Lr4/lm4/lm7 build head/cam questions.
 

Long time lurker, first time poster, glad to be here😊
Firstly, yes I used the search function before I decided to make this thread😂 but after sorting through 19+ pages of results, I couldn't quite find the answers I was looking for.

I'm building a moderate-high rpm mouse(it'll live at 6500-7000). I've got a 5.3 with 706 heads, but I've got access to an early 4.8 if I want it. I'm trying not to open the bottom end, but I know I'll need to do arp rod bolts for the engine to have any kind of life at these revs and that some 5.3s rods will take arp rod bolts and that some won't; I'm hoping mine will but that's not my question.

What I'd like to know is, has anyone figured out what the max duration that an lr4/lm4/lm7 will tolerate from a .600 lift cam is, before piston/valve contact becomes a concern?

I might be way off, but I'm guessing the dished 5.3 pistons won't make a difference on valve clearence, since the intake valves are so close to the cylinder walls, but I'll leave that to the experts on here.

Thanks in advance to any of you who have answers👍🏼

I've got a junkyard 2002 4.8 with 706 heads (never been off the motor) that I've been beating the snot out of for over three years now in my daily beater and I take it past 7k all the time. Don't be scared rev up a stock bottom end and don't waste your time with silly useless upgrades like rod bolts on a worn rotating assembly that will likely cause you more problems down the road. Mine is just literally a used cam and springs only and it's living the tourtured life just fine. Tell us what you are trying to do and we can give you more input on how much cam timing you will need and if anything other than a cam and springs would be needed above that.

Nice! The engine is already getting an intake more suited to make power up high, dual valve springs, ls7 lifters, a trunion kit, upgraded pushrods, an ls2 chain etc and a cam, but I'm undecided on the exact cam, due to the above-stated question. The engine will be going in a drift car, but I'm not concerned about torque with this engine; I want it to be a screamer. So it'll be running at idle and then high-revs for 90-ish seconds at a time, then basically back to idle.

The idea was to get it to live at 6500-7k with as little cash as possible and without taking the bottom end apart. It's only got to make it through maybe a season or two depending on how many events I can manage a year and it won't be spending much time on the street, if any.

Hopefully that answers your question👍🏼

Honestly, a single beehive spring will be fine, take your pick or you could forgo all the stuff you are planning to buy and just get a little bit lower lift cam (higher lift is not at all necessary for what you are doing) that will work with the cheap blue LS6 springs. I've had great success with them on my budget builds. guys with brains and balls are taking them to 7k all the time. If you really need the rowdiest idle possible do an asa cam or one of the clones that works with ls6 springs and have at it. Stock pushrods, stock everything, let it rip.

Gotcha. I honestly don't mind paying for the dual springs since I'm just using summit stuff and they're not much more than beehives and the extra insurance is nice.

Truthfully I don't care what it idles like either, so a wide lsa isn't a turn off for me at all. Also since you mentioned it; I'm more concerned with duration than lift due to the goals for the engine. I just don't want the valves in the way at any amount of lift, ya know?

Ive been loving me some LS stuff since 98' bro, I autox my little j/y 4.8 darling in the summer time and deliver pizza with it a few nights a week for extra cash all year long and my wife drives it to work weekdays and she is not what I would describe as mechanically sympathetic, It runs everyday, I never let it have a break, all you need is a cheap moderate lift cam and simple single springs for what you are doing, no bullshit the duals are a waste and your never going to feel the benefits of. 558 vs. .609 lift in the seat of your drift pants, certainly not in a swap you have never driven with the stock cam. Hell I would run the stock cam with upgraded springs to make sure the lifters are in good shape and then only maybe would I cam it once I felt I had the chassis sorted out for a drift deal, think about what you are doing and get it running and driving right first before you mess with the valve timing if you really think it's going to be a race car

Lol that's awesome. Oh it's definitely a full-on drift build and both engines are basically just long blocks sitting on the floor of my buddy's shop, so if I'm gonna swap any parts, I'd say now's the time!

If it helps, the cam I was looking at is the summit sum-8708(231/242 600/600) more despite its max lift(and that nice low price tag) than because of it. I'd happily run something with more duration and less max lift though, if that .600 lift is a concern and I could find something else similarly priced

That's a huge cam. If you show up with a car sounding like that ppl that know better will laugh at you, I'm in the 11's n/a with my weekend car at 3800 lbs with a 218/224 with .553 lift and the same old factory springs as my 212/218 4.8 setup

Do whatever you want though it's your money

I hear you for sure but it's like I said, I don't really care how it idles and it doesn't have to be that cam either. All that matters to me is where the cam makes its power and whether or not valves will touch.

If I do end up with that cam, it's probably a good thing it's only being used in a drift car and nobody in our scene cares how obnoxious your idle is:burn:

So anyway what do you think? You think I'll have ptv issues with that cam, or anything close to its duration/lift?

You do not need the biggest cam that will fit but you are going to do whatever you want, thats for sure, and it sounds like it's going to be a great success. I'm tired of over cammed LS swapped drift cars, just call or email which ever vender posts in her first and buy everything they suggest you need. Good luck I'm done.

Whoa, no need to get mad bro. Maybe I wasn't being clear, but I don't want the biggest cam I can fit, just one that makes its power in the higher revs.
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I only mentioned that cam because it's $283 and makes power where I want it and I wanted to know if anyone knew whether or not it, or any cam in its neighborhood would cause valves to touch in a stock bottom-end older 4.8 or 5.3. That's it.

I quit smoking for new year's, I'm a little grumpy. I just hate loud, rough, idling 16 sec cars like yours that oil down my dragstrip (between runs in the drift pit) on test and tune nights. You need to start with the stock cam and a nice quiet muffler first, sort the suspension, try to beat a few of those dumbass ppl in your "scene" that already have the stupid setup you think you want. You haven't even mentioned how much you think it weighs, what the driveline looks like, you have no idea what you are doing

As a former smoker I completely get you on the smoking thing, but I'm not sure you're seeing why I'm asking what I'm asking.

1 I'm not taking this on a dragstrip, so your comments about that don't apply to me.

2 this isn't my first drift build, but it is my first ls build so in that regard you are correct; I don't know what I'm doing with them. That's why I'm asking questions.

3 I also hate loud, obnoxious, straight piped ls drift cars, perhaps more than most, because I've found them to be ear-cancer every time I've worked the track but I never said anything about straight-piping my car.

I appreciate you taking your time to respond to my post, but what I asked for was an answer to a specific technical question. Instead what I'm getting is opinions on drifters, opinions on other possible budget-build engines and opinions on how to build a drift car.

If you don't know the answer to my question, no sweat! Maybe we'll both learn the answer here, but I'm not here for car building advice, or opinions on drifting/drifters , just for answers to specific questions on my first ls-build.

Okay then. I just think you should get the thing running and driving first before you change the cam, get used to the power your are starting with before moving it up the rev range. I'm really not sure if that cam would fit, I don't care for anything like that. Need to know the rest of setup first

Im forgetful sometimes, the tick polluter for the 4.8/5.3, that's supposed to be the biggest that will fit, its a 235/239 111+2 iirc, I know I made a thread joking about it a long time ago

Awsome. I'll search your old threads for it😂