BlackGMC

iTrader: (31)

Well 2 of the three were on the same dyno, the 3rd was on a different dyno...

apparently you don't know me at all, i tell the good and the bad... I know my truck is not that fast but at least I am honest about what each mod did. Do a search for my name in the drag racing section... I probably have more track time posted than all the people in the this thread combined. We used to go all the time probably every other week or every week during the good weather... And yes we monitored the DA everytime we went...


I have had 1 -5/8 header on my truck when put on headers... honestly the 1 3/4 actually feel better than the 1 5/8

MPFD

iTrader: (5)

I didn't realize he was speaking of you. But in that case I would argue that lsa made more over all difference in your gains then the slight changes to duration. And I would still recommend a TR220, because Justin will have a easier time throwing him a DD mail order tune without such tight overlap. I also agree with you on 1 3/4 headers.

I agree you report thoroughly, I have read many of your write ups. The Doorman Intake sticks in my mind.

BlackGMC

iTrader: (31)

you know LSA and duration both come into to play on the overlap of a cam....

MPFD

iTrader: (5)

Yes I agree, but your FTI with 108+2 is alot tighter LSA then the TR220 on a 112. I've have been told that tighter LSA makes for a harder tune, on the idle driveability side of things.

PathfinderJr

iTrader: (6)

The difference is the OP has a manual and most here have an auto. High stall speeds make it easy to brush right on past any and all lack of low-end due to one reason or another. With a stick, it's a little harder unless you ride your clutch hard at every stop-light or have some pretty deep gears. On my truck with the 5-spd, the 2-3 shift sucked donkey ***** due to the gearing and torque curve of the 4.8, and I already have 3.73's. As you well know, in stock trim, the 4.8 really doesn't start to wanna move until you north of 3-3.5k rpm a decent amount.

Maybe I'm just old-school cause I cut my teeth on gen I sbc's instead of getting into all this with gen III and later, but a mostly stock 290 - 310hp, 293 cube engine just screams for 1-5/8"s primaries to keep the exhaust velocities up to make the power band half-way streetable, especially for a stick truck.

Hell, my old '66 truck has a 400hp, 415 lb-ft sbc 350 whose limitation is actually the induction (needs a bigger carb) as opposed to the 1-5/8" headers.

But when it comes down to it, this is America and everybody can do what they want... mostly. So party on, Garth. Any header is gonna be better than stock.

BlackGMC

iTrader: (31)

I believe your mixing terminology... increased overlap makes idle harder to tune.... LSA is usaed in calculating overlap, but it is only a portion of the equation...

MPFD

iTrader: (5)

So does your cam have more overlap then a TR220 or am I wrong?

BlackGMC

iTrader: (31)

on what LSA? an easy (but not 100% accurate) way of calculating overlap is (((intake duration + exhaust duration)/4)-LSA) * 2...

For example:
my cam 214/220 @ 108 = +1* overlap

TR220 @ 112 = -4* overlap
TR220 @ 114 = -8* overlap

Now from my understanding the overlap will shift the efficiency of the cam... More postive overlap will make the engine more efficient in the upper rpms and less efficient in the lower, thus the rough idle... This is one of the reasons my HP starts to die off at 6700-6800.... Now the other part of the choosing a cam is the DCR, which no one in the thread has mentioned... my cam has alot more DCR than the TR220 due to the 106 ICL... Decreasing the ICL (or the +2, +4, etc) increases the DCR. although the CR helps increase the DCR, so that also comes into to play.... my DCR is about 8.5-8.6 this is why my cam makes good TQ down low...

MPFD

iTrader: (5)

I understand SCR vs. DCR. My thinking here is that Black bear who is tuning his truck will probably have more experience tuning for the TR220 which is a very popular cam, then trying to dial something like your cam. Your cam was a nice choice for you cause you have the know how to tune for yourself...

BlackGMC

iTrader: (31)

Just as a quick reference of my past H/C setups and times...

stock heads, XE220 @114+4 ran a best of 8.8 i think.
stock heads, XE222/224 @112+2 ran a best of 8.6 i think.
prc heads, XE222/224 @ 112+2 ran the same as above (yes i know it sucked)
prc heads, FTI 214/220 @ 108+2 ran the times in my sig 8.3

This is just my opinion.... a smaller duration cam with a low LSA and low ICL and decent lift is the best combo... Great TQ down low due to the higher DCR, and higher overlap to keep the HP climbing throughout the RPM range...