4.8 heads
Thread Starter
Teching In
Joined: Aug 2013
Posts: 6
Likes: 0
From: Illinois
4.8 heads Hello everybody,
I've read a lot of the newb tech, but still have some questions. I have a running 4.8 truck which is soon to be the engine/trans donor for my Volvo. The truck has 236k miles on it, so I would like to freshen things up and do some light mods before I plop everything into it's new home.
I bought an 01 LS6 cam and new LS6 springs for $80 which I figured would be a nice cheap upgrade, but I thought some heads would be a good thing too. I would like to maintain the higher compression ratio that the 862 heads offer, but I would also like the bigger intake valve. By the time all that work was done, I could probably be close to a way better aftermarket head. Does anybody have any suggestions? I know the 01 LS6 cam has a smaller lift than the later ones, so maybe I should ditch that cam and get a nicer cam AND heads?
I have never built a car for high performance, so I'm not looking to go ham right off the bat. However, every car guy wants to go a little faster. Is there a good head out there that won't lower my compression ratio and works with my stock flat tops? Am I over thinking things? Thanks in advance.
-Jon
P.S. sorry for making such a newb post, but I am a newb.
I've read a lot of the newb tech, but still have some questions. I have a running 4.8 truck which is soon to be the engine/trans donor for my Volvo. The truck has 236k miles on it, so I would like to freshen things up and do some light mods before I plop everything into it's new home.
I bought an 01 LS6 cam and new LS6 springs for $80 which I figured would be a nice cheap upgrade, but I thought some heads would be a good thing too. I would like to maintain the higher compression ratio that the 862 heads offer, but I would also like the bigger intake valve. By the time all that work was done, I could probably be close to a way better aftermarket head. Does anybody have any suggestions? I know the 01 LS6 cam has a smaller lift than the later ones, so maybe I should ditch that cam and get a nicer cam AND heads?
I have never built a car for high performance, so I'm not looking to go ham right off the bat. However, every car guy wants to go a little faster. Is there a good head out there that won't lower my compression ratio and works with my stock flat tops? Am I over thinking things? Thanks in advance.
-Jon
P.S. sorry for making such a newb post, but I am a newb.
I'll try to help you out some.
Heads - Highly recommend the 243 heads. You can mill them to get the compression you want, but they are far better than the 862 / 706 heads the trucks come with. I've seen 4.8's with 243 heads outrun 5.3's with the 862's.
Cam - I put a 04 Z06 cam in a 5.3 thinking it would be a great idea, and it wasn't really that beneficial. I've seen threads where people got insane gains from it, but I didn't see much improvement, except that it sounds cooler at idle. I really think you'd be better off with a cam designed to build good torque, which the Z06 is not.
Overthinking things - Definitely not. Do your homework, ask lots of questions, get a good feel for the people that are generally correct in their posts, get recommendations from vendors. Time spent on research is far less frustrating than time spent doing a mod the second (or third) time, because you got it wrong the first time.
Heads - Highly recommend the 243 heads. You can mill them to get the compression you want, but they are far better than the 862 / 706 heads the trucks come with. I've seen 4.8's with 243 heads outrun 5.3's with the 862's.
Cam - I put a 04 Z06 cam in a 5.3 thinking it would be a great idea, and it wasn't really that beneficial. I've seen threads where people got insane gains from it, but I didn't see much improvement, except that it sounds cooler at idle. I really think you'd be better off with a cam designed to build good torque, which the Z06 is not.
Overthinking things - Definitely not. Do your homework, ask lots of questions, get a good feel for the people that are generally correct in their posts, get recommendations from vendors. Time spent on research is far less frustrating than time spent doing a mod the second (or third) time, because you got it wrong the first time.
The 862 heads have the smallest combustion chambers of all the factory LS heads. You could keep the stock exhaust valves and swap in some 2.00" or 2.02" intake valves. The valves shouldn't cost more than $120 depending on what brand, and the machining (valve job and mill the deck surface) will probably run about $200.
The truck intake is fine despite what the car owners will tell you, if it fits and you don't care how it looks keep it.
Far as the LS6 cam and springs, the smaller displacement will make the peak HP rpm rise, the solid valves are heavier than true LS6 valves, this combines to mean the LS6 springs will not control that cam in this application
Far as the LS6 cam and springs, the smaller displacement will make the peak HP rpm rise, the solid valves are heavier than true LS6 valves, this combines to mean the LS6 springs will not control that cam in this application
On The Tree
Joined: Oct 2014
Posts: 111
Likes: 0
From: Elkhart, IN
Dont want to steal youre thread. But I'm interested in what you said KCS about valve swap with the 862 heads. What would be the benefits of this? Is this something that can be done mechanically with tools or does a machine shop need to be involved?
A machine shop would certainly need to be involved. They will need to machine the valve seat to the larger OD valve.
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Thread Starter
Teching In
Joined: Aug 2013
Posts: 6
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From: Illinois
Thanks everybody! Good stuff here. I have a buddy who has 243 heads for sale. Maybe I'll snag those and get them milled.
My truck intake is staying. It flows well and will fit under the hood of my Volvo. As for headers, I'm considering it. I just don't know if I want to get a turbo later on so I wouldn't want to spend too much money on them. Maybe I'll get shorties so that I can still use them if that time comes.
My truck intake is staying. It flows well and will fit under the hood of my Volvo. As for headers, I'm considering it. I just don't know if I want to get a turbo later on so I wouldn't want to spend too much money on them. Maybe I'll get shorties so that I can still use them if that time comes.
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Teching In
Joined: Jul 2005
Posts: 28
Likes: 0
From: CENTRAL ILLINOIS
My 04 silverado 4.8 has 9.5 compression with the stock heads, which are 61cc I believe. I would like to run the 243 or 799 but want to get about 10.5 compression. can I mill the heads down to achieve this ratio and if so what else will be involved as far needing to change or upgrade?
TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
You will need good valve springs, as mentioned, the LS6 springs are not going to cut it. New pushrods. Upgraded trunions for your rockers. And I, personally, would get a better cam. The 243 heads would definitely be a welcome upgrade over the truck heads, and they will have the larger intake valve already. Truck intake is fine, like you said. Headers are a good idea, even if you have to sell them later when you go turbo.
On The Tree
Joined: Feb 2016
Posts: 102
Likes: 1
From: Leeuwarden
I would ditch the cam and get a Crane 210 cam. If I wanted to go any further with a 4.8, first I would mill the original heads, after that I would install a 2.00" valve and unshroud it and finally I would do a P&P job.