Buford T Justice -- the full tour

[TheSilverBuick]

Scott he had 10 degree initial, and 28 degrees advance, meaning he has 38 degrees total...... it doesn't seem out of line....

That does make sense.

For reference this is what my AFR's looked like when my fuel pump couldn't keep up. I like scatter plot data, though its a little tougher to see than a simple time based datalog. The second chart really shows it, the duty cycle is nearing 100% and pulsewidths are going up, but the colors are turning greener instead of staying blue. The first chart, you can barely see the trail of blue (rich) dots along the top that start turning green as RPM goes up and the AFR's are leaning out.

I was poking through some of Hot Rod Magazine's youtube video's and I found my quickest run on Drag Week. Looking at the datalogs in that air my fuel pump capped out at 4,000rpm. I was right up to 15.0:1 AFR's at the top end :shock: Not good.

http://www.youtube.com/watch?v=3mfFQrQdpxk&feature=youtu.be&t=13m35s

I kept adding fuel to each run and the AFR's were not changing but the duty cycle was increasing so it was getting the command for more fuel, but the fuel pump was coming up short.


Here are scatter plots of the data from one of the runs that day. BTW, scatter plots are awesome. (but apparently the screen captures of them are not.. squint for the blue.)


This plot is RPM (x-axis), Manifold Air Pressure (y-axis) and the color is AFR. This datalog also captures my sad launch technique too. I brought the engine up to about 3,200rpm (where the blob of yellow above the end of the red line), bogged down to ~2,300rpm when the tires bit (the small blue cluster next to the 778.0 at the top if you zoom in), then pulled across the top.



This plot has Duty Cycle (x-axis), PulseWidth (y-axis) and the color is AFR. As the duty cycle is going up the AFR's are leaning out, which is a sign of losing fuel pressure.



It shows very clearly about 4,000 rpm it starts losing control of the AFR as it leans out it goes from dark blue to green. Fuel pump can't keep up.

[TC]

He's running a COMP XR276HR-10 cam. 276/282 Duration (224/230), .502/510 lift, 110 LSA, 106 degrees intake centerline

Thanks Andy.... Brian did you degree the cam in?? and if not how was it installed, did you advance it using the timing gears??.....

Also did a little research on the heads, they say they're not going to support much more than 350hp and that's being tricked out, problem is they flowed less than 200cfm on the intake stock.... They don't have the capability to pull much past 5500-6000rpm.......

Here's a thread over at HotRodders.com that is all about those heads, might want to read it....

http://www.hotrodders.com/forum/14101083-cylinder-head-227854.html

[TC]

That does make sense.

Maybe not to a guy that studies rocks....... You do understand what Initial is right?? it was set at 10, then the bushing in the distributor allows 28 degrees of mechanical advance, so at full mechanical advance the timing on the balancer should read 38 degrees..... or in simpler form 10+28=38.......

[TheSilverBuick]

Maybe not to a guy that studies rocks....... You do understand what Initial is right?? it was set at 10, then the bushing in the distributor allows 28 degrees of mechanical advance, so at full mechanical advance the timing on the balancer should read 38 degrees..... or in simpler form 10+28=38.......

I did just say it makes sense........

[Brian Lohnes]

TC, Randal was agreeing with you.

On the heads, I know. These are only going to be on the engine for a short time. I am trying to optimize this combo before blowing the thing apart for the next round of stuff. Cam is staying the same. Stuff above it is changing.

Cam was installed straight up and not with a degree wheel.

Kris, no evap, emmissions, etc to worry about. We thought the fuel system may be clogged or even potentially had a pin hole that was sucking air. When we ran the car with the feed hose for the pump into a gas can rather than hooked to the factory lines, it acted the exact same way as it did when properly hooked up. No doubt that tank probably has crud city in it, but that does't look like the main culprit here. I have a vacuum gauge in the car and at WOT everything looks pretty good with respect to that end of things.

Randal, those graphs look like fireworks.

[andy30thz]

I have the former return line capped (spoiler alert, I will need it in the future)

Why are we racking our brains when this thing is getting a LS motor with a big turbo!!!!!
I suppose there might be some other reason you'd need a return style fuel system.....

[TC]

I did just say it makes sense........

Sorry Randal I misread, my bad, damn I'm an idiot sometime.....

[TC]

Cam was installed straight up and not with a degree wheel.

Ok that's what I wanted to here.... I hope it's as simple as a fuel pump, at least that would be the easiest fix..... Though I still think the carb's to small, if you can borrow a 750 from someone, it might be worth trying......

[Deaf Bob]

I think Mr4Speed got it the closest...
Take your cap off the tank the next time you run on the dyno..
I have seen guys run boat tanks and stop running.. When the suction was gone (after a derby) it fires right up.. Does not present itself as a problem untill they up the idle and run some RPM's... You will hear air rushing in the tank when the cap is removed..
Running on the street butt dyno is like checking out the car in the lot.. Running on the dyno is like a derby..
Bet your vent is plugged...

[Scott Liggett]

TC, Randal was agreeing with you.

On the heads, I know. These are only going to be on the engine for a short time. I am trying to optimize this combo before blowing the thing apart for the next round of stuff. Cam is staying the same. Stuff above it is changing.

Cam was installed straight up and not with a degree wheel.

Kris, no evap, emmissions, etc to worry about. We thought the fuel system may be clogged or even potentially had a pin hole that was sucking air. When we ran the car with the feed hose for the pump into a gas can rather than hooked to the factory lines, it acted the exact same way as it did when properly hooked up. No doubt that tank probably has crud city in it, but that does't look like the main culprit here. I have a vacuum gauge in the car and at WOT everything looks pretty good with respect to that end of things.

Randal, those graphs look like fireworks.

When you removed the evap cannister, did you plug the line? Cause that is your tank's vent. Plug it and air can't get into the tank. Bad!! Unplug it and put a little filter on it. Spectre makes them. Or, you need to get a vented gas cap.

But, since you had the same problems sucking gas out of a bucket, I'd start with the fuel pump.

[Beagle]

I think Mr4Speed got it the closest...
Take your cap off the tank the next time you run on the dyno..
I have seen guys run boat tanks and stop running.. When the suction was gone (after a derby) it fires right up.. Does not present itself as a problem untill they up the idle and run some RPM's... You will hear air rushing in the tank when the cap is removed..
Running on the street butt dyno is like checking out the car in the lot.. Running on the dyno is like a derby..
Bet your vent is plugged...

The guys running the boat tanks had the wrong kind of cap on it. My old boat tanks were sealed and had a screw in the cap. You loosened the screw in the cap if you wanted to make it out of the marina. Old Echo / McCulloch weedeater gas caps are another good example, there's a neoprene vent that only allows air in when it's working right. A lot of them now have a separate vent, but I'd get them in all the time where the cap was leaking so somebody would put a piece of saran wrap between it and the tank. No more leak, and hey, the damn thing will only run for a couple of minutes.

Where all did you pull your AFR's from? Does it do okay for a while and then go thin? When you jetted it up, did the same range get fatter and then go thin again later? If the pump can't keep up you should have control of it until it can't keep up which is probably gonna be upper RPM's? Randal's star chart kinda reflects that.

ah, I found the charts - kinda hard to see, do you have them as an excel sheet? It looks like they were moving a little?


TC, I'm coming up with about 500 actual CFM - there may be a few HP in a 750 but my math says a 650 DP should get you to 350 hp on this mill. Brian is about 60-70 hp shy of that right now. I think this combo could go 350 fwhp maybe.

[Loren]

I wonder if you could check the float bowl levels w/ the car under power on the dyno. Might be exciting in the wrong way, but seems like there is some basic problem here and that might shed some light.

[Brian Lohnes]

Beags, we were getting the AFRs from the tail pipe, which I know is not idea, but the last time we were getting the readings from the header mufflers and they were virtually identical. I "trust" the readings. Travis was texting me last night and he had a 1400 wheell hp drag car on there he was tuning and the AFRs were moving and accurate to what he was tuning for, so the meter is working OK.

Didn't think about venting the gas tank, but when we made the pulls with the fuel line in the gas jug, it acted the same and made the same hp (with same AFRs) so I don't think the tank is a problem.

Not sure what the max HP of this setup is, but I think it has to be better than the 220 peak we saw. Maybe it isn't. LOL. I don't see how a 650 DP would struggle to feed this thing (assuming that it gets the right amount of fuel).

Detailed list of the parts in use here:

Block is .040 over 350

MSD Pro Billet Distrbutor
MSD 6AL-2 box
MSD coil

Holley 650 DP carb

Weiand Street Warrior Intake

Iron 083 cylinder heads with some bowl and port work, multi angle valve job, and a 12-thousandths shave. Combustion chambers should be 62cc.

.015 -- steel shim head gaskets

Compression math by Summit calculator is 9.2:1

Flowtech 1 5/8 headers

COMP XR276HR-10 cam. Duration is 276/282, lift is .502/510, LSA is 110, and the intake centerline is 106 degrees


Anyone got desktop dyno software?

[Brian Lohnes]

Using an online (and fairly detailed) engine analyzer program it says the engine should make about 310hp (crank) at 4500 RPM with the numbers I jammed into it.

Who knows if that is accurate or not, but what's interesting to me is that the engine is making peak hp at 4500 currently.

[Beagle]

I put it in engine analyzer and came up 354 fwhp / 388 tq , it's where I was "guessing" what it should make earlier so I could get the CFM expectation. I'm lazy and didn't feel like guessing VE.

5500 hp peak fits what Comp says about the cam, torque pk at 3500 should be fun on the street. I used a 1.94 valve head claiming 220cfm at .550 lift, performer intake, 650 carb, 1.525 inside diameter pipe x 28", 800 cfm full exhaust may be "optimistic". 355" with no water pump or fan.