ok need help at my wits end

[1FAST68]

I can't seem to pick up my truck anymore, I know it can't be maxed out. LOL

My engine is very similar to super73 new 418.
This summer in the heat it has been running 11.20's at 116. I have tried several things to make it back to the 10's in the heat but nothing is changing, runs the same.

I bought another converter that is supposed to be 300 rpms looser, but it doesn't feel any different and kinda acts strange. If I shift at 6500 the rpm drops to 54-5500, or if I shift at 7000 it still drops back the same.
The truck runs the same with this converter

I put a new bigger carb (sv1) and nothing has changed, runs exactly the same.

I put new bigger headers, went from 1 5/8 tri ys, to 1 7/8 stepped to 2" long tubes. Truck runs the exact same if I shift at 6500 where I allways shift, but now it likes 7000 and picked up a .10 and 1 mph.

I do have full exhaust. 3" and dynomax ultraflows but I don't think they are a restriction. The ultraflows are straight through.

Last I have done is get another converter, this one will drop to 5800 if I shift at 6500, and drop to 6200 if I shift at 7000. I have not been to the track with this converter yet. All of the converters have been ptc.

The tune looks good, little on the safe side. Really needs about 2 more degrees of timing.

I don't know what else to do. I need about 2-3 tenths more. I want to do this all motor with no power adders.

[midevil1]

Have you checked the health of the engine? Compression, valve lash, vaccum, etc....I had a engine start losing power VERY slowly and it drove me nuts.

[Super73]

I'd check compression and a leak down first.

What RPM are you crossing the traps?

Are you cutting decent 60's?

Do you have a wideband in the truck? Summit sells the AEM ones for $200, comes with a guage and I believe you can dtatlog it to a laptop. Might be worth getting to square up AFR if it's off.

How do the plugs look?

Quite honestly I don't care for the L92 heads and I think with a better set of heads, you might pick up with a set of ported cathedrals.

What Cam is in it again?

[1FAST68]

Originally Posted by midevil1

Have you checked the health of the engine? Compression, valve lash, vaccum, etc....I had a engine start losing power VERY slowly and it drove me nuts.

Havn't checked compression but it has no blowby what so ever. Cam is a hydralic roller.

[1FAST68]

Originally Posted by Super73

I'd check compression and a leak down first.

What RPM are you crossing the traps?

Are you cutting decent 60's?

Do you have a wideband in the truck? Summit sells the AEM ones for $200, comes with a guage and I believe you can dtatlog it to a laptop. Might be worth getting to square up AFR if it's off.

How do the plugs look?

Quite honestly I don't care for the L92 heads and I think with a better set of heads, you might pick up with a set of ported cathedrals.

What Cam is in it again?

Cross traps at 5900-6000, 60ft is 1.57.
I have a wideband and it likes 12.6-8 is where it runs best.
Plugs look good, have never showed detonation, and could use about 2 more degs of timing.

What is wrong with the L92 heads? They seem to do great on everything I have seen so far.

I will post up cam specs tomorrow.

[1FAST68]

cam specs are
243/251 at 50
654/661
lobe sep 112

[1FAST68]

super do you remember what your converter drops to when you shift?

[midevil1]

Only thing that I know of that is wrong with the L92's are that they make huge power....WITH the right cam. The cam you have looks to be a good grind. You should be hitting the traps at your peak HP numbers in your rpm range. Maybe a gear change or tire change is needed. 2 to 3 tenths is hard to come by. Weather conditions were perfect or just the best pass in that combo has already been realized.?

[Shon]

Originally Posted by Super73

Do you have a wideband in the truck? Summit sells the AEM ones for $200, comes with a guage and I believe you can dtatlog it to a laptop. Might be worth getting to square up AFR if it's off.

Quite honestly I don't care for the L92 heads and I think with a better set of heads, you might pick up with a set of ported cathedrals.

I can match that Summit shipped price on the AEM WB, that is what I use to tune.

And I agree that the L92 heads are not producing the results on the track that the dyno would leave one to believe.

Do you have any Density Altitude data and incremental data to compare? Hard to go off just the ET/MPH not knowing what the weather is doing....best mod EVER for a N/A motor is LOW DA.

[1FAST68]

Originally Posted by Shon

I can match that Summit shipped price on the AEM WB, that is what I use to tune.

And I agree that the L92 heads are not producing the results on the track that the dyno would leave one to believe.

Do you have any Density Altitude data and incremental data to compare? Hard to go off just the ET/MPH not knowing what the weather is doing....best mod EVER for a N/A motor is LOW DA.

Well maybe this is all she has in it. I don't see nothing wrong with the l92 heads, but that is what I have and can't change them. I got a screaming deal on them so that is what I ended up with. They are the cnc'd version.

The WB I have is a lm-1.

I will go back with this new converter and see what happens.

[Super73]

Pulled up a data log and this is what I get NA:
1-2 shift extension = 7150 to 5750
2-3 shift extension with the verter unloacked = 7150 to 5850 (7275 to 5227 with the verter locked)

100 hit
1-2 shift extension = 7276 to 6400
2-3 on that pass bounced off the limiter and I don't want to give you false info.


By you trap rpm and shift rpms, I would say some more gear might help you.

As Shon mentioned, knowing the DA would be good.


The reason I don't care for the L92's is lack of port velocity in comparison to a smaller catherdral port flowing similar or even less air. It's not all about peak CFM. The velocity in which the air is traveling will help produce over 100% volumetric efficiancy easier. L92's have a 261ish cc runner with a huge 2.16 valve yet only flow 335cfm out of the box on a 4.155" bore. Compare that to a 225cc AFR. 2.08 valve, on a 4.125" bore they flow 324cfm.

The AFR's flow less right?? But, they are being tested on a smaller bore diameter than the L92's. This is helping to unshroud the valve on the L92 setup even more, enhancing the flow data. Put them on a 4.03 bore and watch their flow numbers drop like a rock with that valve being shrouded by the cyl wall.

Look at efficiancy.
L92 = 56.0% based on a 261cc runner, 2.16 valve and 335cfm @ .600 lift
AFR = 66.3% based on a 225cc runner, 2.08 valve and 324cfm @ .600 lift.

Now, let's add even more insult to injury. The L92's only flow 193.7cfm on the exhaust side @ .600 lift. The AFR flows 250cfm. Talk about needing a huge exhaust biased cam. Look at the intake to exhaust ratio.
The L92 suffers bad here with only 57.8%
The AFR cleans it's clock with 77.1%

I also mentioned it above, but I'll mention it again.. The 2.16 valve gets shrouded fairly easily on smaller bore motors, killing air flow. IMO, L92 heads need closer to 16-20* of exhaust bias.


But these are just my feelings. Can they make decent power, sure. Will I continue to buy smaller cathedral desingns that flow less or similar air.. Yup..

[Shon]

Super SUPER73!

[midevil1]

Originally Posted by Super73

Pulled up a data log and this is what I get NA:
1-2 shift extension = 7150 to 5750
2-3 shift extension with the verter unloacked = 7150 to 5850 (7275 to 5227 with the verter locked)

100 hit
1-2 shift extension = 7276 to 6400
2-3 on that pass bounced off the limiter and I don't want to give you false info.


By you trap rpm and shift rpms, I would say some more gear might help you.

As Shon mentioned, knowing the DA would be good.


The reason I don't care for the L92's is lack of port velocity in comparison to a smaller catherdral port flowing similar or even less air. It's not all about peak CFM. The velocity in which the air is traveling will help produce over 100% volumetric efficiancy easier. L92's have a 261ish cc runner with a huge 2.16 valve yet only flow 335cfm out of the box on a 4.155" bore. Compare that to a 225cc AFR. 2.08 valve, on a 4.125" bore they flow 324cfm.

The AFR's flow less right?? But, they are being tested on a smaller bore diameter than the L92's. This is helping to unshroud the valve on the L92 setup even more, enhancing the flow data. Put them on a 4.03 bore and watch their flow numbers drop like a rock with that valve being shrouded by the cyl wall.

Look at efficiancy.
L92 = 56.0% based on a 261cc runner, 2.16 valve and 335cfm @ .600 lift
AFR = 66.3% based on a 225cc runner, 2.08 valve and 324cfm @ .600 lift.

Now, let's add even more insult to injury. The L92's only flow 193.7cfm on the exhaust side @ .600 lift. The AFR flows 250cfm. Talk about needing a huge exhaust biased cam. Look at the intake to exhaust ratio.
The L92 suffers bad here with only 57.8%
The AFR cleans it's clock with 77.1%

I also mentioned it above, but I'll mention it again.. The 2.16 valve gets shrouded fairly easily on smaller bore motors, killing air flow. IMO, L92 heads need closer to 16-20* of exhaust bias.


But these are just my feelings. Can they make decent power, sure. Will I continue to buy smaller cathedral desingns that flow less or similar air.. Yup..

I totally agree on velocity and port size, but you shouldn't tell a guy his heads are all wrong. GM changed to rectangular ports for a reason.

I think he needs more gear personally. Being in east Texas he shouldn't have much issue with DA. Come late October or early November my L92 in the wife's Denali picks up 3 tenths in the cool dense air around these parts.

[Super73]

The L92 heads were originally being designed for the new Z06. As you can see they did not go on the car. Instead, GM used a 3rd party to design the LS7 head. Since there were tons of RD dollars spent on the L92 head by GM, they had to go on something (new production LS3's).

I'm not saying the L92's are garbage. What I said is "Quite honestly I don't care for the L92 heads and I think with a better set of heads, you might pick up with a set of ported cathedrals." (Not the best english when I re-read it)

Can L92's make decent power yes.

How can you say "Being in east Texas he shouldn't have much issue with DA." Then in the next sentace you say "Come late October or early November my L92 in the wife's Denali picks up 3 tenths in the cool dense air around these parts." That's exactly what DA is. Density Altitude changes based on weather conditions. In the summer it might be be hot and humid making the O2 less dense acting like it's 3,000ft elevation. Then in Oct it cools down and the air get's dense, maybe 200 feet. The reason your wife's Denali picks up. You just seemed to contradict yourself. No biggy, you seem to understand it though..

[Shon]

Thinking more about this, usually the L92s work better with 400+ cubes which this motor is, is the bore small but a long stroke?
If not, wonder if the cam is not matching the charateristics of the heads?
Have you had it on the dyno to see where the power is and when it falls off?
I am also a fan of the Yank or Vigilante TCs, Circle D seems to be doing well too but I know alot like the PTC and other TC companies.
What is the stall speed of these TCs you are getting? Do they mention an STR?

[midevil1]

Originally Posted by Super73

The L92 heads were originally being designed for the new Z06. As you can see they did not go on the car. Instead, GM used a 3rd party to design the LS7 head. Since there were tons of RD dollars spent on the L92 head by GM, they had to go on something (new production LS3's).

I'm not saying the L92's are garbage. What I said is "Quite honestly I don't care for the L92 heads and I think with a better set of heads, you might pick up with a set of ported cathedrals." (Not the best english when I re-read it)

Can L92's make decent power yes.

How can you say "Being in east Texas he shouldn't have much issue with DA." Then in the next sentace you say "Come late October or early November my L92 in the wife's Denali picks up 3 tenths in the cool dense air around these parts." That's exactly what DA is. Density Altitude changes based on weather conditions. In the summer it might be be hot and humid making the O2 less dense acting like it's 3,000ft elevation. Then in Oct it cools down and the air get's dense, maybe 200 feet. The reason your wife's Denali picks up. You just seemed to contradict yourself. No biggy, you seem to understand it though..

You're right I did contradict myself. Got ahead of myself. DA around here gets well below 100 feet. I think he should either change his gears or wait till OCT. and see if the truck will duplicate it's best time.