LM7 build questions
08-12-2013, 01:38 PM
#1
LM7 build questions Hey guys, I am putting together a high CR LM7 for the first phase of my build. After doing some research there are still a few gray areas I'm dealing with and would like some clarification to make sure I'm searching for the right parts.
This was my initial build plan.
Am I missing anything?
With the 243 or 317 heads, how much do you think I could take off for maximum compression without dealing with valve contact issues?
Maybe I'm way off, if you have a better results proven combo please share! I'm all ears.
Thanks guys!
This was my initial build plan.
- 5.3L block - has new thrust, main and crank bearings, need to do a quick hone
- 4.8L flat top pistons - new rings
- new oil pump and timing chain set
- Cam - I was thinking the LS6 hot cam from GM, I have intension of boost down the road, does it make sence to go wit hthe zr1 cam now?
- 243 heads or 317 head milled to 243cc specs
- LS6 valve spring or something similar
- rocker upgrade or comp cam rockers - buddy has a brand new set will to let go for nothing
- push rods? - If I go with the ls6 hot cam should I get new ones?
- Lifters - Should I upgrade to the ls7 lifters?
- Intake - ls1 or ls6 intake depending on the deal I can find
- I already have a ported TB from another build
Am I missing anything?
With the 243 or 317 heads, how much do you think I could take off for maximum compression without dealing with valve contact issues?
Maybe I'm way off, if you have a better results proven combo please share! I'm all ears.
Thanks guys!
Last edited by Ironfreak; 08-12-2013 at 04:22 PM.
08-12-2013, 03:01 PM
#2
I am interested to see replies in your thread. I'm not hijacking here. I'm planning something similar so I figured a couple questions to you might be helpful for both of us.
Why not the factory LM7 heads? Will the 5.3 flow enough to go through the trouble and cost of what you planned?
I am getting new lifters just because you have to take the heads off to change them. Is it worth it not too?
Push rods - Personally that's my last purchase. Can always drop new ones in later as $$ allows. That's easy later.
I have an LS1 intake, I wonder how much of a difference an LS6 intake will make on a 5.3??
Do you plan on the speedpro 4.8 pistons? I plan on using them - I like the coated skirts and they are cheep.
**Have you seen the CarCraft article where they tested all the factory, and a few Crane cams in a 5.3? Just appeared on the web.**
Anyway, Good Luck!
Why not the factory LM7 heads? Will the 5.3 flow enough to go through the trouble and cost of what you planned?
I am getting new lifters just because you have to take the heads off to change them. Is it worth it not too?
Push rods - Personally that's my last purchase. Can always drop new ones in later as $$ allows. That's easy later.
I have an LS1 intake, I wonder how much of a difference an LS6 intake will make on a 5.3??
Do you plan on the speedpro 4.8 pistons? I plan on using them - I like the coated skirts and they are cheep.
**Have you seen the CarCraft article where they tested all the factory, and a few Crane cams in a 5.3? Just appeared on the web.**
Anyway, Good Luck!
08-12-2013, 04:20 PM
#3
I am interested to see replies in your thread. I'm not hijacking here. I'm planning something similar so I figured a couple questions to you might be helpful for both of us.
Why not the factory LM7 heads? Will the 5.3 flow enough to go through the trouble and cost of what you planned?
I am getting new lifters just because you have to take the heads off to change them. Is it worth it not too?
Push rods - Personally that's my last purchase. Can always drop new ones in later as $$ allows. That's easy later.
I have an LS1 intake, I wonder how much of a difference an LS6 intake will make on a 5.3??
Do you plan on the speedpro 4.8 pistons? I plan on using them - I like the coated skirts and they are cheep.
**Have you seen the CarCraft article where they tested all the factory, and a few Crane cams in a 5.3? Just appeared on the web.**
Anyway, Good Luck!
Why not the factory LM7 heads? Will the 5.3 flow enough to go through the trouble and cost of what you planned?
I am getting new lifters just because you have to take the heads off to change them. Is it worth it not too?
Push rods - Personally that's my last purchase. Can always drop new ones in later as $$ allows. That's easy later.
I have an LS1 intake, I wonder how much of a difference an LS6 intake will make on a 5.3??
Do you plan on the speedpro 4.8 pistons? I plan on using them - I like the coated skirts and they are cheep.
**Have you seen the CarCraft article where they tested all the factory, and a few Crane cams in a 5.3? Just appeared on the web.**
Anyway, Good Luck!
I'm on the same page with the lifters, might as well. with the push rods I know that the hot cam and zr1 cam are pretty aggressive compared to stock, if I'm going to upgrade the valve train why leave a weak link. I will add this to the original post but I'll upgrade to LS6 springs or something similar as well.
Intake, I'm not sure how much better the ls6 is, and whether its worth the money. thats why I put both as an option. The truck intake flows really well but it won't fit under the hood of my application so thats why I want to change it.
I'm interested in where you found the speedpro kit pistons. what is the pricing, does it include the rings? I found some sets but they are all on ebay and some random brand, not that appealing. I was thinking junkyard pistons with new rings.
08-12-2013, 04:48 PM
#4
Based on some info here the LS6 intake really outflows the Ls1 intake but don't expect to see a huge increase or difference in HP between them (again just looking at the info here). I got the LS6 intake to maximize intake flow especially since I am personally going turbo with my 5.3L setup and the truck intake will not fit into my 240sx chassis.
08-12-2013, 06:57 PM
#5
The reason I was thinking the 243 or 317 is the exhaust valves are bigger 2.00 verse 1.88 iirc. Plus they have smaller combustion chambers (317 if they're milled). I would save the stock 5.3 for a valve job and clean up when I went FI.
I'm on the same page with the lifters, might as well. with the push rods I know that the hot cam and zr1 cam,..............
I'm on the same page with the lifters, might as well. with the push rods I know that the hot cam and zr1 cam,..............
You mean the ls9 cam when you say zr1 can, right? Big loss down low but big gains up top. I might go with that one. I do wonder how a compression bump might change this.
08-13-2013, 08:01 AM
#6
I need to continue doing research then, I really don't want to lose low end torque, maybe the ls6 hot cam is the way to go.
Anyone else have suggestions?
This might be a really silly question, but if I put new pistons in but do a light hone on the cylinders first, do I still order riings for the stock bore?
I've been reading a lot of threads on bossting these 5.3's........kinda feel like I might be wasting my time with an N/A build. I have a turbo and some 60lbs. deca injectors at home.....
Anyone else have suggestions?
This might be a really silly question, but if I put new pistons in but do a light hone on the cylinders first, do I still order riings for the stock bore?
I've been reading a lot of threads on bossting these 5.3's........kinda feel like I might be wasting my time with an N/A build. I have a turbo and some 60lbs. deca injectors at home.....
