the only thing you can do is compare the engine plate between the cylinder heads, the flat smooth one is 4.8 the one with designs are 5.3. good luck and please accept my answer so i get credit. thanks T-MAN
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other than that there is no other way without tearing it down.
As per your question. first and foremost this motor is from GM performance parts catalog, It is a crate motor. The cast no. is 2551358 (4.8/5.3L) dr. side rear top side. On top side dr. side rear pad there is a (lazer generated no. CYG 183827) also right below this code is another on mounting surface of bellhousing also(lazer generated 9928816 : 403) These nos. look like punch generated but way more percise than by hand. This no. would not be seen if bellhousing were installed. On pass.side frt. casting code J079 appears(not important I assume). There are numerous bar code stickers, 4 to be exact,(10FHB K000980987) one on each side of block and on rear of both heads. If you cannot furnish me with specs like in the performance catalog or build sheet then i will conclude this question to be unanswerable, which means I will have to tear motor down to identify internal parts by nos. My original question was how to find out which engine I have without dismantling it. The first expert told me a boltable on part was the answer.I have been to salvage yards and they do not know how to tell. Also to two chevy dealerships parts counter - no help.
It is a crate motor from GM, never installed in a vehicle. It is NOT a
CYB number - it is a CYG number. Would you please try again? It seems to me I'm going to have to tear the engine down anyway to see what I have. I don't need to waste money and make a mistake. I need to have the specs in order to proceed so I don't duplicate what is already there. Without the specs I don't know if I have the correct cam shaft type (P/N 12561721)This engine has cathedral high output heads. Would those head numbers help identify this motor even thought they are bolt on parts? My need for this information is why I wrote to you in the first place. Once I get the specs, I will consider this question answered. Would "ALL DATA" help? I live next door to an ASE Master Technician and he can't find it. I'm hoping that, with your qualifications, you'll be able to help me. Thanx
I called the man I bought the motor from and he is looking for the paperwork from Sam Taylor buick-cadillac, Inc. It is not a rebuilt motor and has extras in it and was purchased in 2009 as a high output motor. He is not sure if it is a LM7 or LS327. My motor looks identical to the LS327 but looks are deceiving. It does have the cat heads on it. I cannot believe it is a rebuilt motor as this man builds fine cameros, the reason he did not install this motor is because he wanted to install a turbo and he would lose his a/c plus something else I can't remember? So instead he went with a 6.0 engine. If he doesn't find the original paperwork I will still have to tear the motor down and check the parts out before installing this new motor in my high output 2000 1500 chevy. I am still not satisfied with GM for not having the engine no. on file or where to find it. I'm inclined to believe in Rob because he has not cashed my check in over 6 months until I install the motor and am satisfied. Your specs for a basic LM7 motor are basically correct as far as I know. But GM has not told me to my satisfaction the specs on this motor yet. I don't think the question has been answered yet for this motor CYG 183827. there must be a sight somewhere that will have the information I seek.