Cracked 317 heads
Cracked 317 heads I just verified that I cracked the original 317 heads on my 300k+ mile LQ4 that is original to my 2001 Silverado 1500HD. I added the turbo in spring of 2020 (details in sig) and in fall of 2020 noticed it was using coolant. I have convinced myself it started using coolant after a 11psi run on E85 while tuning although I'm not 100% sure. It started out using very little coolant, but lately I was adding a quart or so every two weeks. So I pressurized the coolant system to 15 psi today and sure enough I see coolant bubbling up in the aluminum near two of the head studs under the valve covers.
I have a few questions. I hear about the 5.3 heads cracking, but not so many stories on the 6L 317 heads. Anyone have issues cracking stock heads with a turbo LQ4 or similar? I run on E85 most of the time and only plan to go to 13 or so PSI max because I have a stock bottom end in my LQ4. I did a compression test and all cylinders are between 187 and 196psi, so the bottom end is in good shape and still has life in it. I have a set of 241 heads that came off my 60k mile LS1 that I could swap valve springs on and go, however if it's semi common to crack stock heads or for turbo motors to use coolant with stock heads (i.e. owner hasn't found the issue yet), then I absolutely want to go aftermarket because swapping heads all the time sucks. If I go aftermarket I was looking at Texas Speed 225cc heads with the big 68cc chambers for ~$2000. This truck is my mostly driver and I tow my racecar around with it, so I'm looking for reliability. Not really concerned about making the most power because I can always turn up the boost another psi or two to make up for the poorer flowing 241 heads. This truck never sees the track. Any help or feedback is appreciated.
I have a few questions. I hear about the 5.3 heads cracking, but not so many stories on the 6L 317 heads. Anyone have issues cracking stock heads with a turbo LQ4 or similar? I run on E85 most of the time and only plan to go to 13 or so PSI max because I have a stock bottom end in my LQ4. I did a compression test and all cylinders are between 187 and 196psi, so the bottom end is in good shape and still has life in it. I have a set of 241 heads that came off my 60k mile LS1 that I could swap valve springs on and go, however if it's semi common to crack stock heads or for turbo motors to use coolant with stock heads (i.e. owner hasn't found the issue yet), then I absolutely want to go aftermarket because swapping heads all the time sucks. If I go aftermarket I was looking at Texas Speed 225cc heads with the big 68cc chambers for ~$2000. This truck is my mostly driver and I tow my racecar around with it, so I'm looking for reliability. Not really concerned about making the most power because I can always turn up the boost another psi or two to make up for the poorer flowing 241 heads. This truck never sees the track. Any help or feedback is appreciated.
TECH Resident
Joined: Sep 2013
Posts: 993
Likes: 119
From: Mechanicsburg, PA
Are you sure it's a head crack leaking or did the head gasket go between the cylinder and the head stud? Used to happen all the time on GM 2.5l engines. May be worth a teardown and inspection. Gaskets and a machine shop bill to make sure they're not cracked.
TECH Enthusiast
Joined: Feb 2020
Posts: 734
Likes: 209
FWIW I'm running an lq4 with nearly 200k miles 15000 turbo'd, hitting 15lbs on 91 octane plus 50/50 water/meth - no problem. Heads / pan never off. Running e 85 at 12 psi shouldn't be a problem unless the tune is off . You should be able to get 317s cheap and swap 1 or both on and not have further problems IMO
