Need help calculating 5.3 compression
11-06-2012, 03:35 PM
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Need help calculating 5.3 compression I'm not asking anyone to calculate it for me. I need the dish cc for stock '04 LM7 pistons, and how far out of the hole are they ( if any). I tried the search feature, google, etc. with mixed results.
Last edited by northcorner; 11-06-2012 at 05:01 PM.
11-06-2012, 06:01 PM
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11-06-2012, 10:05 PM
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Thank you for your reply. .005 to .006 has been the consensus on how far out of the hole the stock piston is, so far. The '04 LM7 pistons have a dish, it appears that the dish is the same on all LM7 engines, but so far no one has a spec on them. I thought for sure that GM had some info, but I just can't unearth it. I'm not sure why it's so hard to find a measurement that is blueprinted with GM, on such a popular platform.
11-06-2012, 10:41 PM
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Vortec 4.8 / 5.3 differences: GM used a shorter stroke crankshaft in the 4.8L and a longer connecting rod. 99 to 03 or so, the 4.8L's all had completely flat top pistons. 5.3L's had a slight dish. However, after about 2004 sometime, the 5.3L's could have true flattop's. So really the BEST way to tell is measure stroke, or casting number on crankshaft. Of course if you are standing in-front of a vehicle, you can look at the VIN#. 8th digit is the Engine, 10th digit is the year. T = 5.3L LM7, V= 4.8L LR4, Z = 5.3L L59 Flex Fuel
11-07-2012, 10:47 AM
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Maybe I'm thinking of the L33 having flattops.
When I crunched the numbers on the compression ratio calculator, looks like the dish is probably about -7 to arrive at the advertised stock CR.
When I crunched the numbers on the compression ratio calculator, looks like the dish is probably about -7 to arrive at the advertised stock CR.
11-07-2012, 12:24 PM
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Hello , I measured My 1999 5.3L stock dished pistons at 9cc
Also a really good source for engine and car calculators is Wallace Racing . They have evry calc You can think of and many more like static comp, dynamic comp, all You're cam calcs, 1/4 n 1/8th mile et, gear ratios, check it out honestly there are probably 100 to 150 different calcs maybe more and They're free
As far as piston out of hole ,,,,,,,I could'nt get an exact measurement but I used feeler gauges and it appeared that They were out of hole roughly .015" ,,,,,,hope this helps
Also a really good source for engine and car calculators is Wallace Racing . They have evry calc You can think of and many more like static comp, dynamic comp, all You're cam calcs, 1/4 n 1/8th mile et, gear ratios, check it out honestly there are probably 100 to 150 different calcs maybe more and They're free
As far as piston out of hole ,,,,,,,I could'nt get an exact measurement but I used feeler gauges and it appeared that They were out of hole roughly .015" ,,,,,,hope this helps
Last edited by chrisfrost; 11-07-2012 at 12:49 PM.
