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BossHogg69 · 05-14-2017, 03:33 PM

First thing I'd do is pull the valve covers and make sure it doesn't have Castech heads on it before spending a bunch of money on go fast parts.

https://www.jalopyjournal.com/forum/...ngines.933574/

http://speedtalk.com/forum/viewtopic.php?f=1&t=28519

http://www.gminsidenews.com/forums/f...r-heads-83436/

WELL documented problem and usually only shows up after 100k miles or so. My '05 GMC 5.3 started giving me issues after about 140k, smoking, using antifreeze with no visible leaks, then started running hot and sludgy oil.

Anyway, I had previously installed a Comp Cams LSR 265 cam, long tube headers, Blackbear custom tune and a Yank 2600 stall converter - which really woke things up. After both of the heads cracked, I installed a set of Texas Speed PRC stage 2.5 heads to go along with the other stuff I already had and the thing came alive.

05-14-2017, 03:33 PM	#11
BossHogg69 motor exploder Join Date: Mar 2009 Location: Pittsburgh, PA Posts: 2,346	Re: Updating a LM7 for transplant First thing I'd do is pull the valve covers and make sure it doesn't have Castech heads on it before spending a bunch of money on go fast parts. https://www.jalopyjournal.com/forum/...ngines.933574/ http://speedtalk.com/forum/viewtopic.php?f=1&t=28519 http://www.gminsidenews.com/forums/f...r-heads-83436/ WELL documented problem and usually only shows up after 100k miles or so. My '05 GMC 5.3 started giving me issues after about 140k, smoking, using antifreeze with no visible leaks, then started running hot and sludgy oil. Anyway, I had previously installed a Comp Cams LSR 265 cam, long tube headers, Blackbear custom tune and a Yank 2600 stall converter - which really woke things up. After both of the heads cracked, I installed a set of Texas Speed PRC stage 2.5 heads to go along with the other stuff I already had and the thing came alive. __________________ Adam 1969 Chevy CST/10 stepside, DART Big M/TREMEC Magnum Extreme/3.73's w/Detroit Truetrac 1965 Chevy Bel Air Wagon (daily driver), 327/TH350,10 bolt w/3.08's 1961 Chevy Bel Air Sport Coupe, ZZ454/M21/9" rear w/3.50's & Detroit Truetrac 2005 GMC 1500 ccsb 2wd, 6.0L/4L65e/3.73 G80 2006 GMC 2500HD ccsb 4x4, DMax LBZ/Allison 6spd/4.56's w/Detroit TrueTrac Use the SEARCH function on this forum - it is your friend!!