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I bought an lq4 a couple weeks ago pulled from an '02 2500hd. I have it torn down completely to the block and have some machining questions I'm hoping to find the answers to. This is my first full engine rebuild, so I apologize if these questions seem super basic. Here's what I'm trying to figure out:
1. I will be reusing the stock pistons, new rings and rod bearings of course. The cylinder walls appear to be in great shape and should be fine with a light hone I believe. How do I ensure that the machine shop stays within spec and does not hone too far? How would I go about selecting a ring size to fit this, or would you use factory rings?
2. On an iron block ls, what else must be checked when at the machine shop? Does the block need to be decked no matter what, or can I just use the straight edge method? I plan on having them do cam bearings, hone, and hot tank the block. Is there anything else that's absolutely necessary for a basic rebuild?
3. Help me pick which heads to go with - has stock 317s and I am looking for cheap, readily available heads to find at the junkyard. I'm thinking 5.3 706 heads, but are there any reasons this would not be a good choice? Would any porting/machining be recommended for 706 heads, or are they ok in factory form?
3.1. I have pretty much decided on a cam - SUMMIT 8713R - however, this was chosen based on 317 heads and is what summit recommended for my application. However, would this still perform well with 5.3 heads?
4. Injectors & Throttle body - This may be difficult to answer, due to differences in tuning and other things, but based on other info given, what size injectors would you predict I would need for that cam? I assume stock lq4 injectors would be close to maxed out, but would they still be ok possibly? Throttle Body - going to be running the stock truck intake (shaved). Is there a throttle body that will fit it that's actually worth upgrading to?
I apologize in advance if these have been answered. I researched like crazy, and these are the last couple questions I'm looking for some help on. Thanks
ONE question- WHY did you tear it down?? IF there was less than 200k miles on it, It was good for much more.
Do the bearings and rings, leave the block alone, and use some .040-.045 head gaskets to get tighter quench.
What will you be doing with this? You might want a bit less cam if it's a daily driver, especially with 706 heads, but that's just me.
ONE question- WHY did you tear it down?? IF there was less than 200k miles on it, It was good for much more.
Do the bearings and rings, leave the block alone, and use some .040-.045 head gaskets to get tighter quench.
What will you be doing with this? You might want a bit less cam if it's a daily driver, especially with 706 heads, but that's just me.
Appreciate the response! Super valid question and good info. I tore it down because:
1. This is a frame off restoration for a 1962 K10, and in my opinion, it would be a waste to go through all the trouble of replacing nearly everything and restoring it, only to put a junkyard motor in it. I have owned several LS engines and know they're good for easily 300k in some cases, but I want everything brand new.
2. I wanted to rebuild an engine, and the LS seems like a perfect one to learn on.
This will not be a daily at all, weekend driver mostly, so that is why I wanted such an aggressive cam. Do you think the 706's would be a good choice having said this? Any porting recommended?
Also, stock rings should work ok, or do I need to be worried about finding different sized rings?
That is basically what I was going to buy, minus pistons. I am trying to keep machining costs to an absolute minimum. Keeping factory pistons would mean I would not have to have the rotating assembly balanced, correct? Plus, going oversized on pistons would further add to the machine costs.
Do you see any reason I can't just keep the bottom end completely untouched, minus hone, re ring and bearings? I'm really just trying to figure our if honing will get me into trouble as far as finding the correct rings, and making sure the bore doesn't get too big. I've also considered just buying a flex hone and doing a couple passes, but I'm not sure if I should, or just have the machine shop do it
WS6store is VERY flexible on packaging what you need.
They'll make sure you get what you need, no more and no less.
They have a great rep on these forums.
On another note, you might want to get some 243/799 heads rather than 706's. Larger valves and better ports to feed 6.0 liters.
They came on all Gen IV cathedral port headed truck engines.
Our flat top pistons would not require balancing either.
Having built many low and high mile ls engines myself for my projects and others, if they (machine shop) are going to hone the block, the ptb clearance will be above recommended on a used piston.
I would always ALWAYS recommend new pistons whether you just stay stock bore or go larger. I always recommend larger as machine shop costs for hone vs bore and hone is usually around $100 and the parts are the same price, it doesn't make sense to NOT bore. Its a project that you can take your time on. Build it once with quality parts and be done. You dont have to spend a ton but if you put used pistons in, youll be redoing the engine again. So youre already paying twice.
Too often i hear "well you can still see the cross hatch so its good" even from machine shops. Thats a terrible way of gauging bore wear, taper, or out of round.
There are many ways to go on cam also. Adding lift to the ls cylinder heads, any head, is a great way to make power without any compromise and you can still use beehive springs. Our high lift hot cam is q great option there that would use stock converter and gears also which keeps cost down, but makes more power than similar cams with lower lift, sounds great, and we always use the high quality made in USA Pac beehive springs for it. Just another option no matter the head you use.
Our flat top pistons would not require balancing either.
Having built many low and high mile ls engines myself for my projects and others, if they (machine shop) are going to hone the block, the ptb clearance will be above recommended on a used piston.
I would always ALWAYS recommend new pistons whether you just stay stock bore or go larger. I always recommend larger as machine shop costs for hone vs bore and hone is usually around $100 and the parts are the same price, it doesn't make sense to NOT bore. Its a project that you can take your time on. Build it once with quality parts and be done. You dont have to spend a ton but if you put used pistons in, youll be redoing the engine again. So youre already paying twice.
Too often i hear "well you can still see the cross hatch so its good" even from machine shops. Thats a terrible way of gauging bore wear, taper, or out of round.
There are many ways to go on cam also. Adding lift to the ls cylinder heads, any head, is a great way to make power without any compromise and you can still use beehive springs. Our high lift hot cam is q great option there that would use stock converter and gears also which keeps cost down, but makes more power than similar cams with lower lift, sounds great, and we always use the high quality made in USA Pac beehive springs for it. Just another option no matter the head you use.
Well I guess I'm sold then - sounds like a full kit with pistons is the way to go! So, if I'm reading your website correctly, it looks like the full rebuild kit (suggested above in a previous post) starts at $699, and modifications can be made to the kit? If so, I'll probably go ahead and order soon.
Couple questions - if I decide to go with this kit and get a close-to-stock size flat top piston, this should help bump up the compression which is great. Would you still recommend going with a 706 head? If so, would you do any machining to them or run them as is. Also, Should I order the kit and bring the pistons to the machine shop before going?
The cylinder walls appear to be in great shape and should be fine with a light hone I believe. How do I ensure that the machine shop stays within spec and does not hone too far? How would I go about selecting a ring size to fit this, or would you use factory rings?
This often goes the other way. In general, if you want to build engines, the right way, then you want to 'listen to what the engine wants'. If the block checks out, and just a hone is required, I would expect the machine shop to tell you this info, and not that you dictate it to them.
Originally Posted by trever20
2. On an iron block ls, what else must be checked when at the machine shop? Does the block need to be decked no matter what, or can I just use the straight edge method? I plan on having them do cam bearings, hone, and hot tank the block. Is there anything else that's absolutely necessary for a basic rebuild?
So, again, the machine shop usually knows what is typical here. I think your list looks OK. When it comes to checking the deck, do you have quality tools to detect if the block surface is flat? Lots of straight edges aren't straight...
You might want to get the block work done and assemble the bottom end, and measure how far the pistons are in or out of the hole. And then factor this into your head machining and head gasket purchases to achieve the quench and CR you are looking for.
Originally Posted by trever20
3. Help me pick which heads to go with - has stock 317s and I am looking for cheap, readily available heads to find at the junkyard. I'm thinking 5.3 706 heads, but are there any reasons this would not be a good choice? Would any porting/machining be recommended for 706 heads, or are they ok in factory form?
This depends on your goals. #1: What application and what octane/fuel will you use? Likely, if you go to flat tops, I would suggest 799/243 heads. 6.0 with flat top pistons + 243 heads is an Iron LS2, at ~10.9:1 compression. If you were staying with dished pistons, then the 706s do well in mild-ish applications. They flow less, but the C.R. boost makes up for it. 317s, with some milling done could also work, if they meet your CR goals.
Any head will benefit from a good valve job/port cleanup, or a full CNC port job, if its done well. Cost/benefit depends on what you want to spend. Most say a good performance valve job, and spending a little time smoothing in the casting flaws/corners out is most of the benefit. LS3 style heads will cost more (also need the intake to match) and generally give up power below 4000 rpm (that seems to be the crossover point, usually).
Originally Posted by trever20
3.1. I have pretty much decided on a cam - SUMMIT 8713R - however, this was chosen based on 317 heads and is what summit recommended for my application. However, would this still perform well with 5.3 heads?
I think this will work fine, its a pretty mild cam for a 6.0. I run a 223/231 114+3 cam in my LQ4 on stock compression. This was designed for an LS2 for Trailblazer SS applications, I had it on the shelf, it works great in my LQ4, in my 1971 GMC. I run a Yank 3200 converter, 4L65e, 4.56 gears and 33"s tires, which rounds out the combo.
Originally Posted by trever20
4. Injectors & Throttle body - This may be difficult to answer, due to differences in tuning and other things, but based on other info given, what size injectors would you predict I would need for that cam? I assume stock lq4 injectors would be close to maxed out, but would they still be ok possibly? Throttle Body - going to be running the stock truck intake (shaved). Is there a throttle body that will fit it that's actually worth upgrading to?
If you are running the stock intake, then you are limited on the opening size, so I don't think a different throttle body will benefit you. I swapped after 2 years from stock/stock/stock (TB/intake/injectors) to my TBSS intake / 92mm TB / LS2 injectors. TBSS injectors may get you there (IIIRC, they are 27lb), but Corvette LS2 or bigger were recommended to me. I run the corvette LS2 parts(33 lb), and they are fine for my setup. Injectors do depend on your fuel rail/intake, as to what fits.
I would estimate this engine is making 500-525 at the crank. You can run the numbers and see. Typically, its going to be this: (HP * bsfc)/# of cyl. So, say 525hp * 0.45 BSFC / 8 cyl = 29.5 lbs per injector needed. So 33, 36, 42, something in there is likely what you'll want.
Originally Posted by trever20
Should I order the kit and bring the pistons to the machine shop before going?
I would also have this chat with your machine shop.
I would recommend that you check out a youtube channel: Deboss Garage. Specifically, he has some videos where they tear down engines with his engine builder and they go through what is good and bad, what a machine shop looks at, etc. It might be educational for you to see the process. There was a recent one in the series, I think 'everything wrong with a Hemi', but he has done several of those videos.
I believe in the Hemi video, they have that discussion about "I can still see the cross hatch" and why that doesn't mean as much as you might think.
This often goes the other way. In general, if you want to build engines, the right way, then you want to 'listen to what the engine wants'. If the block checks out, and just a hone is required, I would expect the machine shop to tell you this info, and not that you dictate it to them.
So, again, the machine shop usually knows what is typical here. I think your list looks OK. When it comes to checking the deck, do you have quality tools to detect if the block surface is flat? Lots of straight edges aren't straight...
You might want to get the block work done and assemble the bottom end, and measure how far the pistons are in or out of the hole. And then factor this into your head machining and head gasket purchases to achieve the quench and CR you are looking for.
This depends on your goals. #1: What application and what octane/fuel will you use? Likely, if you go to flat tops, I would suggest 799/243 heads. 6.0 with flat top pistons + 243 heads is an Iron LS2, at ~10.9:1 compression. If you were staying with dished pistons, then the 706s do well in mild-ish applications. They flow less, but the C.R. boost makes up for it. 317s, with some milling done could also work, if they meet your CR goals.
Any head will benefit from a good valve job/port cleanup, or a full CNC port job, if its done well. Cost/benefit depends on what you want to spend. Most say a good performance valve job, and spending a little time smoothing in the casting flaws/corners out is most of the benefit. LS3 style heads will cost more (also need the intake to match) and generally give up power below 4000 rpm (that seems to be the crossover point, usually).
I think this will work fine, its a pretty mild cam for a 6.0. I run a 223/231 114+3 cam in my LQ4 on stock compression. This was designed for an LS2 for Trailblazer SS applications, I had it on the shelf, it works great in my LQ4, in my 1971 GMC. I run a Yank 3200 converter, 4L65e, 4.56 gears and 33"s tires, which rounds out the combo.
If you are running the stock intake, then you are limited on the opening size, so I don't think a different throttle body will benefit you. I swapped after 2 years from stock/stock/stock (TB/intake/injectors) to my TBSS intake / 92mm TB / LS2 injectors. TBSS injectors may get you there (IIIRC, they are 27lb), but Corvette LS2 or bigger were recommended to me. I run the corvette LS2 parts(33 lb), and they are fine for my setup. Injectors do depend on your fuel rail/intake, as to what fits.
I would estimate this engine is making 500-525 at the crank. You can run the numbers and see. Typically, its going to be this: (HP * bsfc)/# of cyl. So, say 525hp * 0.45 BSFC / 8 cyl = 29.5 lbs per injector needed. So 33, 36, 42, something in there is likely what you'll want.
I would also have this chat with your machine shop.
I would recommend that you check out a youtube channel: Deboss Garage. Specifically, he has some videos where they tear down engines with his engine builder and they go through what is good and bad, what a machine shop looks at, etc. It might be educational for you to see the process. There was a recent one in the series, I think 'everything wrong with a Hemi', but he has done several of those videos.
I believe in the Hemi video, they have that discussion about "I can still see the cross hatch" and why that doesn't mean as much as you might think.
Thanks for such a detailed response - it's a huge help. One thing I'm still trying to figure out is the pistons. It seems like I need to decide on a piston, which I would then bring to a machine shop and they could use for whatever they need while working on the block. On the other hand, it seems like a machine shop should maybe check the block first to make sure those pistons wouldn't be an issue? Maybe I'm over complicating it. I plan on calling them shortly, but wanted to have an idea in mind first.
Also, since I'm now thinking it would be best to get new pistons, how would I go about choosing the right size? I definitely want flat top if I'm going to be replacing, but beyond that, I don't know. I'm not going crazy on this rebuild, mostly just a refresh and bolt ons. Would it be wise to go up one piston size over stock to ensure that it will machine out well? If I stick with stock sizing and find out the cylinder walls need to be honed out further than that piston will allow for, then I would be in trouble.
Ok so I called 3 machine shops in my area, and all the quotes are quite a bit different. Wondering if you all could guide me in the right direction.
Shop 1 - $300 for hone, cam bearings, and hot tank
Shop 2 - Roughly $500 for hone, cam bearings, and hot tank. If cylinders need to be bored beyond a regular hone (I don't think this is the case), $100 per cylinder
Shop 3 - $900 for hone, cam bearings, hot tank, magnaflux, and surface the deck (if needed). If surfacing is not needed, then $700 total.
So basically, 300, 500, and 700. Shop 3 obviously is doing a full inspection on it, and thus is more expensive.
Is surfacing generally needed on an iron block? Let me know what you think - if the prices sound about right, or way off. Thanks
For Hot Tank, Magnaflux, Deck square to crank, Linebore (ARP main studs), Cam bearings, Bore and Hone .030 over, and balance rotating assembly, I usually come out to around $900
Trever, if you are going to go the machining route-I've heard that Summit racing sells SEASONED--MACHINED-blocks that are square with the world for something in the $700 range. A block from Summit would already be DECKED, ALIGN-HONED, BORED, HONED, AND HAVE CAM BEARINGS PRESSED IN, AND WASHED/HOT TANKED. In short, it would be ready for assembly with minimal cleaning on your part. I was watching Power Nation and they were saying that Summit had those 6.0 blocks ready to go. That might be cheaper than using your local machinist if those prices are accurate. Keep in mind you CANNOT search the Summit web site. The search function is USELESS.. Are you listening Summit? I would recommend that you call them directly, and mention that you heard about the bare, GM, LS, 6.0L already machined block on Power Nation, for something in the $700+ dollar range.
Trever, if you are going to go the machining route-I've heard that Summit racing sells SEASONED--MACHINED-blocks that are square with the world for something in the $700 range. A block from Summit would already be DECKED, ALIGN-HONED, BORED, HONED, AND HAVE CAM BEARINGS PRESSED IN, AND WASHED/HOT TANKED. In short, it would be ready for assembly with minimal cleaning on your part. I was watching Power Nation and they were saying that Summit had those 6.0 blocks ready to go. That might be cheaper than using your local machinist if those prices are accurate. Keep in mind you CANNOT search the Summit web site. The search function is USELESS.. Are you listening Summit? I would recommend that you call them directly, and mention that you heard about the bare, GM, LS, 6.0L already machined block on Power Nation, for something in the $700+ dollar range.
Thanks, I''ll definitely look into that.
Another question - I considered using just a ball hone to freshen up this block, but I'd rather take it to an actual machine shop. What is the maximum amount of material that can be honed while still being able to use the stock (or stock size) pistons? I've been researching this, but I'm not finding a clear answer. Of course, the machine shop will know how much has to be honed when they receive the block, but I'm hoping I can reuse the stock pistons
Trever, if you are going to go the machining route-I've heard that Summit racing sells SEASONED--MACHINED-blocks that are square with the world for something in the $700 range. A block from Summit would already be DECKED, ALIGN-HONED, BORED, HONED, AND HAVE CAM BEARINGS PRESSED IN, AND WASHED/HOT TANKED. In short, it would be ready for assembly with minimal cleaning on your part. I was watching Power Nation and they were saying that Summit had those 6.0 blocks ready to go. That might be cheaper than using your local machinist if those prices are accurate. Keep in mind you CANNOT search the Summit web site. The search function is USELESS.. Are you listening Summit? I would recommend that you call them directly, and mention that you heard about the bare, GM, LS, 6.0L already machined block on Power Nation, for something in the $700+ dollar range.
theunderlord-is that accurate? It's the 6.2 block, and not the 6.0? My bad. I searched the Summit web site and could not find ANY decent priced 6.0 blocks there... Wonder if Power Nation was BS'ing us?
05-08-2022, 10:25 PM
LQ4 Build - Machining Questions 
You should have said 6.2L blocks.