When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I recently had an LS3 block machined for lifter bore bushings up at Weston Machine and was going to just assemble it as is with new pistons, bearings ect ect.... But I want to build a 427 with it now. My local shop here in Southern MD quoted me $2508 for the sleeve job on it. (nothing fancy, just normal flange sleeves) This engine is for my 96 K3500 restoration project so the more displacement the better. (Its got a stock L92 in it now with piston slap that'll wake the dead) My question is how much will the stock LS3 heads affect the larger displacement? I can have Katech run a CNC program on them, but the valve will be the same. This engine doesn't need to produce max power numbers, it just needs to be torquey and healthy... occasionally pull a 25' boat or car trailer. Will the heads be a real issue, or does it just leave numbers on the table that I'm not concerned about? Also, does the sleeve job sound right? Is it safe to sleeve an LS3 block in all 8 holes with normal, non-interlocking sleeves? I've never had this done before. The only 427 experience I have is my 2015 Z/28, and it came like that. Repaired lifter bores el stock 821s
Sleeving an Ls block is not easy and if you want to go through the process you should only send it to Steve @ RED. The Ls3 heads will definitely choke up a 427 and you would be better off getting a set of used aftermarket Ls7 heads (not gm Ls7). A set of high flowing heads and a small cam can get you high 500’s to the wheels and be very reliable.
Sleeving an Ls block is not easy and if you want to go through the process you should only send it to Steve @ RED. The Ls3 heads will definitely choke up a 427 and you would be better off getting a set of used aftermarket Ls7 heads (not gm Ls7). A set of high flowing heads and a small cam can get you high 500’s to the wheels and be very reliable.
I assume that's Race Engine Development. As much as I'd love to send him my block, I'm almost certain his services are not in my budget. A buddy of mine recently had his LS3 built into a 427 by TSP, that long block alone cost him over 16k. (granted that's including parts and assembly) I'm trying to put together a 427 for less than 5k including machine work. RED is in Oceanside and I'm in MD. Crating a block and shipping is gonna kill me by itself. My local machine shop is Heard Precision Machine LLC, he's pretty knowledgeable and honest. I don't know if I have a better option in my budget.
427 long block for less than 5k is a tall order, don't think you'll get there. Using that budget, I'd use your LS3 block as is, invest in heads, exhaust, and truck cam and go that way.
427 long block for less than 5k is a tall order, don't think you'll get there. Using that budget, I'd use your LS3 block as is, invest in heads, exhaust, and truck cam and go that way.
Well I already have everything picked out for my rotating assembly, and with the parts I already got to put the LS3 together as is, I only need the machine work for $2500 and the rotating assembly for $1980. I already have bearings, gaskets, hardware, cam, lifters, springs.... Its JUST the short block really. The heads can stay the same if all I'm loosing out on is a little top end. I just wanted to make sure it wasn't going to be a reliability issue.
the stock ls3 heads will be just fine, and support a lot of power unported. on the big ls3 head test, ported ls3 heads were only up 30 hp over stock on a 468 ci engine.
Steve is going to charge roughly the same to sleeve your block.. I believe its around 2400-2600 to sleeve a block from him. Shipping will be the only killer.
Steve is going to charge roughly the same to sleeve your block.. I believe its around 2400-2600 to sleeve a block from him. Shipping will be the only killer.
I would just do a 416 and no resleeve with either the stock heads or explore porting them/other options if you want to spend the $.
We built a customer a 416 with stock LS3 heads/intake 11:1 compression with 91 and a BTR stage3 or 4 stroker cam that made 560rwhp thru a T56 Magnum and 335/30/18's out back. It did have an aluminum flywheel and RST clutch that was around 38lbs. The headers were mid length and crappy crush bent 2.5" exhaust. He ended up getting the heads ported with ported and rod modded LS3 intake with a custom cam and LOTS of tuning on 91 octane with same headers but dual 3" mandrel bent exhaust where it made close to 600rwhp. Between the labor to R/R the heads, change the cam, new exhaust and tuning plus all the head work he put another $4-5K into it to gain 30-40rwhp.
The LS3 heads on a 427 will be fine. As an LS7 owner, I can tell you some C6 Z06 owners have put LS3 heads on their LS7s. They may not have the peak power of the LS7 heads, but I'll bet they'll have better torque up to 5,000 rpm, which will be desireable in a truck. IDK if I'd have them ported, or not. One thing for sure, and that is, from a reliability standpoint, the LS3 heads are superior, period.
gnx7 makes a good point on the 416. SOTP youll never miss the 11 cubes. Actually, a well set up 416 will put out a far better power curve than a so-so set up 427.....
I would just do a 416 and no resleeve with either the stock heads or explore porting them/other options if you want to spend the $.
We built a customer a 416 with stock LS3 heads/intake 11:1 compression with 91 and a BTR stage3 or 4 stroker cam that made 560rwhp thru a T56 Magnum and 335/30/18's out back. It did have an aluminum flywheel and RST clutch that was around 38lbs. The headers were mid length and crappy crush bent 2.5" exhaust....
Is there a build thread or dyno sheet posted somewhere for this?
This is pretty much what I'm preparing to do.
Thanks
I ended up sending my block out to RED in CA per @Ls1Rx-7 recommendation. RED is the only one listed by Darton as an installer for the sleeves I need on their distributor list. I just don't want anything to go wrong as I cannot afford a machining mistake on my budget. The shipping turned out to be 1k there and back, so I'll be over 5k because of that but I'll just have to eat it. I thought I'd leave my parts list here to see what people think. They're Summit part numbers. Keep in mind, this isn't a max effort build; it's going in my GMT400. I was originally going to use an Eagle crank, but I've been reading around and a lot of people seem to trust the Summit brand more than the Eagle stuff anymore. Eagle is a couple hundred cheaper, but I want to try out something different. I already have all the other gaskets, hardware and a cam. I just need to save some more for a set of Johnson lifters now that I have to blow 1k on shipping. These parts put my static compression right at 10.57:1, so no problems with pump gas anywhere. If this build goes well, I'll do another with Callies parts for my 69 Chevelle after a while. Thanks for the help.
I had RED sleeve a LS2 then I stroked it to 427 cubes. I bought the block from a friend in CA so no out bound shipping. Steve shipped the bare block to me in a big plastic tube. No crate. Came UPS.
I used a Manley stroker kit. 24 tooth reluctor. The 24 tooth reluctor allowed me to run one computer since I was running a built 4L60E.
Diamond forged pistons. 220/225 cam. LS3 heads. 500 rwhp. Drove great. Per my tuner it was super easy to tune. I had it in a 67 Nova and it would smoke the tires at 45-50 mph. It was a hoot to drive.
Good luck with your project.
I’m in north Georgia and it’s runs me about $950ish to ship blocks to RED and back. That’s round trip, both ways shipping. I just shipped a RED sleeved block to Seattle and it was about $500 also, one way. It’s the insurance that costs so much. I insure the sleeved blocks for $5k.
You'll be glad you sent them to Steve@RED. His mistakes are damn few to none! Ive talked to him several times, and had him do a wet sleeve 427 on an LS1 block in 2005. Superb workmanship. Steve is the kind of guy that if and when he does make a mistake, he'll catch it, and correct it before it ever leaves his shop......
01-15-2024, 11:28 AM
LS3 427 With Stock 821 Heads 
