Hey guys,

I was hoping to get some help spec-ing a custom cam for my Sierra. The mods are all in my sig. I know some will say Pat G. But I what I'm really looking for is your opinions. The cam that's in it now was intended for my 5.3 setup before the stroker, so I truly believe that there is still a lot of hidden potential.

Appreciated!

 

We need a little more info... your sig is really complete, but knowing things like a target shift RPM or how you'd like it to idle make a huge difference in cam specs. With a stroker you can definitely use more duration. Do you have a converter? I don't see that listed. 4x4 truck? Cab config? Have an estimated weight?

If it was my truck I would want a choppy idle (mins isnt a DD, and it doesnt sound like yours is either), but you have to be careful not to go too far. I assume you have strong parts if you upgraded to a 4" crank, but I still wouldnt go crazy with RPM. A target shift point of 6300-6400 would keep me happy. I've never been a huge an of 4" crank motors because of some of the oil consumption issues... I would think that high RPM only makes that worse over time.

That being said if it was my truck it would look like this with a converter and be choppy:
223/234 115+4 .612/.612
Without a converter I wouldnt want much chop at all:
219/230 117+4 .607/.609

On both cams I used an LSL intake and LXL exhaust.

Both would give you pretty similar power curves and would pull to similar RPM. The first cam will chop a lot more and offer a stronger mid range. The second cam will pull just about as high with the same intake close and exhaust open as the first, but the bottom end would be A LOT smoother.

If you have a converter thats on the loose side (like my yank with the power and gearing I have) I may do something as big as a 227/238 also on a 115 but with only 3* advance. With your current combo thats definitely 'max effort'.

 

Always appreciate your replies Vortec350ss!

My truck is a 4x4 RCSB, no torque converter. Estimated weight would be around 5200 - 5300 lbs. My target shift rpm is 6300 - 6400 rpm. Stroker parts are all forged. I'd love a choppy idle but am already having belt throwing issues from time to time even with the HD tensioner from Magna. With that said I definitely want a choppy idle.

The cam I have on is: 218/226 .604/.604 115 LSA +2 Advance

The idle is really smooth and doesn't lope.

 

You need to get your hands on a belt alignment tool... the 8 rib can be very very finicky. I bet odds are you need a blower pulley shim and the PS/ALT need some attention. Mins was a bitch... i had to have them machined to fit right. Some trucks have slightly different alignment on the PS and ALT bracket. Cam or lope at idle shouldn't make it any more prone to kicking a belt.

Your cam is in the right ball park for sure... I wouldnt bother with a swap just yet. My cam was spec'd years ago and I made for NA with the possibilty of boost down the road... 222/226 on a 114+4. I still hit 11's and make about 600 to the wheels. I'll run 11.6 with cooler weather and dialing in my tune further. Is there some power left on the table for you? Yes. Is it worth the swap? HELL No. We're talking 20 HP maybe. I know guys on here who have 1000 lbs on you and they still run 11's with a similar cam.

Keep with it for now. Get the belt squared away and get yourself a nice tight 258mm converter. You will run low 11's with your mods. I would still think that cam pulls to 6200-6300 pretty well.

How much boost are you currently running and what what pulley?

 

Oh wow. That makes sense! I guess I should be thinking about torque converters then. Why did you say 258mm rather than say the 265mm? Also, I'm checking out CircleD and am confused between the single disk and the double disk. I need to find the exact one for my setup.

https://www.circledspecialties.com/p...converter.aspx

 

258 is just a more common size... yank makes them, PI makes them, Circle D makes them etc. Also the smaller diameter converters tend to be much more snappy and feel more race like. It will feel slightly looser around town though. Generally I think you tend to get a better combo of flash and top end efficiency. That means that a 258mm converter that flashes 3000 off the line will be more efficient and have less slip at 6000 RPM than say a 265 or 278mm converter that flashes the same exact speed off the line. Thats why race applications have such small converters. Theyre just not as pleasant on the street.

I went with a multi disc bc my truck is heavy and with the 4 speed trans I thought maybe it was possible I'd lock it WOT. Its just that much more clutch material and its that much more durable. I'm not sure you need it, but I'd never tell you not to get it. In a 6 speed with such a short first gear and much tighter ratios I don't think you need as much converter to make it come off the line hard, nor are you as worried about shift extensions.

I'd go with the 258mm 1b if it were mine knowing what kind of power you make down low. No need for anything looser.

 

Damn good advice vortec. I always agree with what you have to preach.

 

Hats off to you sir Vortec. Really really appreciate all the knowledge and help! I'm sure you're gonna hit close to 11.6's when the weather cools off. I'll let you know once I get the converter installed and take it down the strip sometime in December.

Thanks again

 

You're welcome.

For the heck of it I'd run it as it sits and see where you're at. See what kind of 60' you can get etc. it may help you decide how loose to go. I don't think you have HPT but a scan or a dash video of the run would help a lot too.

To put it in prospective the 4l80e has a monster first gear compared to the 6 speed which will play a big role in how a converter drives. I have a yank 258mm '2800'(the tightest they make it) and look how it behaves off the line. Keep in mind this was also 2.5 psi, and meth ago... Damn near 75 HP. It stretches slightly more now.

http://m.youtube.com/watch?v=dUV_QqCren8 hopefully that works... I'm posting from an iPad.

 

Wow. Your truck hauls ***! I want to see it now with the meth and +2.5 psi. I do have HPT but I am currently out of the country and away from my car lol. I'll see if I have any dash videos with the current mods. What stall would you be looking at if you were me?