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Hey guys just imported a so called 5.3 LS to Australia upon opening it up turned out to be a 4.8 .The car will be boosted with either gt45 or 78/75 polished ported 862s I'm wondering what's a good cam choice the new btr hotrod or truck Norris or also the new sloppy best cam? Or if anyone else can recommend something better? The car is light at only 2400 pounds also running a 4l80 but only a weekend fun car !! Any help appreciated 🙂
If it's mostly street with occasional strip the @Summitracing 8728R1. It'll have great driveability and would pair with a 3000-3200rpm stall. The 8720R1 might also work, since the car is very light. Being bigger, it would be better suited if it sees more regular drag use. Probably bump up to a 3400-3600rpm stall.
Thanks formula68 appreciate it would it be possible to see around that 600 HP mark or possibly a little more ? I believe with the car being so light 600 HP will see some fairly good 1/4 times I'm also doing an upgrade of fuel pumps injectors as well as bigger fuel lines to.
78/75 over the gt45 for sure. The GT45 is a dinosaur... heavy, huge, and performs poorly all around. Honestly a T6 S475 (or knock off s475) would be better than either of those IMO. T4's don't belong on any "drag" LS IMO. As long as you have the converter and cam setup correctly you'll make more power per pound with less back pressure on the larger housing. "Spool up" isn't an issue if setup w the correct parts in my experience.
Summit STG2 8706 would be my pick. Worked REALLY well in my 4.8. The 4.8 wants to rev in my experience. Should plan on 7k minimum and you have to cam it for that rpm. The cams you listed are too small IMO and focus on a low RPM window the 4.8 will never shine in. My super mild SBE 4.8 with stg2 and S480 in my 3100lb car was going 8.70's 7300ish RPM (and thats low) shift point.
At 2400lbs you could hit those numbers with a S475 easy IMO. Just depends what you are trying to build. The converter is also key. Go loose... REALLY loose. Esp at 2400lbs. You won't hit any of the rated stalls on the cheap converters. Unfortunately you almost need to spend money on a good converter for a combo to work well. I run the 9.5 PTC 20-5. Which should stall well over 5k. On a 2400lb 4.8 you'll be lucky to see it flash to 4k. That converter street drove great and I saw less than 5% slip up top. Also run the same converter in my 2400lb Model T.
Thanks for the insight forcefed86 !! That's a nasty little 4.8 how did you find it driving on the street with the convertor mate ? It's good to get this info from guys that have run combos that work it makes me pretty excited to see what it can do ! And yes the car is light so should run some good times hopefully although tire size isn't big that I can fit under the guards so getting that power down will be interesting 😂
It was great! Never heated up, and would smoke a 28x12 slick rolling into the gas with any decent amount of boost in it. I had to take power out. Ran 7lbs (gate pressure) to 50mph or so then slowly ramped boost up to 19-20lbs by 100ish mph on the street. At the track I’d be all in boost wise but pull timing at the TB release over 2-3 seconds to keep it planted. You don’t need much power at that weight. My 2400lb Model T is an SBE cam only 5.3. 5.50 car @ 128 on 14-15lbs. (no intercooler).
But getting a PTC converter may be an issue. I hear they are back logged quite a bit, then there’s the whole international shipping thing. Can’t imagine its magic, I’m sure any good local converter company can take the Nissan 9.5” core and put a decent 20-5 stator in it. The motors don’t make diddly down low, so you need a converter that’s rated at like a 6k stall. At 2400lbs with a 4.8 you’d be lucky to see 3800-4000 on motor I’d bet. The thing with PTC is somehow they get them nice and loose down low, yet still maintain 5% or less slip up top. Which never happened in the “old days” when I was racing turbo cars. If they were loose down low I’d see 16-18%+ slip up top.
Just wondering also is it necessary to put forged pistons/conrods in if I'm spinning high revs surely the conrods will fail with boost as well ? I do know the bottom is strong but with the 4.8 revving like it does just wanted to know whilst I have it pulled down to gap the rings
Just wondering also is it necessary to put forged pistons/conrods in if I'm spinning high revs surely the conrods will fail with boost as well ? I do know the bottom is strong but with the 4.8 revving like it does just wanted to know whilst I have it pulled down to gap the rings
No. factory gen4 rods/pistons are more than capable of 7500rpm. Esp. for moderate boost. Factory bottom end can handle all a 78/75 will throw at it... or a gt45. Guys here in the states are pushing 8400rpm and 45+psi on a factory 4.8/5.3 bottom end and have been in the 4’s with heavier cars than yours. Original rod bolts, bearings, rods, pistons, rings, heads valves etc…
If its a gen3 motor (2004 and older) It has weaker rods. You want to limit it to around 600-700 crank hp IMO 7000-7500 is ok. you just need decent push rods/springs/lifters.
If you don't run heavy boost below 4500 or so it will live a lot longer and be much less likely to spit a head gasket. Use the cam and converter to avoid making a ton of power in that area. Ring gap will depend on the fuel used and intercooling.
I was running mid 9's on a gen3 motor at 3100lbs for about a year. Hundreds of passes. I pushed it to an 8.9x's at 153 and blew the engine the next pass. That was an S475 turbo and ls9 cam on a 5.3 with 317 heads. A combo everyone said wouldn't work well. Less base compression the better if you are new to tuning IMO. Ls9 cam is also dirt cheap and limits power below 5k. Which helps the SBE setups stay alive. Its a great cam for the $. IMO you want to target 5k-7500 for power production with all your parts. Make sure you can stall to at least 4k.
We wouldn't hesitate to put the SUM-8720R1 in this 4.8. Check out the Sloppy stage 2 vs. the world video from Richard Holdener below with a 4.8 as the test mule. He compares numerous "turbo" cams mostly in the stage 2 realm along with our smaller 8720R1 "truck" cam. The 8720R1 made right near the same peak hp as other cams. More importantly, it made more torque under the curve. The 8720R1 would be daily driver friendly but then not miss a lick at the track running it out to 6,500+. You can see Holdener ran it out to 7,000 in the video.
Sloppy stage 2 vs. the world video. See 16:30 to 18:45 in the video to see our 8706R1 and 8720R1.
Not harping on summit’s response above, I’m sure that cam would work well. Its not exactly “small”. Just wanted to say the thing I don’t’ like about Holder vids is he doesn’t race the motors. And always preaches about “low end”. I’ve built dozens of turbo LS motors and I can tell you the last thing any turbo LS needs is more low end! At least not in weekend warrior trim with a healthy converter. I’ve run the baby cams that make tons torque under the curve. Super tight LSA cams similar to the “Truck Norris” that made the 4.8 darn right snappy out of boost… but it didn’t perform near as well out at 7500 where these motor want to be IMO.
The OP is setup in a 2400lb drag toy. IMO He shouldn’t care about torque under the curve. He will be doing all he can to get any sort of traction on the street, I’ve been there… many times. At the strip, you want to be at 4k+ on the trans brake and never see below 5k once you let go of that button. The small bore motors like RPM. Shifting them below 7k usually causes them to fall on their face and lug back down in the danger zone where pistons/rods/HG are more likely to be damaged.
And I’m not talking about all out drag cars. This is SBE budget weekend hot rodder stuff.
Last edited by Forcefed86; Nov 9, 2022 at 01:32 PM.
Thanks forcefed86, I've just ordered pac springs retainers etc for the heads will be getting the heads ported and polished I'm going to run the 862s for now .I have wondered if the valve upgrade is necessary as well on the smaller engine ? My engine is the older gen3 block so I've been looking at getting rods and pistons possibly for it doesn't seem to be to many around for the 4.8 though if I want to keep it together it's money well spent if revving at high revs I believe
. Also looking at intakes I guess if it's wanting to rev the truck intake isn't best choice for that application that another thing I'm looking at possibly the ls6 one would better I've already got the LS2/3 waterpump and relocation kit for the setup of different intake also.
All the factory parts are underrated IMO. Pistons/rods/valvetrain… Including the 862’s. That’s enough head for mid 7’s at your weight. Even the gen3 rods will take your setup past an 8.50 cert. Assuming you don’t lug the motor down below 6k I’ve seen 1000whp out of gen3 4.8’s.
The factory gen4 rotating assy is matched well the factory block. Putting a badass rotating assy in a stock block makes little sense to me as the block is now your weak link. Depending on how hard it is to get engines, I’d just play with the factory long block at first. Keep it simple. You can make every bit of 600whp with a cam and boost. At 2400lbs that will be damn quick! As I mentioned at only 15lbs I was going 5.50’s in my 2400lb setup. And that’s without an intercooler. So its down on power a bit.
Im spoiled here since engines are a dime a dozen. So it makes no sense to me to run any aftermarket parts for my ET goals and budget. In my case the OEM machining is better than anything I’d get from local machine shops. Not to mention down time and $. If it’s costing you thousands for a motor, I can see how you’d want to put good parts in it. I’d still suggest holding off and playing with the factory long block for a while. Work out all the bugs, etc. Getting the car done is half the battle. You can always build the motor after you blow it. At that point things like aftermarket valves are always good insurance... but not needed IMO.
4.8 parts aren’t popular. So you likely won’t find aftermarket 4.8 rods cheap. A more economical route would be to source a 5.3 or 6.0 crank and build a standard stroke 5.3.
perfect forcefed86 it's nice knowing someone experienced with these engines I'm thinking along the lines of around the 550 600 HP with that car being light and try and keep some longevity in it , which I believe with right convertor and gears should make a quick car.The guy importing these engines is getting good $$ I paid 7k for the 4.8 plus a 4l80 mated up with a standalone wiring done on factory ecu definitely don't want to blow up to early haha .The stock set bottom end then should be ok at the 600 HP mark then although an engine builder down here believes the revs would kill the rods more than the power ? I've heard the4.8s are very strong and from what you have said backs it up ! So I'm thinking I could just do what you said intially good size cam good convertor matched and around that hp mark see how it goes !!
Def don’t overcomplicate the motor. That’s the cheap/easy part. Focus on a good trans/converter/ECU/fuel system. Accidents happen, but if the factory long block is healthy, it will do what you are wanting for quite a while with a good tune and supporting parts. 7k is a breeze.
Won’t say your tuner is 100% wrong. RPM is hard on things… But I’ve run a TON of these SBE motors and he needs to look more at cylinder pressure. Pressure peaks at pk torque RPM. Then falls off to redline. Add boost and the pressure peak skyrockets. Cylinder pressure is what crushes the ring lands and bends rods. Even if you don’t detonate, you can easily bend a rod by short shifting and dragging the RPM down near pk TQ at big boost. By keeping the RPM up and being as far form PK TQ RPM as possible, you are actually easier on the motor. IE you see less peak cylinder pressures. Light weight setups help a ton as it puts less load on the motor. Same with a lot of gear.
as far as intakes go, the ls6 and the latest model truck intakes are pretty similar. All less than ideal for 7000rpm but not horrible and will still work. The newer gen truck intake (TBSS) Or the LS6 would work the better, but prob not worth your cost VS aftermarket. If you are going to pay out the nose for OEM anyway. Might look into the cheapie short runner sheet metal intakes. They perform poorly when compared to stock from 5500 and below. But this can be to your advantage, since you want to limit power down there anyway. Above 6k they do outperform the factory manifolds. Then there are all the cast aftermarket long runner manifolds to consider. Holley edelbrock etc…
Ug! That’s crazy! I regularly pay $400-500 for a healthy gen4 4.8. I’m a fan of aftermarket ECU’s and Glides though so never bought them as an “assembly”. Those are about $1200-1500. That said, If you did munch the motor, you likely won’t hurt the crank or block. And it will all need torn down anyway if you stuff an aftermarket bottom end in.
ID get the factory long block in the car and running. You may not need or want more power. I think you’ll be surprised how quick 600whp is at 2500lbs. Want to say I was going 9.3x @ 142 on gate (6-7lbs). Its pretty sketchy in this rig! Enough that I stuck to 1/8th mile after that! This car is almost exactly 2400 with me in it an a full tank.
Last edited by Forcefed86; Nov 9, 2022 at 03:50 PM.
Thank you for explaining that in terms that is easy to follow forcefed86 I'm going to just follow your advice go with the cam you suggested and convertor choice and get a good tuner to tune the car.Btw your tmodel.looks trick and if I can get solid numbers close to that I'd be pretty darn happy with mate cheers 👌
Hey forcefed86 I did re read it all again and noticed you spoke about ring gap with grades of fuel ,as I will be using 98 octane or E85 what size gap would be appropriate ? Thanks again
Generally go .002 larger on 2nd ring. Believe they have tested it and with worn out factory rings the power gains for going tighter vs looser are barely noticeable. Most of my 100k+ motors have around .022 anyway, so I leave them. Never butt a ring on e85. Many go .028 for piece of mind. That seems excessive, but if you are talking a couple HP difference… no reason not to go big. I did .028 my non intercooled motor. I max out the IAT sensor at 250+ before the 1/8th on big boost. Never butt a ring.
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4.8 turbo/ cam/ convertor help 
