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I've got an '07 LQ4 sitting on my shop floor. I want to build a replacement for the 5.3 that's in my car now. I've built SBC's and a couple BBC's in the past, but this is my first dip in the LS pool. Let me know what you think of my plan, and give me ideas.
I'm going to build a 408ci short block; forged and balanced. My goal is to put together a stout NA motor that is full boost ready, run it for a year or so, work the bugs out, then add a procharger later. Probably shoot for about 10:1? I don't want to run past 15 psi.
What rotating assembly should I be looking at? Piston specs? I have a set of cast 799's on the 5.3, and a set of bone stock 823's on the 6L. Should I have either one of these worked up (sent out for porting etc)? Or should I go aftermarket? Of course whichever way I go will determine my intake options. What are the best options for cathedral intake? Rec port intake?
Of course there's the "what cam" question.
I'm not looking to build a full race monster. Just a pump gas, weekend cruiser that's got the power to match the looks. I know there's no such thing as a "best of both worlds" motor.
I don't want to start gathering parts, paint myself into a corner, and waste money going in the wrong direction.
Build me a motor.
Thanks in advance.
If you’re looking for “budget” and boost, there really isn’t much need to stroke the engine. As is a sbe is pretty good to go for 1k hp.
Gen 4 rods are better, but not required.
Open up the ring gaps, run the 823 heads, get better valvesprings, a supercharger cam, larger injectors, and add boost till your at the hp goal.
skipping the n/a build will let you have a boost motor from the get go…
I know it would be cheaper to skip the short block rebuild. But...
A couple years ago, I introduced my 75 yr old dad to YouTube. He's built a lot of SBC's over the years; used to do a lot of hotrodding and bracket racing. Now at 77, he said he wants to build 1 more/last motor. That's why I'm going with a 408ci. My shop, tools, and wallet. Dad gets to assemble his last, best "small block". Pops offering guidance (circa '91) while I reassemble after paint.
In that case I’d look at one of the new l8t cranks, 3.86” stroke. They are forged, center counterweighted, and best of all cheap.
The slightly less stroke would help with longevity. (cyls are short and can upset piston at bottom when skirt drops below sleeve.)
If your also willing to go custom 1.185” piston, it would allow for the top ring to be lower (better for keeping away heat from boost)
shelf pistons are still available if you go with a 6.2” rod and 1.100 ch.
6.250” rod and a 1.065 piston also works.
Id consider drilling the mains for piston squirters. There is a kit out there that has the nozzles and fixtures for drilling. The oil squirters will help keep the pistons cooled.
This can also assist in permitting a higher than normal comp ratio. a higher cr would be beneficial to keep from having a lazy motor when out of boost.
Pinning the mains, arp stud everything, crank scrapper, Johnson tie bar lifters, and a good oil pump would round out a great short block meant to be beat on.
I really appreciate the info. If I (we) build this motor properly, it should be the last motor I ever put in it.
I bought this car 35 years ago and at that time couldn't have conceived of having a street streetable, 1k hp at the crank mill in it.
I'm sure I'll have more questions in the future.
The 2 most important parts are
1. use quality parts
2. have quality machine work
The 2nd is the most important actually.
For pump gas 10:1 is fine for na and boost.
The idea of the cyls being short and to not use a full 4" crank is not correct though. Many many companies have 408s running for years without issue. Keys there are the 2 reasons above. The tune itself also make a big difference.
All parts prices have gone up in passed 3 years with this passed year being a big increase, so shopping around but also comparing apples to apples as far as parts in kits go is important and encouraged.
I am actually building the same thing right now. I went with a Manley rotating assembly but I am not sure if I am going with the 4cc flat tops or the 10cc dish pistons. I plan to stay NA and I am trying to get about 11.5:1 static CR and keep the dynamic CR around 8.6-8.7. I am going AFR 230cc cathedral port heads and looking at the comp cams 235/245 .621/.624 cam. I am hoping to make 625 crank and 500+ RWHP. Good luck with your build.
id say use stock crank, and summit racing pro LS .30 over forged piston/rod kit (prolly around 10.5:1 or so) and youd have a nice 370cu short block to start with. if your going procharger later on the cubes will be fine, the money you save on reusing the crank you can put towards some good heads. just an idea for you.
I've found 2 machine shops. 1 is 6 hours away, and probably pretty good. The 2nd is 15 hrs away and I'm sure top notch. Hopefully the pro shop isn't out of my price range.
I know this project isn't going to be cheap. But if I do it right, it'll only hurt once.
If I use stock cast heads, with spring/rocker upgrades to begin with, which should I use? 799's or 823's? (I already have the 799's set up) Obviously this will determine the intake. LSXR 102 or Performance Design LS3?
This is a 66 SS Chevy II with all Church Boys suspension, 4-link, coil overs, tied sub, DSE mini tubs, etc. But I'm having to start from the basics on the mill and trans. What about ECM suggestions?
The 5.3 that's in it now was running a little warmer than I liked, so I just picked up an Entropy ls swap radiator with 1 1/4" tubes and dual fans. Hopefully that'll work.
That ‘07 6 liter should be an LY6. I had an ‘08 in my Chevelle when I first built it. 3 engines later it’s a 434, with ls7 top end. I get bored easily…
Anyhoo, that engine has good rods in it, and actually makes good power stock. Your basically an intake, headers, and a camshaft away from 500hp. Yes, it’s really that easy. It’s a VVT engine, that you’ll likely want to get rid of, unless your a tech nerd like me, and just want to play with the tech and see what it offers. Not a lot of VVT camshaft options left these days, so the choice is yours. I’d keep the square port heads if your for sure going blower later. Lots of blower options for those heads. Don’t waste your money on the forged stroker if your going blower also. That bottom end can hold 1000 all day for a street car and will last forever as a cruiser with an occasional romp and stomp, like we all do. The Holley electronics are taking the world by storm currently and are very tuner friendly, just an FYI. Oh, and Welcome to LS1Tech!
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LQ4 Build ideas 
