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SBC 305 cracked head, blown gasket or?
Sometimes I think I should just stick to my day job; toss away my tools and find a hobby that involves knitting or paper and paste. I need a little help (again) with a problem with my project truck.
Background: About 4 years ago I embarked on my first attempt at building a rod. I farmed out a 1935 Olds parts car to a local rod builder and had the car sliced and diced into a pickup. Installed it on a 1947 Ford truck frame with a Camaro 2.56 diff and 75 Nova front clip. I picked up a Buick Regal with a 305 SBC for the power plant and mated it to a Turbo TH350. The 305 ran nice when I brought it home; a little smoke when first fired up but otherwise fine (I now know better). I cleaned up the engine and dropped it into the truck frame. Covered it with tarps and let is sit outside while I smoothed out the body. Four years latter and after a severe back injure, job loss and minor heart attack I’m back to work and have the money to work on the toy again. I wanted to toss out all the anti pollution crap on this naturally aspirated engine so I picked up a used aluminium GM intake from early 80’s. Pulling off the original intake I found enough sludge to plant a tree in. Hmm guess the 305 Cam maybe toast! Pulled the Cam out and yup 2 or 3 lobes are worn down. Gee what else could be wrong? I pull off the heads; the right side looks excellent, left side …not so good. Seems even though I’d covered the frame and motor water had entered via the carb and pooled in the # 7 cylinder causing rust on the cylinder wall and ceasing it’s rings. Since the exhaust valves were a little loose I sent the heads out for exhaust valve sleeves, honed the block, changed the rings , rod bearings, installed a low end Comp Cam, new water pump and assembled the engine using a gasket kit from Felpro.. While assembling the engine I lubed up the motor well (maybe too well with oil pooling on top of the pistons. Fired up the engine. It seemed to run ok, maybe a little hot (not boiling), and shut it down after 10 minutes. Checked the oil and water; everything seemed OK. I brought my local mechanic over to see if the engine was not running too hot. He aimed a gun at my exhaust manifolds and said they were fine but suggested I change the thermostat as my lower rad hose was a little cool for his tastes. When I stalled the thermostat I noticed there was no water in the aluminium intake?? So I added coolant (antifreeze) via the thermostat opening about ¼ gallon. Buttoned the end again and went to fire her up when I was struck with an epiphany. Where did the water go the first time (water not antifreeze)? I checked the oil; S—T it was a little white (not foamy but a little creamy coffee in color). Checked the water a found it looked odd. I drained the water and found it looked blackish. (Remember I added antifreeze but did not run the engine before I drained it). The right side of the block appeared to have the clearest water and antifreeze mixture. The Right side (# 7 cylinder had the pooled water rust damaged) appeared to have the most water. Both appear to have oil but the left would have more. FYI: The rad is new with no internal Trans oil cooler. After draining the coolant into a bucket the oil fell out of solution after a short period of time.
Here are the mistakes I know I’ve made: A) I pulled the engine apart before the system was pressure tested. My garage guy’s are some po’d I did this (sorry). B) The heads were not checked for cracks when the valves were ground. C) I used the wrong gasket kit .I used a SBC 350 Felpro set. Seems a 305 has smaller pistons. I missed that part when assembling.
My biggest quandary is how did the OIL get into my Cooling System. I can understand how water can get into the motor oil but not motor oil into the rad.
Do I have a cracked head from the water possibly pooling in the head (#7 intake valve) and then freezing? (I live in up state New York; it can get darn cold here) Did I crack something because the thermostat? Did the head gaskets fail do to the bore size difference? I can see no signs of tracking. Is the used aluminium intake cracked or warped.
Help!
How can I determine what is wrong the least expensive way possible?
Thanks
Oldstruck
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11-02-2008, 07:19 AM
This oil in the coolant has me perplexed. I hope someone out there has had some experience and can provide a solution based upon the same thing happening thier SBC. Many years ago I had a 62 Chev with a 235 six cylinder. Pushed it too hard one day. A smoke cloud form behind me all the way home; boiled over in the lane when I stopped it. Later when I went to add coolant there was oil in the coolant. Scrapped the car the next day. 
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