Big Torque Camshaft

L29er · August 3, 2008

Did a search on here and there was alot of small block info but i`m running a 454 vortec, as some of you know i recentley aquired a whipple supercharger but due to my recent insurance write off on my quad i had to make a hard decision so that i was able to replace it. yup gonna let her go, so my backup plan for the truck is to do a cam and some head/intake work (probly not get bigger valves but some porting for sure), now the stock cam is rated .284intake .286 exhaust (wow MILD) and i dunno the duration or overlap specs, just not in the manual. Valve spring pressure is 238-262lbs. Okay so a engine machinist guy told me the stock springs won`t handle over .500 of combined lift, so with my 1.7 rocker ratio i`m currrently at .482 intake and .486 exhaust so there isn`t much room (that would be worth gain), so obviously i would be upgrading to some performance springs that alow more lift and are stiffer.

NOW the direction i want to go is for more bottom end, as this vehicle does at least 50% of its driving as a tow vehicle, so thinkin probly 1800-4800rpm gain, but it gets confusing abit when i`m looking at cams, some are obviously using advertised duration and some are .050" specs, which makes things kinda all over the map, all i want to know is the recipe for tourque, more lift or more duration? alittle of both?, there are so many options, and i don`t want to do it twice. Which ever i pick can be radical, i will be getting a revised custom tune when shes done, so it can idle like a dragster i guess, I do plan to upgrade the lifters, install full roller rockers (+ valve springs) and maybe the timing set? tell me what you know...thanks

Texsrt4 · August 4, 2008

262lb spring pressure? thats not quite right.

ignore total duration. compare .050 to .050 to select a camshaft for the deciding what rpm to run at. then you can compare total duration to determine ramp-up rates. the smallest total duration cam with the .050 duration you want is the pick...as long as it has lift in the ball park you are looking for.

how important is engine vacuum for you? higher vacuum, from a wider lobe seperation (112° or larger), will make your brakes work better but will sacrifice your torque band a bit, making it a bit peakier. something with a 111° or narrower will make more torque earlier in the powerband but will hurt idle quality and engine vacuum which equates to less braking ability.

you should also pay attention to the heads you have, being a big block, they flow fairly well. if they didnt you would need a larger duration exhaust to compensate.

1800 rpm seems a bit high to be coming in on a tow vehicle. i would usually prefer it to come in around 1200rpm or so. this way it engages right as the torque converter is really locking up and will be making good power at speed.

shoot for a 215-220° duration @.050 on the intake, add 3-5° to the exhaust duration and try for a .510" or so lift if you can get lucky. on my tow rig i would shoot for a 115° duration

L29er · August 4, 2008

thanks i don`t think i have anything that operates on vacuum, ( i have hydro-boost brakes) so does that change anything, so how is the .050 spec made? just trying to clearly understand, its the measurement of duration when the cam is at .050 of hieght either intake or exhaust? as compared to full duration start to finish?

L29er · August 4, 2008

gm performance parts has a cam from there 454HO that is 211intake at .050 and 230ext at .050 and has .510 int lift and .540 ext lift with lobe centerline at 112, does this sound ok?

does the 510 or 540 lift take into acount the rocker ratio aswell? cause otherwise that is nearly twice the factory lift, working out to probly 867 intake and 918 exhaust!! they must already take that into account cause thats a huge difference!

Texsrt4 · August 5, 2008

most of the time the rocker ratio is already taken into account.

duration is a measurement of the amount of degrees on the cam that the lift is more than .050".

if its hydroboost brakes you can get away with a little larger duration and i would still shoot for a 112 lobe.

211/230? you sure thats the big block cam? that seems like LS7 duration specs. i dont think you need that much of a spread unless your heads really suck. i dont know a whole lot about the newer BB truck heads so i cant say with certainty. however, that duration is in the ball park for a good towing cam

Jennabear · August 5, 2008

I have a 206/212 115 LSA. Didnt lose much low end, I actually think I gained. I wanted a mild cam since it is a DD.

black00chev · August 5, 2008

I have a 206/212 115 LSA. Didnt lose much low end, I actually think I gained. I wanted a mild cam since it is a DD.

Justin told me you had this cam today when he was tunning my truck... I think I need to come take it out of your tahoe! haha.

Jennabear · August 5, 2008

If you took it then I would have to put in the LS7 cam shaft that is sitting in the garage! This cam is honestly perfect for the type of driving I do.

BTW- you in the market for a Trans Am?

black00chev · August 5, 2008

If you took it then I would have to put in the LS7 cam shaft that is sitting in the garage! This cam is honestly perfect for the type of driving I do.

BTW- you in the market for a Trans Am?

He didn't tell you that I want one of those did he? lol. I WISH I WAS!!!

Some day I'll own one.

Jennabear · August 5, 2008

Ha- yeah he told me. A guy on another forum is selling a pretty sweet 99, only downfall is that it isn't a WS6 and is an automatic. Justin's is pretty fun to drive, I am not allowed to so much anymore after some "incidents".

black00chev · August 5, 2008

I can only imagine haha... The WS6 we had at Wyotech had only some mild bolt-ons and some tunning and was pushing 400hp at the wheels.

Texsrt4 · August 5, 2008

remember too, that the larger the motor, the larger the duration has to be to work in the same rpm range. the ls7 cam isnt great for typical ls1/ls6/ls2 motors because the exhaust duration is setup to work on a specific head; one that flows great on the intake and not as well on the exhaust. too much exhaust will not scavenge the system well enough

Jennabear · August 5, 2008

I can only imagine haha... The WS6 we had at Wyotech had only some mild bolt-ons and some tunning and was pushing 400hp at the wheels.

You sir, definitely need a cam if you are only pullin in 28lbs of air!!! But based on the logs, looks like your truck runs real well.

remember too, that the larger the motor, the larger the duration has to be to work in the same rpm range. the ls7 cam isnt great for typical ls1/ls6/ls2 motors because the exhaust duration is setup to work on a specific head; one that flows great on the intake and not as well on the exhaust. too much exhaust will not scavenge the system well enough

Yep, all true. I would have to do a lot of changes on my Tahoe to may this work efficiently. This cam was actually bought for the SSS but it has an LS6 cam with a Radix in it now.

black00chev · August 5, 2008

If you can buy me the cam I'll pay the labor to have it installed! haha. Glad to hear ya'll think it runs well. I've had very good luck with these trucks but I try to take good care of them as well. Someday a cam will be installed in it as well as a vette 1-2 servo, dynomaxx long tubes and x-piped true duals.

Then once I'm bored with that... TURBO!

P.S. Tell Justin I said THANKS again

She pursss