Well, I just ordered a set of Trick Flow 23° heads and a new Accel intake. My chip is definetly gonna need some tweaking. From what I know, aluminum heads can take more timing advance since they can resist detonation better. Is that true ? Maybe someone has a combo similar to this and can tell me what way to go when modifying the VE and timing tables. Thanx

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92 Z28 5.7
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Ported stock heads, XR270HR-10 cam, TES headers
Crane AFPR, Flowmaster catback, MSD ignition
#24 SVO injectors, 1LE aluminum driveshaft.

Best ET 13.3@107 mph

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Probably want to increase the higher rpm range. Once you get them installed, see how what your scan tool is saying. That will give you the best idea as to the change in VE.

Good luck with the new heads. It should really make your engine come alive. Also, consider advancing your cam a few degrees if you have no detonation problems, if you haven't done so already.

 

For me to advance the cam I would have to get a different timing set or cam gear. As much as I'd like to do it... I dont think I want to

 

For the moment I'll assume they are small chamber heads. In cruise they will want a tad bit more timing, at WOT you might find best power at 28d, yep.. Running less timing consistant with the same HP is a great thing.

Depending on the chambers finish you might be able to reduce the surface area of the chamber by 40% with some polishing. Just tried the chamber polishing on a 355 and it does make a difference. Took 4d timing out and NO lose of performance. Less timing, same HP, means long life, and less detonation in marginal situations,

 

Well they should be 64cc heads. As far as I can tell from pictures, they're not polished. That's soemthing I wouldnt mind doing with my wirebrush then touching up with glasspaper. My timing can get as high as 36 in the tables at cruise (30-40 kpa). Plus my base of 6, that makes 42. Quite a bit... At WOT the highest is around 35 between 3000-4000 rpm. I'll see what these heads need when I get them installed next week.

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92 Z28 5.7
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Trick Flow 23° heads, Comp Cams XR270HR-10 cam, Accel intake base + ported TPI,
TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.

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With the larger chambers, you have more quench area and more chance for detonation.

No need to polish, just smoothing is fine. What looks pretty to you, at times makes no matter to the engine.

In the area of the chamber finish you want a slight roughness, so that there is a thin carbon accumaltion on the chamber to act as thermal barrier.
You just don't want any **spikes** that can develope hot spots, and reduce the surface area..

 

id think those heads would want less timing at wot, didnt larry widmer have something to do with the design of the trickflow heads? I imagine they have a bit of a fast burn chamber

ive also read that you want to smooth all the sharp edges in the chamber just slightly while you are at it

 

Well I bolted them on and I dont think there's even a SOTP difference. Maybe it's just that I'm still running the same chip, but I really did expect more out them. Oh well...:/

 

You must really need to tune that thing, you should've noticed a big difference. I sure did - I gained a full second in the 1/4 after my engine swap. And that's with no tuning at all.

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Black 88 GTA L98
261 RWHP, 345 RWTQ
13.406 @ 103.72 MPH
ZZ4 bottom end, Edelbrock 6085 heads, LT4 HOT cam, GMPP 1.6 RR's, ported stock TPI, SLP 1 3/4" headers, no cat, Dynomax cat-back, Stock PROM
E.T.F.A Member #11

 

You need to get alot more accurate then guessing. A realy fast car does it so effortlessly that it can feel slow. In the Gn the only real sensation of speed is being pinned to the seat.
Again you need to get to tuning to what the engine wants, I guarantee you the AL heads aren't going to be at their best running Iron head timing, and probably fuel.

 

Very good point. So far I went Michael Davis's webpage and downloaded his bin which was designed for his ZZ4 heads and a pretty much stock TPI with #24 injectors, I made little changes here and there and then burned it. The car runs good so far, but it feels like small shot of nitrous when push the throtle down a little, which tells me it likes more fuel. I'm not gonna go into it too much until I bolt my intake on though. I'll let everyone know how it's gonna turn out