Help with idle EGTs. Can't get 'em down...

Here's the deal. 511 KB hemi. Brad fuel heads. Mert 14 hh. 990 pump. K valve.

Question 1: When I leaked the barrel valve, I capped everything except the hat outlet. I left the hat outlet wide open because I didn't want to blow through my fuel flow meter. Is this OK, or should the hat line be hooked up? It would be difficult to flow just the hats, as the line splits to the hats and ports after the flow meter.

Question 2: What kind of idle timing is typical? I started at 25 which seemed to be way too far back, so I am currently at 30. Keep in mind, my density altitude here, as I type, is 8000 feet and usually worse. Since there is no pressure here, and not much boost at idle, is it possible that it might take even more timing at idle?

Question 3: It seems that I am getting some drop in EGT as I lean the barrel valve. My last measurement was at 65%, measured as described above, and got my EGTs down to high 500 range. That seems to indicate that I am burning fuel in the pipe. So, should I try it at 60% to see if they continue to drop, or should I give it more idle timing?

Maybe I'm wrong, but it seems to me that the only way to adjust idle EGT is with timing and the barrel valve. True?

By the way. Don't worry about the idle timing being advanced. I will use the 8973 to bring it back during the burnout and during the run.

Any help would be appreciated.

-Brian

 

Thanks Mike,

I set TDC with a piston stop and degree wheel with the heads off, so I'm pretty sure it's close. Pulling the engine through clockwise, the 30 degree mark hits the pointer before the TDC mark, so that seems right as well. No flames in the pipes.

I guess the thing that has me scratching my head is that by moving the barrel valve from 87 all the way down to 65 I should have seen HUGE changes in idle EGT, and they just weren't there. 87 sure made my eyes water though!

That's why I am thinking the timing isn't enough for this altitude. The symptoms point to retarded timing and fuel burning in the pipe. I just don't have enough experience with these engines to make that call with confidence.

-Brian

 

Mike, I'm just learning this myself, but, I thought the leak down should go through the hat nozzles?

Won't a .040 nozzle flow differently than .080 nozzle at the same 100 lbs leak down pressure thus affecting the barrel-valve percentage?

I thought the leak down percentage was for setting a specific amount of flow at idle through a specific size opening, the hat nozzles, am I wrong?

Just asking because I want to learn, thanks.

 

Update: I am getting info through the back-channels that the fuel heads take alot more lead than the Fat heads. I set my idle timing at 30 thinking it was a bunch, and it turns out it's probably still way back from where it should be. I'm also going to make sure the ports aren't cracking, which would make the barrel valve not respond to changes. That would certainly explain the symptoms.

I'll do some more testing tonite.

-Brian

 

you need to have the hat hooked up to and then get percentage.

 

Hey Brian, we run the same setup as you, 526kb, 14hh 27% over, brad fuel heads, promag 44. Before the winter when we fired it up we had 30 degrees timing, and i'm looking at our data right now. cyl 4 was around 250, cyl 7 was 650-700. The rest were from 350-500. I believe our leakdown was 75 leak in the motor, however after startup we adjusted the barrel valve until we seen desired egt temps. Idle was about 1800, no boost.

 

We also leaked the barrel valve w/ the hat nozzles hooked up. Even though you're leaking the bv itself, I would think the lack of back pressure on the backside would make a difference? Guess you could hook it up both ways and see.

Josh

 

With the barrel valve leaned out a little I see balanced temps, but high, around 700. If I richen it up I start to see what you show above, the EGTs spread out real bad. I'll drown some out, so they go cold, 100-250 spitting raw fuel, and others are still lit and dry and show 700.

I have been told I should be able to balance them pretty close and be in the 350-400 range, so sump'n ain't right yet.

Right now my plan for after work is to move the timing forward more, and re-blow the bv to 75% and start over. I'll also check to make sure my ports aren't opening at idle.

-Brian

 

Edit. I think I'll set it to 80% instead of 75 for my next start.

Question: Is it common for the pipes to spit fuel at idle? If so, maybe that's an indicator I need to watch for.

-Brian

 

You might see if they even out if you bring the motor up until the port nozzles open up.

 

One other thing I would look at is the butterfly gap before re-doing the leak down.

 

That's true. BV leakage is just a reference. Everyone should be clear however on what the numbers refer to so you're not far off on start up.

 

OK, I just tested it on my system, Bird w/Enderle square bv, and there was a 2% difference between having the outlet wide open versus going thru the hat nozzles.

The wide open outlet showed more flow when compared to the nozzles which is what I expected although I thought it would have been more of a difference than 2%.

Probably not enough to worry about but need to be consistent on method used.

 

Good to know Paul.

 

I ran brad fuel heads for years and ran real fast so I have some knowledge of them. . .First off, you will be safe at 32 degrees. ( i ran as much as 36 with a 44 amp mag in bad air) second. . .are your return poppets pointed in the right direction and are the poppets in the correct place one is an idle check (around 6lbs) and one is a pump saver (around 175 or higher). . I have always set the bv with everything hooked up just cap the two returns (idle check and pump saver) set bv at 78 to 80 percent. your air gap on the blades should be about 10 to 14 depending on the hat and that thing should idle around 1600 to 1800 rpm. (are you using a K-style or square barrel valve) should be the K-style.

 

Bruce,

Thanks for your post. I'll check everything out, fire it with the new settings and report back in a little while. I appreciate the timing advice. We always have bad air, 8500-10,200 feet, so your info gives me some good parameters to work with.

-Brian

 

I had a very similar problem on my blown BBC and it turned out my Enderle pump was bad. I put a new one on and egts at idle came down. My old pump was tested only a few weeks before the problem popped it's head up and it tested within spec.

 

OK, got some improvement finally.

Butterflies: .010
Timing: 36
Idle: 1800
Fuel Pressure: 9.5
Idle poppet: 10
Ports: 14
Density altitude at test time: 8150 feet.

I set the BV to 80% with the backside open. On startup, EGTs climbed hard, head temps went with them. Got pissed, started cranking flats into it until I got spray out #1, then brought it back just enough to dry it up. By this time she had been running for a minute and a half or so, so I killed it.

When head temp dropped to 145 I fired it again. She was fighting the starter just a little, but fired off. I checked the timing real quick and then started a data log. By the time I started the log the head temps were up to 160. Heres the start and finish numbers on a 30 second log:

Start Finish
Head temp 160 183
Egt 1 422 360
Egt 2 432 468
Egt 3 442 423
Egt 4 400 272
Egt 5 560 653
Egt 6 466 578
Egt 7 552 651
Egt 8 518 640

After I killed it I re-blew the BV to see what it was set at. It showed 93%. Again, this is with the hat lines off.

So, here are my observations:

1. EGTs fell on the front cylinders, and went up on the rear during the warmup.
2. The engine liked the timing, going from 30 to 36 and would probably like more, but is starting to work against the starter.
3. The head temp rise, 22 degrees in 30 seconds seems too fast.
4. The BV seems too rich. I wonder if the EGTs would drop if I brought it back to 85%.

What do you guys think. Is this a runnable combination, or do I need to keep tweaking on it and get the EGTs more balanced and slow the head temp rise?

-Brian