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  #16 (permalink)  
Old 09-22-2011, 04:01 AM
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Any non technical comments directed to me? Use the PM.

Not that this thread has any particular technical value anyway, but in the event that it's not locked, I'll expand on my earlier post about the differences in the casting shapes:


SBC 265 CID


SBC 283 CID


SBC 327 CID SJ

The 327 had a closer rib than the 283 that you couldn't get a finger into easily. The 265 lacked any rib.

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  #17 (permalink)  
Old 09-23-2011, 10:53 AM
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AP72

I'll not defend the claim that a 2 bolt main has less parasitic loss than a 4 bolt main configuration.

Actually I was stating a general opinion, "some prefer a 2 bolt main because they believe it has less parastic loss" would have been more correct. I apologize for misrepresenting as a scientific fact.

I tend to agree with you, but I do know some engine builders that prefer the two bolt configuration and claimed this was the reason. When they are winning races with these engines it at least appears they have some credibility.

This would make for an interesting experiment, unfortunately it would be (almost?) impossible to build two engines (1 with 2 bolt mains, 1 with 4 bolt mains) that didn't have other inherent differences that would overshadow any measurable performance differences in the two configurations.

Assuming the same bearings are used, with same clearances, it would seem that the clamping force of the main bolts would have little or no effect on the parasitic drag. Beside, in the most practical sense, the difference would be negligible.

Still, another way to look at it might be: in the glorious search for horsepower, leave no stone unturned.
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Old 09-23-2011, 11:26 AM
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The reason I've heard people prefer a 2 bolt main block is because the webbing is thicker. I use the mortec pages and a set of MSA books to referance any small or big blocks that come my way.
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Old 09-23-2011, 04:02 PM
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I have heard that comment related to 400 CI small blocks. I hadn'd heard it with reference to non-siamesed SBC block castings. Maybe one of the machine shop guys, or other pro builders here could ring in.
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Old 09-23-2011, 06:41 PM
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I'll give Grumpy Jenkins a call. He did autograph a 1/24 scale Camaro for me, I think that makes us great pals.

Now there is some B.S. for you.

There is no reason to get snarky about any subjects, it's just not worth it. It's ok to dis-agree, but let's be civil about and keep things on a non-personal level. If you don't like someone or their answer, rise above playground tactics and have a discussion as to why there is a disagreement. And...read a post a few times before letting yourself get upset over anything in the post. It's tough to comprehend the meaning of the written word, it may sound OK in your mind but comes out like a spew of idiocy ehrn written. Not pointing at ANYONE here but you guys understand what I mean. This isn't the OTHER WEBSITE, let's play nice.
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  #21 (permalink)  
Old 09-23-2011, 06:48 PM
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The reason a 2-bolt 350 block might be the preferred piece over a factory 4-bolt piece, is the ability of a 2-bolt block to be fitted w/4-bolt aftermarket caps w/splayed outer bolts.

With the 400 blocks, it is thought that the loss of material in the critical area where the extra bolts are drilled for the OEM 4-bolt 400 block makes those blocks weaker than a 2-bolt block w/no loss of material in the critical areas.
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Old 09-23-2011, 07:16 PM
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I know an IMSA engine builder (800+ HP range and 8-9000 RPM range) and he uses the 400 2 bolt main blocks because he can splay the addition bolts. He wants the added strength gained from the splay vice threads only for the standard 4 bolt. Getting back to the question on how to tell if a SBC is a 327 or a 350, my answer is tear it down then you will know as long as you have your numbers book handy along with your mics. I have seen such mix match of parts in blocks that have casting and stamped numbers of a smaller displacement engine and even seen epoxy and sand used to modify the casting numbers to get an advantage on the local tracks. The old racers adage of "If you ain't cheating, you ain't trying hard enough" brings out all kinds of innovation. One motor I bought from a racer had the casting numbers of a 283, but it was actually a 350 and the heads had the casting numbers and markings of a small valve power pack but they were the large valve power pack heads. He would lead most of the laps handily but always faded on the last couple of laps to finish in the top 5 and not get torn down.

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  #23 (permalink)  
Old 09-23-2011, 09:17 PM
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Quote:
Originally Posted by starnest
AP72

I'll not defend the claim that a 2 bolt main has less parasitic loss than a 4 bolt main configuration.

Actually I was stating a general opinion, "some prefer a 2 bolt main because they believe it has less parastic loss" would have been more correct. I apologize for misrepresenting as a scientific fact.

I tend to agree with you, but I do know some engine builders that prefer the two bolt configuration and claimed this was the reason. When they are winning races with these engines it at least appears they have some credibility.

This would make for an interesting experiment, unfortunately it would be (almost?) impossible to build two engines (1 with 2 bolt mains, 1 with 4 bolt mains) that didn't have other inherent differences that would overshadow any measurable performance differences in the two configurations.

Assuming the same bearings are used, with same clearances, it would seem that the clamping force of the main bolts would have little or no effect on the parasitic drag. Beside, in the most practical sense, the difference would be negligible.

Still, another way to look at it might be: in the glorious search for horsepower, leave no stone unturned.
This might be apples and oranges but back when I was involved in circle track racing, most of the best engine builders in some of the restricted classes always liked using the small journal blocks due to bearing speed, which might also involve parasitic loss I suppose. The car I was crew chief on was track champion for 3 years with the same lower end which was almost unheard of, most cars had a fresh engine every year, sometimes 2-3 times in one season.
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  #24 (permalink)  
Old 09-25-2011, 02:35 PM
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back in the day when we had a short track locally they had a device they called "the bubble". Looked a little like a compression gauge setup. They would test the winning cars after every race to check engine displacement.
Something like this would be helpful in these situations.
Has anyone else ever seen one of these?
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  #25 (permalink)  
Old 09-25-2011, 05:31 PM
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I have heard of them. Usually, the money winners get checked: finish out of the money, no check.
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Old 09-30-2011, 06:49 PM
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I once got a out dated super trick comp eliminator motor. When I removed the pan it had 4 bolt caps on a 2 bolt block running just the 2 bolts. Go figure
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  #27 (permalink)  
Old 09-30-2011, 10:36 PM
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Quote:
Originally Posted by T-bucket23
back in the day when we had a short track locally they had a device they called "the bubble". Looked a little like a compression gauge setup. They would test the winning cars after every race to check engine displacement.
Something like this would be helpful in these situations.
Has anyone else ever seen one of these?
I've used a P&G cubic inch checker at the NHRA Nationals in the past. You remove the spark plug on the cylinder you intend to check and use a thermometer to check the temperature of the atmosphere in the cylinder. That info gets referenced to the pumped volume. The cylinder is maybe 3 inches in diameter and 2 feet long, clear plastic. You disable the ignition, remove the rocker arms and proceed just like a compression test, through enough "chuffs" to max out the reading.
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