Big Dog Chevy

Have made over 400 rwhp with a 52mm tb showing 100kpa at wot. Fuel press might have went up due to injectors not flowing enough? have you ran the car at the track with the current setup?

gixxer9

1. No, it was a Dynojet.

2. I don't know if it was locked-up, but the run was in 3rd gear and I'm unsure if the converter will lock-up outside of OD.

3a. We did not go any richer than 13 to 1 wide open. It started out at ~16 to 1 wide open, and Ion (madtuner.com) made the necessary changes to enrichen the mixture and bring the A/Fr to ~13 to 1. We did not attempt to go any richer.

3b. We let the motor tell us what timing to run. The run was performed with straight 92 octane pump gas, no ethanol. It never pinged, but the ECM did pull timing once or twice, so we reverted back to the last advance value.

3c. Plugs are AC 41-629 .750" reach gasket seat plugs. Gap was set at .035"

4. The tuner was datalogging while the car was on the dyno, but I do not have the logs. I'm unsure of the injector pulse width, but I know he had to re-burn 3 times, changing only the fuel values, before we got the car in the 13 to 1 range. We were going to increase fuel pressure if the last run did not enrichen the mixture enough. The tuner said that my MAF was maxed at 255 and he needed to do something to allow the computer to compensate (change the resolution, maybe?)

gixxer9

The car has not been to the track with the new motor (or in almost a decade, for that matter). I do plan to make a few baseline runs this year, but want to sort some of these questions first. I don't know what track I'll go to yet, but it'll be one of these 3: Wisconsin International in Kaukauna, Great Lakes Dragaway in Union Grove, or Byron, IL.

Orr89RocZ

iTrader: (20)

Depending on the type of converter, some can be forced to lock up at WOT. In the chip bin file, theres an Unlock Prevention threshold value that controls lockup MPH speed at WOT. Some factory bins are set at 88mph, some higher some lower. Locked up you usually gain 10-20whp depending on the setup. My bolt on TPI car gained 10-15whp and that was on a 240-250whp car.

Let the engine tell you want it wants for air fuel ratio as well. It may want abit richer than 13.0 to 1. Only way to know is to add fuel and see what happens.

Plugs should be fine. heat range appears to be ok. I think they are 1 step colder than stock?

MAF maxed out at 255 just means WOT fueling must come from Power Enrichment fuel tables vs rpm. Not a big deal and actually very common on hotter than stock motors. It doesnt take alot to max out a stock MAF sensor. If all other mechanical and electrical issues are non-existant, then perhaps abit more work to the PE vs rpm tables is whats needed to find abit more power in it.

Cam is healthy, the heads flow well, and the intake can support some power, but I'd like to see the intake port matched to the AFR port size, which is close to a 1205 port but not exactly. Try to get into the runner abit to maintain cross section. I dont think its completely killing the power on your motor box-stock but abit more air flow wouldnt hurt anything.

Whats the complete cam specs? Advertised duration and LSA? Seems like you should beable to peak in the 6100-6200 rpm range with that cam. If power is falling off or getting wavey after 5900 it may be floating. Beehives are nice springs for milder cams but for a good hydraulic roller that has somewhat aggressive lobes, I always liked double springs with 145-150lbs seat pressure and 375-400 open, which basically are the AFR 8019 springs. I turned those to 7K rpms with no issues on my 383.

Big Dog Chevy

If you go to Byron let me know and I'll meet you up there and bring my stang if I still have it.

gixxer9

I installed a Mac testpipe yesterday and the difference in power is noticeable. I have yet to put it on the dyno, but the butt dyno says at least 25 to 30 hp. My friend is more optimistic at 50 hp, but the point is that the Magnaflow cat (single) was costing me power. When I get it back on the dyno, we'll see exactly how much. I did not install the cutout.

gmstrong

Thats funny because i stuck one on my truck and swear i lost power.

gixxer9

Cam Style Hydraulic roller tappet
Basic Operating RPM Range 2,400-6,000
Valve Lift with 1.6 Rocker Arm Ratio 0.569 int./0.585 exh.
Duration at 050 inch Lift 234 int./242 exh.
Advertised Intake Duration 294
Advertised Exhaust Duration 302
Lobe Separation (degrees) 112
Lopey idle, Hot Street and bracket racing. 10.0:1+ compression ratio advised.

Big Dog Chevy

Lol, you will see that the more you let that motor breath the more power you will make as long as you have the fuel to support it.

Orr89RocZ

iTrader: (20)

Good sized cam. LSA is alittle wide but reminds me exactly of the GM/Crane 847 cam that has been used on LT 383 type motors to well over 6500 rpms, with peaks in the mid lower 6000 range so its got the duration to do some rpm. The wide split should hold onto power well past peak. It shouldnt fall off like a rock.

gixxer9

I went with 112 LSA in hopes of cleaning up the rich idle (it was smelly at idle with my 110 LSA solid roller). The 112 LSA cleaned it up a little, but not completely. You're right, it doesn't fall off like a rock as it winds out. It just kind of underachieves... It pulls nicely, and harder, as the revs climb but feels like something is holding it back some. I will try a little more fuel at the dyno to see if it wants more. I still think my single 3" exhaust is my biggest offender here.

Side question:

I am getting a random backfire now, and all that has changed is the installation of the cat delete pipe and my spark plugs. Obviously, it has to be the plugs so here goes...

I have a stock distributor (replaced last month) and an MSD coil (not the streetfire). Plugs are Autolite 3924 gapped at .040". Should I go with a different brand (NGK's are the same length as the Autolites, a little shorter than my AC Delco plugs for clearance) or close the gap some?

Big Dog Chevy

Lean backfire maybe?

Orr89RocZ

iTrader: (20)

Yeah could be exhaust leak getting fresh air in the exhaust and popping... my TA does this. Check all plugs to make sure its not lean on one cylinder or too rich. It can get excess fuel in the exhaust and cause it to ignite