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ENGINE CUTTING OUT

 
silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/06/12 10:43 PM

i have a 427 tall deck that i am running in my pulling truck. having trouble with it cutting out and falling on its face at 4500-5400 rpm when its under a load. a buddy of mine thinks it is leaning out but not sure. im running a reman 800 cfm q-jet off of a 500 caddy so i think it would b putting out plenty of fuel. and the motor also seems to over heat at idle all the time. i have a big 4 row radiator in it and i think its a 7 blade fan with full shroud. but cant figure it out. can anyone help? Confused  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 09/07/12 02:33 AM

Silverado-hd welcome to the forum:

There are so many unanswered questions.
If you are running open headers, the engine will go lean....
Where is the timing set, if the timing is retarded it will not pull either!
Is the Q-Jet properly jetted, and the floats set correctly?
What heads and who's heads are they?
Do a compression check.
The spark plug heat range may not be correct?
When I hear over-heating, is it hot enough to blow coolant out of the engine?
What type truck do you run?
What rear gear?
Who's cam are you using and what are the specs? Just give us the cam P/N, and  the valve spring P/N?Are the heads portede or what has been done to them?    
What trans type, manual or automatic?
Are you sure neither is slipping causing ? You would smell the clutch, the automatic would make the engine over-heat, but not at idle?
Are you sure it's fuel that is causing your problem...Not valve springs floating?
Are you running an electric fuel pump or mechanical?
Can you get a reading from the spark plugs?
Do they look rich, or dark in color or are they blistered?
Is this the first time out with the puller?
Does it do this at the same RPM each run?
Does the truck ever hook up, and pull hard?
Does it fall on it's face at the swame RPM each pull?
What cam are you running,and are the valve springs shimmed correctly?
Are the valve springs the correct springs for your application?
Are you running to much rear gear, and causing valve springs to float?
Are you spinning your Big Block to 9,000 RPM or higher? Big Block Chevy's don't like that high RPM. Unless you have all the good pieces. Grin  Cool

I have been to many of these truck pulling contests, and I've seen valve springs get thrown away after 2 runs or maybe an exhaut spring. It's sounds to me like the valve springs are floating causing your lack of power. Please give us some info so we can help you.

Bob  

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silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/07/12 08:07 AM

open headers, 30 degrees full advance due to cam. as far i
as i know carb is jetted correct and float is set. and yes hot enough to blow coolant out overflow. truck is an 82 chevy 4x4 dana 44 front dana 70 rear with 4.10 gears 400th tranny. the vale springs that my machinest put in the heads he said r good up to 7000 but my tall deck still has the truck pistons in it so it is only rated to spin at bout 5500 rpm redline. im running a electric fuel pump i havent pulled the plugs yet to check them and at one pull it did it at 4500rpm the 2nd pull at 5400 rpm and the 3rd at 5000 rpm. but it hooks up and takes off good till bout 200 feet or once it starts getting under a load. i have a pull comming up on the 22nd at convoy ohio and trying to get this straightend out. i hope the info i have gave will help.  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 09/07/12 09:09 PM

You should check the plugs, If your lean you could lose the engne.

What size fuel line are you using? You need a 1/2" fuel line as a minimum.With an electric fuel pump, you should run a return (bypass)to the fuel tank. This way the fuel isn't dead heading. You want the fuel that you don't use to go to the fuel tank.

If you have a fuel pressure gauge you need to see what the fuel pressure is when the engine falls flat...I don't know where to gp from here. Is there a way you can put a camera on it and watch it through a run.I would run 7 psi of pressure.
Trial and error, is the way it looks now?  

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redneckjoe69
Everything in my driveway’s a Chevy
Posts: 612
Joined: 02/10
Posted: 09/08/12 10:24 AM

i agree with Pepsi,...do a plug reading.    running hot at idle could actually be a rich condition.  use a vaccuum gauge to set your mixture screws.   do you have any exhaust pipe on your open headers?   if not, id install about 2 feet of pipe.  spraypaint a line down the side.   start it up and go for a ride.  where the paint burns off is where you want to cut the pipe.    you can buy a cheap $30.oo air fuel ratio gauge from the local auto store and weld an O2 sensor bung in the headers too.   Bob/Pepsi, covered about everything else i can think of.  

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silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/08/12 11:36 PM

i have 3 inch straight pipe back to the rear axle. and i pulled a plug out and it was clean. very little carbon but the porcelin was kinda carmel/chocolate in color. not very good at reading plugs. im running ngk YR5 plugs. if that helps any. a kid i work with that runs drag cars said the plug looked like the motor was running lean and that maybe i was runnung too hot a plug. i have a set of ngk UR4's that the electrode sticks out further. i dont know if this will help or not. im running a msd digital 6al with billit tall deck distributer. the one with the slip collar.  

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silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/08/12 11:39 PM

no way of putting a camera under the hood but looking at getting an electronic fuel pressure gauge so i have it mounted in the cab. buddy of mine thinks he has a spare one for one of his drag cars.  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 09/09/12 10:21 AM

silverado-hd.

I guess a negative with the fuel gauge under the hood. I was thinking like we Drag Racers run the gauge on the cowl.

If you are running a 3" straight pipe all the way back to the rear axle. That could be what is happening. You engine could be going so lean at WOT you can't tell. When you get out of the throttle the engine will go rich. The plug reading you have is what I would like to see. A Chocolate Color is great,but is it when your at WOT and your pulling a load. Grin  Cool  

I think you hit your problem on the head with a lean condition. The problem is finding out what is causing it. I'm sure you can see that now. If you could just do what we Drag Racer's do. Run the engine through the gears a couple times back to back. Maybe on the second hard run at WOT just kill the ignition. Now you want to read your plugs. Some plugs are tricky to read. On a Small or Big block chevy I like to read #1 and #6 spark plug respectively. #1 and #6 fire at the same time. I like to see if the plugs look the same incolor. This tells me if I am getting the correct fuel distribution to each bank. Confused

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 09/09/12 10:53 AM

silverado-hd.

I use NGK plugs. I can tell you this if you have a stock ignition the PROJECTED tip plug could get the spark blown out. But you are using a good ignition. The same set-up I used 6-AL slip collar.  Try using the retracted tip. NGK also runs their heat ranges oposite most manufacturers.PLEASE READ ON:

NOW THIS IS JUST AN EXAMPLE. UR-4 are colder then a UR-6. NGK runs their numbers backwards.

Where an Autolite or Chanpion: run the oposite.As the numbers go down the plug gets colder. Just some examples below.

NOW THIS IS ANOTHER EXAMPLE: Champion J-8 is hotter then a J-4 plug. they go down inthe colder numbers.

THIS IS AN EXAMPLE ONLY: Autolite AF-22 is colder then an AF-24.
I hope I didn't confuse you.

I like NGK Racing spark plugs and they will color well, and usually easy to read.
I also like Autolite plugs. I don't care very much for Champions. They made a Crappy spark plug back in the '60's and still *** The grond electrodes still blow off or fall off and sometime can mare your block.

It's almost like you have to be inside the combustion chamber of your engine.

Try up-jetting another .002 if you can. See if helps.
Try Zero Lashing the cam.(it will help the higher RPM)
Check the valve springs for their pressure.
If you can get a fuel pressure gauge outside the engine compartment.
Just for some imput take notice does it really fall on it's face or seem like it running out of fuel....

I can't think of anything else without seeing it run.Good Luck.

Bob  

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silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/09/12 01:34 PM

so do u think i should try a hotter ao colder plug? i would jet it up but i dont know where i can find jets for a q-jet. and i think that maybe my fuel pump might b the issue its just a hi volume clicker style pump u buy at napa or advance. i think max psi is like 10 or 11. but not sure. hopefully get the gauge put on it soon so i can watch the pressure.  

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silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/09/12 01:37 PM

my buddy is gonna come over and give me a hand next weekend and if he thinks it is the carb he is gonna bring over a holley 770 that is jetted way up for his drag car and try that.  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 09/09/12 06:42 PM

If your running a Hi Pressure fuel pump 7PSI is about the max pressure you want. I ran a Holley HiPerformance pump but used a pressure regulator in front of it.

Your Q-Jet is a spread bore flange. Unless the Holley has a spread bore flange it will not fit your intake. Holley carbs for the most part are Square Flanged.

That Holley 770 maybe exactly what you need. It's deffinetly more CFM, and More CFM means there is more fuel with it also....GOOD THING FOR YOU... Grin  Cool

If your going to change heat range plugs I would wait until you get that Holley 770 on it. But if you going to change a heat range of plug you want to go colder. Use the guides I gave you. If you have the iron BBC heads.You can use an AC 42 don't use any AC plug that has an "R" that means resistor, and you don't need a resisitor plug unless your watching  (TV while your pulling)...LOL...  Grin

Let us know what you find. I would bet that Holley 770 will kick aarrzz, and will be a big difference. Holley's are easy to tune. Keep a record of any changes you make. You can always start over.  Good Luck...If your new at this it is a big learning curve, and it takes time. So don't get frustrated, and through a wrench threw the windshield...LOL... I've seen it happen... Grin

Bob  

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silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/09/12 09:17 PM

lol ya trust me after these last few pulls i have wanted to but stopped myself. but thank you for all ur help and i will keep u posted on my progress. thank again.  

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silverado-hd
I love my Chevy Chevette!
Posts: 19
Joined: 09/12
Posted: 09/09/12 09:26 PM

oh and i ve an adapter that goes from a spread bore to a square bore and was wondering if i put 2 electric fans on the front of the radaitor do u think that will help with the over heating issue. i know i was kinda sparse on that info but when it idles it gets to bout 215 and hangs there but if i run rpms to 1500 it will cool to 200 and stay if i keep idle that high. but as soon as i go down the track and and they go to unhook i looked at temp gauge and it read 235-240. drove it on the trailer and as soon as i shut it off the temp spikes and poors out the over flow. but like i said i has a big 4 row rad. and like a 7 blade fan on water pump and full shroud. and tranny is not slipping at all so im still trying to figure that out. unless when it leans out at full throttle it causes it to over heat heally fast and once i shut it off it finally shows it? does that sould bout right to u? im not sure just throwing ideas out there. but like i said thanks again for all ur help.  

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waynep71222
My first time was in a Chevy
Posts: 218
Joined: 04/12
Posted: 09/10/12 06:48 AM

when it idles it gets to bout 215 and hangs there but if i run rpms to 1500 it will cool to 200 and stay if i keep idle that high. but as soon as i go down the track and and they go to unhook i looked at temp gauge and it read 235-240. drove it on the trailer and as soon as i shut it off the temp spikes and poors out the over flow. but like i said i has a big 4 row rad. and like a 7 blade fan on water pump and full shroud.

a few things... and this is just theory.. as you are running a very HIGH rpm..

on the cooling system... LEAN will cause it to overheat....

what kind of thermostat or restrictor are you running..

is it a belt driven water pump or an electric water pump with that big fan???

are you running a bypass hose from the intake to the water pump???



~~~~~~~
under normal conditions.. the thermostat is closed on start up... the water pump is pushing water into the block.. forward through the heads.. up to the intake .. past the back of the thermostat . through the bypass hose and around again.. this happens until the coolant passing the thermostat has picked up enough heat to open the thermostat slightly.. at that point the hot coolant is circulated into the radiator..  the cool coolant in the radiator is circulated into the block and heads where it will flow past the thermostat closing it.. the water pump continues to circulate it inside the block and heads until it has picked up enough heat to open the thermostat again..  but while the thermostat was closed.. the coolant was stopped in the radiator.. this allowed the fan to take some of the heat out of it.. so it was ready to pick up more when it exchanged places again.. this is the way it works..   there are a few other neat features. because the bypass hose is smaller than the radiator hoses.. the water pump cannot circulate the coolant very fast through the motor.. so it builds mechanical pressure above system pressure in the block and heads where you really need it to keep the coolant from boiling around the exhaust ports, valve seats and valve guides.

without a thermostat.. the coolant flow through the radiator is so fast that no fan in the world could take the heat out of it...    the water pump can also flow more than the radiator can pass in some instances..  this builds up mechanical pressure and expands your top radiator tank.. usually blowing the seals or cracking the welds...  there have been cases.. on welded aluminum tube radiators.. that the extreme pressure has expanded the flattened oval radiator tubes closing off air flow between them..  ruining your radiator..

you might want to if you have a belt drive water pump and fan... install a 192/195F thermostat.. try to get one of the heavy duty versions that look like this...  as they have less problems with the mechanical pressure built up behind them.




~~~~~~~~~~
you can just for a static test.. install a 50 pound pressure gauge on the front of the intake manifold.. work the throttle once and see what the mechanical pressure in the cooling system behind the thermostat comes up to..

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


lastly... on the high rpm issue....  i wonder if you are draining the fuel bowl because the stock sized quadrajet needle and seat cannot pass enough fuel to keep it filled...

with a holley.. or perhaps there are increased size needles and seats for your quadrajet..

i have some walker products quadrajet parts catalogs that might offer a solution..  can you post the carb number stamped into the side of your carb so i can see which needle and seats might fit..???

edit.. i looked in my walker products catalog.. the largest quadrajet needle and seat orifice is 0.132" part number 31-546... and might be available at your local carb rebuilder..   it might have that size in it already.. this is just an idea..  the needles for the 7 available sizes from .106 to .132 are the same part number...  just the seats are different..

on high performance engines.. GM always installed holleys.. as there are 2 entry points for fuel to get into the bowls..  but the quadrajet was never really designed for that kind of max power max rpm big motor operation..  post a carb number or look over at the walker products online site..

these are just my opinions..  

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