95Blackhawk

OK,

I have ALL new electrical from battery to plug. I mean EVERYTHING so don't ask me about coil, opti, etc.

I checked fuel pressure and it is fine at all RPM ranges.

I have changed over to VE thinking it was the MAF with no change.

this eliminates Fuel, air, spark.

The car will miss at high RPM only after the car gets above 190 coolant temp. Could this be weak valves?

They are 978-16's with 130 seat pressure and about 100 hours of operation on them, granted all at road racing RPM's.

Before I go further, give me some idea on if this could be the issue.

Thanks,
Ben

WS6T3RROR

If it doesn't do it ALL of the time then it is not springs. Springs don't relax when they heat up. So if it revs out clean at 120degrees and it doesn't at 190 then it likely is not mechanical/springs.

Although if its something you wish to explore then pull a rocker or two off a lot of times if they are floating that bad the tip of a roller rocker will usually leave an X type scuff on the valve. You could also always go up to a comp 977-16 spring which should be a direct drop in. I wouldn't be afraid of up to 165# seated with hyd roller lifters, and I even run a little more than that on my beater. But.. I would not do that if your cam has a cast iron core (junk) because you will likely break through the heat treat on it and ruin a lot of parts. Just as a general side note, just because thats the spec comp says doesn't mean thats what they are. Test every spring you get when its for something like this, then test them after they've been run because some of them fall off bad after some thrashing. And always measure installed height don't assume anything (probably preaching to the choir there but its worth saying).

What exactly are you calling high rpm (where does it miss)?

Does it miss sitting still revving or is it only under a load?

Describe the miss, does it bang out of the exhaust or does it just lay down and act like crap?

What kind of plug gaps are you running?

How do the plug gaps look on the grounding strap are they correct heat range for the application, what plug?

I am guessing this is a new problem that has cropped up and it was not always this way?

Do you have any logs of the car doing this that you care to share?

Do you have access to another set of injectors that you could try, maybe you have a couple that are stuffed up and the drivers have problems at higher temps. Stock will work even, just don't test under load.

Do you have oil temp data? Could be an issue with the oil and lifter valving. If you are crafty you could always take a set of old hyd lifters and make pieces to go in them and make them solid just for an a b test to eliminate the hyd lifters as a last resort before trying springs.

Btw, on all of the lt1's I work on I move the icm and the coil off the cylinder head and mount it on the body then make a new longer coil wire. I am sure you could find a place for them under the hood. The cooler those two items run the longer they last.

If you have any parts of your harness that are pulled snug to connect to critical sensors I would extend them. I have seen problems with that on swaps before, ran just fine until the engine rocked in the mounts then it would spit and nearly die.

Apologies for the length of the post, but I'm kinda starting to feel bad for you with all the brain damage that car has been dishing out.

MachinistOne

I have seen this happen when the valves are getting sticky at higher temps. More info on the heads?

95Blackhawk

To answer each question and help in this discovery:

Now it seems to be 5500+ rpm when this happens. As the car gets warmer, it gets worse and as the car has been driven more over the period of a few thousand miles, the condition has become worse.

it is especially prevalent under load however part throttle seems to also be missing at these high rpms but it is just not as obvious.

It lays down. Upper RPM becomes a combination of misses and laboring to increase.

Gap of 0.035 with plugs 2 heat ranges colder than stock.

This is a "newer" problem that cropped up probably 8 road racing hours ago. This is about 1 year.

No scans because this is a track condition issue but plan to "cheat" and have the computer on during one of my runs today.

Stock injectors are still with me so I CAN try this but seems a distant shot and would prefer to pursue common knowledge of weak springs first.

Head oiling is confirmed not to be an issue. I prefer to replace valve springs before I crack into my intake for lifters.


Valvetrain (all new):

lift just under 0.600 with 1.6 NSA pro mag rockers, 7/16

CC hardened pushrods with guide plates

LS7 lifters

heads: AFR 190

intake valve: Manley Severe Duty 11828, 2.055 dia, 128 grams
Exhaust: Manley Severe Duty 11827, 1.600 dia, 98 grams

Springs: CC 978-16 with spring pressure confimed before heads installed

Installed height: 1.850 intake and exhaust

Installed Seat pressure: 130 lb @1.850

Installed Open pressure: 355

coil bind: 1.195

Retainer: Titanium

94 Sunburst formula

I had the same problem about a year or two ago. In open loop driving car would run fine all rpms, as soon as it went to closed loop it would miss only with a load on it. Had no codes. Ended up being a o2 senser.

JAKEJR

With all you've done already I suspect you've done this, but have you had the valve covers off to have a look-see?

If you suspect the springs, you can check them whilr they're still installed. All you need is the tool; another necessary addition to the tool collection. I use to check 'em after every 10passes or so or at the end of the day at three or four day meets. I learned early on that in racing applications springs and spark plugs are expendable items.

Jake