WOOS1

First off, let me get the fact that I am a dumbass out of the way. I have a 73K mile 1996 T/A with an M6 that I purchased new. Previous mods were Hooker L/T's and a CAI kit and it dynoed 292 on a DynoJet several years ago. Since then I installed a 12 bolt. Studied up for months and purchased all of the parts for a H/C swap over a year ago, but just recently was able to install everything with the work being done by a very knowledgable friend (both LT1 & LS1).

We installed new Trick Flow 185cc 21 deg heads, medium sized cam 22X/23X on a 110 LSA, Comp Cam Ultra Pro-Mag RR's, LS7 lifters, GM timing chain & gears, 58mm, 30lb Delphi injectors, a fully ported intake, and some additional things that I am sure I am leaving out. Finally got to dyno the car today (different DynoJet) and do some tuning. Was very disappointed in the results. A/F is in check. Running about 37 degrees of timing. Minimal knock retard.

Looks good & smooth down low, but starts breaking up around 4K. I am thinking that it might be the opti. It is the original one and it has lived for 9 years after the original water pump puked. What is everyone's opinion? I don't mind shelling out for a new opti, but do not have the time or money to just throw parts at it. I am just a little bummed with the results after being this long in the making. Thanks in advance.

RamAir95TA

Any amount of knock retard, IMO, is unacceptable. "Minimal" doesn't count as acceptable.

What valve springs? Might be valve float?

Plugs look okay?

Might be the 9-year old opti. The ignition system has to work harder under higher cylinder pressures so ignition issues usually rear their ugly heads much easier. I would suspect the opti first and foremost.

bw_hunter

I'd also look at plug gap. Shrink the gap down to .035 and you'll probably see an improvement as well.

what is the combustion chamber volume on those heads?

Mystery Bird

My first thought too was valve float. Also, what about your exhaust? Stock? plugged cat?

96capricemgr

I would echo the valve spring concern, lift capacity is NOT all you have to worry about.
Some of the custom cams available are not going to be happy with the generic single springs that come on most aftermarket heads and there are even some custom cams out there that need endurance racing springs. Someone who was popular around here a few years back ended up losing a LOT of popularity because one of his favorite grinds was destroying valvetrain in 2-3K miles.

37degrees sounds like a LOT of timing to me.

WOOS1

My installer also mentioned that the graph looked odd and that the first thing that came to mind was valve float. But even at that, he felt that is was awful low in the RPM range for that. The combustion chamber is 54cc. Exhaust consists of Hooker long tubes,Y-pipe, no cats, and stupid loud Corsa that is beginning to get on my nerves. The springs are the stock springs that came on the heads which I was told would be acceptable for my combination. I'll call the place I ordered the cam from tomorrow and try to get some reassurance.

ACE1252

Can you be more specific on the cam? Lift numbers? Is it an off the shelf grind? What is the ratio of the rockers(1.6 I assume...)?

Just looking at the slope of the graph(before it breaks up), you should be around 350@5200rpm.

henryz28

Opti maybe even rotor screw backing out.

WS6T3RROR

Probably should take a good hard look at what the a/f ratio is doing as it falls on its face.

If you had a datalog from the pcm that may offer a clue as to what is going on.

37 deg of timing isn't too far out of the ordinary. HOWEVER, if that is what is commanded in the timing map, you are getting MORE than that at higher rpm. Its just a function thats hard coded into the ecm. Better be commanding 31 or 32 above 4000 if actual timing is going to be around 37. The log is where you can see what the ecm is really commanding vs the map.

Should be no knock retard at wot, gotta get that worked out if there's any it will kill performance.

FlatIronsZ

So, what ever became of your issue(s)? Am keenly interested in this head also.

Injuneer

You might want to send WOOS1 an e-mail. He has not been back to this site since 6/26/11.