4.8 Pistons in 5.3 LM7, worth the trouble?
07-17-2014, 04:34 PM
#1
4.8 Pistons in 5.3 LM7, worth the trouble? So I currently have a 5.3 swapped into my '81 Volvo wagon. On just the bench tune from PSI Conversions, it made 253whp and 296wtq through a T56. I plan on adding a cam to push it over 300whp but want to get closer to 400whp with some additional work.
I have a friend building an engine for his 240sx, and already dropped some 4.8 pistons in his 5.3. He needed to rebuild it to replace a bent rod so it made sense while he was in there. I suggested the pistons after reading a number of threads and seeing the thread and associated videos from AGearhead4Life. Poking around in the classifieds, I found a set of 4.8 pistons for super cheap and thought, "why not?"
Before pulling the trigger, I wanted to run this by the forum for some input on my "plan". So here goes.
- '02 LM7
- 4.8 flat top pistons compression @ 10.6:1
- 706 heads milled to bring compression to 11:1
- 228/230 .585/.585 112LSA cam from Jegs (for $290 BRAND NEW!)
- Valve springs and pushrods
- LS1 Intake and TB
- Hooker Cast Manifolds (rated by Hooker to 500 NA HP and almost required for steering shaft clearance)
Hoping that could get me to 375whp with a good tune.
Here is where I have some questions.
I might be able to get the heads ported and polished for CHEAP, is it worth the $? (I know the answer is yes but will the $/hp make it worth while?)
If I am having the heads machined, should I try and score some 2" intake valves and have the heads cut for them? (again $/hp and how much does something like this cost)
Lastly, is the trouble of doing a budget rebuild like this worth it? I have no trouble working on the car, I did the swap myself and love having an ongoing project. But will the ho be there after all the work or am I just wasting time for minimal gains.
Thoughts, criticism, ect? Goal here is something that will be reliable, make plenty of hp and torque for an old wagon, and still surprise people on the street and at the track.
I have a friend building an engine for his 240sx, and already dropped some 4.8 pistons in his 5.3. He needed to rebuild it to replace a bent rod so it made sense while he was in there. I suggested the pistons after reading a number of threads and seeing the thread and associated videos from AGearhead4Life. Poking around in the classifieds, I found a set of 4.8 pistons for super cheap and thought, "why not?"
Before pulling the trigger, I wanted to run this by the forum for some input on my "plan". So here goes.
- '02 LM7
- 4.8 flat top pistons compression @ 10.6:1
- 706 heads milled to bring compression to 11:1
- 228/230 .585/.585 112LSA cam from Jegs (for $290 BRAND NEW!)
- Valve springs and pushrods
- LS1 Intake and TB
- Hooker Cast Manifolds (rated by Hooker to 500 NA HP and almost required for steering shaft clearance)
Hoping that could get me to 375whp with a good tune.
Here is where I have some questions.
I might be able to get the heads ported and polished for CHEAP, is it worth the $? (I know the answer is yes but will the $/hp make it worth while?)
If I am having the heads machined, should I try and score some 2" intake valves and have the heads cut for them? (again $/hp and how much does something like this cost)
Lastly, is the trouble of doing a budget rebuild like this worth it? I have no trouble working on the car, I did the swap myself and love having an ongoing project. But will the ho be there after all the work or am I just wasting time for minimal gains.
Thoughts, criticism, ect? Goal here is something that will be reliable, make plenty of hp and torque for an old wagon, and still surprise people on the street and at the track.
07-17-2014, 05:46 PM
#2
Launching!
If the porting is done correctly for the application you couldnt spend better money imo. Such a thing as too much;problem is good portwork is never cheap. .
If it were me and just looking for torque id run a smaller stick,keep the truck manifold.So many ways to skin a cat when youre doing it "on the cheap".
Gears converter etc can give you more leeway or take from on internals.
Doesnt really give you the solid answer youre looking for but stuff to consider
If it were me and just looking for torque id run a smaller stick,keep the truck manifold.So many ways to skin a cat when youre doing it "on the cheap".
Gears converter etc can give you more leeway or take from on internals.
Doesnt really give you the solid answer youre looking for but stuff to consider
07-17-2014, 07:50 PM
#3
You can get a head start on heads by looking in this ad https://ls1tech.com/forums/parts-cla...retainers.html
If the heads need work done any way, I would go with the 2 inch valve and at the very least clean up the bowls in the heads. You can blend the bowls your self, save money, and get good gains.
I would also swap the pistons to up the compression as it will help with a larger cam.
It's tough to make 400 RWHP with a 5.3L NA. All those little things will help you get there.
The LS1 manifold isn't going to make you any more power, so unless you need it for hood clearance or just want it for the visual look, I wouldn't waste the money.
It can all be done on the cheap provided you start with good parts.
If the heads need work done any way, I would go with the 2 inch valve and at the very least clean up the bowls in the heads. You can blend the bowls your self, save money, and get good gains.
I would also swap the pistons to up the compression as it will help with a larger cam.
It's tough to make 400 RWHP with a 5.3L NA. All those little things will help you get there.
The LS1 manifold isn't going to make you any more power, so unless you need it for hood clearance or just want it for the visual look, I wouldn't waste the money.
It can all be done on the cheap provided you start with good parts.
07-18-2014, 10:44 AM
#4
You can get a head start on heads by looking in this ad https://ls1tech.com/forums/parts-cla...retainers.html
If the heads need work done any way, I would go with the 2 inch valve and at the very least clean up the bowls in the heads. You can blend the bowls your self, save money, and get good gains.
I would also swap the pistons to up the compression as it will help with a larger cam.
It's tough to make 400 RWHP with a 5.3L NA. All those little things will help you get there.
The LS1 manifold isn't going to make you any more power, so unless you need it for hood clearance or just want it for the visual look, I wouldn't waste the money.
It can all be done on the cheap provided you start with good parts.
If the heads need work done any way, I would go with the 2 inch valve and at the very least clean up the bowls in the heads. You can blend the bowls your self, save money, and get good gains.
I would also swap the pistons to up the compression as it will help with a larger cam.
It's tough to make 400 RWHP with a 5.3L NA. All those little things will help you get there.
The LS1 manifold isn't going to make you any more power, so unless you need it for hood clearance or just want it for the visual look, I wouldn't waste the money.
It can all be done on the cheap provided you start with good parts.
The LS1 is on there for hood clearance. I picked it up super cheap, and with the original plan for boost in a different car, the extra cash for an LS6 would be better spent else where.
What I am realizing is things are starting to add up, head work or used heads, gaskets, valves, machining costs, porting, most likely a custom cam to make it work together correctly. Thinking boost may be the answer after all. I can leave the engine as is, add a 70mm or 76mm eBay turbo and have a fairly reliable 500whp+ on pump gas, with most likely better street manners, and gobs of torque on tap when I want it. I am aware this will be more cash, but I think when the dust settles I won't be in search of more power, I will just be looking at how to harness the potential of the power I have, i.e. suspension, tires, rear diff
07-18-2014, 10:52 AM
#5
Don't run the 706 heads unless you want problems. Go with the 862 casting heads and port those and throw the 2" valves in. Its a great setup for your combo. A LS6 intake is a great addition if you can grab one.
05-16-2015, 11:53 AM
#6
If you are planning to boost it do not cut the heads. Leave them stock height. Add the valves, clean the bowls, and talk with Martin @Tick about a bump stick instead of the off the shelf. You can also get a package deal if you get hardened pushrods and springs from him at the same time.
I was just thinking of piston swapping a 5.3 because I plan to run nitrous but no boost.
I was just thinking of piston swapping a 5.3 because I plan to run nitrous but no boost.
