No ****. I've been saying this exact same thing for months now. There is no point of going with anything over .550 lift on stock heads. Scientifically it doesn't make sense. The stock 5.3L heads stop flowing right around .500(that's no typo) so you're only going to gain about 2-3 rwhp from using a .500 cam to a .600 but you'll go through valvesprings 10x faster.

How do you explain how guys like TXsilverado didn't drop much time from going to a full bolt ons no cam to adding a cam. Or how AdrenalineP(I believe is his name or something similar) has run a 13.6 in an extended cab with just a z06 cam.

The fastest n/a 5.3L silverado runs a tr220

There's just no point in running a big cam. Hell if I had time I would be swapping my 224/224 to a tr220. There's just no point in all the headaches tuning it just for 10 rwhp up top but a 20 rwhp LOSS down low.

Oh and for those who know him this isn't Eric(Hit Man X). We do talk a lot though.

 

what about smaller duration cams with big lobes like the lsk lobes. when you have a set of heads that flow well up top but alo flow well down low. with the lsk lobes you get more duration at low lifts than the same duration cam with shorter lifts. which would yeild more torque under the curve right.

 

I think GEN 3's like big cams, but its not all about duration, lift and lsa. The truck intake sucks, period. The truck guys with that manifold need a cam with the PROPER valve events, not just a shelf cam for an F-body. I would almost bet that a good reverse split would make more power than most single pattern and conventional split cams, because of the intake restriction. I WOULD SERIOUSLY SUGGEST THAT ANYONE WANTING TO CAM A TRUCK MOTOR SHOULD PM PATRICK G, FILL OUT HIS APPLICATION AND TAKE HIS SUGGESTION SERIOUSLY. That guys does nothing but spec cams out. I recently had him spec one out of the Wood Hauler's 408 (10.75cr, Victor Jr., 4bbl tb). He cam up with a cam for me, and I learned from him that the Victor Jr.s flow very differently thatn the Fast manifolds and therefore they need the proper Intake valve opening point. I was surprised to see what he speced and cant wait to get the cam in and see what kind of difference it makes.

Just my .02, but most shelf cams aren't designed for the restrictive truck induction.

 

The XFI lobes are great lobes also, LSK's require a serious valvetrain to keep everything under control, the XFI's are supposed to be better than the XER lobes. But you are correct that the lobe design can make all the difference, thats what I mean in my above post about the valve events. All most people look at is duration at .050", rarely do people study whats going on at other lifts like .200" etc.

 

cam?.......

 

true but its not the entire story. i went 13.26 on a LQ9 cam in great weather with a 1.88 60'. i was also stripped down without a front seat, back seat, spare, gate or system. my front tires were aired up to 60psi

i went 13.00 with the cam in weather that was nowhere near as good. i was also spinning bad, on a slipping transmission that would bang the rev limiter before it would shift, tuning not complete, and my only weight reduction was the spare, gate and subs. front tire psi was at 32psi. my 60' times after the cam were still 1.88 so i dont know where your getting that huge bottom end loss at. look at AP's 60' times on the same cam. 1.6x. then again his heads flow better than mine so the cam probably works better for him.

not doubting that there are other cams out there that would suit my truck better. just getting all the facts out there so randy can make a more informed decision on his homework

 

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Now that I think about it you're probably a bad example anyways. that 226/226 (assuming you still have it) is equivalent to about a 220/220 in a 5.3L.

The biggest issues with the trucks is first the heads. They max out even before the intake does. Even if you switch out to 317's you'll see better flow numbers but you'll see a drop in compression, not to mention the valves are too big for that small of a cubed motor.

There's kind of a cool idea floating around about doing a small valve 317 head milled for compression on a 5.3L. I wonder how those would do on a full bolt on/cammed 5.3L with a better intake?

EDIT-I was also a bit perplexed by SportSide not gaining much from the milled 243 heads. That was a bit weird.

 

what about 5.3l heads from patriot performance?

 

6.0 valves arent too big for the 5.7 ls1. factory 243 heads that came on vettes have the same size valves as the 6.0 heads but with more compression. im almost willing to say that the 5.3 heads are better than my 853 ls1 heads. ive really been debating stepping up to the patriot stage 2 ls6 heads milled down.

http://www.patriot-performance.com/w...06263&DID=1225
cant beat the price

 

stock 5.3s flow the same as stock ls1 heads. also the intake valve that is in the 241 are same as the ones in 317s and 243s [minus the ls6 ones]

since the ls1 head and 5.3 heads flow the same then explain to me why you can stuff a Trex in a motor or a Ms3/4 and see serious gains of 60-80rwhp but then you install a 224 cam and only see 30rwhp all with proper supporting mods.

as for tunning, you guys mention what seems to be the hard part about the tuning? i havent encounterd anything to hard yet