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LS 243 milling

General engine tech -- Drag Racing to Circle Track

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turbo camino
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Re: LS 243 milling

Post by turbo camino »

They are sold as a pair at Summit, I think that 'each' just means 'one package of two gaskets'.

https://www.summitracing.com/parts/nal-12498544/
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Re: LS 243 milling

Post by CGT »

Yeah, thats how it reads to me also....has to be a mistake but I'd definitely try to capitalize on it.
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Re: LS 243 milling

Post by turbo camino »

I think it's the everyday price, range is $49-$52 at Jegs, Amazon, SDPC, gmpartsdirect, etc. Of course there are fly by night sellers (coughEBAYcough) marking them up to ~$100 hoping some sucker will bite without doing any research.

ETA: $45 here - https://www.pcmofnc.com/product/gm-ls1l ... -12498544/
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Re: LS 243 milling

Post by Jarmo »

I have no experience of those LS MLS gaskets but I have disassembled similar gaskets and used what amount of layers have suited my needs many times on high cylinder pressure Japanese turbo engines.
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Re: LS 243 milling

Post by FC-Pilot »

Jarmo wrote: Tue Sep 08, 2020 2:43 pm I have no experience of those LS MLS gaskets but I have disassembled similar gaskets and used what amount of layers have suited my needs many times on high cylinder pressure Japanese turbo engines.
I have done that many times with high compression race engines, but never turbo. Why pay double for less layers when I can take out the rivet holding them together and remove a layer or two and get what I need. Have don’t that on twelve or so engines without any issues.

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Re: LS 243 milling

Post by LSP »

turbo camino wrote: Mon Aug 31, 2020 3:01 am How much can 243s be cut down before they get too thin? Is it possible to get down to ~58cc (.050"ish)? I'm trying to puzzle out the best way to get a Gen4 5.3L from 10:1 up to around 10.8 or so.
I cut mine .110", no issues with Cometics at 12.8-1 and 615 hp
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Re: LS 243 milling

Post by turbo camino »

LSP wrote: Thu Sep 10, 2020 9:31 pm I cut mine .110", no issues with Cometics at 12.8-1 and 615 hp
Wow. Around 50cc?
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Re: LS 243 milling

Post by turbo camino »

Exhaust valves in these heads are non-magnetic!?

These are apparently pre-2010 or whatever the year break is, all the stems are chrome not nitrided.
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Re: LS 243 milling

Post by LSP »

turbo camino wrote: Thu Sep 10, 2020 11:34 pm
LSP wrote: Thu Sep 10, 2020 9:31 pm I cut mine .110", no issues with Cometics at 12.8-1 and 615 hp
Wow. Around 50cc?
48.5 cc
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Re: LS 243 milling

Post by turbo camino »

Well this is going well. About typical.

First, used core heads arrived with intake valves bent.

Apparently, used valves are as rare as rocking horse shit. Can't find any.

Spent money I really didn't have on Manley stainless valves.

FedEx lost the package. They say it was delivered, it was not.

If anyone wants a pair of nice unmolested bare castings you can come get them. Free. I can't afford to keep spending money on vapor.
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Re: LS 243 milling

Post by turbo camino »

12498544 appears to be two of the 12589226 gaskets in a single pack, for less money. The listings that show a 3.91" bore are incorrect (or they have been changed). Markings are identical to the 12589226 ("57/HO53").

There's two embossed .0075" outer layers and a single plain flat .030" shim in the center. Measuring across the embossing I get a total uncompressed thickness of .060". So no drilling rivets on this version unless you need a ~.020" gasket.
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