Jacobs serial number 85654

 

I'll let you know. Thanks!

 

Finally got the belt situation ironed out and got it tuned a bit better. Took it to the track for some run and best was a 7.75@91mph in the 1/8 mile. Needless to say, either spark is still being an issue or there is a bigger issue.

 

Fixed belt right? So once again moving along from that issue. Now, those numbers above equate to low 12's in the 1/4 mile, which would put you at 500 horsepower if the vehicle weighs 4500 pounds (or 400 horsepower if your vehicle weighs 3500 pounds) and these numbers are calculated with the 8-psi of boost pressure you stated as well as based on the numbers taken from the 1/8th and mph. If you still say your seeing 8-psi of boost pressure, that would mean 335 naturally aspirated horsepower on the engine alone at 4500 pounds of vehicle weight, or 250 horsepower naturally aspirated on the engine at 3500 pounds of vehicle weight, which brings us right back to what we were discussing in the other thread. The math does not lie, and neither does your 91 mph in the 1/8th, and your again saying your belt issue is fixed, correct? I was pointing towards your skewed timing this whole entire time. In the other thread you felt your engine should be good for over 400 horsepower on engine alone, and if that is the case, 8-psi will obviously net you way over 600 horsepower IF your base horsepower number is correct, so either your engine isn't as efficient as you originally thought (these are the calculated numbers that I am presenting), or there is something effecting the combustion of your engine holding back power. If your fueling is good and is verified by your wideband, and again there are no belt issues which you again are stating there aren't, then it has to be your timing...

 

Hey Street;
Belt is good and holding with the new tensioner. No belt slip present. Datalog is 8-8.5 psi now. Plugs look rich on one side and lean on the other side which is probably a weak spark or valve train issues.

The engine N/A ran a 7.9x at the same mph through a 700R4 on street tires. Truck weighed around 4000 lbs roughly then with a 3000 Edge stall and 3.73s. It weighs about 4200 lbs now, 4L80e and Edge 3400 stall with 4.30 gears.

However, I did up the timing to 34* at WOT and decreased the timing over the curve in the boost retard table and threw in 3 gallons of 120 octane VP race fuel just to be safe during that run making 28* of timing, up from 24-25* of timing during that run and that netted the same results. Plugs look the same and mph gained a little. It also spun the tires on that run about 40' out for about 100' or so but the truck should be running in the 6's and it's no where close.

 

I agree 8 psi should give you near 500 whp if that motor is as stout as the specs say it is.

Not sure whats goin on there.

 

Find a local chassis dyno and get some data.

 

with both of these guys, especially the data that a dyno can provide. It'll surely provide some analysis of what your valve train is doing. Because I believe you may have a valve train issue?

 

Yeah, I don't know what's going on either guys. I'm debating pulling the engine and start digging into it. I would think the engine itself would be about 400rwhp N/A and 8 psi should be good for 550-575rwhp. I have two post that I tune between for timing adjustments and while its not as great as the track or dyno, its local and not 2 hours away. Between the two points, holding 3rd gear with the 700r4 not letting it downshift, it would pull 3rd gear from 60 to about 97-100. Now, its about 102-104. Its gained but again....not even close to where it should be.

I know the headers are a bit of a restriction at the exhaust port and probably needs to be a 1 7/8" for the added pressure of the supercharger instead of a 1 3/4" and the ignition needs to be upgraded most likely. But, either has to be valve train or something else.

 

Pop a rocker off on an intake valve and see if your guides are worn. Usually that would show up acting like a limiter tho but def would show up on dyno as wiggly line as it floats the valves

 

I'll knock that out tomorrow.

 

whats good about a chassis dyno is problems like this will show up so you will know for certain. valve float in my experience showed up as a sudden cliff where hp fell off by 30-40+ or so way before the hp peak should have been. (on a n/a 350) after the cliff the graph went pretty chaotic.
guides are a possibility as they could keep the valves from sealing up correctly, but i would tend to think you would have seen some smoke out the exhaust by now from trashed seals. the guides would have to be REALLY worn.
you could have some sort of converter problem or something too, and that would also show up and allow you to nail it down.
one thing thats hurting a teensy bit is the less efficient transmission and the extra 200lbs over what you had when it was n/a.