TIMSPEED

I'm looking at Comp Cam's XR258HR cam. It says it's good for TPI cars. My question is, it's got a 112 LSA...would a 110 be better, for giving more torque? I am NOT at ALL concerned about idle quality, as I WANT a pretty damn mean sounding idle. My next question is, the OTHER cam I was looking at was Comp's 260HR, with the 110 LSA. It doesn't SPECIFICALLY say it's for computer cars, but wouldn't it work with the right tune?
My motor will be Stock Bottom End L98 with LT Headers, LPE SR Base, Ported Stock Runners/Plenum, ProTopLine 180cc Heads. (Shown to flow 260 @ .500 lift)
Lastly, will there be a BIG difference in idle sound between the 110 and the 112 cam?
The specs for the cams are:
260HR = 206/206 @ .050, .500/.500 lift with a 1.5:1 rocker, 110 LSA
XR258HR = 206/212 @ .050, .480/.488 lift, 112 LSA


[Modified by TIMSPEED, 4:27 AM 12/15/2003]

Vic'89

Both of those Cams are very small and not worth it.

I ran a 210/220 Comp Cam in my old Irocz and that Cam was too small.
I then upgraded to a TPIS 224/224 and it was much better.

Good luck. BTW, I'll be running the 219 Lingy Cam in the Vette.

Vic

TIMSPEED

All of that is very good info to know...hmm..but how about the different LSA's? Would 110 be BAD for a TPI engine, or would it be better for making more torque?

vader86

I wouldnt want either, because the durations are too short on the intake side. The stocker is only like 202, Id go with at least 210 on the intake side.

tjwong

The 112 LSA will give you a broader torque band. The TPI compatitble cams means that they are computer friendly. The short duration with the 112 LSA means it has virtually no overlap which means its going to idle and sound like a stock engine.

Your best bet is to go with a LPE 74219 cam, it will give you a decent sounding idle that you want and will give you some decent power increase. It is a tried and true cam, especially if you step up to the SR runners and box.

scorp508

Wimpy cam, don't bother. The 219 like tons of us have does have a nice bumpity idle (especially with 1.6 rockers), but you really should plan on upgrading the intake and other components later on.

65Z01

Timspeed, it is the combination of lobe duration and LSA, or lobe overlap, that makes a cam choppy an loses torque at or near idle. If you want good low end torque chose a cam with overlap in the 25-35deg range. This applies to cams with lift around .500", per David Vizard's books on SBC buildups.

So if you want more low end torque you want to keep the LSA larger, to reduce overlap at low RPM.

I agree with the consensus that those cams you discussed are too small to be effective. Think about the LPE 219 or TPIS ZZ-9 cam for you intended application.

Further I suggest you port your stock intake base (better would be a BM style base) and add a set of AS&N LT runners to take better advantage of the new cam & heads. Anyway, you can easily do these intake mods after cam & heads if you still need more.

Brian, since you have the LPE 219 cam can you tell me what are the "advertised" durations (i.e. at 0 deg lift).

I notice that LPE even advertises this cam has a choppy idle whereas TPIS does not do so with their ZZ-9 cam. Though the ZZ-9 has less lift on each lobe and is a dual pattern cam it does seem to have the same over lap at .050" lift (I see that the average ZZ-9 duration at .050" is 219deg and the LSA is also 212deg, what a coincidence).

So I was curious as to why the 219 cam was "choppier" than the ZZ-9, thanks.




[Modified by 65Z01, 1:23 PM 12/15/2003]

Curveit

You sure about those flow numbers for the heads? That sounds really high for a 180cc head. They might be Race heads that don't flow well at low lifts. You should look for good numbers at .300" & .400" also. You do want to stay in the 170-180cc range for a street motor IMHO. Too big a cam and/or heads will kill a motors good street manners. You would do well to search some proven combos here on the Forum.

:chevy


[Modified by Curveit, 9:23 PM 12/15/2003]