fb305svs

Here's the brew-haha....

zz3 350 shortblock

Trickflow 23* heads, 64cc chambers, cnc chamber option, angle plugs

hooker 1 3/4 LT headers

edlebrock victor jr, cnc matched to 1206 intake gaskets (ones i am using, recommenced for these heads)

holley 670 carb (dont tell me its not big enough, on the previous dyno with the curent cam it pulled in only 5 hp and 15ftlbs less than an 800 cfm with 1000$ of work done to it)

current cam is:

comp cam XR288 - Specs here:

Dyno chart here (engine dyno)engine dyno

One current issue is the following- comp without me knowing, ground this cam 2* retarded. since i did not know, it was installed straight up. According tyo the engine builder, he recommended putting it to 4* advanced, and said my torque will come down into the 3500-4500 range instead of peaking out at 5300....

My problem is this...

Whats the max lift people have run on zz3/zz4 shortblock? i measured, and this cam is close... i know 525 lift is ok, since the hot cam works with these motors...

So does anyone have a recommendation for a different cam? and if so, explain your reasoning.

I'm looking to bring the torque number up closer to the hp number, and maybe add a few hp too...

Thanks for your input guys, my goal with this motor was to hit 475 hp, and im pretty far short... altho i don't think its going to happen, i would like to see if anyone else has any experiances with these heads and what kind of cam combo works best...

RB83L69

The short block has relatively little to do with piston-to-valve clearance, except for whether the pistons are flat-top or domed or dished or whatever. The HOT cam working in ZZ3 has nothing to do with what will work with those heads.

The thing that makes the difference is the heads. TF heads, in particular above all others, create clearance issues, as an unavoidable artifact of their design. The valves aren't in the same place as stock; which is part of how they work.

Call Trick Flow and ask them, or simply install a cam as much as possible like one you want to use that you know the specs of, and measure the clearance. That will at least give you an idea of whether you're close or not. You CAN NOT just add or subtract the peak lift numbers for 2 cams and know that your clearance will change by exactly that amount; duration, especially the steepness of the ramps, has alot more to do with it than peak lift. Obviously the valves are near their seat when the piston is at TDC (closest to them), so relatively small changes on cam design at those points can produce big changes in clearance, even if the peak lift stays the same; but when they're at max lift, the piston is an inch or 2 down into the bore, and there's certrainly no clearance issue there.

4 degrees of cam timing isn't going to move your peak torque RPM by 1500 RPM. 150 RPM maybe, but not 1500. It's a tweak, not an overhaul.

fb305svs

Ahhh yes, RB to the rescue! whats up?

Yes, after re reading through, i realised i had made that mistake in my thinking. deck height, valve position etc all making a difference in how they clear.

What does everyone think of calling up trickflow- you think they might be able to offer some usefull advice?

I'd love to find someone with these heads- but they don't seem very popular (doh!)

i have a feeling i should have gone afr or pro action... they seem like good heads however, and seem to be on the vortec level of efficiency- max spark advance is only about 34*, just didn't want anymore than that (a sign of good chamber design i guess)

Also RB, could i paraphrase what you said about ramp speeds and such and say and be correct that i could put a 650 lift cam in this motor, and still get away with it, aslong as the closing side of the lobe is steep?



Also, i do have the afr rev kit... motor spun to 7200 which was where we started to hear a little valve float through the air intake system for the dyno. I'm assuming that will help signifigantly, and i beleive my springs are good to 600 lift... hmmm. Makes me wonder, since all of trick flows cams seem to have a lot of lift...