I questioned the cam grinder on the 10 degree split. He said he felt the exhaust needed some help due to the flow numbers I provided him.
FLOW NUMBERS:
0.200........144/110
0.300........197/142
0.400........243/177
0.500........286/188
0.600........291/196
0.650........293/199

He wanted to get it closer to 70% exhaust to intake, from 0.500 up they are around 67%.

It starts to put you in the seat around 4200. It runs and idles great on the street without any surges (due to drilling the tb).

And yes it plateaus from 5400 to 5800 then wakes up again at 5800 and runs out of steam at 6200, then plateaus again.. The problem is I'm running from 5500 to 5900 in third gear at the track. And that's in the really poor part of the power band. I can't get over that hump.

Can you explain the ports going sonic? I'd like to understand this better.

 

"sonic" is when the speed of the air in the port starts approaching the sound barrier. Not good for air flow. Not likely that is what is happening in your case.

You have an airflow problem somewhere. It will just be a matter of figuring out where it is at. I would start at the airfilter and work my way back through the motor to the tailpipe. You don't want any steps or ledges in the way of the airflow.

 

As for the restriction, it's down to the following:

Throttle body
Nitrous plate (bored out for 58mm TB)
intake manifold (ported and port matched to heads)
Heads

a) I've run it in Speed Density with all the intake parts off (elbow, MAF,CAI, filter) for a best of 11.87 @ 111 with no difference in 3rd gear (5500-5900)

b) I have long tube headers that exit straight out through electric cut-outs, so that eliminates the exhaust system.

 

Have you ever used DataMaster to look at MAP over a full 1/4-mile run?

 

"I have long tube headers that exit straight out through electric cut-outs"

Actually that could be "a" problem. The cut outs need to be properly located in the exhaust system as part of the "collector length". Typically the best location for the cutout would be 18" beyond where the primary pipes end in the collector of the headers. Other lengths would be 36 and 72". In your case I bet something an inch or two shorter would be best.

Those dimensions may not be optimal for your car but they are in the ball park. If your cutouts are at say 27 inches or 54 inches that would be the worst locations and you could actually lose a few ponies. This is "wave" tuning.

Collector diameter is the next most important thing regarding the exhaust. I would suspect your best collector pipe diameter is somewhere 2 3/4" and 3". What size exhaust collector pipe do you have?

 

I have enough experience to say, it depends. On an EFI car, the speed the ECU responds to changes in TPS voltage and the vacuum signal from the MAP sensor is the limiting factor. I have put a single plane manifold and a large TB on a '92 350 and there was just no way it could be tuned for throttle response. We must have burned 50 chips proving it and burned through a tank and a half of gas. Slapped the original TB back on and voila - it ran fine. OTOH, I am using a 2,200CFM TB on my race car (with an Electromotive TEC3r) and the throttle response is fine. LT1's seem to do fine with 58mm TB, I have not tried larger.

Rich

 

Is that cam a solid roller cam? I sure hope so as that is a huge hydraulic cam for a 355 that could be taxing the lifters.

BTW, I will send you a couple lt1 edit files to try tonight. FWIW, my cam was a 235 242 .567 .592 (with 1.6's) 112lsa.

 

Here is a snapshot of three 1/4 mile runs:

This is in speed density mode with all intake parts removed except TB:
MAP averages 98.5+
11.87 @ 111

laptop lost connection right after launch - you'll notice the missing data from 1st gear



This is in MAF mode with all intake components attached (elbow, maf, cai, filter):
MAP averages about 97
12.13 @ 110




This one is in MAF mode witha all intake components and THRU MUFFLERS
MAP averages about 96
12.43 @ 108

It pulls timing thru the mufflers at launch - my guess is some added vibrations due to exhaust going thru entire system.

 

I have 3" diamater collectors on Hooker Super Comp headers.
I have a set of Flowtech Race Readies (pictured) attached to the collectors and the cut-outs are on the straight end of the race readies.


They are 10 inches long - so add 10" to the collector length on the header (I can measure later when I get home) for the entire length of the system.

The "wyes" angle toward the center on both race readies (assume the race ready pictured is on the drivers side collector - looking from behind). Both "wyes" join together into one pipe that rides along the driveshaft and goes into a dual outlet Flowmaster system. I do not have cats.

I will get an exact collector length when I go home for lunch.

 

It is a hydraulic roller.

I have the stock lifters. I didn't want to mess with the Comp R's because I drive it to the track and around town on Saturdays.

I intended to buy a set from Cam Motion (I do not remember the name) when I got the cam, but I waited 3 months for them and I was told they were still 3 months out on back order, so I cancelled the order.

That's great for the LT1 edit files. I plan on going to the track tonight and getting the AFR down to 12.5 or so and start working up. I am very interested in the timing tables.

Thanks

 

lightbulb starting to come on:
18, 36, 72 = full waves (waves lengths appear to be doubling -yes?)
27 = half wave (1/2 way between 18 and 36)
54 = half wave (1/2 way between 36 and 72)

Very good information

 

That is correct. To get the lengths absolutely correct you would have to test at the track, dyno or buy a program like PipeMax to dial it in further.

 

What was the barometer for each of those pulls?

 

#1 = 100.8 kPa
#2 = 99.7 kPa
#3 = 100.8 kPa

 

The collector lenght is 22 inches from the beginning of collector (at weld to primaries) to the cut-out. They cannot be cut shorter, as seen in this picture:



It seems hard to describe so I added a picture. Here's what it looks like from the front showing how the wyes turn to the inside and enter the single pipe to the muffler.