When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Is there a cut off on when the head bolts changed on 5.3s? Most of the information I have found searching is for LS6 blocks which I am aware there is no clear way to know if they use the early or late design without pulling the bolts out.
We have a 04 LM7 with 706 heads in a GMC Sierra which we are pulling the heads on. Did the 5.3 make a mid year transition like the LS6 block vehicles or is the transtion more clearly defined, is there a casting number to verify which head bolts were used?
I would pull one in the middle and check. Can put it back in and it'll still run. I've done it without issue, look up what the equivalent torque is to the stretch method the original installation calls for.
Yes it changed sort of over the course of the 04 year. AFAIK it's not a casting feature at all; only post-casting machine work.
My 04 has all the same length bolts.
The middle ones aren't the ones that vary. It's the end ones in the top row if memory serves. (the row of big ones, not the little ones next to the intake)
Yes it changed sort of over the course of the 04 year. AFAIK it's not a casting feature at all; only post-casting machine work.
My 04 has all the same length bolts.
The middle ones aren't the ones that vary. It's the end ones in the top row if memory serves. (the row of big ones, not the little ones next to the intake)
Incorrect.
10 total 11mm Bolts.
Early design: 8 long, 2 short in the middle row on the ends.
04-up: all 10 same length.
Pulling the middle bottom one will either be a long or a short. That's how you tell.
Middle row = the top row of the larger bolts (the ones that make a square around the cyls; not the little ones along the intake flange that don't do much of anything)
The ones in question are the 2 bolts at the ends of the upper row of large bolts(front- and rear-most); not bolts in the middle.
Middle row = the top row of the larger bolts (the ones that make a square around the cyls; not the little ones along the intake flange that don't do much of anything)
I'm glad you can read and comprehend what I typed. Thanks for sharing with us. Now read this whole post before chiming back in.
Those little M8 Bolts seal in the Water Jacket on the ends, all together bolt the top of the Head to the Block and make it more rigid. So yes, they have a purpose.
Originally Posted by RB04Av
The ones in question are the 2 bolts at the ends of the upper row of large bolts(front- and rear-most); not bolts in the middle.
Absolutely not true, all of them are different. Have you ever pulled Heads from both types of Engines? Clearly not. Now sit down and learn.
As I said above for those who want to argue...
10 total 11mm Bolts.
Early design: 8 long, 2 short in the middle row on the ends. 04-up: all 10 same length.
Attached pics for the reading impaired. Get back to me..
Last edited by the_merv; Jul 31, 2024 at 07:47 PM.
The short ones, in the older engines that have them, are at THE ENDS of the head.
There's a row of 5 across the bottom, next to the exhaust, and a row of 5 kind of in the middle of the head butt closer to the intake side. Then a row of 5 across the very top next to the intake flange, which are itty bitty things, totally different from the main 10.
Those main 10 make a pattern of 4 around each cyl.
The 2 short head bolts in the first design ARE NOT in "the middle" of the head. They are at THE ENDS. On the driver's side, they are the ones IN FRONT OF cyl #1, and BEHIND cyl #7; on the top row of significant bolts (disregarding the little weenie ones that are about the same as timing cover bolts except longer).
Note carefully, they are at THE ENDS of the head, NOT "the middle". If you pull a bolt out of "the middle" of the head, it will be a long one EVERY TIME IN EVERY ENGINE. (again, disregarding the little weenie ones that are about the same as timing cover bolts except longer) If you pull ANY of the ones next to the exhaust, it will also be a long one EVERY TIME IN EVERY ENGINE. To make a valid check, one has to pull one of the bolts from the TOP ROW of significant bolts (again, disregarding the little weenie ones that are about the same as timing cover bolts except longer), either the front-most one or the rear-most one. NOT "the middle".
The short ones, in the older engines that have them, are at THE ENDS of the head.
There's a row of 5 across the bottom, next to the exhaust, and a row of 5 kind of in the middle of the head butt closer to the intake side. Then a row of 5 across the very top next to the intake flange, which are itty bitty things, totally different from the main 10.
Those main 10 make a pattern of 4 around each cyl.
The 2 short head bolts in the first design ARE NOT in "the middle" of the head. They are at THE ENDS. On the driver's side, they are the ones IN FRONT OF cyl #1, and BEHIND cyl #7; on the top row of significant bolts (disregarding the little weenie ones that are about the same as timing cover bolts except longer).
Note carefully, they are at THE ENDS of the head, NOT "the middle". If you pull a bolt out of "the middle" of the head, it will be a long one EVERY TIME IN EVERY ENGINE. (again, disregarding the little weenie ones that are about the same as timing cover bolts except longer) If you pull ANY of the ones next to the exhaust, it will also be a long one EVERY TIME IN EVERY ENGINE. To make a valid check, one has to pull one of the bolts from the TOP ROW of significant bolts (again, disregarding the little weenie ones that are about the same as timing cover bolts except longer), either the front-most one or the rear-most one. NOT "the middle".
For the 3rd ******* time, the long bolts in the earlier stuff are different from all 10 of the later stuff, that's how you can tell the difference. Are you blind to the pics I just posted?
Stop focusing on #9 & 10 in the torque sequence, and see what I'm talking about. You stated you were quoting from "memory", and I posted pics. Done it too.
The only problem with that is it does not match literally what I've seen out there and have done with the newer style of bolts, as you see in the pictures above also.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
04 LM7 head bolt design 
