Author Topic: Engine damage during dyno run (428 CJ Resto build cont.)  (Read 1878 times)

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FElony

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #15 on: April 16, 2019, 11:51:55 AM »
Pressure differential.

You mean, like when you suck a drink through a straw?

FElony

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #16 on: April 16, 2019, 12:02:00 PM »
My question was a valid one. Barry treated it as such. I have a '67 Mercury that came with a 350 cfm 2V on its 390. You can accelerate it in second gear until it just stops increasing speed. I wonder what the mixture is doing.

So Drew, I realize spending a month on a tuna boat in a sausage fest with all those sweaty mens gets you a little askew, but let's not get into theory. Just the facts, ma'am. Put a stock 350 cfm 2V on your Galaxie and run it down the road in 2nd until its done, and data log the A/F so we know what's really going on. What is learned, is learned by all. Don't let your ego get in the way. Again.
« Last Edit: April 16, 2019, 12:42:57 PM by FElony »

shady

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #17 on: April 16, 2019, 12:21:39 PM »
Don't do it Drew. A Chevy motor in your Galaxie? Anyway, a stock 352 with a 2bbl will run out of valve train b4 it ever leans out.
What goes fast doesn't go fast long'
What goes fast takes your money with it.
So I'm slow & broke, what went wrong?

Falcon67

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #18 on: April 16, 2019, 12:22:02 PM »
It's running out of fuel.  If it feels like it just gives up, or comes to some RPM and just "flat lines" - it's most likely out of fuel.  Lean out, whatever - it's lacking fuel.  The first 351C I put in the Falcon, before I went to a full cell/return fuel system, flat lined in 2nd at 5200 with 5 psi of fuel pressure at the carb (650DP Holley).  The pickup out of the tank was 3/8" but it necked down to 1/4" as it passed through the plate that mounted on the stock tank.  Got another tank, drilled the sump and installed a #8 bulk head with a #8 bulk head in the top for a return line, ran new lines with a return regulator - 6800 in first two gears no problem.

>You mean, like when you suck a drink through a straw?
Sorta.  There is a column of air sitting over the carb that varies in weight depending on how the atmosphere feels on that day/that time.  The piston starts down, intake valve is opening and creating a low pressure area in the cylinder.  The weight of the air above the carb plus the restrictions between there and the cylinder along with piston speed affect how much air actually gets to make it trough the carb to pick up fuel and deliver it to the cylinder.  No "suckage", the piston movement creates to opportunity for air to start moving.  Since it has weight, it has inertia so now you can start thinking about the effort required to get the column moving, what speed it can reach, what happens when the valve closes - inertia means the air/fuel is still moving even with nowhere to go - and all that stuff.

Why as a bracket racer my weather station updates the prediction computer every 30 seconds with air density, water grains, RH, temp, baro pressure, etc.  The amount and quality of air available to make power varies by the minute.

FElony

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #19 on: April 16, 2019, 12:45:00 PM »
Don't do it Drew. A Chevy motor in your Galaxie?

Funny boy. Fixed.

jayb

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #20 on: April 16, 2019, 09:11:51 PM »

Hey, what did I ever do to you? The only thing that depresses me about this forum is the ever-dwindling lack of humor too many members exhibit. I guess there is truth behind the old fart crotchety meme.

It's good to have an ego. It keeps you grounded, aware, and forward-focused. Just ask Jay.

I'm thinking that there's plenty of humor on this forum.  Maybe just not your kind of humor...  ;)

Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

Drew Pojedinec

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #21 on: April 17, 2019, 12:28:08 PM »
My question was a valid one. Barry treated it as such. I have a '67 Mercury that came with a 350 cfm 2V on its 390. You can accelerate it in second gear until it just stops increasing speed. I wonder what the mixture is doing.

I actually thought you were joking when you posted the original question..... *shrugs*
When it became obvious that you were not joking and were serious I asked the question of how an engine gets it's fuel from a carburetor.  Not for the sake of delving into theory, it was with the intention that you would figure out how to answer your own question, as that is often more rewarding than being spoonfed an answer that you may or may not believe anyway.

Quote
So Drew, I realize spending a month on a tuna boat in a sausage fest with all those sweaty mens gets you a little askew, but let's not get into theory. Just the facts, ma'am. Put a stock 350 cfm 2V on your Galaxie and run it down the road in 2nd until its done, and data log the A/F so we know what's really going on. What is learned, is learned by all. Don't let your ego get in the way. Again.

If this was your idea at humor, I'll admit, I don't really get it, seems like you were trying to be intentionally insulting so I just ignored it.  If this was indeed your idea of humor, I can see why you do not find the place very funny.
I haven't bothered datalogging anything as I'm too lazy to drive around with a laptop attached to the O2.  I still visually note the O2 meter and have tested out literally hundreds of carburetors in the last few years this way.  There is certainly a lot to learn from this, more to learn by making big changes to the calibration and seeing where and why the engine does what. 
My LM2 has the capabilities, and one of these days I'll do it with some of the more common carb combinations I build just for the sake of having a print out.

Running out of air, is running out of air.
Carburetors meter fuel into the air as it passes the venturi, calling it sucking/blowing/depression/etc is just semantics and not terribly important to the fact that if air becomes the limiting factor it wouldn't go lean unless there is a calibration issue or the carb is magically getting unmetered air from somewhere else.
Calibration issues like jet/pvcr too small, HSAB/emulsion waaaay too much, etc.  (or as Chris mentioned, the engine is running out of supplied fuel)
As Barry mentioned, if anything secondaries not opening cause the engine to go rich due to pulling harder through the venturi than the carb was designed for.  Maybe some instance does it differently, but I haven't witnessed this.


FElony

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #22 on: April 17, 2019, 10:13:51 PM »
The problem with having a reputation is that some people think I'm still joking when I'm just curious. In-depth carburetion science is an area I really haven't delved into, as my main interest the last few years revolves around restoration techniques and parts refurbishing (you know, like carb plating). We all have our areas of expertise.

In this particular case I was trying to come up with one more idea for the original poster to consider concerning his lean A/F. I really don't know what happens if the secondaries don't open. Once again, trying to think outside the box gets the lid slammed on my fingers.

My first car had an 8k rpm small block with a 750 double pumper. The "power range" was 4k on up. During the week commuting to school I drove with the secondaries disconnected, as the low end driveability was much better without them. The engine was pretty well finished at 5k, though. I never really knew what, if any, damage I was doing at that particular point. So I'm curious. Or was. Really don't give a shit anymore. Thanks.

Falcon67

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #23 on: April 18, 2019, 08:26:49 AM »
Without secondary opening, it's just run out of air.  It's a lean out as the engine would just run out of fuel and air to keep going.  But you'd have to be hammering it to get there, just driving around on a 2 bbl isn't going to make any difference.  IMHO what happened on the dyno was just what the other engine guys said - nobody bothered to check the A/F on a light pull to see if the carb was even close to right.  If I'm worried about the jetting on a new carb on a bigger engine, I'd just go up 2 steps front and rear - rather be fat than other.  Most Holley's, though, work well enough right out of the box.  The old 650DP on the Falcon is stock front, two steps up in the back for best MPH. 

Talking carb is fun, and frustrating sometimes.  I love the tunnel ram, as much for the "1200 CFM is too much for a 302" as anything else.  :)  "Would you put a 275 CFM 2 bbl on a 4 cylinder?"  "Sure."  So why not 2 of them on an 8 cylinder?"  "Oh." 

gt350hr

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #24 on: April 18, 2019, 11:33:09 AM »
   You can only go lean if you don't have enough fuel . Except for a forced induction application , the maximum amount of "potential air flow " is limited by the cubic inches and maximum rpm so you aren't facing "too much air" so to speak , just too little fuel due to supply or calibration. When you limit air entry to less than the maximum air flow capacity of the engine , the vacuum "pull" on the carburetor is greater ( similar to a choke) and the engine  goes rich unless the calibration is changed to correct it.

aj

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #25 on: April 19, 2019, 11:18:03 AM »
Any whooo...in closing,  I’ve decided to make the 4 hour drive to Kuntz & Co. for version 2.0 of this build. I need to focus on rest of the car (paint , susp, etc). I’ll circle back with those follow up dyno numbers in a couple months. 
Adrian Jacobs
Weatherford, TX
1970 Shelby GT500 
1970 Boss 302
2012 F250 6.7

jayb

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Re: Engine damage during dyno run (428 CJ Resto build cont.)
« Reply #26 on: April 19, 2019, 12:30:42 PM »
At the request of several members I've deleted some non-pertinent posts in this thread.  Let's try to keep it on topic, folks...
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC