Head

[LordAthey]

Alright guys got a couple more questions for ya. So if I'm running stock crank, 1g rods and 2g pistons what would be a good cam size? I was thinking about using 272's, but people tell me i should go for 288's. I just think that the 288 are to big. I'm going to have head work done. Almost going to be running e85 with about 450 to 500 hp for a daily let me know what you think of the cam size and or what i should do to the head to make this work. I'm not on a limited budget, but i can't do extreme stuff. /ubbthreads/images/graemlins/mad.gif

Thanks again for help on the build,

Scott

 

[belize1334]

It depends on the turbo and desired characteristics... there's not simple answer. IMHO 272 is enough if not too much for the vast majority. Also, maybe you could clarify what it means to almost run e85 /ubbthreads/images/graemlins/dunno.gif

 

[LordAthey]

o my bad, i'm going to run e85 sorry accidently put almost in there. I'm going to be running an 18g.

 

[Diego]

Imo 272s are good enough for anything beside zomg power.....

I'm a fan of 264/272 cams.... brute power, can come from that setup...

 

^^Not to mention improoving spool up time.

 

[AnotherNewb]

Um... at the expense of moving your power band up, higher into the RPM range.

 

^^ why is that a bad thing? These cars could use a little more on top.

 

[Muskrat]

Quoting Dbossman:
^^Not to mention improoving spool up time.



Smaller cams = increased spool.

In lamens terms: A larger cam opens the airway further, slowing the air down (but letting more out). Airspeed is what spools your turbo.

 

^^ It would Probably depend on how big of turbo you were running then. I know more than one person running this cam combo, and claim it spools faster. Me myself, I'm running stock cams, so I wouldn't know.

 

[Muskrat]

Yeah, I suppose there's a point of dimished returns, where the cam doesn't allow enough flow to properly spool the turbo.

Typically speaking though, stock cam's will spool faster (by a few hundred rpm) than 272s. But 272 will allow more airflow at higher RPMS, netting higher peak HP. Picking the right cam is usually a trade off between driveability down low, and peak power, and where the power-band is located in the rpm range.

 

[381gvr4]

I have 9.0:1, gt30r dbb and bc272 and I'm a little disappointed in the lack of low end torque. I daily my car and find myself downshifting instead of pulling thru at low, off boost rpm's! Considering a 264/272 combo to hopefully help here.....

 

[belize1334]

^^ What IM are you running. I'm a big fan of the cyclone over stock as it flows just as well up top but spools the turbo MUCH better down low. A while back I posted back-to-back dyno pulls with the cyclone activated/deactivated. click The functional cyclone lowered the boost-threshold by a full 100rpm and increased peak torque by ~40 ft-lb at 17psi. Now, granted, we're talking about cams here. But a cyclone-style manifold could be used to help recover a little of the low-end grunt that is lost with hi-flow cams.

 

[LordAthey]

Ha ha thanks guys I'm liking the "almost runs e85" tag lol thats some good stuff. Now I can't decide if i want the 264/272 combo or just go for 272's

 

[belize1334]

I can't remember who did it but there was a test a while back that compared stock, 264, 264/272 combo, 272, and a few others on back-to-back dyno runs with a 16g-esque turbo. Basically they determined that 264/264 had NO downside over stock. The car picked up torque over the ENTIRE rpm range. The 264/272 lost a little torque down low but picked up some more hp up high. It was still better than stock over the ENTIRE range. 272/272 had slightly LESS torque than stock down-low but even more hp up high. And so on and so on...

So, it seems to me that both 264/264 and 264/272 are no-brainers. They're both improvements over stock-cams in every measurable way. It's just a matter of whether you prefer low-end or top-end...

Once you hit 272/272 or beyond then you're actually giving something up to the stock cams in the low-rpm range so it's a bigger decision as to whether it's the right choice for you.

Of course let's not forget that choice of turbo and cam-timing each play a factor so the above commentary is at best a rough guide.

 

[AnotherNewb]

Cam test

Here you go. There is another link somewhere buried in the .org but I couldn't find it.