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Old 09-20-2010, 12:33 AM
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Bored block runs same temp as stock

All my life I have been told that if you bore the block and install new pistons the engine will run hotter than a stock engine. Even the radiator people tell you this.

I have just rebuilt a 232 6 cylinder, bored the block, installed new pistons, along with a complete re-build, used the same radiator, and the car does not run 1 degree hotter than it did before.

Has anyone else had this experience?

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Old 09-20-2010, 12:43 AM
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I had a .60 350, that was worn out to .65-.70 (I was told it was a "new" engine...yeah) but it wouldn't stay under 260! It was in a circle track car, its last night i pulled off the track, by the time i got it on the trailer the water temp was up to 325. Lets just say...its dead.
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Old 09-20-2010, 02:17 AM
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Quote:
Originally Posted by HotRodMan
All my life I have been told that if you bore the block and install new pistons the engine will run hotter than a stock engine. Even the radiator people tell you this.

I have just rebuilt a 232 6 cylinder, bored the block, installed new pistons, along with a complete re-build, used the same radiator, and the car does not run 1 degree hotter than it did before.

Has anyone else had this experience?
Yes. Unless it has been bored a large amount(.060" or more) and made the cylinder walls excessively thin it shouldn't make any more heat unless it has been altered to make more power, like more compression, bigger cam, more head flow, etc.

Heat is directly related to power made, if it is a basically stock rebuild to original specs the overbore should not make it run hotter as the engine isn't making any more power than it did on day 1 from the factory.

Of course a rad company will tell you rebuilding an engine will make more heat and require a new radiator, they want your money
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Old 09-20-2010, 06:38 AM
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Quote:
Originally Posted by BigRoy1978
I had a .60 350, that was worn out to .65-.70 (I was told it was a "new" engine...yeah) but it wouldn't stay under 260! It was in a circle track car, its last night i pulled off the track, by the time i got it on the trailer the water temp was up to 325. Lets just say...its dead.
What was it originally? A 230? I never heard of a 232.

Is it not true that excessive piston to cylinder wall clearances will actually make your motor run hotter due to the piston be less able to transfer heat to the cylinder walls and coolant? I realize lotsa people slap a motor together with loose tolerances with the intent of racing a few short races and the looseness reduces friction for a few extra ponies.

As far as the 230 not running hotter maybe the radiator is plenty big enough for the amount of heat a 230 can make, even tho it may now be larger. My experience is that my ford 240 six that I rebuilt ran hotter than I would have like until it was broken in, but I had a tiny radiator made for the 170 ci six I replaced. The 170 was a fine motor, I should have maybe just rebuilt it looking back on it. I still have the van, a 1965 ford falcon type econoline. I kinda want to put one of these 283 chevy motors in it that I have using the chevy to ford adapter tranny plate now that I have learned so much about them and how much cheaper it is to build than the ford six. But I always loved the ford 2000cc ford pinto engine, that might be even cooler(pun intended hardy har har). Lol my little rust free Scooby Doo mobile...And I would have gotten away with it too, if it weren't for you meddling kids!
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Old 09-20-2010, 08:24 AM
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The ability of gas to burn is why we use it, and like every other fuel, the heat given off from this is a constant. It can be measured in btu.

If no other changes are made in a motor to increase the amount of fuel burned each stroke, then the fuel should give off the same btu when burned.
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Old 09-20-2010, 09:07 AM
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Stock 232 AMC engine

The engine was a stock 232. This is an American Motors engine installed in a 1973 Javelin , but was more popular in the jeeps in the early 70's. The block was bored .030 over, and the rest of the engine was a stock re-build.
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Old 09-20-2010, 09:53 AM
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There's a ton of info in Smokey Yunick's Power Secrets book. One of the things Smokey explains is that the thickness of the cylinder walls makes a difference in heating.

First off, as the rings slide up and down the cylinder bore, they skid and skip. They do not slide smoothly as you might think. This skidding generates vibrations which are subdued by the mass of metal in stock or near-stock cylinder walls. When the walls become thinner, with less mass, due to boring the block, there is less material to quell the vibes and therefore they are transferred to the coolant side of the cylinder walls where they tend to separate out air bubbles. These bubbles cling to the cylinder walls, preventing cooling water from carrying heat away from the walls and resulting in overheating. According to Smokey, a minimum wall thickness of 0.135" is required to dampen the vibrations. So, as you are preparing your block for an engine build, check thickness with ultrasound to determine finished wall thickness.

I know nothing about the validity of this myself, but I do know that Smokey cut blocks apart, installed glass and good lighting, then ran the motors on a dyno to observe what was going on inside the motor at speed. He was one of a kind.
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Old 09-20-2010, 11:21 AM
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Quote:
Originally Posted by techinspector1
There's a ton of info in Smokey Yunick's Power Secrets book. One of the things Smokey explains is that the thickness of the cylinder walls makes a difference in heating.

First off, as the rings slide up and down the cylinder bore, they skid and skip. They do not slide smoothly as you might think. This skidding generates vibrations which are subdued by the mass of metal in stock or near-stock cylinder walls. When the walls become thinner, with less mass, due to boring the block, there is less material to quell the vibes and therefore they are transferred to the coolant side of the cylinder walls where they tend to separate out air bubbles. These bubbles cling to the cylinder walls, preventing cooling water from carrying heat away from the walls and resulting in overheating. According to Smokey, a minimum wall thickness of 0.135" is required to dampen the vibrations. So, as you are preparing your block for an engine build, check thickness with ultrasound to determine finished wall thickness.

I know nothing about the validity of this myself, but I do know that Smokey cut blocks apart, installed glass and good lighting, then ran the motors on a dyno to observe what was going on inside the motor at speed. He was one of a kind.

I went to Borders(a bookstore) looking for that book yesterday, it wasn't even in there computer.


They could get Smokeys "The best **** garage in town" tho, for 30 dollars. They said it would take 4-6 weeks to arrive!!!!

I'm still in search of it though, I know it's out there!
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Old 09-20-2010, 11:30 AM
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I have a copy, I got it like 10 years ago, they go on ebay from time to time, but be ready to pay for it.
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Old 09-20-2010, 12:23 PM
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Quote:
Originally Posted by HotRodMan
All my life I have been told that if you bore the block and install new pistons the engine will run hotter than a stock engine. Even the radiator people tell you this.

I have just rebuilt a 232 6 cylinder, bored the block, installed new pistons, along with a complete re-build, used the same radiator, and the car does not run 1 degree hotter than it did before.

Has anyone else had this experience?
Certainly thinning the cylinder wall would increase the rate of heat transfer, but typical over-boring on modern thin wall castings where oh-30 is about the safe limit only takes .015 off the wall at any instant place so it's not very much.

Also, if the cooling system is sufficient to control operating temperature, the thermostat would automatically keep the temp at typical levels regardless of heat transfer rates within the engine.

Bogie
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Old 09-20-2010, 11:22 PM
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Quote:
Originally Posted by Dirty Biker
I went to Borders(a bookstore) looking for that book yesterday, it wasn't even in there computer.
Here's one used and in good condition for 55 bucks. I don't think I'd pay 55 bucks to see a mosquito's *** stretched over a rain barrel though!!!
http://www.amazon.com/gp/offer-listi...condition=used
Check at your local public library. At least you can read it and make copies out of it cheaper than 55 bucks.

Last edited by techinspector1; 09-20-2010 at 11:33 PM.
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Old 09-21-2010, 09:46 AM
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Kinda off the topic a bit and I apologize but one of Smokey Yunick's friends was Fireball Roberts, the same guy known for winning races with the fish carburetor! So it can't be all that bad, and you guys seem to give me a pretty hard time over the fact that I think it is pretty nifty!! LOL! But I am going to get me a copy of that book even if I have to pay 50 bucks, I am betting if I don't get grease all over the pages it may still be worth 50 bucks to somebody somewhere.. So I can rationalize the cost expenditure in that way and still get to read it if I will just consider it as an investment... Thanks you guys, sorry, not trying to hijack the thread at all.

Is it true that a loose motor runs hotter than a motor that has the proper tolerances? That is on the topic and is the way I understand it because the piston doesn't cool itself as well when it is loose in the bore. It needs to transfer heat to the cylinder walls by being as close as it can without being too close as to create more heat by being too tight. Is that right?
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