, but will do so soon. Thanks in advance for any advice.
 

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The clean cylinder is the one with the coolant leak. The steam removes the carbon deposits. It must not have been leaking very long or the piston would be completely shiny clean. If this was phone company engine we'd throw new head gaskets on there, slap the old heads back on and it would go another 50,000 miles but those were not 50 year old engines. You could have a valve job done on the heads. You might as well since they are already off. See if you can clean off the top of a piston and find a measurement on it. there should a STD, .010, 020, 030 stamped on top. That will let you know it its been rebuilt. The bore limit on a 289 is I think .030 because of the thin wall casting. If its at .030 already the block might not be a candidate for a rebuild, if so I'd have the heads rebuilt and leave the short block alone. Your compression rates are good except that they should all be within 10% of each other. So the 132 lb. cylinder is a little low. If you decide to just replace the head gaskets do not use a Roloc surface conditioning disc on the block, those little fibers get in your engine and scratch stuff.

If you tear it down to hone it you might as well rebuild it. With all that rust in the block and the slightly lower compression in #1 I'd probably rebuild it and be done with it forever. Except changing the coolant ever 2-year's so it does not end-up looking like that! Depends on your financial situation and how long you plan to keep the car.
 

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It needs to be cleaned 1st before anyone can tell what it looks like
Not that I probably would but a 289 can go to more than .030 over
What I might do is be on the look out for a GT40P
 

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What did the head gasket look like between 1 and 2? Milky substance is definitely oil/antifreeze mix. As mentioned above I would not just hone it, if you are going through that trouble I would rebuild it.
 

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If you have no obvious signs of coolant leaking past the head gasket and no coolant in the crankcase then I'd probably have the head on that cylinder bank magnafluxed and look for a crack.
 

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Dill, continue with your cleanup. You may want to have the heads magnafluxed and checked for cracks. Some places can pressure test the casting for cracks, and vacuum test the ports for valve sealing. Do you have the old head gaskets ? maybe you can see, with a careful eyeball, where the gasket leaked, if that was the problem. What are your plans for this engine ?

Vintage Ford Guy, you are VERY mistaken. Where did you get the idea .030 was the limit ?! I have recently retired from an engine building shop, and they have spent the last 35 yrs at it. The generally accepted limit is .060, some can go .080. The .060 over jobs are SO common, you don't even check the block, it was generally considered that they ALL can go that far. If you have a pin hole leak in a bore, you have a pinhole. That is not caused by overboring, you need a sleeve in that hole. Some guys have had to fix a pinhole on standard bore engines. And I wouldn't be suggesting a valve job just because 'might as well',......done correctly, a valve job could add $6~700 to his repair. Shouldn't we find out what his goals are first ?

LSG
 

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I just read the .030 over was the maximum on some other site. Might have been over with the Falcon guys. That was my fault for not investigating it further. I hate it when I screw-up, sorry about that. I was into these SBF engines 40-year's ago and then I switched to flatheads. I'm trying to relearn what I have forgotten about 289s.
 

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... The generally accepted limit is .060, some can go .080. The .060 over jobs are SO common, you don't even check the block, it was generally considered that they ALL can go that far.
Um... for years here I've read that if you want to go over a .030" bore then you really should do a sonic check to make sure you won't get too close to the water jacket. It seems like you're saying it is not necessary to check this?

I don't anywhere near the experience you do, but just want to clarify this point.

Harry Z
 

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Harry, if one wants to check you can, but it used to be that we didn't have anyway to check, and it was normal to go to sixty over when doing a block that was already .030 or .040. Long ago, there weren't sonic checkers out there. I never saw a block go .060 and have a problem. Yes, these blocks are 'thinwall' as compared to a flathead, but it is not as though they are paper. Now, the 70~73 351C I would like to see stay at .040 or less. There are .060 pistons readily available for them, but the C seemed to have more issues with core shift. LSG
 

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Discussion Starter #10
Hey guys, thanks for the responses. Good point on getting head checked for cracks.

Top and bottom of gasket, cylinders 1 & 2. I don't see anything that obviously looks like a leak. Is there something I'm missing?
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Worst area I see is on cylinder 3:
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I hoped to get the 289 back together pretty cheaply. My plan was to start collecting parts over the summer to build up a decent 302/331 so I don't love the idea of a full rebuild of the 289 at this point. Let me know if you see anything wrong with the head gasket. If not, I'll take the head in to get magnafluxed and decide what to do from there.
 
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