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Topic: Need Help Guys.... (Read 2714 times) previous topic - next topic

Need Help Guys....

I have that m90 on my 5.0 carb setup, it runs and everything, BUT, after hitting the throttle the rpms drop (OBVI) but when they drop it stalls right out unless i hit the throttle again... so it idles but then drops off.. what is causing this ??? any help would be greatly appreciated.. Thanks in advanced guys.....

Re: Need Help Guys....

Reply #1 –
ok heres a few questions

what size carb is it? and what brand with part number..

it may be rejeted and ajusted..

and what did you set the spark plug gap at? it needs to be at about .030-.035 ;)

and pictures please  :D

oh and whats the timming set at are you useing a boost retard?

and whats the motor setup like
Quote
there's only about a half a dozen man made objects that are herd by the human ear below 40Hz,a pipe organ,thunder,the space shuttle lifting off,a jet airplane taking off or landing,a large canon,an atomic bomb ignited in your back yard and the heat wave afterward oh wait you would be dead so you would'nt hear it scratch that!,and maybe beating your hear against a wall less then 40 times a second..rap music is'nt one of them!thats 40-60Hz@100+db the moving air is under 40Hz

Re: Need Help Guys....

Reply #2 –
the carb was a 750cfm double pumper but i took the body off and used a 650 dp instead , i havent touched the plugs so im not sure on that . Im not using a boost retard but am thinking of that now (thanks) , the timing is set at 8 degrees advanced.. motor is a stock 85 Gt 5.0 (stang) e7's ported , eddy alum intake , longtube headers , stock cam , stock bottom end , flat top pistons , double roller timing chain , stock distributer , and its a 5 spd (for those who have to ask) PLUS the m90 .. any help would be great ...

Re: Need Help Guys....

Reply #3 –
when you say 8 degrees advanced do you mean 8 degrees  before top dead center or 8 degrees  after top dead center? you need to be at about 8 degrees before top dead center..

and as for the plug gap you better check and if at stock set the gap at .035 ..... if it's at .045or.055 the car will fall flat on it's face ..


Nick
Quote
there's only about a half a dozen man made objects that are herd by the human ear below 40Hz,a pipe organ,thunder,the space shuttle lifting off,a jet airplane taking off or landing,a large canon,an atomic bomb ignited in your back yard and the heat wave afterward oh wait you would be dead so you would'nt hear it scratch that!,and maybe beating your hear against a wall less then 40 times a second..rap music is'nt one of them!thats 40-60Hz@100+db the moving air is under 40Hz

Re: Need Help Guys....

Reply #4 –
sounds like it could also be too much gas at idle. The air helps mix it out and that will help stop it from stalling.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Re: Need Help Guys....

Reply #5 –
the gap is stock ,and the timing is 8 degrees after top dead center (advanced). i worked on it today and im still getting the same problem after i hammer the gas, the rpm's drop right off and stall on the decrease.

Re: Need Help Guys....

Reply #6 –
Quote from: ONEpissedOFFstang
the gap is stock ,and the timing is 8 degrees after top dead center (advanced). i worked on it today and im still getting the same problem after i hammer the gas, the rpm's drop right off and stall on the decrease.



well like i said you have it all wrong

you need 8 degrees before top dead center..(retarded) and you need to gap the plugs at .035

oh and what plugs are you useing atuolite 25 next plug change go with 24's
Quote
there's only about a half a dozen man made objects that are herd by the human ear below 40Hz,a pipe organ,thunder,the space shuttle lifting off,a jet airplane taking off or landing,a large canon,an atomic bomb ignited in your back yard and the heat wave afterward oh wait you would be dead so you would'nt hear it scratch that!,and maybe beating your hear against a wall less then 40 times a second..rap music is'nt one of them!thats 40-60Hz@100+db the moving air is under 40Hz

Re: Need Help Guys....

Reply #7 –
Quote
and the timing is 8 degrees after top dead center (advanced)
Quote
you need 8 degrees before top dead center..(retarded)
Umm... are you guys living in a reverse universe or something? The last time I checked, "advanced" meant the spark happened sooner, before the piston was all the way up (BTDC) and "retarded" meant it sparked later, after the piston had passed the top (ATDC).
Death awaits you all with nasty, big, pointy teeth.

1988 5.0 Bird, mostly stock, partly not, now gone to T-Bird heaven.
1990 Volvo 740GL. 114 tire-shredding horsies, baby!

Re: Need Help Guys....

Reply #8 –
Blow thru or draw thru system???

Not all carbs can be used as a blow thru, the pressure pushes the fuel through the boosters back into the bowl.

Re: Need Help Guys....

Reply #9 –
sorry blown306 , ill try it...

Re: Need Help Guys....

Reply #10 –
get a wide band o2 sensor, check your A/F ratio, sounds like your running to rich,

Re: Need Help Guys....

Reply #11 –
some people are telling me to get a fmu, but im running carbed , so i know that wont work, today im going to try what blown306 has told me to do..anyone that has a idea or suggestion please leave info... thanks again guys..

Re: Need Help Guys....

Reply #12 –
retard the timing. You are running rich as anything.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Re: Need Help Guys....

Reply #13 –
Quote from: ONEpissedOFFstang
some people are telling me to get a fmu, but im running carbed , so i know that wont work, today im going to try what blown306 has told me to do..anyone that has a idea or suggestion please leave info... thanks again guys..


 :rollin:  :rollin:  a FMU will not work in your case

carbs don't use a return fuel line  well if you use a three port carb regulator you can put a return line but it's not really needed your going to run about 14PSI  and more pressure will blow the floats apart

and to lay to rest the whole advance/retard theory

in one way your right dude

and i'll try to explain this as easy as i can

it's something like when some people call a car engine a motor

a few exsamples

a boost retard.. retards the timming IE base timming is say 14 degreesBTDC and the retard is set at 1 degree per pound of boost.. if the motor"engine" makes a max of 6psi it will retard the timming 6 degrees which equals 8 degrees total timing but!!! thats the base total not the total timming @ 2500RPMS the ford ECM "A9L/A9P/A3M and so on adds if i remember corectly 22 degrees to the base timming which if you had 14 degrees of base would equal 36 degrees minus the boost retard of 6 which equals 30degrees..
anyway..
in this case there is no ECM theres a carb

which raises another question of which distributor he's useing if he's useing a dura spark type distributor then it has a cutrifical advance..which would be fine
but if he managed to get a TFi distributor to work. that might allso be a problem to.. it won't work right.with out an ECM  two difrent types of distributors TFI uses a halafect pickup and a dura spark one uses a magnetic pickup..

oops back to the whole advance/ retard theory  :sorry:

anyway most motor heads but not all of them say retard the timming and some say avdvance the timming depends on how you look at it ..

the reason why i say retard is because i'm a retard:raspberry  :giggle:

no the reason why i say that is because i base it on how the cam,igntion timming and motor"engine" works
ie cam timming and ignition timming .. when you retard a cam the vavles open closer to top dead center and close closer to topdead center.. and when you advance the cam opens the valve sooner before top dead center and the valves close sooner to top dead center..

there are a few reasons why race shop do either one of these in a motor"engine"

when you retard the cam the motor"engine"  will make more power in the lower rpm power band but loses some top end power

and when you advance the cam timming you gain power in the upper rpm power band but loses the lower rpm power gains..

but there is another reason why race shop advance cams..

sometimes the pistons used don't have the clearance for the cam they are useing and if it's only buy a very small amount you can advance the cam to gain the clearance back that you need.. ie by the time the piston hits top dead center the valve will be closed..



now igntion timming

now if the igntion fires @14 degrees BTDC it's firing 14 degrees before the piston hits TDC right and so then the timming is retarded and ie you set the timming @ 8 dgrees BTDC its closer to TDC so it's advanced..

now if you set the timming at
let say 14 degrees ATDC that would be advanced because the piston allready hit TDC.. and then if you set the timming @ 8 degrees ATDC that yes would still be advanced timming because it's still ATDC but it's a retarded timming. because it's closer to TDC.. sorry i can't help it if the igntion is dumb :crazy:  :giggle:

i'll try and give it to you this way..

math..
.4-0 would be retarded and 0-4. would be advanced..

there for BTDC is "retarded" plugs fire before the piston hit TDC and ATDC is "advanced" the plug fires after the piston hits TDC..

thats where i get my advance/retard theory from..

i hope this clears things up ;)

Nick
Quote
there's only about a half a dozen man made objects that are herd by the human ear below 40Hz,a pipe organ,thunder,the space shuttle lifting off,a jet airplane taking off or landing,a large canon,an atomic bomb ignited in your back yard and the heat wave afterward oh wait you would be dead so you would'nt hear it scratch that!,and maybe beating your hear against a wall less then 40 times a second..rap music is'nt one of them!thats 40-60Hz@100+db the moving air is under 40Hz

Re: Need Help Guys....

Reply #14 –
All that's good Nick, but a few degrees of timing advance/retard ain't causing the problem.

That said, no I don't have the answer either....