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If a block is bored 2 or 3 thousands too much ...

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Old 08-21-2004, 08:50 AM
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Default If a block is bored 2 or 3 thousands too much ...

... what would the results be?

How would the motor run?

What are some of the signs?
Old 08-21-2004, 09:03 AM
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You could break into a water jacket outside of the cylinder sleeve. This would cause overheating, poor engine performance, oil in coolant, etc.
Old 08-21-2004, 01:03 PM
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Break into a water jacket at .002 or .003 too much?
Old 08-21-2004, 01:49 PM
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Not sure I understand either ...

And could you define "overheating"? Are we talking 15* or 20* over normal or 250*?
Old 08-21-2004, 02:12 PM
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I wouldn't think that going 0.002-3" overbore would cause you to break into a water jacket however that's the only thing behind the sleeves.

If you weaken the cylinder sleeves enough you could have hot spots form on the cylinder sleeves and lead to weakening, cracking, and/or leaking of coolant into the cylinder bore. The sleeve may warp due to the thinness of the material left over too.

As far as how much overheating, I couldn't say. If the coolant wasn't getting in above the top of the piston to interact with the air/fuel mixture then it should run/idle without misfire, etc. However, you could be getting coolant into the oil. You could do a midstream catch of the oil and have Blackstone labs analyze it for the presences of coolant. The dipstick may have some frothyness or the presence of coolant on the dipstick if the leak was severe enough. Check/monitor your coolant level, too.

I'm just looking at scenarios based on the anatomy of the cylinder block.

What symptoms are you having?
Old 08-21-2004, 02:20 PM
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You could also get massive blow-by.
Old 08-21-2004, 02:35 PM
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Excessive piston slap/noise and quicker ring/skirt wear - depends on factors like piston material though. Doubt only .002 or .003 would cause heating problems.
Old 08-21-2004, 02:39 PM
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Piston slap.. noise.. as stated above.

I have a SBC 357 bored that much over on purpose.. its not uncommon for nitrous motors seeing a 200+ shot to be bored .001-.003 over depending upon the setup.

Josh
Old 08-21-2004, 03:49 PM
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Originally Posted by jswhite
Break into a water jacket at .002 or .003 too much?
I interpreted the original post to indicate boring 0.002 or 0.003 past the MAX bore allowed. I misunderstood.
Old 08-21-2004, 05:03 PM
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Originally Posted by CANNIBAL

What symptoms are you having?
A '97 block bored to 3.905" with less than 1000 miles on the motor. I have custom tuning, the fans are working as they should (on 185 off 170) and the air has been purged from the block. I use a 160* thermostat.

After about 15 minutes of time on a road course, reving between 4500-6000 in 3rd and 4th gears, I see water temps at 215 and oil temps over 300 and oil pressure is 60psi running Mobil 1 5W40.

I am taking the water temps at the outlet of the water pump. I drilled and tapped the water pump, just below the throttle cam. I read oil temps in the pan, having removed the oil level sensor and inserted the sending unit in it's place.

I am running a Howe Crossflow radiator with built in oil cooler.
http://www.howeracing.com/Radiators/...-Crossflow.htm

I'm just trying to figure out the possible causes ...
Old 08-21-2004, 05:43 PM
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Any white smoke out of the exhaust?

Are you able to keep track of your coolant level? What were your coolant temps running before in the same conditions?

I assume the only thing changed is your new shortblock, correct?
Old 08-21-2004, 05:57 PM
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No smoke ... the motor runs very strong.

And the coolant temps aren't all that high. But the oil temps concern me, especially running the oil through a cooler.

I didn't have aftermarket guages before the motr change, however, the coolant temps appear to be as they always have been according to stock dash gauge (98 TA).
Old 08-21-2004, 08:24 PM
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With a new engine the high oil temps aren't uncommon. Pull a sample of the track oil and have it analyzed, Blackstone Labs gets like $20 and the wear metal data will give you a starting point for further testing. Also gives you a go/nogo on further track use, as in a bearing really getting munched.

Put plenty of street miles on it, hit the track again, and have a sample of that oil analyzed. Wear metals should be trending downward.

Speaking of oil, what are you running? I was getting 305-310*F on the Bondurant Vette earlier this year, using their Mobil-1 15W-50.
Old 08-21-2004, 11:00 PM
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5W40

My oil temp guage only sweeps to 300*. And it pegs the guage.

However, the oil temps come off of pegged very quickly on the cool down lap. So, I surmize that the temps are in that same range ...
Old 08-22-2004, 07:03 AM
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I saw your write-up of the first track day, just couldn't find a mention of what oil you were running.

I'd send a sample to Blackstone Labs.
Old 08-22-2004, 01:26 PM
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I have seen where LSx race motors in race conditions do get the oil temps up that high and above. Most of the rags and engine articles I have read suggest an external oil cooler to keep things in line. I think there was an article just recently done, I'll look in my stack and try to get back to ya.
The Blackstone Labs analysis is definitely a good sanity check tho.
Old 08-22-2004, 02:16 PM
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Originally Posted by ktmrider
I have seen where LSx race motors in race conditions do get the oil temps up that high and above. Most of the rags and engine articles I have read suggest an external oil cooler to keep things in line. I think there was an article just recently done, I'll look in my stack and try to get back to ya.
The Blackstone Labs analysis is definitely a good sanity check tho.
He has a massive external oil cooler.
Old 08-22-2004, 06:27 PM
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I guess what I'm really asking here is would a '97 block bored to 3.905" be more prone to higher coolant and oil temps than a stock bore?

Or are the temps I'm seeing be attributed to a new, close tolerence motor?
Old 08-22-2004, 06:38 PM
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Originally Posted by mitchntx
Or are the temps I'm seeing be attributed to a new, close tolerence motor?
I think it's more attributal to this reason. The tighter the engine is setup the more friction it will generate vs a looser race type setup where less friction will free up that extra few HP out of the motor.
Old 08-22-2004, 06:50 PM
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Originally Posted by mitchntx
I guess what I'm really asking here is would a '97 block bored to 3.905" be more prone to higher coolant and oil temps than a stock bore?

Or are the temps I'm seeing be attributed to a new, close tolerence motor?
The thinner cyl liners could contribute to higher coolant temps, it's been my experience with iron SBCs in marine applications that a 0.060" overbore runs higher coolant temps. Same RPMs, same water pump, pushing same boat through same lake. No longevity issues, just ~10deg higher reading on the temp gauge across all encountered ambient lake temps.

The cyl liners wouldn't have any effect on oil temp that I can imagine. Bearing clearances set on the tight side are the usual cause of high oil temps on a newly assembled engine, and as long as they're not so tight the bearings get damaged then you'll see the oil temps come down as the engine breaks in.

It'll throw off a lot of tin in the process if you ran conventional tri-metal bearings, which is why I'm saying to have oil analysis done on the track fill. If it's tossing copper or lead in big quantities, you'd change the oil and put some street miles on it for another analysis before it goes back on the track. If it's still throwing off major copper or lead, pull the engine and start over before it spins a bearing.



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