IndigoBlueBeast

Since you brought up compression, (no pun intended) I got another set of 862's a couple days ago so they'll get milled around .030 or .040 with the .040 gaskets to bump it up about as much as possible with the dished pistons. Pr length checked, ls7 lifters and new trays included. Also clean them up without removing too much material too keep maximum velocity, so how would this affect the LSA of the 212/218 or 216/220? Still have them cut on a 112+2 or just keep the off the shelf 114+4?

03klugss

iTrader: (1)

That's probably the best statement made about picking out a camshaft! It's not rocket science really if you know how the valve events truly work. As oakley6575 said also DCR (dynamic compression ratio) is a number you definitely want to keep up there. One of actually I should say the most important factors in picking out a cam is the IVC (intake valve closing).


It's just all about getting the valve events just right for your particular setup and what exactly you are wanting out of the truck and how the truck is used also, towing etc.... On my own truck with my old setup as far as duration goes I had a custom grind baby cam for it being in a 6.0 and with nothing more than the cam, longtubes, stall and tune my setup was a 13.4-13.5 consistent quarter mile truck, with the heavy factory 20's oh and that was thru the stock catback exhaust system too. I spec'd a cam that was tailored perfectly to my setup.


Cam companies make some GREAT off the shelf cams but I'd go with a custom grind any day.

05HD1500

Do you remember the basic specs of the "custom ground baby cam"?

IndigoBlueBeast

03klugss, I always read you match your cam to your heads so how would someone spec a cam for heads that aren't TEA, WCCH, AI, etc without flow numbers or volumes? I'll have around 10.5 since that's about all you can get out of the stock dished pistons although around 11.5 would be ideal. Definitely want the dynamic at the iirc 8.5? I love the big block like, off idle torque. Therefore I want to stick with the lower duration cam and it seems everyone's custom grinds start getting higher in duration than I want.

Camin00

A 5.3L is limited as far as tq #s go. I think around 350-370 rwtq is max for a N/A 5.3L. A lot of guys with the bigger cams traded their tq for more hp. The biggest cam you can put in a 5.3L with stockish heads only makes 10-15hp more than the range your looking at and makes for a terrible daily driver.

I dont think changing the LSA to 112ish is going to have a real noticeable impact vs the 114Lsa other than sounding more badazz haha

Camin00

To much compression means less advance in the timing.

With 93 octane!!!

say you have 10.5 compression, then the amount of advance should be around 20-24 degrees

Now if you have 11.5 compression your probably only going to be able to run 16-18 degrees of advance

My point is more compression and less advance is not the best way to make power. There needs to be a nice balance. All your new lowend tq will be coming from the compression jump not so much the cam. The stock cam probably makes the most tq from idle to 1500rpms. Most small duration cams keep the stock lowend tq #s, they dont really add any more tq

Go check out vincis cams and look at the 210/218 .551/.551 on a 112Lsa. This is the same cam I have except 116Lsa and look at my dyno #s in the cig. I dont really see any 212/218 comp cams putting down those #s on 83lbs 20" rims just sayin lol

IndigoBlueBeast

Your numbers look really good for a cam everyone considers "small". Iirc the famous 220/220 makes around 325 or a little more. I'm assuming your Vinci has more aggressive lobes than the the comp 265 because of the higher hp numbers with the lower duration? What I've read is the high lift 212/218 (similar to your specs) makes really close to the same numbers as the low lift 212/218. You said you only milled your heads, so why no clean up or valve job? Would the very mild clean up not increase flow while maintaing if not increasing port velocity?

Camin00

I do believe vinci made the ramp rate faster on my cam than the comp and I know the cam has +4 degrees of advance built into it. I think roger took the comp 212/218 ground and tweaked it to get full potential out of the stock heads.

You can make your exhaust ports larger with out effecting the velocity as long as the exhaust ports stay smaller than the manifold/header diameter. Don't want the exhaust to hit a lip from the headers.

A light clean up job will net maybe 10hp more to the wheels. I personally didn't spend money on a port job b/c I didn't have the money I know the first thing porters/ machines remove is the rockers stud lump and the ramps in the runner. The ramps is what makes these stock high flowing heads maintain tq. Old school top of the line small block heads wish they flowed as well as our stock truck heads

My future goals are texas speed and performance stage 2.5 5.3L heads and fast truck intake with 102 throttle body. This combo will probably hurt my current lowend tq but add a soild 40-50 more hp at the wheels and 20-30 more peak tq

IndigoBlueBeast

Mainly just looking to clean up the intake runners and smooth out around the valve guides with a nice valve job and some light bowl blending. Not hogging out the exhaust but working the short turn radius and polished up. All the port work Ive see done has the rocker bosses cut down along with the swirl ramp but their usuall for cars wanting big hp. So cutting those down will hurt low end?

Camin00

cutting the rocker lumps down shouldn't hurt low end b/c it is a speed bump for air but cutting the ramps all the way down like in big cars will net in more hp from flow but loss in tq b/c the swirl ramps keep velocity up.
Velocity = tq
flow = hp

Make sure to use a high temp sealant on the rocker arm bolts if the rocker lumps are removed

I like your idea for cleaning them up probably make them close to a set of 243s except with small valves and more compression

Another Idea for a cam could be the isky triple 12 - i think it is a 212/212 on 112Lsa dont know the exact lift, but this is an amazing turbo cam and great N/A cam. would put you in a good position for turbo build later down the road. Just a thought