These particular heads flow 277 on the exhaust. The LS3s are 252.
I am not trying to get caught up in flow bench stuff, but
over-scavenging has crossed my mind. Just thinking out loud a little here.

 

IIRC Kip is offering the OP these Dart LS3 heads to try to solve the issue before dropping the coin on them......SO it does somewhat require the limitation of other variables.
Speaking of variables, the OP is spraying so if the cam was spec'd for juice then the shape of the intake runner really don't mean **** anymore....it's all about the E/I balance at that point.
MPH lost NA and spray or just one or the other ??
you did jump the static compression up from 11.5 to 13 correct ??
There is belief that while that should help NA, spray, like forced induction prefers lower cranking pressure to do it's thing.
Back when Billy Glidden was running 400 inch Cleveland headed SBFs up all the Rat motored guys back sides, he found that his 11:1 engines ran the same ET at the track as his 14:1 combos which would dyno a few more ponies. He said if it limits the longevity and doesn't get the car from A to B in less time then he ain't doing it.

I agree on the flow bench only being a small "guage" for discussion, as it measures air, yet engines burn atomized fuel. There's also many variables to the listed flow numbers which requires knowing how to compare.
Size of bore plate, radius on the intake port, exhaust with or without pipe and what diameter and or length of pipe....blah blah blah....nauseating really.
More crap to add to this **** storm of analytics is the exhaust seat height to intake seat height relationship. Nitrous specific set ups apparently change this to minimize reversion as well as over scavenging during cam overlap.
Tony Mamo explained this really well in another thread how if an NA head flows too high E/I ratio, he'll change this seat relationship as well as valve job angles to better optimize said combo. Class racers have been using 50 and 55 degree valve seat angles for years to enhance the .600" to .900" flow numbers.
I remember from my GEN I juice days (late 80s-early OTs), NOS loves more exhaust duration, high lift, big header pipes, and low compression ratio. "Bottle Baby" engines were absolute sacks of **** on NA but became Frankensteins on the ****. It really is difficult to have a streetable; runs well NA and on spray with just one heads cam combo.
I really do hope you figure this one out, cuz the EB FRC is one of the coolest body/color combos ever......

 

precisely what I was thinking. The heads need to be isolated for testing. There is no other way to do it but leave the current cam in. The cam can be changed later if necessary.

No I have not run it on the juice, only N/A. Once I'm good with it N/A, juice time.
Note, I only added compression so that I could gain those few extra ponies, but moreover so I could cam the engine how I wanted.

So last night, I was thinking maybe the cylinder pressure isn't high enough for 110 octane. While I realize it could gain pressure while wound up, it does not as its down on power. Checked cylinders for static compression and found 6 at 190psi and 2 at 210psi. I am going to compare the cylinders for lash and see what I find a little later today. Also, at 205psi on my last engine, I had 3 pump gas : 2 -110 as a fuel mix that worked well, so fuel adjustments may be necessary.

...more to come.

 

Just doing some basic lash experimentation:

Exhaust Lash changes did not affect compression, changing it from 0 to 0.013. I also closed lash to zero, then slightly opened the valve, noting a loss of about 5psi as a test. It appears the lash is not as sensitive on the exhaust w/regard to adjustment, at least not cold.

The following are results for the intake lash:

Intake Lash / Static Pressure:
0.0015-0.003" 190psi
0.004- 0.005" 210psi
0.007" 220psi
0.008" 230psi
0.010" and greater, 240psi

Is that normal?

I'm trying to figure out how much cam duration is reduced by lashing at
0.010" cold. So, when engine warm, what 0.020/1.7, 0.011"?? I'll be testing static and lash when warm on next track visit.

Kip, how much cam duration do I lose with this cam by doing this? I'm not really approaching 0.050" yet right, still on the ramp. But, also is is safe to lash this way w/this cam?

 

About every .009" -.010" of lash is about 5 degrees of duration, I would not loosen up the lash too much more than it was designed for. If you run it too loose, it will be harsh on the valve train.

 

BS.....she's smaller than my Impalas :p ..... LOL

KW

 

speedtiger, where did you pick up those heads? Also, I see you used the 1208X springs, but what install height? Just curious why you didn't use the Dart Springs?
This basically make their heads $2550 from Summit + cost of springs. Spring rate too low on the Darts?

 

The standard springs are 650 lift springs. I wanted a springs that could take more lift. In case I wanted to go more aggressive on the lift.

 

might have found one bugger, not sure how much it is worth in hp.
What do you guys think about high crankcase pressure? Last time at track,
it blew off a push-on oil cap. Today, as I was pulling the intake, I noticed the guy who put the engine in plumbed the valve cover and valley cover wrong.

I completely disassembled the intake and found nothing wrong there. Valvetrain looks stable. Am going to lash the rockers, correct the pcv plumbing, then back to the track.

 

I said it would work in the sense that the cam is optimal for a square port head,

What I also said was, "How will you ever know if it was the heads or the cam, if you change both at the same time?"

If you don't, you'll never know what caused the issue.

I didn't want this to sound like I was saying what Paul said was wrong, I just wanted to clarify my statement on the cam and testing things one at a time before changing multiple parts.

I was going to suggest if possible to advance the camshaft at least 4 degrees, if not 6 degrees to be more favorable to the larger port cross section and shorter manifold runner as it seems that is the way Paul is leaning currently.

Hopefully the p to v is there to do it.

 

I'm guessing the power is secret?

 

By the time I'm done w/this thread, dyno graphs, cams, heads and 1/4 times to be posted. I'd rather not discuss dyno data without 1/4 mile and especially 1/4 MPH to back it up yet.

 

Current cam clearances: Intake: 0.170" Exhaust: 0.180", so looking good.

 

NVM, I see that is P to V.

You should have enough to go 4 degrees advanced if not 6 degrees. I can ask Kip for your current lift at TDC figures and plot it from there to see how much further the intake valve would be lifted at TDC by advancing the cam 4-6 degrees. Exhaust p to v will gain clearance from advancing the cam since the valve will close earlier.

 

Update:

Checked lash on all the valves. Found 3 or 4 rockers close to 0.004", 1 around 0.008" and one way way off at 0.014". Note, nuts were loose. Engine still new and this was the first adjustment since break-in, so ok, no problem. I set all lashes to 0.0015". Note, lashes above are COLD. I have not had it running long enough to check them hot.

Fixed crankcase venting. No more blowing the oil cap off and crankcase pressure appears back to normal.

On Sat, brought it back to the track for testing. As soon as I took it off the trailer, notice that light vibration still there. Drove it around the parking lot. Engine is not smooth and I feel some vibration, in particular a light vibration as I bring the rpm up slowly. Put it back on the trailer.

Monday, just got around to looking at it. Pulled codes and found P0200 and 2048 misfires on cylinder 3. So I check all the injector for resistance and test for 12v at the connector. Nothing wrong w/3. So, I check resistance on all 8 injectors (~12 ohms), verify voltages at connectors (12v), coil resistance(~same from one to next), plugs, plug wires(~44 ohms), and see nothing wrong. Next up, injector harness ground checks.
Number 6 harness connector is broken clean but the wire was so close to it, it was near impossible to see.

I am not sure how long the injector connector has been this way, but between this and the previous valve lash, maybe I found some lost power.

 

That lash being off that amount on a few cylinders will not make any notable performance difference, but having a dead injector sure will. I could see a dead injector causing a vibration too.

 

Keeping the fingers crossed for ya!

KW

 

Hope that fixes it!

 

Yeah, I'd say a misfire is going to cause a vibration or two lol.

 

If it runs well at the track, Holley HiRam is next.

Anyone notice summit has dropped their prices big time on this intake ? Got to find a dbw TB for their 300-123 intake.