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Let's Talk 262 Timing and Performance

shorthunter

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What stops the charge in the transfer from combusting if there's backflow of exhaust down into them?

Is the charge always fully combusted by that point under all circumstances?

I'm just thinking out loud for proof that there is indeed backflow, and its not just a burn of residual accumulated oil during deceleration.

The answer to your question can be found in your transfer thread. The presence of carbon tells us that transfers absolutely do back flow with exhaust gases
 

shorthunter

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I believe I am misinterpreting the meaning of what you wrote. Using the stock numbers Al posted of 103/115/69 I was under the assumpition to lower case comp you would either have to decrease blowdown or add intake?

Also, wouldn't a longer blowdown give more time for ex to escape and not be mixed with incoming charge?

Your first assumption would be correct. Although I am not sure either will drastically affect case compression

Answer to the second question is also yes. Keep in mind that the exhaust gases are under extreme pressure immediately after combustion, the are looking for the first outlet which would be the exhaust port. That being said, no engine will ever be 100% efficient at expelling exhaust gases. A piped engine will be the most efficient at pulling exhaust gases out of the engine but even they are not 100% efficient.
 

David Young

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I think one of the challenges with trying to figure this stuff out is that we often start by lowering exhaust and significantly increasing compression. Also we always open up the muffler changing blowdown characteristics.
so with the compression increase we have numerous side effects as far as altering the port timing.

what if the increase in compression masks the impact of some of the other changes.
 

lwhaples

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A lot of good reading here,and perfect timing. Picked up low compression 261 today.And the only reason I bought it was it came with an NOS 262 jug w/piston along with the two Top covers.I knew the dealer had the 262 parts,today was the day to make it all mine. Keep all the info coming.
 

cus_deluxe

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I dunno anything about the 262 'cept I want one. Great thread thanks.
as said earlier in thread, they run very well out of the box. good power-to-weight. 2-series durability. i loves the ones i have/had and cant wait to reassemble a couple that i have in parts.
 

drf256

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Doesn't Carbon mean incomplete combustion?

Why are there flow marks on a piston?

So if transfers received backflow, why would the carbon not be flushed out by mix?
I see no carbon deposit at all on my hybrid jug. I pulled it today and was gunna give some feedback on the transfer theory but nothing but oil.
View attachment 11941
I got jugs here with carbon down through the lowers.

Gotta ask myself why?
 

drf256

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I cannot accept that carbon in the transfers is absolute evidence of significant backflow.
 

PA Dan

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I don't fully understand all this but keep it coming! I'll be up all night! Maybe by morning...na probably not!
 

smokey7

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Very interested in this topic. It seems as tho we have a blend between the transfer thread and this one. I enjoy them all the same tho.
The theory of all the "what's happening and when is confusing and enlightening at the same time. I have seen some carbon in the strait verticle places of transfers but at the curved lip of them is always washed clean. I am mainly speaking of light soot really and after a ton of run time as I don't pull my motors down for nothing.
 
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