Lm7 5.3 rebuild
Thread Starter
Teching In
Joined: Apr 2013
Posts: 6
Likes: 0
Lm7 5.3 rebuild Goingto do my first rebuild, found a lm7 5.3 engine with iron block, the heads are 706 castech heads that had at least one bad valve. The heads did not leak any water that I understand is a common problem. The engine hade bad compression on one cylinder, and probably the valve was stuck.
It didnt have any intake, harness or pcm.
-what heads should I buy?
-can I use a used ls1 intake? Or a newer intake?
-camshaft?
I probably put the engine in a Chevelle and use it as a driver, not for racing. Looking to get around 400-450hp
Does anyone have a list of parts from a similar rebuild?
It didnt have any intake, harness or pcm.
-what heads should I buy?
-can I use a used ls1 intake? Or a newer intake?
-camshaft?
I probably put the engine in a Chevelle and use it as a driver, not for racing. Looking to get around 400-450hp
Does anyone have a list of parts from a similar rebuild?
Teching In
Joined: Oct 2015
Posts: 34
Likes: 0
From: Midland, TX
You can switch to a LS1or LS6 intake, this would be mostly for aesthetic or clearance purposes though. If you go that route you will likely need to buy spacers and go with an F body water pump out and rearrange some pulleys. This is the route I am going (slowly).
There are others here who are much more well-versed on the heads so I will leave that to them.
What transmission are you going to run? A lot of factors involved in choosing which parts to assemble it all with. I am going to shoot for the same sort of hp numbers you are looking for and you can attain them without doing anything crazy really, a cam and tune will get you very close to that even with stock heads.
A good place to start with the cam would be something like the 228R setup from Texas Speed, good street manners but a nice sounding idle and great performance still. There are a ton of articles available from car craft and hot rod and the like that compare a number of cams on the dyno and there are some easy gains to be had just camming and tuning these engines.
There are others here who are much more well-versed on the heads so I will leave that to them.
What transmission are you going to run? A lot of factors involved in choosing which parts to assemble it all with. I am going to shoot for the same sort of hp numbers you are looking for and you can attain them without doing anything crazy really, a cam and tune will get you very close to that even with stock heads.
A good place to start with the cam would be something like the 228R setup from Texas Speed, good street manners but a nice sounding idle and great performance still. There are a ton of articles available from car craft and hot rod and the like that compare a number of cams on the dyno and there are some easy gains to be had just camming and tuning these engines.
TBSS intakes work really well and they can be had for very reasonable prices.
I'd go with 799 or 243 casting heads. They are identical visually and dimensionally, but cast in different foundries. I'd mill them back to the factory 5.3 combustion chamber volume of 61cc to keep factory compression ratio.
A lot of people will also swap junkyard flat top L33 pistons in lieu of the dished LM7 pistons. This would also be a step in the right direction to making more HP and torque if you wished to go that route.
The factory 5.3 cam is 190/191 duration with barely .470" lift. Anything in the low to mid 21x intake duration range and high 21x exhaust duration range with .560"-.580" lift would be a huge upgrade if you're looking for a driver.
I'd be glad to help with the camshaft selection and I can be reached for any other help pertaining your build at the phone number and email in my signature.
Hope this helps!
I'd go with 799 or 243 casting heads. They are identical visually and dimensionally, but cast in different foundries. I'd mill them back to the factory 5.3 combustion chamber volume of 61cc to keep factory compression ratio.
A lot of people will also swap junkyard flat top L33 pistons in lieu of the dished LM7 pistons. This would also be a step in the right direction to making more HP and torque if you wished to go that route.
The factory 5.3 cam is 190/191 duration with barely .470" lift. Anything in the low to mid 21x intake duration range and high 21x exhaust duration range with .560"-.580" lift would be a huge upgrade if you're looking for a driver.
I'd be glad to help with the camshaft selection and I can be reached for any other help pertaining your build at the phone number and email in my signature.
Hope this helps!
Staging Lane
Joined: Dec 2013
Posts: 85
Likes: 1
I have a 2003 LM7 325 cid engine that, aside from a few shiny things, is pretty much bone stock.
Mine came with, and I am still using the 862 heads.
In regards to intakes, if you put any faith into the test and reports you find here on the forum, the truck intake manifold is one of the better intakes available, in your options available from GM, but second to the LS-6 intake. The TBSS is also suppose to be better than the standard truck intake, but also behind the LS-6.
In original format, the truck intake is ugly as hell. If you haven't seen any of the smoothed truck intakes, there are several threads, but I think that this is the best thread:
https://ls1tech.com/forums/conversio...k-intakes.html
My LM7 is installed in my SUV, a 1970 International Harvester Scout. I wanted to preserve bottom end torque and have the (exhaust) reliability that comes with exhaust manifolds for my specific application, and ended up going with LS-2 exhaust manifolds from a Cadillac. Pics below are after they came back from ceramic coating. My only regret was that I didn't go after them with a die grinder first. I still think that the exhaust manifold look great though.
Mine came with, and I am still using the 862 heads.
In regards to intakes, if you put any faith into the test and reports you find here on the forum, the truck intake manifold is one of the better intakes available, in your options available from GM, but second to the LS-6 intake. The TBSS is also suppose to be better than the standard truck intake, but also behind the LS-6.
In original format, the truck intake is ugly as hell. If you haven't seen any of the smoothed truck intakes, there are several threads, but I think that this is the best thread:
https://ls1tech.com/forums/conversio...k-intakes.html
My LM7 is installed in my SUV, a 1970 International Harvester Scout. I wanted to preserve bottom end torque and have the (exhaust) reliability that comes with exhaust manifolds for my specific application, and ended up going with LS-2 exhaust manifolds from a Cadillac. Pics below are after they came back from ceramic coating. My only regret was that I didn't go after them with a die grinder first. I still think that the exhaust manifold look great though.
Staging Lane
Joined: Dec 2013
Posts: 85
Likes: 1
another thread commenting on the truck intake, assuming you have the room.
1s1 < ls2 < truck intake < ls6 intake .OP don't go crazy on the porting ,the walls are thin .and consider a BBK intake if you want more power .they go for $300 .
https://ls1tech.com/forums/new-ls1-o...l#post18007233
1s1 < ls2 < truck intake < ls6 intake .OP don't go crazy on the porting ,the walls are thin .and consider a BBK intake if you want more power .they go for $300 .
https://ls1tech.com/forums/new-ls1-o...l#post18007233
Teching In
Joined: Oct 2015
Posts: 34
Likes: 0
From: Midland, TX
There are a lot better places to put the money than into a 102 intake for what your desired outcomes are. There's nothing at all wrong with that intake, just way overkill for what you're trying to do.
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I wouldn't waste your money on a Fast 102. Get the TBSS intake I mentioned and a NW cable driven 90mm throttle body which I can get for you as well if you like.
Richard Holdener did a test not too long ago where he tested IIRC 30+ LS intakes on the same engine. The TBSS intake came within 5 peak hp of the Fast 102 and made more torque up to 3500rpm IIRC. I believe they made within 1-3tq of each other at peak torque as well.
So, for the money the TBSS is a very underrated intake manifold that is very cost effective.
Agreed 100%!!!
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Thread Starter
Teching In
Joined: Apr 2013
Posts: 6
Likes: 0
Thanks for all the inputs and suggestions.
I will skip the Fast intake as you suggest.
If the block is ok after the visit at the engine shop I will put new rings on the pistons and change the bearings in the block.
I also found a used Ls1 intake for 100$, I think I will go for the smother "look" under the hood. I also thinking of the ls6 intake, alot of them on ebay both aftermarket and used.
Also found 243/799 rebuilt heads on ebay. Also found this heads on ebay:
http://www.ebay.com/itm/141800051570
What do you think about them?
Then it comes to the cam, Smallwood can you give me a qoute and suggestion on the cam?
Will use the car on the road, and with a little torq at the red light.
Am I on the right way now?
I will skip the Fast intake as you suggest.
If the block is ok after the visit at the engine shop I will put new rings on the pistons and change the bearings in the block.
I also found a used Ls1 intake for 100$, I think I will go for the smother "look" under the hood. I also thinking of the ls6 intake, alot of them on ebay both aftermarket and used.
Also found 243/799 rebuilt heads on ebay. Also found this heads on ebay:
http://www.ebay.com/itm/141800051570
What do you think about them?
Then it comes to the cam, Smallwood can you give me a qoute and suggestion on the cam?
Will use the car on the road, and with a little torq at the red light.
Am I on the right way now?
Last edited by Bosing; Feb 6, 2016 at 08:53 AM.
Cam would be 400.00 ground on a 5150 core and 450.00 ground on a 8620 core, both ground by Cam Motion.
Shoot me an email to the address in my signature and I'll be glad to give you a recommendation.
Shoot me an email to the address in my signature and I'll be glad to give you a recommendation.