nightman06

So I'm no expert on cam selection. But I did request a custom cam spec from a very reputable source and I'm curious what you guys think about it. I understand I may be asking for a layman's interpretation of an expert's advice. But I know at least a few people on here TRULY know what they're talking about.

My build is a remote mount TT setup similar to UPP with Garrett GT3076r's .63 ar. 317 heads, .051 gasket, stock bottom end LS1.

Cam spec: 226/235 .605/.610 114+5.

I asked for good streetability, quick spool and more emphasis on room under the curve than top end power numbers. This is a "near" daily driver but I want to feel it quick when I hit the pedal.

nightman06

Someone has to have thoughts on this. I see random posts on cam size guesses almost on a daily basis. Here are some actual numbers.......anyone?!?!

0CK@UPPCOS

SpinMonster would be the one to talk to, but he's rarely on here anymore. We generally use his cam (or a variant thereof), 230/234 .605, 114+3 and it seems to work out pretty well. It's a little laggy on my tiny 4.8L, but all the 6.0/6.2 it works wonders.


CK

5 Liter Eater

I'm no "expert" but I can dig that cam. Very little overlap based on the poor mans overlap formula. And advancing it will shift the power band up a little. Those are some baby turbos but should do well on a stock bottom end car. What turbine housing are they (T3/T4)? What are your power goals? They will be in their sweet spot ~600 RWHP IMO.

5 Liter Eater

For reference, the cam I've run for the last couple years on my 10:1 408 is a BTR
231/239 .617/.623 on 118+2

Went a little bigger for the 9.5:1 422 LSX I'm building. An LJM 232/246 .610/.596 on 120+4. Basically, IMO, as much duration as you can get without introducing overlap.

PEETYZ

I ran a similar cam 227/235 .608.621 on a 116 with I believe +4 degrees in it on my stock bottom. This was 10 PSI (P1SC-1 Blower) and it was great

StatmanRN

For a remote mount, I would consider a reverse split [more intake than exhaust] to help with the spooling in normal driving. Also consider a wider LSA to decrease overlap. It will cost some power on the top end but build boost faster.

romandian

so is everybody advancing the cam? why is that. shoud they not be ground so they work as is?

StatmanRN

You have to look at the timing card and where the intake CL is
Common to have advance built in ~4 degrees

MVP'S ZO6

Not an expert by any means.

Looks like he has 5 degrees advance ground into the cam based on specs. 109 ICL.

I'm curious as to what size your engine is and its compression ratio as well as intake? And intended rpm range. This will give way to determining amount of over lap needed.

Pay attention to the camshaft overlap period and Lobe Centerline Angel. Critical in cam performance. (More important than duration)

Shorter exhaust overlap will bring vacuum up.


Open exhaust valve easy and early instead of fast and late.

BLOWNBLUEZ06

Cam selection for your case would be based not only on your engine specs and performance desires, but also the turbine housing size. You'll make plenty of power under the curve if the turbos are sized appropriately, which they seem to be.
Based on what you posted, assuming you're running a T3 housing, I would probably be selecting something with a smaller intake lobe and wider LSA. Something like 218/230 118.

BLOWNBLUEZ06

Forgive me if I'm wrong, but I'm guessing you're misunderstanding the + in everyone's cam specs, thinking they're advancing their cams. That plus is ground in, in most, if not all these cases.
example:
231/239 116+4

LSA = 116
ICL = 112

nightman06

Thanks for the input everyone. It sounds like I'm in the ballpark. The 3076's are T3 housing.I wanted to stay all the smaller side (turbos) to avoid as much lag as possible. This is a garage build for spirited driving only. Given that I am still running the stock bottom end, Im trying to get as much "fun" out of this setup as possible without causing added stress on the bottom end. I'm going to give this cam a try and see what I can get out of it.

Oh and to answer the goals question, I'm hoping for mid 600's rwhp. I'll be sure to post up pics and results.

romandian

thats weird. either you advance/retard the cam or not. but maybe im just old fashioned.

i would apppreciate somebody to explain.

MVP'S ZO6

I'm not quite sure what you are looking for but I think this is it.

The plus number you see after a Lobe Separation Angle (LSA) figure is nothing more than the amount of advance ground into a camshaft. The Lobe Separation Angle (LSA) is the distance in camshaft degrees That separate maximum lift between the intake and exhaust lobes. For the purpose of this post / conversation; let's say your camshaft has an LSA of 120 degrees. (keep this number in mind I'll use it again later in the post) The LSA is ground into the cam. You can not change that manually (i.e. Turning the cam gear to advance or retard the cam)

The Intake Center Line (ICL) is The maximum lift of the intake lobe as it pertains to piston Top Dead Center (TDC).

So.. In a given engine if top dead center is fixed and the maximum lift is fixed and I said that the LSA is ground into the cam (in other words it's also fixed) the item that is not fixed or can vary is the ICL. This can be changed by design(e.g. Advance ground into the cam A.K.A. The +4 you see in the given example) or mechanically (physically installing the camshaft either advanced or retarted) if you understand what I've said to this point and I gave you a camshaft with 120 degree LSA +4 (the +4 being amount of advance ground into the cam) then you can see by looking at that number "120 +4) that the intake centerline would be 116 degrees. The camshaft ICL is 116 degrees because when installed "straight up"

When you manually advance or retad the camshaft, the intake centerline changes the relationship of maximum lobe lift on the intake and the piston top dead center. (Refer back to the definition of ICL)

If you take that same camshaft with the advance ground into it and you physically retard the camshaft in the engine, if you were to put a degree wheel on it, you will (or should if the cam is ground correctly) get an ICL of 120 degrees.

Note just FYI: the Exhaust Center (ECL) Line goes in the opposite direction. 120+4 would be an ECL of 124.

I hope this makes sense.

romandian

makes sense now, thanks.

BLOWNBLUEZ06

T3 vs T4 doesn't help with lag. It helps with power capability. the AR of the turbine affects lag. .63 will spool early and blow its wad early. 1.15AR will take time to spool, but have a higher power capability due to blocking less exhaust, creating lower back pressure.
BTW, IMO, the lower the AR and smaller the turbine housing, the more back pressure you can expect (as just stated) and therefore the less overlap I like to see. Higher back pressure means (to me) with a cam with any significant overlap, when the exhaust valve opens at the top of the power band, there can be so much back pressure that much of the exhaust (and heat) will remain in the chamber, making it harder for a fresh intake charge to come in and do its good work.

nightman06

Yes, understood. I should've clarified what I was trying to say better by completing that statement with the fact that the turbos are .63 AR. (for that reason). I figured I'd give the smaller option a try first and see how it does. After a complete build, swapping out turbine housing and re-tune doesn't seem like much of a hassle (if desired).

5 Liter Eater

I wouldn't waste time swapping the turbine housings on those turbos on a built motor. They're way too small. I'd move to at least GT35Rs with a 1.0x AR. They'll be in their sweet spot @ ~800-900 RWHP.

slow ride

I think they would be great in a rear mount setup for a nice driving combo in the 600-800 range. I like 35r's, but not on a 5.7 rear mount if you are looking for fast spool. Turbine wheel size plays A LOT into max flow of the system also. The jump from say a 62mm exhaust wheel to a 65mm will make a larger difference in spool and power than a step up in turbine housing in most cases.

As far as the cam goes who knows at this point. I've seen large split, reverse split and single pattern cams all perform well, but I know my single pattern 226 seems to be getting it done without much drama. Power numbers are so hard to track with turbos as little differences happen so easy with say 10 more kpa up top, etc. I'd love to see a good dyno session on turbo cams with good control on parameters, but those are few and far between. Keep things matched up and the combo will be happy. Larger cam, larger turbos, etc, etc vs medium size cam, turbos, stock intake, etc, follow the powerband. I know that is way oversimplified, but good practice to start out and fine tune the parts as you go.