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LQ9 based 408 2 part article

 
b_onliest b_onliest
New User | Posts: 2 | Joined: 09/09
Posted: 09/10/09
10:08 PM

This articled interested me because my son had previously suggested the same basis for people that want to build their own.  He has a Sierra with the LQ9.
I logged in to ask what the correct spec for the main bearing clearance is, and  what were your final measurements for the successful dyno pull?  Did SAM use the incorrect spec?  Other than getting different bearings, how would clearance adjustments be made?   First time post.  

 
Scott_at_GMHTP Scott_at_GMHTP
Moderator | Posts: 140 | Joined: 12/07
Posted: 09/11/09
11:32 AM

Check out Part 1 in the August issue, just one of the mains was out of spec...easily correctable with a different bearing. No matter how good of a machinist you have, it's quite common to use various thickness bearings to compensate for slight inconsistencies. I will get back to you on what clearance they went with.  

 
mpayne mpayne
Enthusiast | Posts: 263 | Joined: 10/07
Posted: 09/11/09
01:09 PM

Here is a digital link to the story Scott is referring too. http://www.gmhightechperformance.com/tech/0908gmhtp_lq9_408_stroker_budget_build/index.html  

 
BillK71 BillK71
New User | Posts: 1 | Joined: 09/09
Posted: 09/15/09
05:43 PM

Scott,
I am also very interested in this information. The factory clearance spec for the mains is .0007" to .0021" so .002" or even a little tighter is well within reason. I am also preparing for my first complete LS build based on a 6.0 block and would not have had any problems with that clearance.

In all fairness to your readers, it would be interesting to know if it was definitely determined that the bearing clearance was really the issue with the failure on the dyno. I have built many "traditional" small blocks with less than .002" mian clearance and have not had issues.