klrz28

Here is the dyno sheet and engine build sheet from my engine. Why does the dyno show it fall off at around 4500 rpm? This is a m6 3.42 gear car. Does it need more air? It has a holly 52mm tb with moroso cold air intake. Lt4 heads and intake ported. 30# svo injectors. Ltcc setup. tr55's Gapped at .060. 2.05 1.60 valves. and this is a solid roller cam with 1.6 roller rockers. D&D M6 transmisson centerforce dual fricton clutch. Aluminum driveshaft. Shouldn't it put down more hp and tq than this? Am I losing out from this cam? It was dyno tuned for WOT. What is it lacking?

http://i109.photobucket.com/albums/n...CamCard001.jpg
http://i109.photobucket.com/albums/n...006/Dyn001.jpg
http://i109.photobucket.com/albums/n...006/Dyn002.jpg
http://i109.photobucket.com/albums/n...006/Dyn003.jpg

my1994z28

Is there a reason why you have your plugs gapped at .060?

klrz28

Ltcc instructions say they can be gapped at .060 and other posts Ive read on here others have as well.

96capricemgr

The dyno charts are very hard to see.

Looks like the pistons are .018 down and you used the Felpro .039 gasket? So no quench and mediocre compression????

You put bigger valves in?

mile wide plug gap

rather short duration for a solid roller

The Holley 52mm TB was a poor choice but it is not the big issue.

I would start by bringing the gap down to .040-.045 and see if it then keeps pulling.

my1994z28

I have the LTCC conversion as well,but my plugs are gapped @.045..What plug wires are you using?

klrz28

Taylors, it doesn't misfire

klrz28

I had a 94 Z28 stock motor with the gm 847 cam m6 and I thought it pulled way harder then this current motor does. And it seemed more fun to drive.

my1994z28

Who did the tune for you?Where are you from?I see that you had the motor built in chesterfiled mi.

klrz28

Im in rochester hills, when we finished putting it back together we took it to a dyno in novi and tuned it for Wide open throttle. I think the cam is too small that or the heads are too small. also forgot to mention it has long tube headers with 3'' true duals with dynomax bullets.

96capricemgr

LT1 heads opened up to 200cc with 2.00/1.56 valves can take a 3400lbs 383 car into the 9s with over 500rwhp.
LT4 heads are 195cc out of the box before you went and blindly threw bigger valves at them, now port volume alone is not that telling a thing, cross section means more but in simple terms and from other LT4 results the only way the heads are the problem is if they were ruined by an incompetent porter. IMO the heads were poorly chosen but are not the prime issue here.


Put in some TR6 or Autolite 104s gapped no more than .045 and see what happens. This is the cheapest and simplest thing there is to try right now and several of us who have replied see an issue with .06 gap. Even if Bailey says you can run that gap if you actually asked him I doubt he would suggest it on an engine that should make an easy couple hundred hp more than stock. I really think he would only suggest that on very near stock setups.

Do you know what the compression is?

bw_hunter

At a 90% duty cycle your injectors are good for 500 flywheel horsepower so they aren't the issue. Before you guys rip me up on the calculation remember they're rated at 38 psi, not our 43.5 psi. anyway, after the plug remapping, look at the fuel pressure. Check both static and while driving.

Run a scan and check for timing retard...pulling timing due to knock really affects power.

Decent heads with a decent cam will put down over 400 horsepower on the standard displacement, this is pretty low and there may be several reasons...

Good luck!

96capricemgr

The injector this is grossly missunderstood. over on the other forum there have been some lengthy discussions and turns out some of the higher level guys are finding ET, mostly 60ft. in running as small an injector as possible. I know of an over 500rwhp car using 30lbs SVOs. They can see commanded duty cycle well over 100% but the AFR is good so it is fine. People claim running 100% DC will hurt something but if you stop and think about how brief a time they are at 100% during a 10-11second pass and then consider they are held static for a minute to test flowrate. Rather unreasonable to think a second or two at the top of each gear during a pass would cause failure.

Kevin Blown 95 TA

IS there some information on the AFR? Or did I miss it? Also AFR can get all jumpy if it was misfiring from the big plug gap.

klrz28

The a/f ratio was fine through out the run. I currently have the lt4 knock module in it. Should I take it back out? Ive heard good stories and bad. I will shrink the plug gap and see what happens. Does this cam seem pretty good for this 383? Compression ratio is 10:5:1 If I install solid motor mounts is this going to make it detect even more knock? Forgot to add too it has the walbro racetronix fuel pump set up.

joelster

It doesn't really fall off like the chart shows. Look at the scale on the left. At 5500 it still has 330 ft-lbs. If you overlayed the torque curve over the hp curve with the same scaling it would be normal.

That cam is tiny. 230/236 at .050" and you have 383 cubes to feed. That cam would behave like a hydraulic roller with around 224/230 duration. The first few degrees of LOBE lift on a solid roller simply take up the lash void, they don't actually move the valvetrain.

380rwhp is probably around 440-450 at the crank through an M6 car.

A quick way to see if it needs more cam is to tighten up the intake lash. If it's set at say .018", back it down to .013" or so. If it picks up power (i'd bet money it will) it could use more duration. The motor makes peak power at just under 6k. It will be a good street motor but not good at all at the track. Who ported the heads?