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I have started the process of building up a 5.3 for my daily driven 2003 Silverado RCSB. The engine I have to swap in has 150,000 miles on it, and it came out of a 2000 model truck. The engine in the truck now is an LM7 as well, and has 237,000 miles, so I figure it is on its way out anyway. The donor will be receiving a full rebuild, along with upgrades. Plans are as follows:
· Full rebuild using a WS6Store LS Engine Complete Rebuild Kit
· WS6Store High Lift Hot Cam w/ PAC 1218 Beehive Springs & Chromoly Pushrods
· Straub Bushing Trunion Upgrade
· LS7 Lifters
· GM FlexFuel Injectors
· Reuse the stock truck 3-Bolt Intake and port the stock 78mm TB
· Either ported 862 Heads (what are on the engine) or ported 243/799's
· Bore to 3.898 to make an iron 346
· Mid-Length Headers (I would go with long tubes, but the truck is lowered 4-6 and ground clearance is an issue)
· Cold Air Intake (obligatory)
I am shooting for 425 horsepower at the crank. (I think this is possible)
I have some questions though.
· Can all 5.3 iron blocks safely be bored to 3.898 or will I need to have the block sonic tested to be sure?
· Tech@WS6Store: is the rebuild kit available with flat top pistons instead of a stock style dish? Upcharge for this?
· Is there any real advantage to buying a set of 243 or 799 heads over using the 862 heads that I have now once ported? I know that the 862 has a smaller intake valve as well as a smaller chamber. Can they be made to flow as well as the better castings or are they just junk?
· Will the FlexFuel injectors do what I want them to and be easy for the tuner to work with, or would I be better off buying something like the 36lb FAST injectors?
I have just started disassembling the engine and plan to update this thread with photos along the way...I always enjoy reading well documented build threads from guys like of JakeFusion and Darth_V8r, so here is mine. It's not for an F-body, but this is by far the premier LS engine forum on the internet so I hope my build is welcome here.
This is the truck the engine will be in.
Last edited by BuschPerformance; 07-11-2017 at 03:38 PM.
Some have bored out to 4" and been fine, if it were mine I would go larger than 3.898 Edit: I don't recommend going to 4" I just mean there is more there you can bore above 3.898 and be safe, not much but a little.
Those wheels look good (and the truck does too) what are those?
With a cam and some headwork even minor 425 should be no problem
Last edited by 00pooterSS; 07-11-2017 at 05:30 PM.
4 inch on a 5.3l gen3 iron block? id say no on that. We have 3.898 and 3.908 but 3.910 is as much as i have and would go.
Our 3.898 and 3.908 pistons are flat top.
The flex fuel inj are easiest to tune and work with your factory connector so i would use them. The tables are as easy as copy from flex fuel tune and paste into yours for the 5 to 8 parameters needed
The 243 or 799s will flow better already and need only a good valve job even to make am better.
Ported its no contest, but do you really need it? That part is up to you!
The 243 or 799s will flow better already and need only a good valve job even to make am better.
Ported its no contest, but do you really need it? That part is up to you!
Whichever head I use, I will end up porting them, it won't add any cost on my end, as well as a multi angle valve job. So will a ported 862 do what I need? I hope so, because it would sure save me a lot of money. But if I'm missing out on 50-75 horsepower or something by not going to a ported 243/799 I'll have to reconsider.
Based off the same hot cam and ported 862 to ported 243/799 youd prob miss out on 20hp honestly. most change cams when they port and its hard to say exactly but 20 would be about max ported vs ported imo. Torque would be a little hard to say really. Maybe 10 to 20.
4 inch on a 5.3l gen3 iron block? id say no on that. We have 3.898 and 3.908 but 3.910 is as much as i have and would go.
Our 3.898 and 3.908 pistons are flat top.
The flex fuel inj are easiest to tune and work with your factory connector so i would use them. The tables are as easy as copy from flex fuel tune and paste into yours for the 5 to 8 parameters needed
The 243 or 799s will flow better already and need only a good valve job even to make am better.
Ported its no contest, but do you really need it? That part is up to you!
I wouldn't like it either and I didn't mean to recommend it, I was just saying I would go bigger.
Based off the same hot cam and ported 862 to ported 243/799 youd prob miss out on 20hp honestly. most change cams when they port and its hard to say exactly but 20 would be about max ported vs ported imo. Torque would be a little hard to say really. Maybe 10 to 20.
Imo the 862 will do what you want in ported form.
So in that case would you recommend a different cam for the ported heads? I still don't particularly want a stall converter.
Inside the knock sensor holes, yucky. The plugs were very brittle as well, both of those broke in the removal process.
Knock sensor out, I guess I won't be reusing these. Notice the standing water still in the hole.
Second hole, no better than the first.
The goop that fell into the valley from this, also I am beginning to notice that the previous owner of this engine did not change the oil every 3,000 miles.
This is why regularly scheduled oil changes are important.
Intake, valley cover, valve covers, and most of the accessories removed.
I am using this empty roll cart I had to store and organize the parts as they come out.
It's definitely a 5.3 now. The cylinder walls look excellent, and the piston tops aren't that bad at all either.
Other side also looks good. A couple of the lifters were very hard to remove though.
This engine has sat a couple of years in the shop, with the oil drained, but fully assembled. look at the fuzzy goop formed on the counterweights. I'm not sure how that was possible, but it shouldn't hurt anything.
What is nice about having the 862 heads ported you can mill them to 58cc for more compression. I don't think you can mill the 243's that much without running into problems.
What is nice about having the 862 heads ported you can mill them to 58cc for more compression. I don't think you can mill the 243's that much without running into problems.
The more I read into them, I think the 862 head is the best choice as well. I should be able to port 300 cfm out of them with a bigger intake valve.
What port volume/cfm would you go for? The TSP 862 CNC Stage 2.5 port is around 235cc and flows 308 @ .600 with a 2.02 intake valve, I was going to use a stock LS1 2.00 valve.
I have the block all stripped and ready to take to get cleaned. I ran into a question I hadn't thought of.
I have heard that you should never replace the cam bearings in an LS engine, because they are installed from the factory and then line honed through the bearings, so therefore the actual block's cam bore isn't necessarily straight, and upon installation of a new bearing in the bore, it will eat the new bearings nearly immediately.
The cleaning process would necessitate new cam bearings.
Does that mean that I will just need to get the block line honed before putting new cam bearings in? Or what should I do?
07-11-2017, 03:27 PM
LM7 Daily Driver Build 
