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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Remember, there's no such thing as "too much cam"; only, "not enough motor".
The LG4 falls into THAT category.
The XE256 is a WONDERFUL match to a stock LG4. Resist the temptation of "lumpy". It leads to soggy bottom end (EEEeeeeeewwwwwwww), no leave, the Venus of Lespugue (yeah look it up) with steatopygia in a minivan humiliating you at traffic lights, and ... it just kinda goes downhill from there. DON'T.
The stock LG4 cam is the beloved "peanut" cam. It's something like 190°/194°, .375"/.390". I don't recall the exact specs but it's somewhere close to that.
The stock LG4 cam is the beloved "peanut" cam. It's something like 190°/194°, .375"/.390". I don't recall the exact specs but it's somewhere close to that.
Oh my, OK so the XE256 is quite a bump over those numbers!
Yup, a pretty significant bump. The 262 obviously would be even more. It's simply too much for that motor, especially with its very low stock compression, the stock converter, and the stock gears. The 256 works pretty well but really needs headers and complete exhaust, for something OTHER THAN LG4 or L03.
The XE262 or even XE268 works well in a 305 with a stick or higher stall converter behind it.
My normal cam for a 305 is a 218/218 @ 0.050, 110 LSA, .454/ 454 lift installed on a 102 ICL. I had the Lunati version in the 305 Vortec in my Tahoe. With the stock converter it was a little sluggish off the line with 32" tall 20s and 3.42 gears but cruised effortlessly and had alot lof midrange and top-end power. I put Rhoads lifters and a S10 converter in it and with more low-end torque and a ~2,500 stall speed it really woke it up off the line. When I swapped the stock 350 vortec exhaust manifolds and cats out for long tubes, dual 2.5" pipes to the muffler with high flow cats it gained power everywhere. A Volant cold air intake for a Vortec truck and later model electric fans also added to the power. What did the 4L60E in on that Tahoe was a 75 hp dry shot into the MAF. 75 hp dry shot gave about 100 hp. I think some of the extra power came from intake charge cooling as the evaporating nitrous chilled the whole intake path.
That being said the LG4/L03 love a small shot of nitrous. In that application a wet shot is necessary.
I used a Summit K1103 cam kit IIRC on an LG4 once and it perked it up a good bit. Used stock springs. That along with headers and a 650 Holley improved the car a full second in the 1/4. Looking back a lil stall converter and some gears would have really helped that combo.
Im sure I put new springs I think they were just run of the mill Z28 springs nothing special.. I would consider those stock I guess. For my Vortec build I used Alex Spring kit. When we put an engine together they have all been "succesfull" they don't have to be worked on other than changing oil Lol. That 256 cam is only a tick over stock.
"Z28" springs may be "stock" or at least "stock replacement" for SOMETHING, but they're not stock for a LG4.
The XE cams are CONSIDERABLY more aggressive than stock, peak lift notwithstanding. There's ALOT more that goes into spring requirements than just the peak lift #. Mostly, how steep the ramps are, which determines how hard the valves are to control; especially when they slam back onto the seat when closing, and bounce. That's just about the worst thing that can happen in a motor; it DESTROYS parts. Good springs prevent that kind of damage.
I’ve been looking at plausible cams for the LG4 for the entire summer and have read at least each related post twice, and am torn between two either the L82 or summit 1103 due to the 700R4 with standard converter. My 1985 LG4 should be the 9.5:1 variety with 416 heads. I have 2.5” headers and an old school Edelbrock 2101, standard q jet, 700R4 and 3.27 axle.
From what I’ve read, the exhaust flows about 65% of the intake on the 416 head, so I’m inclined to look at cams with more exhaust lift/duration to even things out.
Whichever I choose I will be doing new springs, but which to choose? I’m thinking the VSA3 / ERV943 would do? Just life everything off that’s present and install the new springs - I am stumbling across some posts indicating there is some sort of spacer at the base of the spring? I’ve done valve seals on these heads and did not see this?
It's really not too hard at all. Plus, if you're doing a cam change, odds are you'll want to change the timing set too; you can get a kit with all that stuff in it, all at once. Might have to buy shims separate and of course a spring height mic. You can "rent" a spring compressor at your local parts store. Good idea also to put new seals in at the same time. For the seals, don't bother with the O-rings, or "umbrella" type. Use only "positive" type.
Those springs should be set up at 1.70" if memory serves. Since you're not trying to max them out, getting each one to anywhere between about 1.69" and 1.70" should be plenty good.
It's really not too hard at all. Plus, if you're doing a cam change, odds are you'll want to change the timing set too; you can get a kit with all that stuff in it, all at once. Might have to buy shims separate and of course a spring height mic. You can "rent" a spring compressor at your local parts store. Good idea also to put new seals in at the same time. For the seals, don't bother with the O-rings, or "umbrella" type. Use only "positive" type.
Those springs should be set up at 1.70" if memory serves. Since you're not trying to max them out, getting each one to anywhere between about 1.69" and 1.70" should be plenty good.
09-05-2020, 09:55 PM
